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Dimension control on injection molding parts
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Dimension control on injection molding parts
Dimension control on injection molding parts
Dimension control on injection molding parts
Dimension control on injection molding parts
Dimension control on injection molding parts
Dimension control on injection molding parts
Dimension control on injection molding parts
Dimension control on injection molding parts
Dimension control on injection molding parts
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Dimension control on injection molding parts


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Some Related Topic Tags
dimensions, injection molding, plastic injection molding
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  Post Number #1  
Old 12th April 2018, 06:54 PM
Jafri

 
 
Total Posts: 20
Question Dimension control on injection molding parts

Hello,

This is about one of our suppliers who will be sending us injection molding parts.
They are going to do First Article Inspection on all dimensions in 3 samples initially. Some of these dimensions are difficult to check without CMM, which they don't possess. Nor do they have any checking fixture.

I am thinking what should I ask them to ensure that these dimensions stay in tolerance after some passage of time?

Should I ask them for yearly CMM check, even if from outside? Or do customers usually just don't ask for such verification?
*confused*.

Thanks.

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  Post Number #2  
Old 12th April 2018, 08:47 PM
Ninja's Avatar
Ninja

 
 
Total Posts: 1,017
Re: Dimension control on injection molding parts

Do you have a CMM?

If you are specifically concerned with tool wear and dimensional creepage...can they send ahead first and last article for you to verify?

Just thinking out loud...
Thanks to Ninja for your informative Post and/or Attachment!
  Post Number #3  
Old 12th April 2018, 09:13 PM
Golfman25

 
 
Total Posts: 1,404
Re: Dimension control on injection molding parts

I think you both need to sit down and develop and agreed checking methodology. Gauging and fixturing may help.
Thank You to Golfman25 for your informative Post and/or Attachment!
  Post Number #4  
Old 12th April 2018, 09:19 PM
Jafri

 
 
Total Posts: 20
Re: Dimension control on injection molding parts

Quote:
In Reply to Parent Post by Ninja View Post

Do you have a CMM?

If you are specifically concerned with tool wear and dimensional creepage...can they send ahead first and last article for you to verify?

Just thinking out loud...
No, we don't have CMM either.
Yes, I'm concerned about too wear, and how the supplier will be able to find out about it before it starts making bad parts.

The supplier will do FAI 100% once, but I don't understand what is last article?!
  Post Number #5  
Old 12th April 2018, 09:28 PM
Jafri

 
 
Total Posts: 20
Re: Dimension control on injection molding parts

Quote:
In Reply to Parent Post by Golfman25 View Post

I think you both need to sit down and develop and agreed checking methodology. Gauging and fixturing may help.
Checking fixture might be too expensive, but seems like this is the only option besides CMM. I will try to convince our guys to pay for it.

If it doesn't work then probably ask the supplier to check critical dimensions from outside source?
  Post Number #6  
Old 12th April 2018, 10:13 PM
Ron Rompen's Avatar
Ron Rompen

 
 
Total Posts: 568
Re: Dimension control on injection molding parts

This appears to me to be a case where a supplier has agreed to make a part without properly assessing how they are going to satisfy the customer (you) and ensure that they supply defect-free parts.

To be blunt, it is THEIR responsibility to determine their measurement strategy, which includes frequency and method of measurement. YOUR responsibility as the customer, is to review their proposal and identify any concerns you may have.

One of the things to be considered is the rate of wear - if the die feature in question is (as a general rule) expected to stay within spec for 100,000 cycles, and the annual volume of the part is 75,000 pcs, then tool wear should be caught in the annual part layout (presuming you have this as a part of your requirements).

Please keep us informed on how this progresses - I for one would love to hear the final resolution, and I am sure there are others as well who are taking an interest.

Thank You to Ron Rompen for your informative Post and/or Attachment!
  Post Number #7  
Old 12th April 2018, 11:08 PM
Golfman25

 
 
Total Posts: 1,404
Re: Dimension control on injection molding parts

Quote:
In Reply to Parent Post by Ron Rompen View Post

This appears to me to be a case where a supplier has agreed to make a part without properly assessing how they are going to satisfy the customer (you) and ensure that they supply defect-free parts.

To be blunt, it is THEIR responsibility to determine their measurement strategy, which includes frequency and method of measurement. YOUR responsibility as the customer, is to review their proposal and identify any concerns you may have.

One of the things to be considered is the rate of wear - if the die feature in question is (as a general rule) expected to stay within spec for 100,000 cycles, and the annual volume of the part is 75,000 pcs, then tool wear should be caught in the annual part layout (presuming you have this as a part of your requirements).

Please keep us informed on how this progresses - I for one would love to hear the final resolution, and I am sure there are others as well who are taking an interest.

I disagree. There are too many drawings these days drawn with zero thought on how to check the part in the real world. Everytime we ask the designer "how are we going to check that" we get a blank stare. They'll defer to their quality people who will respond "good question." Both sides need to be on the same page regarding measurement.
Thanks to Golfman25 for your informative Post and/or Attachment!
  Post Number #8  
Old 13th April 2018, 03:35 AM
AgnieszkaSz

 
 
Total Posts: 81
Re: Dimension control on injection molding parts

Perhaps it is possible to damage (cut) some samples from each production order or work shift so that these dimensions that are hard to access could be measured in some easier way? Depends on part shape an size, of course.
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