Best Way to Remove Knife Edge from Molded Parts
Best Way to Remove Knife Edge from Molded Parts
(OP)
Hey Gurus,
I'm doing a production run of some glass-filled PP parts. I'm getting a knife edge at the parting line that needs to be polished down to a small chamfer/fillet. Due to the geometry,schedule, and cost, we cannot change the mold.
Is there any special abrasives that will not leave any residue on the parts, machinery, or tools that will quickly and consistently polish the knife edge? Costs need to be low and quantity is less than 10k pieces.
Currently, the most effective way is with a sanding block and person doing each part by hand. There are inconsistencies and time involved. I was thinking about maybe a special heated tool that will melt the edge of the parts that will quickly melt down the knife edge.
Any ideas are appreciated.
Thanks In Advance.
I'm doing a production run of some glass-filled PP parts. I'm getting a knife edge at the parting line that needs to be polished down to a small chamfer/fillet. Due to the geometry,schedule, and cost, we cannot change the mold.
Is there any special abrasives that will not leave any residue on the parts, machinery, or tools that will quickly and consistently polish the knife edge? Costs need to be low and quantity is less than 10k pieces.
Currently, the most effective way is with a sanding block and person doing each part by hand. There are inconsistencies and time involved. I was thinking about maybe a special heated tool that will melt the edge of the parts that will quickly melt down the knife edge.
Any ideas are appreciated.
Thanks In Advance.






RE: Best Way to Remove Knife Edge from Molded Parts
The typical method is with a simple knife or sometimes a special shaped blade.
Sometimes moulding technique and material grade selection can eliminate or reduce it.
A machine with clamp capacity to spare and good injection stroke control helps a lot.
Regards
Pat
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RE: Best Way to Remove Knife Edge from Molded Parts
RE: Best Way to Remove Knife Edge from Molded Parts
H
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RE: Best Way to Remove Knife Edge from Molded Parts
This is just one of the designs that virtually makes it impossible for a worker to accidentally cut themselves if that's the issue.
Regards
Pat
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RE: Best Way to Remove Knife Edge from Molded Parts
If you are material safe on the tool and have the tolerance on the part, the parting line faces can be re-ground to help eliminate flash.
A picture or drawing would help greatly.
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Best Way to Remove Knife Edge from Molded Parts
I understand that we could have put a radii on the part and then shift the parting line up. Likely, down the road we will make this change.(When time/money permits)
We're going to try the safety knife and will report back, but still open to trying other things.
Thanks.
RE: Best Way to Remove Knife Edge from Molded Parts
My other thought is tumbling, but that will likely cause a very disagreeable surface finish on glass PP. Years ago the factory that I made a number of transfer molds for did de-flashing by freezing their elastomeric and rubber parts and tumbling them.
Just a couple of thoughts.
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Best Way to Remove Knife Edge from Molded Parts
To mould the dad on the leading edge you need to cut a cavity in the other half as well. I agree that substantially increases the cost of tooling.
The safety knife is the way to go if the rad or chamfer can be small and precision is not required.
Regards
Pat
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RE: Best Way to Remove Knife Edge from Molded Parts
Pat, yes, it kinda is!
We will try adding the fillet to the flat side on our next parts. Like .010" rad.
For now, looking forward to results of the safety knife.
Thanks
RE: Best Way to Remove Knife Edge from Molded Parts
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RE: Best Way to Remove Knife Edge from Molded Parts
http://www.mcmaster.com/#bur-tools/=irv8dq
RE: Best Way to Remove Knife Edge from Molded Parts
I tried some deburring tools and they did not yield consistent results. Sometimes the blade will really dig into the edge and gouge it., but a B-70 style looks promising.
RE: Best Way to Remove Knife Edge from Molded Parts
Regards
Pat
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RE: Best Way to Remove Knife Edge from Molded Parts
Scotchbrite is also an option. You will have to find the right grade through trial and error.