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旧 2009-09-04, 04:54 PM   #1
huangyhg
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默认 assembly drawings - or instruction manuals

assembly drawings - or instruction manuals
here's one i didn't see in any recent posts.
what is people鈥檚 common practice for assembly drawings?
by this i mean do your assembly drawings essentially just show the assembled condition with all the information (parts list, notes etc) needed to define it or are they more like the instructions you get with flat pack furniture from ikea/home depot/homebase etc?
my principle which my colleagues in my sub department share is that assembly drawing, like piece part drawing, details the finished component and says what is required/what you鈥檒l accept & not how to get there.
asme y14.24 seems to support this, although not that strongly it says at 4.1.3 (d) 鈥渄epiction of the items in the assy relationship, using sufficient detail for id and orientation of the items.鈥?br />
i鈥檇 be interested to hear what others have to say. as part of our trying to introduce drawing/documentation standards one of the things we鈥檙e trying to do is get away from assy drawings that double as assembly instructions and instead create true work instructions as required.
we鈥檙e facing a lot of resistance, especially from people that perceive this as being extra work and i鈥檇 be interested to hear what other people do.
thanks,
ken
we create cad exploded assembly drawings for mechanical assemblies. these are used by the assembly line to build our products and are also used to create images in our manuals for service and repair part ordering for our technicians and customers. if there are specific assembly steps or requirements (bolt torque or lubrication) we create work instructions that utilize digital photographs.
weldments are shown in the assembled condition. we also have application drawing sets, these show our products in the assembled condition as well, and define all mechanical and electrical interfaces for our customers.
art without engineering is dreaming; engineering without art is calculating.
steven k. roberts, technomad
we will also create exploded assy dwgs, but do not define the proceedure for assy in those dwgs. the exploded views are to clearly define what component goes where, not how to get there (as stated in asme y14.24 p4.1.3(d)). there are separate work instructions to be followed to ensure correct assembly.
we had a shortage of drafters for several years and were forced to do most of our assembly documentation in proceedure form. this worked but it was hard to get good photographs that conveyed the information clearly. also we had a hard time with written documents not being used because people didn't want to read a 10 page document telling them how to properly install a part, consequently things got assembled improperly. now due primaily to requirements from one of our distibuters, we are using exploded view drawings for assembly manuals (sort of "ikea style" for our complex assemblies). this allows us to get the information across to not only our employees that may not read english very well but also to our distibutor's foreign service engineers.
" my principle which my colleagues in my sub department share is that assembly drawing, like piece part drawing, details the finished component and says what is required/what you鈥檒l accept & not how to get there.", i agree, with the caveat that sometimes assemblies are too complex or large to detail properly in assembled form and on a single sheet. we don't tell our people in our drawings what tools to use or how to do an operation unless it it has special requirements that may not be intuitive.

