.

ROLLING SUGGESTIONS
5. GENERAL USE INSTRUCTIONS

5.1. INTRODUCTION
IMPORTANT: It must be always considered that plate
quality is very important in order to obtain a good
rolling result, especially on machines for high precision
works, like CNC equipped machines or pre-bending
machines. Certified sheets with distension treatment
(stress released) are ideal for this type of plastic
forming machine.
The sheets characteristics the greatly influence the
forming result are indeed: resistance homogeneity,
thickness, planarity, lamination fibres direction
(parallel or transversal to the rollers), the residual
stressing, squaring.
Using sheets with different mechanical, physical or
chemical features determines the differences in rolling
diameters, thus making tolerances, results and rolled
part quality poor. The more the plates are of high
quality and consistent among them, the more the rolling
results will be similar in diameter and of improved
quality.
The most frequent and clearest evidence of this
situation is well known to the operators every time they
roll on their machine an entire pack of sheet supposed
to have the same features.
More often it happens that, even if moving the rolling
cylinders always at the same position, the final rolling
diameter will result different almost on every shell.
This is the actual proof, directly verifiable by the
operators, that the difference that makes the final
diameter different, resides in the sheet itself, having
faithfully repeated the same positionings on the
machine for each following operation.
The sheets were therefore different among them in one
or more characterizing parameters influencing the
diameter, whether noticeable or however physically
verifiable (thickness, resistance, fibres cutting sense,
planarity) or unknown and difficult to verify (yield
point, elastic return, residual stresses, weight of the
sheet), but often mostly responsible for differences of
diameter.
The most evident demonstration of this is easily found
on Numerical Control machines. The repeated
positioning repeated by the high precision automatic
control devices assure a precise repetition of the rollers
positioning.

e5.1-A.eng.rev00.doc

ROLLING SUGGESTIONS
But more often the final rolling diameters are different
because of the different features of the sheet.
Moreover it is hard to compensate these differences
using compensation devices installed on Numeric
Controls, since they are able to detect and compensate,
only some of the diameter influencing factors (like
thickness, tensile strength, weight), and very rarely
some others (resistance, fibres cutting sense, planarity,
elastic return, residual stresses).
But what makes actually difficult to compensate sheet
differences is that all the differences influencing the
diameter get summed.
A compensating device could correct one of these
factors but its action could be nullified by other factors.

e5.1-A.eng.rev00.doc

ROLLING SUGGESTIONS
5.2. PLATE PREPARATION

5.2.1. An accurate sheet preparation improves the

rolling quality and preserves the rolls surface,
avoiding scratches.
Before being inserted among the rolls, the sheet
must be cleaned and prepared as follows:
- Remove every flash slag or residue produced by
cutting the sheet along the edges, especially if the
sheet has been cut by flame; any metallic residue
must be removed carefully because excessive
hardness could seriously damage the rolls surface.
This operation can be done with an abrasive wheel
and must make the edge perfectly smooth, like if
bevelled. (5.2.1-A).
- clean the entire sheets flat surface until it is
completely free of welding residues, rust and any
outrigger that could cause damage to the rollers
(5.2.1-B) or modify the rolling diameter, by
changing the sheet thickness (absolutely
unacceptable in case of CNC application);
- if necessary proceed with complete sandblasting of
the sheet

5.2.1

5.2.2. Some suggestions to reduce working defects

and to improve rolling quality.
- The sheet must be completely flat. It must not be
waved, bent in any part of its surface, deformed in
any direction (5.2.1-C). This is required because
rolling is a deforming process and if the sheets
surface is (totally or partially) deformed, rolling can
result irregular or of poor quality.
- The sheet should be sustained during all rolling
phases (from introducing the sheet into the machine
up to the rolling of the final diameter) because the

e5.2-A.eng.rev01.doc

ROLLING SUGGESTIONS
weight of the sheet could modify the rolling
diameter. (5.2.2).
The above mentioned instructions become
imperative when using CNC machines, because the
final result could be dramatically influenced by
these factors, getting absolutely useless the high
precision CNC.
Since rolling results depend more on the sheet that
on the machine, for this reason the only
responsibility bore by the manufacturer when using
the CNC is the accurate repeatability of the machine
positioning.
No responsibility can be bore by the
manufacturer for the consistency of diameters
rolled on the machine, as the diameters depend
mainly by the plate tolerances, rather than by the
machine itself.

5.2.2

e5.2-A.eng.rev01.doc

ROLLING SUGGESTIONS

5.3. WORKS MEASURES

5.3.1. PINCH PRESSURE REGULATION

This is one of the most important phases of the rolling cycle.
To guarantee a good rolling result and protect the bending
rolls and the whole machine, it is important to adjust the
pinching pressure according to the type of plate to be rolled.
The adjustment of pinching pressure is made through
commands placed on the console (for further details see
controls and commands manual.
To help the operator in finding the correct pinching pressure,
the machine can be equipped with an optional device which
shows instantaly the used load.
Hereunder you can find a description of the correct
operations to be made while bending plates with different
thicknesses on machines equipped with such device.

THICKER PLATE

A) Keep the pinching pressure as low as possible; the

eventual graph bar where available that
monitors the pressure of the clamping roll, is in the
YELLOW COLOR
B) While the side rolls raise and bend the edge of the
plate, clamped, the pressure inside the clamping
cylinders, raises, inducted by the plate, and the
graph bar will change into GREEN COLOR, that is
the optimal to not have any concave (canoeing) or
convex (hourglass) defects on the plate.
If the graph bar should raise into the ORANGE
color zone, it may produce a concave (canoeing)
defect on the plate.
Do NEVE work in the RED COLOR zone of the
graph bar, as the result on the plate would be a
excessive concave (canoeing) defect on the plate,
and a high overload to the machine, easy to be
badly and dangerously damaged.

e5.3-A.eng.rev04.doc

ROLLING SUGGESTIONS

THINNER PLATE
A) Use the
COLOR.

optimal

preload

pressure,

GREEN

B) While bending the plate by the side roll, the graph

bar will remain on the GREEN COLOR zone,
(optimal to not have any concave or convex defects
on the plate).
If machine works on ORANGE COLOR zone, it
may produce a concave defect on the plate.
Do NEVER work in the RED COLOUR zone of
the graph bar, on the result on the plate would be a
excessive concave (canoeing) defect on the plate,
and a high overload to the machine, easy to be
badly and dangerously damaged.

5.3.2 NARROW PLATES

Position narrow plates always at the centre of rolls for a
better rolling result. Mantain a pinch pressure as low as
possible, just enough to move the sheet; this will avoid to
concentrate excessive efforts on a short section of the rolls
(5.3.2.1).
EXCESSIVE PRESSURE COULD PERMANENTLY
BEND THE ROLLS (5.3.2.2)
IMPORTANT: to reduce risk of damages when using
narrow plates, the side rolls pressure MUST NEVER
EXCEED the values indicated in the following chart
(when pinching, check carefully the pressure value
indicated by the gauge).
Sheet length L

100%
80%
60%
50%
40%
30%
20% or less

Maximum
Pressure Allowed

100%
85%
75%
70%
65%
60%
55%

For plate with length smaller than 25% please contact the
PROMAU customer service.

e5.3-A.eng.rev04.doc

5.3.2.1

5.3.2.2

ROLLING SUGGESTIONS
If exceeding these values, please ask for written
authorization by the manufacturer.

