Assembly Drawings consisting of a Bill of Materials only
Assembly Drawings consisting of a Bill of Materials only
(OP)
Our Director of Engineering wants to release Solid Edge Assembly Drawings with nothing more than a Bill of Materials on the drawing, no views at all. These "drawings" would then be turned over to Manufacturing Engineering to create Assembly Instructions. The thought behind this new process, would be that it would free up engineers much sooner to work on the next new product. Does anybody else release assembly drawings that are just a Bill of Materials?





RE: Assembly Drawings consisting of a Bill of Materials only
This sounds like an excellent strategy for making sure things cannot be put together.
A huge advantage of 3D CAD is that you can generate manufacturing documentation early in the design process. It will update as you change stuff. Meanwhile, everyone, including the designer, can evaluate fabrication and assembly procedures. If the documentation is someone else's job, that someone else will have to generate documentation that makes up for shoddy design.
It would be so nice if there was such a thing as a can of DFMA that you can spray on your CAD station at the completion of your design.
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JHG
RE: Assembly Drawings consisting of a Bill of Materials only
If I understood correctly, your design engineers create 3D assembly models; they just leave it to manufacturing engineers to make exploded views out of them. You may get away with that.
I used to make assy dwgs with iso view, not even exploded; but they were intended for our own shop, so the guys could just walk in and ask “what’s that?”
Today, when design is actually done in 3D, importance of old-school layouts and assemblies diminishes; assembly drawings are often reduced to exploded views/ assembly instructions anyway.
So, if your bosses put the procedures in place to make sure no important data is missing in action, it doesn’t really matter who will prepare said exploded views.
It almost looks like a political problem rather than technical. It could be worse: they could put making assembly instructions on designers and get rid of manufacturing engineers altogether.
RE: Assembly Drawings consisting of a Bill of Materials only
RE: Assembly Drawings consisting of a Bill of Materials only
The auto balloon function means you can get a half assed one almost for free.
You're saying your Director doesn't even want to go to that much effort? In that case why bother with even a BOM drawing, why not just show them the assy model and tell them to get on with it?
I get the feeling we're missing a lot of the information we'd need to really answer this question as CH hints at.
I'm all for getting the 'how to' information off of the engineering drawing and leaving it up to manufacturing engineering to address.
However, the engineering drawing still needs to cover the 'what' as in defining the finished product and I don't see that just a parts list/BOM truely achieves this.
(There have been previous threads about what should go on an assy drawing and what should be in a separate travelor or assy work such as thread1103-157857: Assembly Drawings - Or Instruction manuals instruction etc. maybe take a look http://www.eng-tips.com/search.cfm?pid=1103&ac....)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Assembly Drawings consisting of a Bill of Materials only
Yes, the design engineers create the 3D models of components and create the 3D assemblies. The design engineers also create all of the exploded view assembly drawings/instructions. And yes, it is a political problem.
RE: Assembly Drawings consisting of a Bill of Materials only
"Our assembly drawings up until this point in time, have been exploded step-by-step assembly instructions."
Yes that can be time consuming and it's not unreasonable to propose that manufacturing engineering be required to do the detail assembly process part.
Take a look at ASME Y14.24 if you can - though it doesn't have as much detail & examples as might be liked. A classical assembly drawing per this standard shouldn't take as long to prepare as what you're currently doing.
However, a good assy drawing isnn't just a parts list - or even a parts list with token views. You need enough views to show where every item ends up. You also need to capture all other requirements/definition of the end item that define the finished item.
This doesn't mean the CAD data can't be used to generate the detailed assy procedure stuff though - and there are ways to directly use the 3D data for that.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Assembly Drawings consisting of a Bill of Materials only
RE: Assembly Drawings consisting of a Bill of Materials only
I'd definitely suggest investigating the idea of Engineering releasing a classical engineering drawing in lieu of your current hybrid assembly drawing/work instructions.
(By the way your description of your employer sounds eerily like my employer.)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Assembly Drawings consisting of a Bill of Materials only
Think hard about your office politics.
