Secondary Operation Drawings 4

[securitech]

Here is my situation:

We have a part that we would like to have machined by a local fab shop or our overeas plant. These sources can produce large quantities of the basic machined parts at a significantly lower cost than our in house machine shop. However, the secondary operations drastically increase the price of the part, so it would be more cost effective to do the secondaries in-house. So we need one drawing that shows the basic machining sizes and one that gives the finished part.

Here is my question:
Is there a standard in existance that defines how the drawings should be organized? For example, should we have two drawings with distinct part numbers that reference each other or should it be one package with multiple pages (Page 1 - Basic Machining or Casting, Page 2 Secondary Operations)?

If there is no standard in existance, what is the recommended approach.

I have done my research and was not able to find anything "conrete". Your help would be much appreciated.

Adam Vega
Securitech Group, INC

 

[MikeHalloran]

I think you need a separate part number and a drawing for the part you purchase overseas, with no reference to what you make from it.

Having a single part number/ drawing set for an item that may be in inventory in multiple stages of completion is just asking for trouble. It will drive your materials management people crazy.

Yeah, small companies do it that way all the time ... until the first time they miss a shipment because they only have semifinished parts in stock, or anger a customer by shipping semifinished parts.




Mike Halloran
Pembroke Pines, FL, USA

 

[ewh]

I am not aware of a standard that would cover this, but one may exist. I would handle it as two separate drawings, much as a machined weldment or machined casting for example. This would clarify what is required at each stage of the manufacture of the part, and would help eliminate any confusion of the fabricator.

 

[tbuelna]

A drawing that controls the configuration of a part produced by an outside source is generally referred to as a Source Control Drawing.

To maintain configuration control over your primary-sourced part, I would recommend creating a drawing or document that fully defines the part (with part no.) as you would like to have it delivered. That way you will have no confusion over what is expected of your overseas supplier. You can also control configuration through drawing or document revisions.

The primary-sourced part no. can then be called out as a material on your next assy level drawing, any necessary machining or manufacturing operations can be defined, and it can be assigned a new part no.

 

[ewh]

As for referencing the parts on each drawing, many companies do reference where the part is to be used, and I would include that on the first drawing. You pretty much have to reference the first part on the second drawing.

 

[fcsuper]

Make-from drawings are handled a variety of ways, depending on what systems you have in place. If you have full-fledge PLM/MRP routing, then I believe you can just specify the steps on the drawing (perhaps 1 sheet per step?) and then set up the system to route the material/parts. If you have a less robust system in place, you may need to create two drawings; one for the original part, and one that modifies that part (make-from). At my current company, we make a drawing for each step, each with its own part number, and then structure the BOM's to track where-used. On the make-from drawing, note 1 listes the original part at the material. I'm sure there's other ways to handle this too. Can you provide more information about your systems?

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

 

[securitech]

Thanks all for the helpful input.

fcsuper: Funny you should ask about my company's system! Before I joined the company, there was no system in place. Just a folder on the network with CAD files and a spreadsheet for assigning drawing numbers. No consistent part numbering system, no "used-on", no source control, no BOM's!!! You can imagine what I am up against.
We have since purchased an ERP system (Infor - Visual Enterprise) and I have the enormous task of configuring all (active) products that we make. Assembly components number into the 100's.
I was not involved in the selection of the ERP system, so I am in the beggining stages of learning it's capabilities. It seems very robust, with full-fledged routing capabilities. However, I am not 100% sure as Engineering is not covered until the 3rd phase of implementation. Financials/Customer service will be first (of course), manufacturing will be second, and engineering will be implimented last.

How would this affect your approach?

Adam Vega
Securitech Group, INC

 

[fcsuper]

Perhaps take a tiered approach. Create documentation that the current system can use, but that won't conflict with the new system once it is implementated (so you don't have to update documentation right away). Sorry for not being very specific. Hope you don't do too much .

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

 

[KENAT]

My place used to do some things relying on routings (to different vendors) of a single drawing with different stages on different pages and it caused all kinds of problems. This was with an ERP system that could supposedly handle routing etc. I'm also inclined to think it goes against the principle of defining the finished part on the drawing not how you get there.

We actually redrew a number of items as 2 separate drawings.

To me you want a separate drawing fully detailing what you get from the vendor so that you have something to specify to and inspect to. Otherwise you're relying on purchasing when they put the order to say something like "we want the item to drawing 1234 but leave of the .25 hole at grid E7, and the surface finish on surface at grid B2" or something like that. Recipe for disaster (although of course it does happen regularly with certain processes such as heat treatment & plating etc). Even if you put the 'external' details on a separate sheet it's confusing.

In my opinion it's best to make a drawing pack that can survive without a specific PLM/PDM/ERP system while taking advantage of its benefits where possible. This way if the ERP/PLM/PDM system ever becomes obsolete/gets replaced or you outsource the entire product etc the drawing itself has all the necessary detail.

I don't think the application you are talking about really suits a source control drawing as such, since you are fully designing/defining the part and maintaining the drawing etc. Source controls are more when the vendor designs the part and you just want some control over what they supply. (This a simplification from memory, for the detail see the relevant ASME spec)

I'd go for 2 seperate drawings. The second one would say something like 'make from drawing XXXXXX' in the material box/note; and would be routed like this in the ERP system. Effectively the second drawing would have a BOM of a single item. As to whether you put a 'used on' on the first drawing is up to you. This is useful information but notoriously difficult to keep up to date unless you have a really good configuration control system.