Its strongly suggested to square the sheet on the long side of

the sheet. Squaring on the short side against the side rolls
could not be accurate because of wrong cutting operations.
5.3.3 WARNING
Before starting a work, make sure of the complete closing of
end yoke, by using the appropriate lever on the control panel.
5.3.4 COMPULSORY REQUIREMENTS
One of the major risks that can occur during the PREBENDING phase, is to bring the edge of the plate beyond the
tangent point of the pinch between the pinching rolls
(5.3.4.1).
This can easily generate very strong cavitations on the
hydraulic motors of the machine. These very strong
cavitations occur when the motor, even for only a few
seconds, instead of pushing the rolls to rotate, is instead
trailed, pulled by the load, so it doesnt work as a motor
but as a pump.
For this reason, since the motor is not able to suck enough oil
for the required revolution speed, the pistons inside the motor
risk to break the axial supports that keep them fixed on the
motors shaft.
This generates a violent expulsion of the plate, outside the
pinch point, through the rolls, so that the load goes from
maximum to zero, giving back all the potential energy of
elasticity accumulated from the mechanical components and
could make the motor turn backwards, therefore work as a
pump.
On the machine, valves have been mounted so that in normal
working conditions check the motor, avoiding cavitations, but
in extreme conditions as when the plate is expulsed violently
from the pinch between the rolls, cannot completely protect
the motor (when the plate is brought beyond the tangent
point).
Also the re-rolling phase could be at risk of cavitations that
could destroy the hydraulic motor. During calibration, it is
recommended to reduce the thickness down to about 75%.
5.3.4.1

e5.3-A.eng.rev04.doc

ROLLING SUGGESTIONS

NOTES FOR THE OPERATOR:

WARNING:
1- Avoid absolutely to bring the edge of the plate beyond the
tangent point of the lower roller, keeping a minimum part
of the plate always pinched, thus having a safety margin,
not to risk expulsion.
2- When re-rolling welded plates, its important to select
re-rolling mode and, it is recommended to reduce the
thickness down to about 75% and lower completely the
bottom roll.
One of the most dangerous conditions, that can cause
damages to the machine, its inserting an over thickness
between the sheet and the two pinching rolls (5.3.4.2).
Should rotating start under this condition, permanent
damages to the roller or to the entire machine could occur
(up to make necessary roll replacement).

Another high risk situation occurs when completely

lowering (till the mechanical stop) the central roller, and
introducing a plate or profile between the rolls trying,
consequently, to bend it moving another roller of the
machine or introducing an over thickness between the
plate and roller and starting the rotation (5.3.4.3). This
extreme condition could cause serious damages to the
rolls as well as to other machine components (bearings,
pins, cylinders, gearbox, frame).

5.3.4.2

5.3.4.3

Another dangerous condition that should never occur is

to place the rollers under load between them, especially
when rolling conical parts and therefore the rollers are
not parallel between them. (5.3.4.4)

5.3.4.4

e5.3-A.eng.rev04.doc

ROLLING SUGGESTIONS

5.3.5 ENVIRONMENT
The machine must be installed in an appropriate working
environment, the area surrounding the machine must always
be kept clean, free from obstacles and well lit. The machine
should not get in contact with water, oil and other liquids.
The machine should not be stored or work in dirty and dusty
rooms. Too high or too low environment temperatures, as
well as too much humidity could influence the proper use of
the machine. Soil, smoke, vapours could enter inside machine
devices, causing damages, impeding the proper functioning
and causing extreme wear of electric, electronic and
hydraulic components.
Waste disposal is the responsibility of the user, according to
local regulations.
Oils recovering and disposal must be done with the use of
suction devices foreseen by the user.

5.3.6 HOT ROLLING

Use of hot plates is allowed ONLY AND EXCLUSIVELY if

the machine is specifically designed for Hot Rolling. If it is
not or if you have any doubt, immediately advise the
manufacturer.
On plate bending machines, which are specifically designed,
following procedures must be respected:

Keep hot plate in machine for the shortest time

possible (reduce to the shortest time the plate rolling
cycle)
DO NOT let the plate sit/lay on rolls (once the rolling
cycle is finished, IMMEDIATELY remove the can
from the machine)
Frequently measure the temperature of the rolls
surface, at least after each hot rolling process, with
proper instrument (available on the market or as an
optional tool from the manufacturer)

e5.3-A.eng.rev04.doc

ROLLING SUGGESTIONS

Monitor the top roll, with special attention, as it is

more affected by the heating. The plate rolls around
the top roll and therefore it is where the most heat
transmission is concentrated (the more the plate rolls
around the top roll, the more it will warm).
Keep the temperature of the rolls, measured by the
suitable instrument, within the MAXIMUM limit
value, as indicated in the below table
Such value, variable depending on the Hot Rolling
package available on the machine, MUST NEVER be
exceeded, to avoid permanent and serious damages of
the rolls.
NO Protection

100 C

212 F

Warm Rolling Package

180 C

356 F

Basic Hot Rolling Package

380 C

716 F

Intensive Hot Rolling Package

500 C

932 F

Besides, to prevent the rolls from being permanently

and seriously damaged, it is essential that the operator
progressively reduces the machine force (hydraulic
pressure of the rolls movement) at the increase of the
temperature of the rolls according to the following
table:
ROLLS TEMPERATURE
C
Up to 100
from 101 to 130
from 131 to 170
from 171 to 220
from 221 to 300
from 301 to 350
from 351 to 400
from 401 to 450
from 451 to 500

F
Up to 212
from 213 to 266
from 267 to 338
from 339 to 428
from 429 to 572
from 573 to 662
from 663 to 752
from 753 to 842
from 843 to 932

It is therefore necessary to constantly measure the

temperature of the rolls, especially in the areas which are
mostly in contact with the plate.

e5.3-A.eng.rev04.doc

ROLLS MAX PRESSURE

100%
95%
90%
85%
80%
75%
70%
62%
55%

ROLLING SUGGESTIONS
In order to protect the Plate roll, special machine-temperature
sensors can be provided; they will automatically reduce the
max pressure on the rolls when pre-determined threshold
temperatures are reached.
In the event the machine temperature reaches the critical
point, the machine STOPS.
No further rolling can be done, operator MUST remove the
plate from the machine, IMMEDIATELY AND IN THE
SHORTEST TIME, (without leaving the plate stationary on
the rolls) only using rolls and the yoke opening. This to
prevent permanent serious damages on the rolls.
Operational pressures must be reduced further more if the
width of the plate is narrower than the rolls width (as
described in the specific paragraph regarding reduction of
pressures for narrow plates).

Never cool down rolls or other machine parts with water

or other liquid coolants, to avoid permanent and serious
damages on the rolls

It is peremptory to follow the above mentioned procedures in

order to prevent rolls and other machine components to be
permanently and irremediably damaged.

e5.3-A.eng.rev04.doc

ROLLING SUGGESTIONS
5.4 ROLLS CAMBERING
The rolls are supplied with cambering in order to partially
compensate the deflexion due to the load during rolling.
The upper and lower rolls have a central cylindrical
segment (whose length can change) and the remaining side
parts shaped in two, four (or more) conical segments, in
conformity with machine sizes and rolling applications
(Fig 5.4.1).
This operation is performed to avoid one of the most
common defects on the plates after rolling: the BARREL
defects of the edges (5.4.2).
A - The barrel defect makes the shell tightly closed at the
ends and lightly opened in centre (5.4.2). This occurs
because of the rolls deflexion, that makes the plate free
and not pinched in the centre. This defect worsens when
increasing the thickness (thick plates); to reduce it, the
pinching pressure must be reduced (5.4.3). The rolls
cambering could, on the other side, generate the opposite
defect: the reel defect.