thanks for the responses.
just to clarify i鈥檓 not saying that the assembly drawing should be just a single sheet with just a parts list and a ballooned orthographic view.
all the views necessary to fully detail where parts end up should be there. my preference is first try and do it with ortho views, then sections then views with certain items hidden and explosions as a last choice. if multiple sheets (or my preference one large sheet) is needed so be it. i was also taught not to balloon/detail on iso views but am not sure i can justify that from the standard.
my concern with using exploded views as primary views in a drawing is that you鈥檙e not really showing where the part ends up, typically you鈥檙e showing it out of position with a 鈥榝low line鈥?to where it ends up. also certainly in our cad system good explosions can be time consuming, especially maintaining them after revs (supposedly improved at the next version).
i strongly support the use of exploded views in work instructions (assembly manuals etc) and generating them from the cad data makes a lot of sense and is something we do and are looking to improve. however i feel they are of best use in this type of document not in the controlling drawing. from my experience it鈥檚 relatively rare that you can show something in an exploded view that you can鈥檛 show in a section or one of the other types of view i list above.
i agree that wordy assembly documents can be hard to use, we currently emphasize use of pictures and are working on getting those images from cad data rather photographs.
any more opinions/comments would be appreciated.
ken
i have found that many people can't read an orthographic drawing and have a hard time visualising part locations from a section veiw. we use inventor and it has worked pretty well for us, it could be better but such is life. i always try to put a fully assembled veiw on the first page or if the drawing is only one page, in an upper corner. i agree that if the assembly is not shown complete the drawing can be next to worthless.
here i will give my two cents worth:
1.) are the pieces drawn in 3-d?
2.) if drawn in 3-d, then time is to make the exploded view will be shortened.
be sure that when you show an expolded view use phantom lines when necessary to show assembly.
then if there are any revisions they will automatically update as long as you re
namdac, thanks for the response.
1. the assemblies are modeled in solid edge (3d cad, no not a version of solid works incase anyone didn鈥檛 know).
2. a default explosion can be generated very rapidly (about 3 mouse clicks if i recall) unfortunately this default explosion is not usually adequate and requires editing.
you鈥檙e generally right about showing phantom 鈥榝low lines鈥?as i noted in an earlier post. sometimes however they can create a cluttered drawing, especially when you try to do too much on one view.
the problem in revving comes if one of the 鈥榣ower level鈥?parts in the 鈥榚xplode tree鈥?type functionality is replaced by a 鈥榙issimilar鈥?part. this causes large sections of the explosion to collapse or otherwise fail. (essentially i believe because you鈥檝e changed to original assembly constraints.)
it would appear that at the next software release they鈥檝e improved the explode environment somewhat which should speed this up however slow generation of explosions wasn鈥檛 my main concern.
my fundamental concern is not so much whether explosions should be the primary method of display on the assembly drawing (though i鈥檓 inclined to think not) but as to whether the assembly drawing should double as an work instruction giving detailed instruction in how to assemble the item.
from what i鈥檝e seen here this leads to a cluttered drawing which still doesn鈥檛 really have a full set of assembly instructions and yet, because primarily exploded views have been used, can鈥檛 really be used to check that the part was assembled correctly.
i think aardvarkdw has hit the nail on the head. with the phasing out of truly skilled labor the people putting the item together often can鈥檛 read a conventional drawing. this is where i thought manufacturing/production engineers were meant to step in and take formal design documentation and come up with process etc to simplify this for the production line maybe i misunderstood. (yes i know not all companies have the resource for dedicated manufacturing engineers etc. but i mean the principle.)
ken
ken,
i strongly agree with your rational. i have done exploded assy dwgs, but that is not my preferred method. sometimes we are constrained by situations out of our control, such as shortages of labor, budget, and the most common - time. it can save hours in work instruction and proceedure illustration to use exploded views.
bottom line, you are correct that orthographic and section views can define nearly every assembly (i can't think of any exceptions, though), and the product is better defined using that method.
ken
we use mdb (model base definition) and do not have any drawings. this is for airbus & boeing alike.
the planning is similar to what aardvark posted and is the only paper that is generated from the mbd....
there was somewhat of a struggle with manufacturing but that was only in house. the vendors seem to jump on board pretty quick.
the assy is handled by m.e.'s and their planning which include illustrations relative to the assy level or process.
cheers
i have on a few occasions generated an entire tree of assembly and subassembly drawings, and had to re-do them to match the sequence of the build process, and re-do them again every time we got a new manufacturing manager who re-"engineered" the process his way. it was really aggravating. it would have been much easier if "re-do" didn't involve erasers and pencils.
eventually, cad made it nominally easier to do stuff like that, but cad was paid for by shrinking staff, so it really wasn't any easier or quicker.
then, jit came along, and did away with any necessity for 'structure' in bills of material, or assembly drawings.
on the other hand, the 'manufacturing instructions' associated with jit are in the aggregate much more detailed than any assembly drawing/ bom for a product of similar complexity. i don't know if cad models could help make them more easily; ours were generated by 'artists' who had no idea how to import a cad file even if they wanted to, and they didn't want to, because they were paid by the hour.
jit was a net positive for the company, but doing it for the first time was painful.

mike halloran
pembroke pines, fl, usa
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