Definition of Transfer Moulding
The molten resin is transfered by pressure from a meltpot into a mould which is at a temperature above the meltpoint of the resin. ( For comparison: in injection moulding, the mould temperature is below the resins meltpoint).

This higher temeprature is important for the filling of moulds with high flow lenght: wall thickness ratios and to allow for shrinkage compensation, otherwisen jeopardized by premature gate freeze-off and cooling in the mould.
Static Plastification - Meltpot Technique
The resin is heated in the meltpot either in an oven, by heater bands around the pot or in trays prior to scraping off into the pot. Minor plastification occurs during melt transfer through pot and mould gates
Dynamic Plastification
Different techniques are used:
Injection moulding machine with the screw acting as the piston after retraction or intrusion. Disadvantages are often a mismatch of necessary shotweight and unit size and space requirements for mould clamping. The vertical platen arrangement complicates mould handling and cooling.

Extruder for transfering the melt by intrusion into the mould with the inherent problem of generating aqnd keeping a necessary and steady pressure during the hold (cooling) period. A clamping mechanism is needed for mould fixation. Another method is transfering the melt into a meltpot which the is places on top of the mould in the press.

Transfer moulding press combines the advantages of the discussed techniques:

button Homogeneous melt.
button Highest Quality of lining or part through tight temperature control at extruder and transfer pot as well as controlled rate of transfe, fill and hold (cooling) pressures. Best possible melt homogenity results in better packing, less shrinkage and improved dimensional control.
button Costum-tailored sizing of extruder and transfer pot for small to big transfer volumes, for minimum resin hold-up times and maximum melt turn-over.
button High productivity and yield.
button Reproducible quality, Automation as option.
button Horicontal Press platen for easy handling of moulds and efficiant cooling arrangements.
button Compact design
button Easy to work with and to readcontrol and display panel.
button Long service life through heat-resistant hydraulic system and corrosion-resistant alloys for all parts in contact with melt.
button Safety through safety-conscious design

WK Transfer moulding presses are available at the moment with a force of 300 and 500 kN as well as a shot (feeding) wight from 1.5 kg till 15 kg. WK offers standard systems but, if requested, we are also in the position to supply costum-tailored systems according to the demands.

The following three transfer moulding systems we can offer as basis systems:

button system I for small series - melt-pot technology
button system II for intermediate series - melt-pot technology
button system III for bigger series - pre-plastification technique

Furthermore, we can offer a system for big series according to drawing no. Mb002/98 (process of PFE transfer moulding). With this system 6 dies can be heated on two levels.

Here you are able to choose a corresponding system according to your kind of application and number of requested parts.


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