5.4.1

5.4.2

B - The reel defect makes the shell tightly closed in the

centre and lightly opened at both ends (5.4.4). This occurs
because of the rolls cambering that make the plate free and
not pinched at the ends. This defect worsens by reducing
the thickness (thin plates); to reduce it, the pinching
pressure must be increased (5.4.5).
Cambering is designed for an average application within
the machine capacity, between the barrel (on thick
plates) and reel (on thin plates). Being the cambering
calculated for an average application, a thick plate must be
barrelled, as well as a thin one must be reeled, while
rolling. It is however suggested to have an average
cambering, in order to obtain acceptable results on a wider
range of thicknesses.
It is however possible, on pre-bending machines, to
partially correct the defects due to the rolls cambering
with pinching pressure.

bar

5.4.3

5.4.4
bar

5.4.5

e5.4-A.eng.rev00.doc

ROLLING SUGGESTIONS
Cap. 6 MAIN APPLICATIONS
6.1.
6.2.
6.3.
6.4.

Pre-bending
Rolling defects
Conical rolling
Profile rolling

6.1 PRE-BENDING
The following procedure is based on the feeding of the machine
from the right side; in case of opposite feeding the procedure
must be inverted.

6.1.1. CLOSING IN ONE PASS.

PHASE 1 - Feeding and squaring of the plate (6.1.1.1).
The two central rolls are opened (The lower P roll is in its
lower position)
The right front roll Y is slightly higher, in order to obtain a
slightly tilted plane where to feed the plate between the rolls.
The left rear roll X is at a height so that the plate can touch the
roll at approximately 25 mm below its horizontal axis.
Feed the plate between the two central rolls pushing it against
the rear roll X , obtaining a perfect squaring. (Should the plate
be too narrow, dont rely upon this squaring against the rear roll,
but check the square of the plate on the longer side of the plate)
Once the plate is squared, raise the lower central roll until it
pinches the plate against the top roll at the desired pressure
setting the pinching pressure (6.1.1.2).
You can set the desired pressure from the main page of the CN
or, is some cases, from the hand wheel on the machine.
You can read the desired pressure (once set) just pushing the
lower roll against the plate.
The plate pinching will be maintained for the whole rolling
process, to have an optimal control of the feeding of the plate.
After pinching, check that the plate is still in the squaring
position.
Then go to the following step.
NOTE: The squaring is a very important phase: a non-correct
squaring will give poor final results. The four rolls-machine is
the most suitable machine for the squaring of the plate. Using
the side roll as reference and keeping the two central rolls
pinched, the squaring will be maintained for the whole rolling
process.

e6.1-A.eng.rev03.doc

6.1.1.1

6.1.1.2

ROLLING SUGGESTIONS
PHASE 2 Return to the tangent point (6.1.1.3)
After squaring, keep the front roll Y at approximately the
same height of the lower central roll P, to hold the plate
horizontally. Feed the plate backwards to bring the plate to the
nearest tangent point, at which the two central S and P rolls
pinch the plate.
WARNING: This phase is very important for a good prebending. The further the plate will be to the tangent point, the
poorest the pre-bending and the long flat side will be.
Nevertheless, the nearest the plate will be to the tangent point,
the higher will be the risk of slipping or escaping of the plate
from the rolls.
FOR THIS REASON ITS STRICTLY FORBIDDEN TO
ANYONE TO STAND NEAR THE BENDING MACHINE
DURING THE ROLLING PROCESS, FOR THE HIGH
RISK OF SLIPPING AND FALLING OF THE PLATE.
Furthermore it is suggested to always hold the plate by means of
a crane or to support it on a feed table or a side support, to avoid
dangerous and not desired collapses.
Its also suggested to protect the front area, to prevent the access
of non-authorized personnel.

6.1.1.3

PHASE 3 Pre-bending (6.1.1.4)

Lower completely the rear roll X, used for the squaring and
not necessary in this phase.
Lift the front roll Y up to the rolling position, to obtain the
desired diameter.
This position must be estimated by the operator or it can be
found by trial.
Go immediately to the following rolling phase, to avoid that the
plate, if tilted, slips from the machine and falls.
WARNING: This phase must be executed with extreme care.
If lifting too much the Y roll:
- The plate would bend excessively, thus requiring
excessive torque during the following rolling process;
- Even if having the necessary torque, the diameter could
be too close. (very difficult to correct)
WARNING -DANGER !!
ITS FORBIDDEN TO ANYONE TO STAND AT THE
REAR OR UNDER THE PLATE IN THIS PHASE.
IT COULD HAPPEN THAT DURING THE LIFTING OF
THE SIDE ROLL, THE PLATE SLIPS OUT FROM THE

e6.1-A.eng.rev03.doc

6.1.1.4

ROLLING SUGGESTIONS
PINCHING POINT, BETWEEN THE TWO CENTRAL
ROLLS.
This danger could be caused by a wrong manoeuvre of the
operator to feed the plate (verify carefully the feeding direction
by means of the arrows placed on the front console).
Moreover its suggested to keep the plate lifted with the crane (if
a feed table is missing) to avoid unwanted movements.
Therefore follow the plate during the feeding using the crane,
allowing a good feeding of the plate and avoiding to keep it
blocked.
Should the machine have the side support, use it to always keep
the plate lifted.
The use of a feed table is strongly recommended to lift the plate
and to protect the front area preventing the access to
unauthorized personnel.

FASE 4 . Feeding (6.1.1.5).

Control the rolls rotation and feed the plate: WARNING! Pay
attention to the sense of rotation, checking the rotation
arrow on the front console.
If the rolls shouldnt move, lower the front roll a bit (the one
used for the pre-bending), reducing the requested torque and
allowing the plate feeding.
The initial feeding must be short; the plate, tilted, could be
subject to excessive stress and loads, increasing the concave or
convex defects.
Usually the rotation is enabled until pre-bent edge reaches half
of the distance between the axis of the central rolls S and P
and the rear roll X.
Nonetheless, the bent sheet must be touched by the rear roll X
in order to go to the following phase.

6.1.1.5

PHASE 5 Side roll change and rolling. (6.1.1.6).

Lower completely the front roll Y (until it reaches the 0
position.)
(Should a feed table be present, stop the lowering of the front
roll Y at the height of the central roll P, keeping the plate
horizontal, just above the table).

e6.1-A.eng.rev03.doc

6.1.1.6

ROLLING SUGGESTIONS
The plate, that now is tilted, will descend below the horizontal
axis. The plate end already pre-bent will change position
approaching the top roll.
Lift the side roll X up to the position that will give the desired
diameter to the shell. Obviously the right position will be found
by the operator, but it will be always higher than the one of the
Y roll.
WARNING: This phase must be executed with extreme care.
If lifting too much the X roll:
- The plate would bend excessively, thus requiring
excessive torque during the following rolling process;
- Even if having the necessary torque, the diameter could
be too close. (very difficult to correct)

Having placed correctly the X roll, control the rotation of the

upper roll, to feed the plate and obtain the correct diameter for
the entire process (6.1..1.7)

6.1.1.7

PHASE 6 Closing the shell (6.1.1.8).

WARNING: the approaching of the plate (near to finish the
shell) to the central rolls is a delicate moment of the whole
process, very important for the quality of the second prebending. The further the plate end will be from the tangent
point, the poorest the second pre-bending and the long flat end
will be.
Nevertheless, the nearest the plate end will be to the tangent
point, the higher will be the risk of slipping out of the rolls.
Should the plate not be completely closed, therefore prisoner
around the upper roll, it could exit and fall from the machine.
ITS ABSOLUTELY FORBIDDEN TO ANYBODY TO
STAND NEAR THE MACHINE DURING ROLLING FOR
THE HIGH RISK OF PLATE FALLING.
Moreover its suggested to keep the plate lifted using the crane
to avoid unwanted movements.
Should the machine have a vertical or side support, use it to
keep the plate lifted.
WARNING: In case of closed shells, another risk is posed by
the possible overlapping of the two edges of the plate (6.1.1.9).
The first pre-bending (already rolled and swinging from the
top), due to the weight of the shell that tightens the diameter,

e6.1-A.eng.rev03.doc

6.1.1.8

ROLLING SUGGESTIONS
could overlap with the other, still flat edge, and enter,
overlapped, inside the two central rolls.

