DD200075A1 - PROCESS FOR CUTTING POLYMETHYL ACRYLATES - Google Patents

Abstract

The invention relates to a process for cutting polymethylacrylates with jet-polished plasma cutting torches. The goal is to increase the effectiveness of cutting such materials. The process to be developed is intended to ensure the production of any shape cuts on polymethylacrylates with crystal-clear cut surfaces and burr-free cut edges with high cutting performance and low smoke development. According to the invention, in contrast to the conventional plasma cutting technique with an unusual small nozzle spacing of 0.5mm, which is to be maintained constant with an accuracy of about * 0.4mm, worked and used as plasma gas is a mixture of 50-80% argon and 20-50% hydrogen is set, wherein a gas quantity Q = K ind B (1 + lg (10 + P)), a burner power P = K * s and a cutting speed (formula). The explanation of the formula symbols contains the description of the invention.

Description

M * f> -

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Process for cutting polymethylacrylates Field of application of the invention

The invention "relates to a process for cutting polymethylacrylates, in particular polymethamethylacrylates, using plasma cutting units known in the art with jet-polished plasma cutting torches, to achieve glassy, clear cut surfaces and burr-free cut edges in the case of" high cutting power and low-friction. " smoke. ...., ·

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Characteristic of the known technical solutions

It is known that non-metallic materials can be cut by means of indirectly polarized plasma cutting torches. However, there is no knowledge of the cutting of polyethyl acrylates with the aid of indirectly polarized plasma cutting torches. A obvious measure would be that with the known method of indirect plasma cutting for other materials, eg , This known procedure consists in the fact that a nozzle distance of 5 "to 15 πιπί and a cutting speed in dependence on the material thickness and the burner achievement according to given table values or experience values are adjusted _{e However,} it has been found that with It is not possible to avoid the above-mentioned disadvantages even by the usual variation of process parameters in plasma cutting with indirect arc, it is not possible to avoid crystal clear cuts, to avoid a burr attachment and to produce disturbing whitish smoke To be avoided «According to the current technical standard, polymethyl acrylates are cut either by means of mechanical separation methods or by means of laser cutting machines or high-pressure Elüssigstrahlanlagen.

In laser cutting, although narrow kerfs are achieved and, after parameter optimization, crystal-clear cut surfaces are achieved, there is a great deal of smoke, which makes a suction device necessary. The high cost of laser cutting for the purchase and maintenance of laser cutting systems and the elimination of pollutants (smoke) is disadvantageous. When mechanical separation, the cut surfaces are not crystal clear. In addition, the burr attachment at the cutting edges affects the possible uses. For high quality, d. H.

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Burr-free and crystal-clear cuts require reworking, which entails additional costs and time. Furthermore, contour cuts are possible only conditionally and with great device expenditure by means of mechanical processing methods.

Object of the invention

By the invention, the effectiveness in cutting polymethylacryates u. Ä. To increase materials with low equipment costs.

The essence of the invention

The invention is therefore an object of the invention to provide a method for cutting Polymethylacryiaten using known plasma cutting machines with nozzle-polar plasma cutting torches to develop, which is to be designed so that the production of any shape cuts to polymethylacryates u. Ä. Materials with crystal-clear cut surfaces and burr-free cut edges with high cutting performance and low smoke development is ensured ·

The object of the invention is achieved in that, in contrast to the conventional plasma cutting technique with an unusually small nozzle spacing of 0.5 mm, which is to be complied with an accuracy of about - 0.4 mm, worked as a plasma gas and a mixture of 50th .- 80 % argon and so forth. ' 20 - 50% hydrogen is used, with a gas quantity Q corresponding to '»

Q = K _B (1 + log (10 + P))

a burner power P accordingly

P = K * s

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a cutting speed V accordingly

to adjust is »mean;

Q = amount of gas in m-Vh

V = cutting speed in m / min

Kg = constant of the burner, which is between 0.5 .. * 2 K = power constant, is about 0.3 ... 1.2 Ktp material constant, is about 0.16

P = burner output in kW kcal

c = specific heat of the material to be cut in

kg.grd

= Heat conductivity of the material to be cut in

kcal

m.h.grd s = cutting thickness in mm.

The surprising effect of the procedure according to the invention is that a harmful formation of smoke is suppressed. In the development of the invention, it was found that the known smoke formation has its cause in cracking processes which develop on thermal effects on the polymeric material. Such cracking processes therefore also take place when a laser beam or a plasma jet acts on the material. The extent of such Grackprozesse is determined by the volume of 'kerf and the acting heat energy and grows with increasing!? Material thickness, kerf width and electrical cutting performance. It is well known that by means of laser cutting, it is essential. by about one power of ten narrower kerf than can be achieved by means of plasma cutting process. The person skilled in the art would therefore seek the solution of the present task in the laser cutting method, especially since the energy conversion during laser cutting

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When using plasma cutting, the skilled person would have to assume that "with very small nozzle spacing between the burner and the material surface, the cracking processes would be intensified because the areas of the plasma torch with the highest temperature now act on the material ,

By the invention it has been demonstrated that under the process conditions of the invention emerging on the underside of the workpiece plasma torch is capable on the one hand suck in the cracking products from the kerf due to their Injektorwirkung and on the other hand due to their high temperature of several thousand degrees completely disassemble and in the presence of the likewise sucked in or present I) oxygen from the outside to CO ₂ and HpO, which is harmless in itself.

embodiment

The invention will be explained in more detail below using an exemplary embodiment:

For the cutting of 3 wm thick Polymethamethylacrylat plates a plasma cutting machine is used, the nozzle-piloted burner is operated with 4 kW power. The material has

ie c ^kl

kcal

Tr-Λ ο Τ

a specific heat c = 0.3 and a heat conduction_

ability j [= 0.16

m.h.grd

According to the process conditions according to the invention, the plasma gas used is a mixture of 65-70 % argon and 30-35% hydrogen in a gas quantity Q = 1.5 m-yh, the cutting speed set at V = 0.253 m / min and the nozzle spacing during the held throughout the cutting process between 0.2 and 0.5 mm, so that the development of harmful fumes is reduced to 5 % of the resulting laser cutting amount. The cut surfaces are glass-clear and burr-free.

Claims (1)

invention claim Process for cutting polymethylacrylates, in particular polymethamethylacrylaben, using "known Piasmaschneidanlagen with jet-polished plasma cutting torch to achieve crystal clear cut surfaces and burr-free cut edges with high cutting performance and low smoke, characterized in that in contrast to the usual plasma cutting technique with an unusually small nozzle spacing of 0 , 5 mtn »is to be kept constant with an accuracy of about 0.4 mm, worked and as plasma gas a mixture of 50 - 80 % argon and 20 - 50% hydrogen is used, wherein a gas quantity Q = Kg (1 + log (10 + P)), a burner output ρ = K ♦ s and a cutting speed V = K ° _L. is set