Design Tip - 11

On the Design Tip - 2 I talked about the fillets of the holes. The fillets are very important on a plastic part, so here you are another design tip about them.

The 2 pictures have the same plastic part sketch. It is a flat shaped part with a round slot. The top picture do not has fillets, and the second one has fillets (red color).
The fillet is useful from the design point of view, the part will be easier to be correctly filled and also easier to be painted. Sharp edges are not good for painted parts.
But the point I want to talk about on this tip is the mold construction process. The not filleted part has to be done with an EDM mold, while the filleted one could be done with a machined mold. 
When I worked for EU and US automotive marked this was not an issue, most of the molds were done by EDM, but now I'm working for another market and all our molds and production is in China. I've seen our toolmakers prefer to machine the molds (not to EDM), some of them only have small EDM machines to make small ribs, gussets and things like this.
In that case to add a radius on the part design could help our tool maker to make a cheaper mold, apart of this, some moldmakers simply add the fillet thew want/need. I prefer to add the fillet on the part so I'm able to define the radius (not to leave the decision on the moldmaker hands). To leave the decision on the mold maker hands usually means you will have fillets bigger than you wanted, if they can use bigger drills the machining time will be shorter.
So the final comment is, you have to talk with the toolmakers, know their skills, their facilities and see what they are able to do and what they are not able to. Then design taking into account those inputs.