AVOID IT CAREFULLY TO PREVENT DAMAGES TO

THE MACHINE, TO THE ROLLS AND TO THE PLATE.

PHASE 7 Plate Tac-Welding (6.1.1.10).

The machine has been designed and built only for plate rolling
and not for plate welding (after rolling).
Only tac-welding operations are allowed. Tac-welding operators
can stay only on skidproof plates. All others positions are
strictly forbidden, especially inside the shell.

6.1.1.9

If tac-welding is complicated along the longitudinal seam, is

necessary tac-weld the two ends.
Warning: Turn off the machine rotating the key-switch to 0
(red light on console). Take out the key and keep it closer to the
person to prevent that someone will move accidentally the
machine.
Connect the ground ONLY on the plate; Dont connect
ground cables on the machines frame to avoid electric shock
on bearings and others parts.
6.1.1.10
PHASE 8 Machine opening (6.1.1.11).
After having rolled a cylindrical shell, it will be necessary to
open the machine to remove the shell.
- Check that the joint of the shell is in the lower position;
- lower the two side rolls, to release the pressure from the
plate;
- Move the bottom roll down until its lower position (it
will stop automatically);
- Hook the shell at the two ends;
- should the machine have a block for conical rolling,
remove it.
- Open completely the end yoke using the lever on the
console.
- Dont lift the shell too much, but keep it lifted between
the upper roll and the two side rolls, that could be used
as guides on which to feed it;
- After shell removal, close the end yoke.

e6.1-A.eng.rev03.doc

6.1.1.11

ROLLING SUGGESTIONS
WARNING: During the extraction process of the shell, with the
yoke open, no additional load (than its own weight) must be
weigh on the top roll in order not to damage the machine and the
roll itself.
After opened the yoke, tilt the top roll till the max inclination.
After the shell has been removed, bring the upper roll to its
horizontal position, by keeping this command enabled for a
few seconds, to lift the tilting cylinder.
At this point it will be possible to close the end yoke.
The machine must remain open for the time strictly necessary to
extract the shell.
WARNING: On machines with the tilting upper roll, a safety
device prevents erroneous operations.
The electric by-pass prevents:
- To tilt the upper roll with the end yoke in the closed
position.
- To close the end yoke if the tilting cylinder isnt
completely lifted from the upper roll.

In case of maintenance activity, check that this electric by-pass

(proximity or transducer) is placed exactly as at the beginning.

e6.1-A.eng.rev03.doc

ROLLING SUGGESTIONS
There are two ways to round a plate into a rolling machine:
they are called Rolling and Prebending.

6.1-A ROLLING PROCESS

The Rolling process uses both side rolls of the machine,

pushing against the plate, bending it around the top roll.
This condition has the benefit to add the power of both side
rolls at the same time, at the same geometrical position.
To get this condition, the plate must be positioned above
both side rolls, and pinching with the lower roll at one max
pressure of 30/40 bar (6.1-A.1).

6.1-A.1

With this procedure, however, a flat edge remains straight,

long almost the distance between the top and the side roll
axis (6.1-A.1).
This flat edge remains straight also at the other end of the
plate. This could be a problem for the geometry of the
cylinder (6.1-A.2).

There are however some cases when the two long flat edges
remained straight could not be a major problem, or could
however be accepted on the rolled cylinder:

6.1-A.2

1) if a long flat edge should be required by the product

geometry (buckets for excavators, U or oblong shapes,
square tanks, and any eventual other part where a long
flat edge should be required) 6.1-A.3.
2) if a long flat does not disturb the geometry if the
diameter of the cylinder should be very large.

6.1-A.3

e6.1a-A.eng.rev01.doc

ROLLING SUGGESTIONS
When, instead, a more accurate roundness is required, the
long flat ends could be corrected as follows:

(Prior to roll on the rolling machine)

a) to previously round the two edges on a press-brake by
further bumping bending (6.1-A.4)
6.1-A.4

(after having rolled the cylinder)

b) cutting out the two long flats, and closing tighter the
remained all round section of plate (6.1-A.5)
c) over-bending the ends at an apple shape and rerolling after welding (6.1-A.6)
6.1-A.5
To make the re-rolling of the shell, move down the lower
central roll bringing it to its lowest position. Select
REROLLING so that the rotation dregging will be made
by using the top roll only. For the complete procedure see
cap 6.2.3.

6.1-A.6

e6.1a-A.eng.rev01.doc

ROLLING SUGGESTIONS
6.2 ROLLING DEFECTS
S

First of all the rolling defects, or more precisely, the non

compliance with the rolling tolerances (especially if very
tight), are usually due to the operator experience, to the
material and, very rarely, to the machine. The following is
the list of the most common rolling defects.

6.2.1 CONCAVE OR CONVEX DEFECTS

These are the most common defects as regards the shells.
They are very well known to the operators, because
common to all the bending machines, depending on the
physical roll deflexion.
Experience suggests that both these defects occur mainly
at the initial plate segment and less on the whole
circumference. At 100-150 mm. (4"-6") from the edge the
shell is usually quite straight. Also, these defects are more
evident on the leading edge than on the final edge.
CORRECTION
The operators are aware about different correction
procedures in order to limit such kind of defects. The
following is a list of the most common:
A - SHORT DRIVING
Keep the first pre-bending as short as possible. The more
the edge will be driven in this phase, the more the defect
will dramatically increase.
Pre-bend a section of plate corresponding to half the
distance between the lower central roll and the roll
opposite to one for pre-bending (sometimes even less)
(6.2.1.1)
Never roll a long section of plate during this initial
phase of pre-bending. This is unnecessary and can only
worsen the defect.
B - PINCHING PRESSURE
CONCAVE DEFECT
The concave defect could be reduced by keeping the
pinching pressure between the two central pinching rolls
as low as possible by means of a proper valve (5.4.3),
before the last sliding feed, to obtain the required diameter
in multi-pass feed process or on the following plates of the
same type: this manoeuvre will make a longer flat edge
but will improve the concave defect.

e6.2-A.eng.rev03.doc

S
X

6.2.1.1

ROLLING SUGGESTIONS
If not sufficient, after having placed the plate at the
tangent point with the pinching pressure at the minimum,
drop slightly the lower central roll to further reduce the
pressure.

CONVEX DEFECT
The convex defect can be reduced by increasing the
pinching pressure (5.4.5) between the two central rolls,
before the last sliding feed to obtain the final diameter, or
on the following plate of the same type. Being the convex
defect more frequent on thin plates, pay attention to the
risk of lamination and, eventually reduce the pinching
pressure if needed.
WARNING: To change the pinching pressure, the weight
of the plate must be shifted on the roll.
Therefore balance the weight, putting it in the central
position and lower the side rolls so that that it does not
weight on the lower central roll.
Make sure that the plate doesnt move out of control in
this phase in which it will not be blocked by the pinching
between the two central rolls.
Having to increase the pinching pressure (to reduce the
convex defect), raise the lower central roll and, while its
pushing the plate against the upper roll, check the pressure
on the pressure gauge, increasing it by rotating the
regulation valve clockwise.
To reduce the pressure, in order to reduce the concave
defect, turn the valve counter clockwise, reducing the preload pressure before raising the lower roll, then raise the
roll that, pinching the plate will allow to read the actual
pressure. If too low, increase it by rotating the valve
clockwise; if too high repeat the above procedure dropping
the lower central roll.

