Would you up issue after DFM? 6

[DRobbo44]

Just wondering really as a few companies I've known do this differently.

If the design is frozen and released to purchasing, you then recieve feedback via a DFM from an injection moulder requesting some tweaks, would you up revision that design or would you make the changes and re-release at the same level?

 

[LittleInch]

DFM??

Revision control is critical - If it has been fully reviewed and issued / signed etc then you mkae changes releasing as the same revision is not normally permitted.

It's not that hard surely to issue the next rev?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DRobbo44]

So a Design for manufacture review from a toolmaker. Normally very minor tweaks like increasing a draft angle for example. I guess my thought would be it can go through a few rounds of these changes to improve the manufacturability so could end up a fair few revisions deep before the tooling has even been comissioned.

 

[SWComposites]

Well, don't officially release the design until the DFM process is complete.

 

[drawoh]

DRobbo44,

You need to know which version of your drawing got issued to the fabricator. Any change for any reason is a revision, and ought to be documented that way.

--
JHG

 

[LittleInch]

The risk of the wrong drawing being used is normally significantly more than any minor benefit you get from saving a few minutes going through the uprev process.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[CWB1]

Revision numbers are assigned at release approval, until then you track changes based off the date. If you need a change you blank out the revision until released.

An internal process or manufacturing engineer/manager should be attending design reviews to ensure the design team is addressing any significant manufacturing concerns prior to release. Parts that are outsourced generally aren't modified to accommodate specific suppliers to ensure that purchasing can easily re-source the part as needed. Given a willingness to accommodate these changes suppliers will quickly back you into a corner via design so that production cant be sourced elsewhere and your employer has to pay an inflated price.

 

[Gr8blu]

Agree with CWB1 - if you're seeing this "request to tweak" from multiple manufacturers, then there is a chance your design review missed something. On the other hand, if it's only one or two, then they probably shouldn't be the manufacturers you choose. The design is, after all, your responsibility - the injection mold team is not going to be held to account for a failure if they build it to the print - even if they requested the change from the original.

Converting energy to motion for more than half a century

 

[dgallup]

You never ever make changes and release at the same level. You can have a lot of marked up versions going around for discussion. Generally they should have some kind of stamp on them like "PRELIMINARY" or "DO NOT MANUFACTURE TO THIS DRAWING" and a date or something to identify them. But once you decide what the changes are then you release at the next level. Does not matter even if you are just correcting one misspelling.

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[Arnaud Divialle]

I really like the different opinions presented.
Overall, it assumes that the Part OEM has enough process expertise to run rigorous design reviews internally.
There is a bit of a disconnect from what I heard.
I had a chat with a Molder with 40+ years of experience and he told me "50% of the parts I've quoted were not moldable at all."

 

[geesaman.d]

If the design changes are the kind of thing that any molder would need to incorporate for manufacturability, then yes incorporate the changes and document with a revision. I revise any drawing that permanently changes once it leaves our building (and if we were a larger company, I would tighten that to any time a drawing leaves the department)

If the design changes are specific to that manufacturer and would either compromise other molders from making the same design well or not apply if I changed molders, I would document it with a per-PO deviation. My company has a Vendor Request for Deviation form that covers those situations and applies for that purchase order only.

 

[CWB1]

Overall, it assumes that the Part OEM has enough process expertise to run rigorous design reviews internally.

If management isnt hiring competent staff then they should be fired for-cause immediately. With software tools and training being so cheap and readily available today most generalists are expected to run their own flowsim for molded and cast parts.

Manufacturing reviews are an easy, low-value step in the design process. If the team is screwing that up then the design likely has major functional issues

 

[drawoh]

CWB1,

Would you trust the results of a CAD operator running mould flow analysis? I would continue talking to whoever it is is an expert in the process. Let them run the mould flow analysis.

--
JHG

 

[CWB1]

Yes. The supplier will almost always do a basic analysis to validate your work and their process, so your simulation isnt the end-all analysis. Running a preliminary simulation in-house helps guarantee that you're providing the supplier a known good design so they're not charging you for needless engineering, and helps you to understand the process. You can optimize the design to minimize wasted material (cost) and identify potential quality issues before involving the supplier. If a critical feature is prone to porosity or other issues then you can either redesign or ensure its on the inspection plan. You can also identify/control areas needing trimmed and again, redesign or identify for inspection up front so there are no surprises on the first batch. Its worthwhile IMHO. I usually share step files of both the part and the part with initial gating so the supplier can see my assumptions. I'm also very direct that the supplier can use, modify, or scrap my gating, and that I am open to comments/suggestions for improving future analysis.

 

[Inund8_ca]

If management isnt hiring competent staff then they should be fired for-cause immediately

My initial reaction to this thread which I fully wrote out was "Why are you asking this on Eng-tips? Do you not have competent colleagues you can discuss this with?" Oh well. I would make sure to take good notes on what you do in this scenario, so that you can document the process. If not for your colleagues, then for your eventual successor when you leave for a more functional (or less dysfunctional) workplace