Blow Moulding
Blow Moulding
Blow Moulding
SUBMITTED TO
Assistant Prof.
M.P.Gururajan
Department of Applied Mechanics
SUBMITTED BY
Nivesh Pandya
2008AMD3104
Historical Development
Year
Development
1930
The first applications for blow molding were for cellulose nitrate
1940
1942
1950
Introduction
Blow molding : Definition
There are several methods of blow molding plastic parts.They all have five stages in
common :1. Plasticizing or melting the resin
2. Parison or preform production
3. Inflation of the parison or preform
4. Ejection of the part
5. Trimming and finishing of the part
Extrusion blow
molding
Injection blow
molding
(Courtesy
: http://www.et.byu.edu/groups/mfg355/pages/lectures/powerpoint_ppt/13%20blow%20molding.ppt )
Step 1
Step 2
Step 3
Step 4
(Courtesy
: http://www.et.byu.edu/groups/mfg355/pages/lectures/powerpoint_ppt/13%20blow%20molding.ppt )
N e c k r in g in s e r t
M o ld g u id e
p in s
C o o lin g
c h a n n e ls
M o ld c a v ity
P in c h - o ff in s e r t
F la s h p o c k e t
(Courtesy : http://industrialblowmolding.com/?page_id=22)
1.
Neck-ring insert
2.
3.
Cut-off insert
(Courtesy : http://industrialblowmolding.com/?page_id=22)
Injection-Blow
Injection-BlowMolding
Molding(IBM
(IBM))
(Courtesy :http://www.me.umn.edu/education/courses/me3221sum/Lab/BlowMolding/blowmolding.html)
Injection-Blow
Injection-BlowMolding
Molding(IBM
(IBM))
Advantages
Eliminates the weld line
Disadvantages
Extra steps in manufacturing
Stretch
Stretchblow
blowmolding
molding
(Courtesy :http://www.me.umn.edu/education/courses/me3221sum/Lab/BlowMolding/blowmolding.html)
The biggest disadvantage of blow molding process (above all three) is that
these are limited to hollow parts.
Material Requirements
Good melt strength ( i.e low melt index)
Melt index : Measures the rate of extrusion of thermoplastics through an orifice at
a prescribed temperature and load. Melt index gives the processor a rough idea of
what to expect from the flow behavior of a resin during processing.
Reasonable blow ratio capabilities
Mold Diameter
Blow Ratio
=
Parison Diameter
Application
Most thermoplastics can be blow molded
Some typical applications are
HDPE : High Density Polyethylene (stiff bottle, toys,
cases, drum)
LDPE : Low Density Polyethylene (flexible bottle)
PP : Polypropylene (higher temperature bottle)
PVC : Polyvinyl Chloride (clear bottle, oil resistant
containers)
PET : Polyethylene terephthalate (soda pop bottle)
(Courtesy : http://industrialblowmolding.com/?page_id=22)
Process Parameters
Parison characteristics
size, shape, straightness, wall thickness, mechanical properties
Inflation pressure
Mold design
cooling, venting
Blow ratio= Mold diameter/Parison Diameter (1.5 to 3 are common
Thank You