C ROLLING BEFORE PRE-BENDING

Change the usual and quicker rolling procedure, therefore
roll the central plate section first, and then form the two
edges.
This slows a bit the execution timing but gives 2
advantages:
- avoiding to start from pre-bending (reducing the defects);
- the concave or convex defects are reduced because the
already rolled central plate section offers more rigidity
and resistance to the whole shell (the two ends as well).

e6.2-A.eng.rev03.doc

ROLLING SUGGESTIONS
D SHIMMING
Insert the shimming material in the more opened areas
(stripes of plate with 1, 2, 3 mm thickness, from 200mm to
500mm width and length) in order to create, in those areas,
a sort of artful crowning that will improve the final
result (6.21.3.)
CONCAVE DEFECT

6.2.2

CONICAL DEFECT

It can sometimes occur that a shell is not cylindrical but

lightly conical (6.2.2.1). The diameters of both ends are
different; tighter on one side and more open on the other
side.
This can be due to:
- A non perfect parallelism between the rolls (that must
then to be correctly set);
- A harder or thicker plate on one of its sides.

CONVEX DEFECT
6.2.1.3

CORRECTION:
The side rolls should be tilted (only one or eventually both
if necessary) raising them on the larger diameter in order
to tighten it slightly, till it is the same as the tightest
diamter (6.2.2.2). Being the side rolls inclinable ONLY if
they raise near the end yoke, if the larger diameter is on
the other side of the rolls (near the motor box), the shell
must be removed and reintroduced after turning.

6.2.2.1

6.2.3 OUT OF ROUND (OVALIZATION)

It could occur that a shell is not rolled at a constant radius,
being instead ovalized (6.2.3.1).
a

CORRECTION
To make the radius uniform and avoid ovality defects, reroll the plates (method well-known by skilled operators).

6.2.2.2

The maximum re-roll capacity is limited to 2/3 (65%)

of the maximum pre-bending thickness.

The shell should be removed by the machine and totally

welded. Then the welding must be carefully cleaned by
removing, inside and outside, all the dangerous, extremely
hard and sharp parts, making them totally smooth.
6.2.3.1

e6.2-A.eng.rev03.doc

ROLLING SUGGESTIONS

Then the closed, rolled and welded shell can be

reintroduced into the machine for the re-rolling.
Bring the tightest diameter of the shell at the lowest
position, just under the upper roll.
Keeping both side rolls at the same position, raise them
until they touch the shell.
NB: The lower central roll it is in its lowest position.
Then raise them more, for another short stroke, sufficient
to deform the shell, bending it a little more, with a shape
of a pear (6.2.3.2).

6.2.3.2

Select REROLLING mode, in order to excluded the top

roll rotation (allowing the dragging of the plate to be
rerolled by using the top roll ONLY)
Enable the rotation: the shell will start to rotate.
At each turn, slightly drop the side rolls, continuing to
rotate the shell, always in the same direction (6.2.3.4).

6.2.3.4

After a few side rolls are lowered, alternated with

complete rotations, the thrust of the rolls on the shell will
be completely nullified and its position will be the one
correspondent to the final right diameter.
WARNING: the re-rolling must be done using ONLY the
upper roll and both the side rolls. THE LOWER
CENTRAL ROLL MUST NOT BE USED (6.2.3.5)

6.2.3.5

6.2.4

LAMINATION

If a plate should be scratched or laminated, the pinching

pressure must be reduced between the rolls, by means of
the proper reducing pinching pressure valve (6.2.4) till the
problem disappears.
6.2.4

e6.2-A.eng.rev03.doc

ROLLING SUGGESTIONS

6.2.5 MISALIGNMENT
This defect (6.2.5.1) could depend on:
- plate with irregular shape (edges out of squaring);
- an incorrect plate placing on the machine (plate
erroneously squared when placing it into the rolls);
- a non perfect rolls parallelism (which allows more
driving where rolls are tighter).
CORRECTION

6.2.5.1

Defect not correctable if depending on a plate with

irregular shape. In the other cases the machine could help
by tilting the side rolls one opposite to the other (6.2.5.2),
raising them alternatively in correspondence with the plate
side. By enabling the rotation by a few revolutions, the
defect will be reduced.
6.2.6 PRE-BENDING
The value of the flat end (pre-bending) of a shell depends
on several factors.
The bending machines are designed to obtain a flat, nonrolled end, of 1,5 to 2,5 times the sheet nominal thickness
value, considering: the sheet maximum loading equal to
450 N/mm2 and Yield equal to 280 N/mm2 (40,000 Psi),
its length equal to the length of the rolls, an inside
diameter of 1,5 times the upper roll diameter, and as
thickness, approximately 50-60% of the nominal rolling
thickness of the machine.
If only one of these data should change, the flat end
obtained could immediately change.
The machines are usually rated as nominal capacities for
the capability to bend a plate, on the whole rolls length,
with a max rolling (without pre-bending) thickness on a
diameter 5 times larger that the upper roll diameter, in
materials with 280 N/mm2 (40,000 Psi) yield and in a
multi-sliding feed procedure (therefore using the max
available machine force and load).
It results that the best theoretical pre-bending capacity is
approximately 50-60% of the nominal rated rolling
thickness of the machine (as indicated by the capacity
charts). Its obviously possible to pre-bend thicker plates,
but on larger diameters or on shorter width or, moreover,
with longer flat ends.

e6.2-A.eng.rev03.doc

6.2.5.2

ROLLING SUGGESTIONS
A longer pre-bending procedure is often due to light sheets
rolled on machines of bigger size, (it is difficult to reach 2
mm. flat on a 1 mm. plate rolled on a 30. mm sized
machine).
Another flat ends lengthening factor is the plate flame cut
(it hardens the edges). This condition makes more rigid the
edge, harder to be bent and consequentially, lengthens the
flat ends.

6.2.6.1

For safety reasons, flat ends are often worsened: the

further the sheet end is from the tangent point (with central
rolls), the longer the straight end will be (6.2.6.1). Getting
too close to the tangent point increases the risk of sheet
slipping and, for this reason, the operator often prefers to
keep the sheet end more inside the machine, thus
lengthening the flat end.
Obviously, to obtain the best pre-bending results
according to these standards, the cambering of the rolls
should be done for the specific considered shell.
By cambering the rolls to a medium value, this perfection
is hard to obtain, in favour of wider machine flexibility
(wider range of thicknesses quality acceptable).