I have worked at a site where engineering generated a stack of fabrication drawings for a product, then they handed to manufacturing. There were no assembly drawings and no parts lists.
Manufacturing eventually got the thing working. The process was not trivial. They wrote their own assembly procedures. They worked out what stuff MRP had to order and stock. Try to imagine the respect manufacturing has for engineering in a situation like this. Manufacturing took complete control of the product.
If you want to control the design, you must control all the drawings. If you want to control the drawings, you must meet everyone's requirements, including those of manufacturing.
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JHG
RE: Assembly Drawings consisting of a Bill of Materials only
JIT changed all that.
After JIT arrived, we didn't even have a BOM in the form of a final assembly drawing with no views. The product's BOM structure was reflected and recorded in the MRP system, only. You could get a BOM sliced and diced any way you wanted it, but it came from a line printer, not a drawing.
The assembly sequence was recorded in the Manufacturing Instructions, comprising detailed illustrations of what part came from which bin and went where in the assembly under construction at each JIT station.
I don't want to understate the cost of producing the first set of MIs. It took a team of specialists most of a year. It should be much easier now to pick them out of a 3D CAD system, but it's still a substantial investment.
The thing that was hard to accept at first was that the MIs were under the control of Manufacturing Engineering, not Design/Product Engineering. After we got over that shock, we were told that the 'master' MI for each sheet was the actual markup at the JIT station, and the reproducible versions in the office trailed behind them and were updated as time allowed. ... but process changes could happen instantly.
It all worked like a charm.
Mike Halloran
Pembroke Pines, FL, USA
RE: Assembly Drawings consisting of a Bill of Materials only
I certainly appreciate what Mike says about having to update assy drawings every time manufacturing changes their process.
I'd also like to back up what drawoh says - if engineering no longer documents the assy process they need to be careful to still consider it when designing. While I don't enjoy doing it much I have found that creating the detailed assy work instructions get me thinking about the 'design for assembly' aspects.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Assembly Drawings consisting of a Bill of Materials only
I recently inherited a drawing package of a fairly complex system, all divided into sub-assemblies. My first impression was that the drawings were not very good or informative. When I got further into it, I realized that it was not possible to assemble the sub-assemblies, place them on a shelf, and later install them as is on the final assembly. The original designers ignored modularity. If this system had been passed on to a manufacturing organization such as the one MikeHalloran is describing, they would have had to reject the engineering documentation, and create their own system.
If engineering, as per DFMA, breaks the system down into separate modules, manufacturing has the option to build and warehouse the sub-assemblies, or to do the whole build, in sequence, on the one workbench. Either way, engineering's drawings are being followed. If engineering and MRP/ERP talk to each other, the engineering BOMs can be imported electronically into the database.
The fun starts when manufacturing concludes that the engineers are a bunch of idiots. There is no point talking to the engineers about design changes because they have no clue of what they are doing. Now let's review them weld specifications!
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JHG
RE: Assembly Drawings consisting of a Bill of Materials only
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Assembly Drawings consisting of a Bill of Materials only
DFMA does not require modularity; it only deals with the difficulty of assembly, for a module, or for an entire product, or for a particular JIT workstation's operations.
There are good reasons to make modules, but they don't all have to do with assembly sequence.
Example: I bought a replacement handle for my Ford van door. But dealers don't stock the handle. They stock a 'door kit', which includes every removable part for a given door. Which reduces the number of items a dealer has to handle and stock, and makes it unlikely that I'll walk away from the parts counter without handing the dealer $100 or more.
Similarly, for any product, you might want to group individual parts into kits for your service people or your dealers, reducing the number of Field Replaceable Units everyone has to document, handle, store, and deliver.
So a given product could have several BOMs, all structured differently, and several sets of MIs, depending on whether you are building final product or FRUs or something else.
Product engineers are not all-knowing about this stuff, though it is to their great benefit to understand it. Just don't assume that you know the best sequence of assembly, even if you designed the product; especially if you designed it.
Mike Halloran
Pembroke Pines, FL, USA
RE: Assembly Drawings consisting of a Bill of Materials only
Engineering managers should have some experience with drawings to be an engineering manager.
