Preventing warpage in a flat plate
Preventing warpage in a flat plate
(OP)
Morning all,
I have a plate plate that will be molded out of PC/ABS(Cycoloy). This part is approximately 10 " long x 5.5" wide and .10" thk. This is a cover to a battery box that has 8 even spaced countersunk holes around the perimeter of the piece. The are two pieces of text that are raised .050 above the surface at each end of the piece as well. The part is presently being gated at the top surface directly in the middle of the part. I am sure I need to put some ribbing on the underside of the part to help with stiffness and to help prevent warping. I am just unsure of the thickness, height, spacing and orientation of the ribs with regards to the gating and flow. Any help would be greatly appreciated. I am going to try to attach a pic of the part as well.
Sid
I have a plate plate that will be molded out of PC/ABS(Cycoloy). This part is approximately 10 " long x 5.5" wide and .10" thk. This is a cover to a battery box that has 8 even spaced countersunk holes around the perimeter of the piece. The are two pieces of text that are raised .050 above the surface at each end of the piece as well. The part is presently being gated at the top surface directly in the middle of the part. I am sure I need to put some ribbing on the underside of the part to help with stiffness and to help prevent warping. I am just unsure of the thickness, height, spacing and orientation of the ribs with regards to the gating and flow. Any help would be greatly appreciated. I am going to try to attach a pic of the part as well.
Sid






RE: Preventing warpage in a flat plate
Ideally, it should have a fan gate at one end.
As an observation, if the c/s holes are for fasteners, it is bad practice to use c/s in plastics due to the high pressure contact points on the c/sink angled faces (creep). Use c/bores with pan head screws if possible.
H
www.tynevalleyplastics.co.uk
It's ok to soar like an eagle, but weasels don't get sucked into jet engines.
RE: Preventing warpage in a flat plate
I also saw where the shrinkage rate for PC/ABS was low. Curious to know why you opt for a fan gate at one end rather than the center surface tab gate that the molder indicated he would use? Just trying to learn. I agree with the C'sink holes not being optimal but really had no choice or room for c'bores. What do you mean by "creep"? The plastic moving or being displaced over time?
Thank you again.
Sid
RE: Preventing warpage in a flat plate
RE: Preventing warpage in a flat plate
As far as the part design is concerned, flat parts in the food packaging industry use a feature called an "angular panel" which acts like a rib but is not a rib. This helps to keep the part flat, reduces rejects due to hesitation effects or venting issues and keeps a low nest height for stacking. For more information go to:
http://www.improve-your-injection-molding.com/plas...
RE: Preventing warpage in a flat plate
I have another question regarding some additional features I'd like to add to the present parts. We have some wiring of various gauges in and about the plastic parts. Can anyone give some examples or point me in the right direction of possible wire retention features. One that comes to mind is something I have seen inside of close/tight space tools. Drills, weedeaters, and things like that. It is basically a small track or channel that is sized for the appropriate gauge wire running through it. Inside the track on either or both walls that form the track ar little "nubs" or bumps that protrude from these side channel walls in effect making an interference fit in that area for the wire. The channel routes and the the nubs hold. Any additional help would be most welcome. I do not want to buy little aftermarket press in clips, or tie wraps or anything else that I have to purchase. I am already buying the mold, so in essence these features are free.
Thanks guys.
Sid