OK

Upon becoming familiar with the machine and upon

reaching a good training level, the operator can obtain an
excellent pre-bending result, even less than 2 times the
thickness (especially on short plates).
WARNING: The flat end must be measured with a
radius-template INSIDE (and not outside) the shell and
NOT at the edge of it, but at app. 100-200 mm (4- 8")
inward (6.2.6.2).

e6.2-A.eng.rev03.doc

6.2.6.2

ROLLING SUGGESTIONS
6.3 CONICAL ROLLING
The most common machine optional application (besides
the cylindrical) is the conical rolling.
This is the most difficult application of the machine, being
an irregular work, requiring a very high experience,
special care and however very long execution times, with
rare good final results.
The conical rolling depends exclusively on the operator
skills and experience and very little on the machine.
For this reason, the standards and the tolerances of this
application MUST necessarily be kept wider than on
cylindrical applications.
The plate must pass through the rolls with a variable
surface: shorter at the front and longer at the back
(because of the two different cone diameters).
Therefore the plate must slip on the surface of the rolls: an
irregular condition, which cannot be guaranteed by the
machine, because no controllable by driving. In fact, the
plate often slips in an unwanted way, assuming a wrong
position among the rolls and must be repositioned
carefully and patiently.
WARNING: Concentrating the maximum strength
near the end yoke (the side of the small cone diameter)
on all the bending machines, the cone thickness must
not exceed 50% of the nominal thickness of the
machine.
This occurs by using the same material and type of
work (rolling, pre-bending and diameters, considering
the smallest diameter of the cone when comparing
with cylindrical rolling). In practise, the type of
material to be rolled must be evaluated, as well as its
small diameter, comparing it with the capacity chart of
the machine, and the maximum thickness must be
obtained from the chart and for conical rolling, never
exceed 50% of the length of the rolls.
The length of the conical plate MUST NEVER exceed
50% of the length of the rolls.
If sometime it is exceeded, a safety rule could be the
following:
- using from one half to three quarters of the length
of the rolls, the thickness must never exceed 40% of
the nominal thickness on the chart;

e6.3-A.eng.rev02.doc

ROLLING SUGGESTIONS
- when exceeding the three quarter of the length of
the rolls, never exceed 30% of the nominal capacity
on the diagram.

6.3.1. PRELIMINARY OPERATIONS

The first compulsory condition for conical rolling is to
prepare the plate as follows:
A - accurate plate edges grinding to remove all the flash
and slag (very difficult because flame cut) till they are
perfectly smooth as if lightly bevelled.
B - Surface cleaning (sandblasting, if necessary)
WARNING: This perfect plate cleaning is absolutely
necessary to avoid high risks of serious and permanent
scratches on the rolls surface because of the very high
friction and the frequent and hard slips that conical
rolling irregular driving requires by the plate.
6.3.1.1
C - (further suggestion) Tracing on the plate a certain
number of cone generatrix (6.3.1.1) to keep under control
the correct plate perpendicular squaring during the conical
forming on the machine.
D - prepare some templates, built based on the final
required diameters (6.3.1.2).

6.3.2

THE CONTRAST GUIDING

The contrast guiding is a solid element against which the

plate edge (by the side of the smallest diameter) should
slip or roll during the driving. It is the task to maintain the
longitudinal shift
of the cone on the machine, to block the shifting of the
plate (on the smallest diameter), to have a suitable position
of the cone generatrix during the rotation.
The friction between the plate and the guide, in fact,
contributes to stop the plate, slowing its speed in
correspondence with the smallest diameter, while the
bigger diameter must rotate at a higher speed.

e6.3-A.eng.rev02.doc

6.3.1.2

ROLLING SUGGESTIONS
Pay attention to not damage the contrast guide, not to
bevel the edge of the plate which pushes against the
contrast die.

6.3.3. LOCKING THE END YOKE

On some machines, BEFORE conical rolling, it is
necessary to lock the end yoke with the specific S rod
(6.3.3.1). The D nuts should just lean on the rod (to
keep it in its correct position) but not be tighten (to avoid
further problems to open the end yoke, if it is pressed and
locked too tightly by the nuts).

6.3.4 CONE ROLLING PROCEDURE

CONE ROLLING DOES NOT ALLOW
PRE-BENDING
Since it is not possible to pinch the plate edge while
rolling cones, it is not possible to shorten the flat end
significantly, as achievable on cylindrical applications.
The simplest procedure (remaining within 50% of the
thickness and 50% of the length) is the following:
Before inserting the plate into the machine, in case of fix
sliding type guide, it is necessary to prepare the contrast
guide by greasing it to facilitate the sliding and turning
while it is conically formed and rolled.
- Preset the pinching pressure with its valve at its lowest
just to let the roll raise (NEVER exceed 50 bars - 700
Psi), and tilt the lower central roll raising it at the rear,
pinching the plate on its long side (large cone
diameter);
This condition has two advantages:
- a precise space where the plate is forced to move,
avoiding wrong movements and erroneous positioning
among the rolls;
- help the driving, because pinching lightly the plate on
its rear long edge (large cone diameter) helps it moving
as regularly as possible, fastens its speed (because
pinched between the driving rolls), opposed to the
slipping brake of the contrast guiding on the front short
edge (tight cone diameter) of the plate.

e6.3-A.eng.rev02.doc

6.3.3.1

ROLLING SUGGESTIONS
To move easily, the plate must be lightly pinched ONLY
ON THE REAR EDGE, only for a small segment, at the
large cone diameter (6.3.4.1). Pinching a too long segment
of plate, serious damages can occur to the machine and to
the plate.
- The plate has to be placed with its tight diameter edge
frontally, near the end yoke, in contact with the contrast
guiding. (6.3.4.2);
- place the short plate in contact with the contrast guide;
- keep the plate edge parallel to the axis of the two
central rolls and let it project out of the vertical axis of
the two central rolls 3 to 6 times its thickness;
- raise the lower central roll till it touches (due to its
tilting), and lightly pinches the plate on its long side
(large diameter);
- lightly tilt the front roll, above which the plate is leaned
(the tilting angle should be found only by trial and
error, as no suggested tilting indications are available).
The side rolls must be tilted as the cone, raising
frontally (near the end yoke);
- control the raise of the front roll (tilted) that will bend
the plate (6.3.4.3);
- control the raising of this front side roll (tilted) which
will bend the plate (6.3.4.4);

6.3.4.1

6.3.4.2

This procedure reminds the initial pre-bending of a plate

with the cylindrical procedure. Obviously, in case of
conical rolling, the remaining flat end will be much longer
than when pre-bending cylindrically.
6.3.4.3
- When the front roll reaches a position considered to be
sufficient to give the plate the required diameter (this
research has to be made by trial and error, as no
suggested positioning indications are available), control
the rolls rotation, to drag the plate forward (6.3.4.4).
Be very careful to move correctly the rotation joystick
driving the plate forward, as operating backwards the
rotation the plate can cause it to slip-out and fall down
from the machine.
THEREFORE IT IS ABSOLUTELY FORBIDDEN
TO ANYBODY TO STAND BEHIND THE PLATE
WHILE ROLLING, BECAUSE OF THE HIGH RISK
OF PLATE SLIPPING OUT AND FALLING DOWN
FROM THE MACHINE.
WARNING: check constantly in this phase that the
front end of the plate (corresponding to the small

e6.3-A.eng.rev02.doc

6.3.4.4

ROLLING SUGGESTIONS
diameter) remains perfectly in contact with the
contrast guide.
This allows the cone to move into the machine following
its generatrix (this does not occur if the plate looses
contact with the contrast guide or it moves out of axis;
therefore stop the rotation and correctly reposition the
plate, changing the rolls parameters as probably
erroneously set.
- As soon as the leading edge of the plate (just bent)
reaches the rear roll position (actually down), stop the
rotation and change the rolls positioning;
- Reset the horizontal and the front roll previously tilted
and lower it, to its lowest position;
- the leading part of the plate, actually bent, changes
position approaching the upper roll;
- lightly tilt the rear roll, actually below the leading edge
of the plate already bent; this tilting must be made only
by trial and error, as no suggested tilting indications are
available. A help is given by the actual position of the
plate, that allows contact with the plate all along its
width;
- raise the rear roll (tilted), which will bend the plate;
- when the rear roll reaches a position considered to be
sufficient to give the plate the required diameter (this
research has to be made by trial and error, as no
suggested positioning indications are available), control
the rolls rotation, to drag the plate forward.
This procedure reminds the calendaring and final prebending of a plate with the cylindrical procedure.
Obviously, in case of conical rolling, the remaining flat
end will be much longer than when pre-bending
cylindrically.

