Not sure what you mean by "two cavity" mould - unless you want to make two at a time?

For me, I would see no problem moulding it. Side cheeks, stripper plate ejection with some additional pins ejecting on the inside of the base. Commercial polish finish. 0.5 to 1 deg should be fine for the core. The outer faces can be of zero draft. Direct sprue feed onto base (or a hot tip).

You might get movement of the core, degree of which will depend on what you make it from. Cycle time likely to be extended due to limited cooling in the core (although it might be 3" thick?).

As an an aside - countersunk screw holes are not good in plastics. The wedging action cause by the inevitable line contact on the countersink will cause rapid creep, if not cracking.

Cheers

Harry

www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

Unless he was planning to split the part down the middle and glue/weld two halves?

Quote (PUD)

Not sure what you mean by "two cavity" mould - unless you want to make two at a time?

For me, I would see no problem moulding it. Side cheeks, stripper plate ejection with some additional pins ejecting on the inside of the base. Commercial polish finish. 0.5 to 1 deg should be fine for the core. The outer faces can be of zero draft. Direct sprue feed onto base (or a hot tip).

You might get movement of the core, degree of which will depend on what you make it from. Cycle time likely to be extended due to limited cooling in the core (although it might be 3" thick?).

As an an aside - countersunk screw holes are not good in plastics. The wedging action cause by the inevitable line contact on the countersink will cause rapid creep, if not cracking.

Cheers

Harry

Thanks Harry, great information.

I was thinking of using PC/ABS blend

PC/ABS should be fine. Note that only the core needs polishing to assist ejection. Probably be ok with zero draft, but anything more than zero would be useful - outer faces can be any finish.

H

www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

thing is that even if I draft only the inside and not the outer surface, I end up with about 1mm thickness difference at the top as opposed to the bottom, 4mm vs 3mm because of the draft 0.5 degrees. Is this too thick, or maybe an issue with sink marks or cooling issues or deformation?

• http://files.engineering.com/getfile.aspx?folder=456c6096-cc2c-41ef-810c-01

Just leave it as zero draft, but get the core polished/smoothed off (not gloss), just get any cutter marks out. Polish in line of draw. Toolmaker should know what to do.

PC/ABS has minimal shrinkage as it's amorphous - there is only the thermal shrinkage. Sink marks are like warpage in glass-filed material: usually designed in. Your part looks ok. (You may get a witness of weld/flow lines around the holes).

You should add a small rad to the bottom inner face corners as well. Sharp corners not good....

H

www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

Thanks Harry