Wabash Transfer Molding help

[dozer67]

I am not super knowlegable on Transfer molding presses. I have a Wabash Tranfer Press
Model VT 75H-24-x

It is a vaccum assist process and vertical clamping where you add resin wafers on top

I am running: Hysol MG18 it is a transparent epoxy molding compound, developed specifically for the encapsulation of
optoelectronic devices..

If anyone knows about these machines I am getting a super low yield manly due to bubbles. I have no idea where to start looking. There are yeild variances operator to operator but is there anything I can do from a processing stand point??

Link to actual press I need your help on...

http://www.wabashmpi.com/transfer_molding_presses.html

 

[patprimmer]

I would be looking at temperatures and clamping pressure

Regards
Pat
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[supercub]

Do you mean that it is pnuematic assist, or do you have a vacuum supply at the mold to remove air? The bubbles are caused by entrapped air. You can cut air vents in the mold so that the air will pass but not allow the resin to escape.
I have used a Wabash to mold hypalon rubber. The biggest issue that I had was non-fill due to the mold gates not being large enough.
Try less injection pressure and longer cycle time, that will reduce the chance of air entrapment.

 

[btrueblood]

When transfer molding rubber, our vendors use a "bump" cycle to help air purge thru vents. A "bump" is a cycle during the closing of the press, consisting of unloading the press, allowing the mold to partially open and air bubbles to squeeze thru the vent slots, then reclosing and repressing to full mold pressure. Sometimes as many as 10 or 15 bumps is required to see no further venting occurring (you can hear the air popping and material being pushed thru the vent slots as this proceeds).

You may also want to look at the load in the transfer pot - one thick slab of material will give less places for air to be entrapped than many smaller chunks or wafers.

 

[patprimmer]

The OP has not been back since July.

Regards
Pat
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[btrueblood]

Wheee...

 

[supercub]

Good observation. I bet his epoxy has self-cured by now.