WARNING: continue to check constantly, while the

plate is inside the machine, that the short edge of the
plate (corresponding to the small diameter) remains
perfectly and constantly in contact with the contrast
guide. This makes the cone turn lightly on its
generatrix, while moving.

After having driven the entire plate surface, the cone will
be formed.

e6.3-A.eng.rev02.doc

ROLLING SUGGESTIONS
In case the diameter is not as tight as required, and in case
it is desired to obtain the final diameter by multi-pass feed
procedures, (if the power of the machine was not sufficient
to close the cone in single-sliding feed procedure), once
arrived at the end of the above mentioned procedure,
repeat the whole cycle, from the opposite direction,
tightening the diameter by further side rolls raising.
If the machine is supplied with the re-rolling device (that
cuts the oil feeding to the lower roll, letting only the upper
roll powered), it is possible to enable it in case of
difficulties in dragging or risks of a too high friction
between the plate edge and the rolls, thus avoiding to use
the lower central roll (except when the plate is blocked, a
light pinching is needed). Basically, in this situation, the
machine is operated as a three- rolls machine.
A good improvement of the cone quality is obtained by
performing the cone calibration (as well as the cylindrical
shells).
Then remove the cone from the machine, weld it totally
and strongly.
Then the welding must be carefully cleaned by removing,
inside and outside, all the dangerous, hard, and sharp
elements, making the surface totally smooth.
Re-insert the welded and smoothed cone inside the
machine, tilt the rolls as they are in contact with the whole
cone length, then press it and start to turn the rolls,
dragging and rotating the cone applying the calibrating
procedure as mentioned above.
For high precision cones, in case a very short flat end is
required, it is necessary to pre-bend the two edges with a
folding press, parallel to the generatrix, that execute
irregular bending, determining a cone shape. After prebending, the plate can be formed, in its central section,
conically, into the plate roll.
When approaching the max capacities of the machine, in
order to avoid high stresses at the contrast guiding and at
the roll bearings, it is suggested to pre-bend the plate roll,
by further bumping procedure.
This procedure must be performed ONLY by highly
experienced operators and it allows to pre-bend edges on
the machine, as in a folding press.

e6.3-A.eng.rev02.doc

ROLLING SUGGESTIONS
The two edges must be formed not rolling them but
folding them, rounding the edges by further bends, as if
made by a folding press, as follows:
1 - Keeping the lower central roll parallel to the upper roll
and set the pinching pressure the same as for the
cylindrical rolling; place the plate edge to be formed,
making the rolls axis parallel with the traced plate
generatrix (6.3.5.5-A).
Tilt the side roll and raise it, bending the plate (6.3.4.5B).
2 - After pressing the plate, instead of driving the rolls
rotation to drag the plate, stop the process, lower the
side roll and open the pinching. Move the plate by hand
(if light) or by means of a crane, and place it on the
following generatrix repeating completely the previous
phase 1. Execute various bumped presses until
obtaining a long edge (6.3.5.5-C), longer than the
distance between the central pinching rolls and the side
roll. The plate roll must operate similarly to a folding
machine.

6.3.4.5

WARNING: in that phase the plate MUST NOT

ABSOLUTELY BE in contact with the contrast
guiding, but placed at the rolls centre.
3 - Check the radii with the templates.

WARNING: while checking, keep carefully tilted the

templates of a half cone angle (6.3.4.6).
6.3.4.6
4 - Repeat the same sequence for the opposite edge of the
plate (6.3.4.7).

5 -The cone can be completed by rolling its central

section. This must be done using the upper roll and the
two side rolls.
6.3.4.7
Both side rolls must be tilted and raised ALWAYS AT
THE SAME POSITION, in contact with the plate.

e6.3-A.eng.rev02.doc

ROLLING SUGGESTIONS
6 - Place the plate with the tighter diameter edge in contact
with the contrast guide(6.3.4.8)
7 - Control the rolls rotation, to drag the plate forward and
backwards, for the entire surface (except the two, already
bent, ends). After each sliding feed, lightly raise both side
rolls, to obtain the final diameter (keep the rolls always at
the same position).
8 - The top roll could slip, or stop against the plate surface
and not be able to drag it. Try to lower lightly the two side
bending rolls, increasing the number of sliding feeds to
form the cone and, eventually, use also the lower central
roll, tilting it, and pinching the plate ONLY on its longer
side (large diameter, 6.3.4.9-B) with a minimum pinching
pressure (NEVER over 50 Bars - 700 Psi).

6.3.4
6.3.4.8

For the safety of the machine, it is COMPULSORY to

operate strictly as follows:
The pinching pressure (raising the lower central roll)
MUST BE KEPT AS LOW AS POSSIBLE (NEVER
EXCEED 50 BARS - 700 Psi).
A - (WRONG) If the pinching segment is too long
(6.3.4.9-A), the plate slipping and turning, while
driving, is not allowed. This generates very serious and
dangerous stresses on the plate, on the rolls, on the
contrast guiding with very high risks of serious
damages.
B - (RIGHT) If, while rolling cones, the plate is not
driven by the only upper roll, the lower central roll
MUST be tilted (up near the motor box, opposite to the
side rolls tilting) to touch the plate ONLY on a very
short segment of its rear edge, near its large diameter
(6.3.4.9-B).

WARNING: ITS ABSOLUTELY FORBIDDEN TO

CALENDER CONES WITH THE CENTRAL ROLL
HORIZONTAL AND PARALLEL TO THE UPPER
ROLL. THE LOWER CENTRAL ROLL MUST BE
TILTED.

e6.3-A.eng.rev02.doc

6.3.4.9

ROLLING SUGGESTIONS
Appendix 1 - Simplified Cone Rolling
If the small diameter is however large enough, and
depending on the end yoke geometry, a different
procedure could be applied, to allow an excellent prebending of the edges without any prior pre-bending on a
folding press or by further bumping on the plate roll. It
works as follows:
A

1 - Trace the cone surface on the plate leaving two

segments to be cut off after rolling (6.3.4.10-A).
2 - Roll the plate with the previous 5-6-7-8 procedure and
form the B sections to the final diameters, leaving the C
segment formed to a much wider diameter (6.3.4.10- B
and C).
3 - Remove the plate from the machine; cut off the two A
edges, clean perfectly the two cut edges.
4 - Reposition the plate into the machine and close the
cone tightening the C section to the final diameters
(same as the Bsections).