Chris
SolidWorks 11
ctopher's home
SolidWorks Legion
RE: Assembly Drawings consisting of a Bill of Materials only
RE: Assembly Drawings consisting of a Bill of Materials only
RE: Assembly Drawings consisting of a Bill of Materials only
There was nothign wrong conceptually, just no process in place to make sure the work was done
RE: Assembly Drawings consisting of a Bill of Materials only
The 3D Solid Edge Assembly Models along with the hybrid assembly/exploded drawings have worked for years. They have allowed us to manufacture, trouble-shoot, and service our products.
The hybrid assembly/exploded drawings are under ECO control, so there is only one document per assembly that needs to be maintained. I see that as a plus.
In our case, it usually takes an engineer along with a designer/draftsman a couple of weeks to create all of the hybrid assembly/exploded drawings for a new product. You may reduce this time in engineering to a couple of days by going to BOM only drawings from engineering that are under ECO control, and having manufacturing engineering create assembly instruction drawings that may or may not be under any sort of control. The question is... is it worth it?
RE: Assembly Drawings consisting of a Bill of Materials only
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Assembly Drawings consisting of a Bill of Materials only
Logically, I would think that engineering would want to keep control of the definition, but I'm not a manager.
“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV
RE: Assembly Drawings consisting of a Bill of Materials only
RE: Assembly Drawings consisting of a Bill of Materials only
Good question actually.
If the drafter works for production, who interviews candidates? Who evaluates their work? Who defines and enforces company drafting standards?
I have worked in a place where each department had its own mechanical designer. There were no company standards. There was no capability to detect and either correct or fire idiots. There was no capability to treat mechanical design as a general task that should be reviewed and continuously improved.
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JHG
RE: Assembly Drawings consisting of a Bill of Materials only
As a former mechanical engineer, and now a project manager, one thing that I have always believed is that mechanical engineers, and especially the lead mechanical engineer on a project, end up being somewhat of a project manager themselves. If there is going to be any modularity and serviceability in a design, it is typically the mechanical engineer that makes that happen. Project managers can help facilitate making it happen, but it is the mechanical engineers that actually makes it happen through his/her design work. DFMA and collaboration may increase the time it takes to complete the design phase of project, but I believe it is always in the best interest of the company.
How this all plays into the development of assembly documentation isn't crystal clear to me right now. It does appear that there are many different ways of skinning the assembly drawing cat. One thing that I am certain of, is that at the end of the design phase of most design projects, there is no one that knows how a new product is supposed to be assembled and at what level it is supposed to be serviced, better than the mechanical engineer that designed it. The big question always is, how do you transfer that knowledge to the rest of the company, and how do you maintain and preserve the original design intent?
RE: Assembly Drawings consisting of a Bill of Materials only
If Engineering only hands a BOM to Manufacturing, how are design specifications communicated to the production floor? Things that come to mind are torque specifications, tolerances for assemblies, adjustments (spring preload, gear backlash, assembly clearances etc.)? The engineers designing the products have all these things in mind and it seems that sooner or later, they will have to pass along that information either on the drawing or through a series of meetings. It's kind of like sending a 3D CAD model to a vendor without any other data such as tolerances, finish, material etc.
I handle the design, fabrication documentation and assembly drawings. I find that creating assembly drawings, even though time consuming, forces me to think about how the product will be built, locate problems and hopefully solve them before they hit the floor. I do work with Production to refine the drawings and consult with them during the creation of the drawings so we are all thinking about how it will be built, how inventory will be managed and any gages, jigs or other tools needed before production starts. It's a "necessary evil" but helps avoid major problems later.
Regarding the drawings themselves, I've used Solid Edge for over 10 years and I'm still spoiled over what I had to do years before using Cadkey. Things that take 10 seconds in Solid Edge to create views, section views etc., used to take me hours or sometimes days in Cadkey. As KENAT mentioned, you do have to avoid the temptation to create a bunch of views just becuase they are easy to throw down on the screen.
Kyle