Machine shops and metric drawings

[LONDONDERRY]

So I had this meeting today with SMC, a machine shop and material manager and have any of you guys ever experience a fabrication house that says "...well the reason the we're late on deliveries is because the drawings are all in metric and we're not use to that standard, if they were english, things would go smoother" Now I'm being asked by SCM (supply chain) to change all the drawings to english, my response "I'll look into it"; but what I really want to do is give SCM and the shop the middle finger and then say a number is a number regardless if its imperial or metric, or we'll find a new shop

 

[powerhound]

I've heard lots of excuses, but never that one. Pretty lame.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[Belanger]

Lame indeed. If they want to stay in business, they need to be more up to date with the trends. I suppose they still base their manufacturing on scaling dimensions from the print with a ruler?

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[Tunalover]

LONDONDERRY,
You mean you have some choice as to who your suppliers are? I would get your Purchasing Manager to call the machine shop manager to get him to change his way of thinking. That's almost as bad as the shop complaining that all the holes in a surface are not ordinate dimensioned to save on having the machinist to do arithmetic!


Tunalover

 

[Keith1029]

I hate this; to me that translates as "it was late because we are not very good at certain parts of our jobs, if you came over here and did part of our jobs for us (for free) we might be on time." OK that might be the cynical version but the spirit is spot on.

I've gotten a version of this a few times (enough that without this forum I would think that I'm the crazy one for thinking the way I do). It's usually up front at the time of order in the form of a request from the job shop for me to produce a metric drawing, or for me to approve their re-creation of my drawing to a metric/JIS standard. Most of the time, their re-creation is filled with errors like bad tolerancing, and missing dimensions and dimensions that have been just plain converted to metric incorrectly. (It makes me wonder about the attention to detail on a finished product if you can't just multiply 20 or 30 dimensions by the same conversion factor and get the correct answer 100% of the time.)

I understand that some people are working to JIS/ISO etc. and may not be familiar with the particulars of ASME GD&T (I don't claim to be a master myself) but the solution IMHO is for the job shop to learn the standard, ask the questions needed to understand it up front, or just no-quote the part. Customizing your prints to cope with a particular manufacturers ability to read it is a nightmare and the first step down a bad path of wasted resources and quality compromises. The SCM should be made aware of this as well; I've seen it happen and it has always ended up costing more than the perceived savings (time/cost etc.) was worth.

On a related note, I design a fair amount of cylindrical parts. Every time I get one of my drawings back that has been converted to JIS, they move one of my diameter datum feature callouts to the centerline of the part; I call them up and we play the datum/datum feature game before finally agreeing that they can make whatever print they want to manufacture, but acceptance/rejection will be based on my print.

Is attaching datum label directly to a centerline (common centerline) allowable in JIS? How is this to be interpreted if so? Or is this just a case of poorly prepared drawings?

 

[KENAT]

LONDONDERRY, when we were revising standards when I first joined the company we looked briefly at this and consensus was that most of our current or likely machine shops were more comfortable with inches so all* drawings were to have linear units in inches, even if the threads etc. were metric.

To my mind this is one area where it makes sense to work with supply chain and say 'what are our machine shops more familiar with' and then go with that as general policy.

* exception for certain items such as optics where metric dims are more common.

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[ctopher]

I good machinist, or fabrication house, will know both and know how to translate unit.
We had to drop one because they refused to follow GD&T.

Chris, CSWA
SolidWorks 14
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[juergenwt]

I would just find another shop capable of working in metric.
Nothing will get their attention faster than loosing a customer.
Why would you do business with a company using such a lame excuse?

 

[MikeHalloran]

A big part of an SCM's job is finding shops that can work with your documents.

Asking you for a wholesale change of your documents to help out an incompetent shop suggests rather strongly that the SCM is just as incompetent as the shop, and needs to be discharged immediately.



Mike Halloran
Pembroke Pines, FL, USA

 

[CheckerHater]

Truly, whoever wants to do the job, is looking for ways and means, who doesn't is looking for excuses.

 

[LONDONDERRY]

Oh but you see I'm the new kid in the company and SCM, materials manager, config manager all think I work for them and love to dictate what they want me to do.

 

[CheckerHater]

Could you argue that the reason your drawings were delivered late and had several errors was because drawings were converted between the systems back and forth?

 

[berkshire]

The "You sent us Metric and we work in inches", excuse has not worked in shops for the past 10 years. Unless that shop is still working in the "stone axes and bear claws" days. Most machines these days have digital readers that can convert from inches to metric at the flick of a switch. Even tape measures can be bought with inches on one face and centimeters on the other, other measuring devices such as digital micrometers, calipers, and height gages can also switch scales.
B.E.

You are judged not by what you know, but by what you can do.

 

[KENAT]

Let me make it clear that if you've already got a drawing I wouldn't propose redrawing it - it shouldn't be that hard to work around as almost everyone above suggests.

However, I am suggesting that for future new drawings it's worth chatting with other drawing users in the business & supply base to see if one or another system appears to be preferred. I'm also suggesting that as the new guy you probably should have done this before starting to create drawings for your new employer - though it's not necessarily something that immediately springs to mind amongst all the other stuff going on as a newbie.

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[powerhound]

In my opinion, units should never be an issue. I have never worked at a place where the units of a drawing ever determined or even influenced any decision of any kind.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[BillPSU]

The supplier quoted the job and knew before it accepted the PO the part design(metric), quantity required and due date. They should have not accepted the PO if they couldn't meet your companies expectations. They should have no quoted the part if the design was not acceptable. Tell SCM if they had a qualified supplier they should be able to make the part. My company including the large multi-national above my local plant purchase over 20 billion dollars of metric parts/materials every year.

This supplier must be a favorite company for someone in SCM and gets special considerations. Good luck Londonderry.

Bill

 

[cowski]

This supplier must be a favorite company for someone in SCM and gets special considerations.

The one that puts in the lowest bid almost always gets special consideration...

 

[KENAT]

If only it were always that simple cowski.

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[3DDave]

What a pickle. As a company, they misrepresented their side of the negotiation. Either they really can't use metric or they are late for some other reason and are using this as an excuse. Perhaps the people involved are nice, but if a company is going to be a legal person, this one is not a nice person.

Often the contract is so large or so far behind, SCM can't move the contract elsewhere so it gets taken from the engineering budget to make what SCM did look OK by making what will be called 'easy changes.' It means a chance for engineering to add errors during this rush to save the outside firm, but SCM gets to look good in saving a bad situation and then it's engineering's fault for any delays due to any errors. I hate that.

If someone, up front, said 'we can save $XXXX and it will cost $YYY to change the design, so let's change the design', that's OK. Unless it really takes $YYYY to make the change over the $YYY budgeted. Free overtime! Yeah! So SCM can golf on Friday afternoon.

But come in late and then make this suggestion? That's not OK.

Please, save the middle finger for filling job applications. Waving it around with the other fingers on your way to a new job will feel much better than waving it alone on your way to a new job search. I know you know this. Just reinforcing the thought.

 

[LONDONDERRY]

Often the contract is so large or so far behind, SCM can't move the contract elsewhere so it gets taken from the engineering budget to make what SCM did look OK by making what will be called 'easy changes.' It means a chance for engineering to add errors during this rush to save the outside firm, but SCM gets to look good in saving a bad situation and then it's engineering's fault for any delays due to any errors. I hate that.

Wow thats exactly what happens here I was warned by my boss the SCM has lots of pull. The metric issues is just a small one. I've been here for just abotu 1 year and from concept design to fabrication is a mess