WARNING:
By keeping the bottom rolls at the same bending position while
rolling cones, it is possible to obtain the plate horizontal
position in its contact point with the contrast guiding.
If this does not occur, if the bottom rolls are not at the same
position, the plate could tilt and touch the contrast guiding.
If the plate moves from the bottom to the top when raising, the
friction against the contrast guiding could make it raise from its
correct position and the plate could pass through, below.
Less disturbing is the opposite case, when the plate slips
against the contrast guiding, moving from top to bottom.
Then follow these instructions:
.
Keep as long as possible the plate HORIZONTAL while it
slips against the contrast guiding.
In case of tilted cone rolling, check constantly the correct
contact between the front surface (tight diameter) of the
plate and the contrast guiding. A slip of the plate WHILE
RAISING, against the contrast guiding, could make it raise,

e6.3-A.eng.rev02.doc

6.3.4.10

ROLLING SUGGESTIONS
and the plate could pass through below, with risks of
damage.
If the above mentioned instructions are not followed, and if
using incorrect rolls positions, problems related to the
quality of the plates and damages to the machine could
occur.

e6.3-A.eng.rev02.doc

ROLLING SUGGESTIONS
6.4 PROFILE ROLLING
As the plate bending roll is primarily designed to roll plates, the
level of precision in rolling profiles is generally poor; however
never as accurate as on a specific profile rolling machine, which
is also provided with a lot of adjustable guiding, to correct the
material twist defects.
The more experienced the operator will get in rolling profiles,
the more the result will be acceptable, even in this ancillary
application.
When profiles are rolled, a minimum rolling diameter is difficult
to be estimated, depending not only on the machine power and
by the shaft resistance, but it depends mainly on the profile
rigidity.
By tightening the diameter too small, the profile is permanently
damaged, seriously twisted and impossible to be used. A generic
rule is to limit the diameter to be rolled between 20 to 40 times
the height (vertical edge), of the profile; below such diameters,
and according to the profile, a deformation could be obtained.
However this final tightest diameter is reached in several sliding
feed procedures, reducing it progressively in order to smoothly
roll the material at its final round shape. The best result and the
lowest deformation is obtained on the symmetrical profiles as T,
flat on edge, square, channels and beams (these last two with
special dies).
In case of asymmetrical profiles as angles or T on edge is useful
and common among the operators, to improve the result,
limiting the deformations and material twist and making the
final shape acceptable, to join two profiles together to obtain a
final new symmetric profile (6.4-C). In many cases this is the
only way to roll acceptable angles.
Joining together two angles to obtain a T profile some welding
tacks are performed on both up and low material faces (6.4-C).
A perfect cleaning must be done to avoid the welding
sharpness (very hard on surface) to damage the dies.
After rolling (6.4-D) the two parts of the composed profile are
separated, removing the welding (6.4-E).
Two rolled angles, pretty similar, are then available (6.4-F).
Profile rolling can be done either OUTBOARD (when extended
shafts are supplied) or INBOARD (on predisposed machines,
with special rolls) On both cases a set of special DAVI dies is
required.

e6.4-A.eng.rev00.doc

6.4

ROLLING SUGGESTIONS
6.4.1

OUTBOARD

The machine has to be ordered with the extended shafts, and

with a set of three dies to be applied on, outboard. These dies are
made in harden steel. Profile rolling dies could be machined in
fixing configuration (with a groove where to set the profile to
be rolled, of fixed type) or could be adjustable to receive a wide
range of different profiles to be rolled (adjustable type). With
reference to (6.4.1), they are composed in both cases of a main
frame A, internally drilled to allow to set on the roll shaft
B. The die set on the powered roll has to be fixed by a key
D, to drag the material. After setting the dies on the shafts,
fix them by the relative blocking flange F and bolt V1. On
the adjustable type, it is necessary to create the groove H
(adjusting the ring B) where to insert the profile to be rolled.
A convenient clearance must be left, to avoid side friction while
rolling. After releasing the blocking screws V2, turn counterclockwise the adjustable ring B. When the groove H is fine,
fix it by locking the position with the screws V2.
WARNING: to keep fixed the position of the adjustable ring
B the locking flange C must be lightly spaced and
NEVER in contact (otherwise no locking is made). Therefore
leave between B and C a little space S of about 5-10
mm). To lock them strongly, turn tightly the screws V2.

6.4.1

e6.4-A.eng.rev00.doc

ROLLING SUGGESTIONS

6.4.2

INBOARD

Upon request, setting on the rolls special rings, the inboard

profile rolling can be performed on the machines, by the
following special configuration:
- 4 rings are set on the side rolls (2 on each roll) - (6.4.2.1),
(6.4.2.2), (6.4.2.3);
- on some models with a too small passage between the rolls,
the final section of the upper roll, near the end yoke, a sleeve
must be removed to create a wider gap with the other rolls
(6.4.2.1).

6.4.2.1

The rings are made in hardened steel; assemblable in two halves

by screws, and they are axially adjustable to create the
convenient groove to accept a wide range of profiles. Then guide
the profiles while rolling keeping perfectly orthogonal in
relation to the rolls axis. Its necessary to leave a small
clearance between the rolls and the profiles, to limit the friction.
Its also possible to roll square and rectangular sections, solid or
void, flat on edge, angles, etc. Upon request, very rarely, a
further couple of dies could be added on the top roll, to better
guide the profile.
Some examples of INBOARD profile rolling are shown on
(6.4.2.4). Its also possible to roll square and rectangular
sections, solid or void, flat on edge, angles, etc. Upon request,
very rarely, a further couple of dies could be added on the top
roll, to better guide the profile.

6.4.2.2

ROLLING COMPULSORY REQUIREMENTS

WARNING:
Profile dies have to be set on the rolls ONLY when profile
rolling has to be performed and MUST be removed
immediately after finishing to avoid damages to the machine,
and rolling plates.

6.4.2.3

WARNING: A very high risk of permanent damages impose

the highest care in using profile rolling (especially with the
outboard dies).
The rolls extended shafts are not strong enough to hold all
the hydraulic pressure of the machine. If the operator will
supply all the pressure while rolling profile, the extended
shafts WILL be permanently bent (or break) requiring the
roll replacement. (not covered by warranty).
6.4.2.4

e6.4-A.eng.rev00.doc

ROLLING SUGGESTIONS

To roll profiles safely, follow this procedure:

PROFILE ROLLING HAS TO BE ALWAYS DONE
WITHOUT PRE-BENDING. THEREFORE THE TWO
SIDE ROLLS MUST BE ALWAYS MOVED AT THE
SAME POSITION (6.4.2.5).
The best suggestion is to raise lightly, very lightly, both side
rolls, bringing them at the same position, and then drive
completely the full profile development, from one edge to the
other. Then raise a little more both side rolls and perform sliding
feed. And so on, alternating light raising with whole sliding
feeds, deforming progressively and smoothly the material.
During the rotation, stop the drag BEFORE exceeding the
previously bent end. Over passing it, forming a still flat section,
a sudden and high load raise could permanently damage the rolls
shaft (and over-rolling the profile diameter, worsens its shape).
Raising too much the side roll at one step, the profile is bent too
much, making the further driving by rotation difficult (if not
impossible). On the 4 roll machines to roll profiles pinch the
two central rolls or the set of the re-rolling device, to help the
upper roll to transmit sufficient torque. It could occur that
profile drag is difficult and the driving rolls slip on it, because
the light structure of the profile does not allow the transmission
of a too high torque. In this case the driving must be helped by
pushing the profile by hand, or by other device outside the
machine.
IT IS ALWAYS FORBIDDEN TO PRE-BEND PROFILES.
SIDE ROLLS MUST BE ALWAYS KEPT AT THE SAME
POSITION.
NEVER PINCH PROFILES WITH ONE SIDE ROLL AND
THEN BEND IT WITH THE OTHER. THIS WILL BEND
OR BREAK THE EXTENDED SHAFTS.
- While rolling profiles the manometer pressure gauge MUST
be always kept under control by the operator. While raising
the side rolls the hydraulic pressure MUST NEVER
exceed 40 bars (600 PSI). This is the safety limit and
exceeding it will damage the rolls shaft. To help movement
and limit the scratches between materials because of the high
friction, it is necessary to grease the profile surface and the
dies concerned (side) areas. To limit the flat ends on the final
ring it is suggested to cut them after rolling.
ONLY ON OUTBOARD: If more than one ring is required, it is
suggested to roll the profile in spiral (if possible). Then
removing the two ends affecting only the first and the last ring
allows to save on costs and improve the result.

e6.4-A.eng.rev00.doc

6.4.2.5