Detailing Complex Geometry
Detailing Complex Geometry
(OP)
We have a part that is very complex. Our vendors can make if from a parasolid, but we have yet defined it on a drawing. The part has three features; one end is slotted and flat, the other round and tapered. In between is a complex twist extrusion. Overall length is about 2 inches. How can we detail the twist? Does anyone have sample drawings?
thanks,
Stumped in Seattle
thanks,
Stumped in Seattle





RE: Detailing Complex Geometry
You can try section views or call out the twist, similar to a screw thd.
Hard to tell without seeing it.
Chris
SolidWorks 07 3.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 03-26-07)
RE: Detailing Complex Geometry
This is how I've seen it done on pre CAD drawings for aerofoil type shapes.
Depending on what standards you draw to this may be a case where Model Based Definition makes sense (ASME Y14.41).
If nothing else you could give outline/interface information on the drawing, along with material notes, tolerances etc. You'd then refer to the model file on the drawing as defining anything not on the drawing. If you go this route you need to carefully consider how you are going to control the 'rev' of the model etc but it can make sense.
RE: Detailing Complex Geometry
"Wildfires are dangerous, hard to control, and economically catastrophic."
Ben Loosli
Sr IS Technologist
L-3 Communications
RE: Detailing Complex Geometry
To define the twist:
1. Take as many sections as needed. (Is the section a constant?)
2. Define the distance between the twist (path).
3. Define the diameter that the twist (helix) follows.
Heckler
Sr. Mechanical Engineer
SWx 2007 SP 3.0 & Pro/E 2001
XP Pro SP2.0 P4 3.6 GHz, 1GB RAM
NVIDIA Quadro FX 1400
o
_`\(,_
(_)/ (_)
(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right." -- George Best
RE: Detailing Complex Geometry
Chris
SolidWorks 07 3.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 03-26-07)
RE: Detailing Complex Geometry
Also, the twist I described was not created with a helix. It's less pronounced. Sort of like grabbing a piece of licorice, twisting 10 degrees and raising one end.
RE: Detailing Complex Geometry
I'm in a medical device company with FDA approved products, and ISO-9001/ISO-13485 certification. There are no requirements for "robust drawings". Only that you fully document what you make and change. We have many parts that are defined in the way that looslib suggested. Have at it. :)
Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
http://sw.fcsuper.com/index.php
RE: Detailing Complex Geometry
David
RE: Detailing Complex Geometry
Thanks for the encouragment Matt. Hearing from the industry helps immensely.
Phil
RE: Detailing Complex Geometry
Don't ask why we are still on 2005; there's not enough room here...
Phil
RE: Detailing Complex Geometry
Anyone would be able to build it from that data no matter what system they are using..
After all we made the SR71 without computers LOL
Cheers
I don't know anything but the people that do.
RE: Detailing Complex Geometry
Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
http://sw.fcsuper.com/index.php
RE: Detailing Complex Geometry
Regards,
Namdac
RE: Detailing Complex Geometry
In fact the drawings I was referring to on my first post were on linen.
You can describe it in 2D if you need to, just may take a lot of time & effort. If however you can ref the model without violating whatever standards you work to (be they industry, company or just your training/experience) and the people making it can work from the model then why not use it?
I worked on one project with a fairly complex shaped conduit several years ago, (before I'd heard of 14.41 and in the UK anyway) and it basically had a drawing with tolerances, material and overall/interface dimensions plus a couple of sections to give you a general feel for the part. It then referenced the model for the rest of the geometry. So even if your software isn't fully 14.41 compliant in 3D you should be able to find a way around it. I thought 14.41 allowed for hybrid model/drawing definition so the CAD systems limits shouldn't be a problem but I may be wrong.
RE: Detailing Complex Geometry
RE: Detailing Complex Geometry
It does allow for a combination 2d/3d definition but you still need to be able to give someone a model that they can query for the feature information not specified on the 2d print.
David
RE: Detailing Complex Geometry
David
RE: Detailing Complex Geometry
So as long as your 'drawing' or spec details what tolerances to use on 'model geometry' that isn’t detailed on the drawing, and you are able to export your model in a format the manufacturer can use, you should be covered right? Maybe not as simple as it seems (especially as sometimes when creating/translating ‘generic format models’ like step, iges, stl etc things go wrong) but manageable by most 3D CAD systems I would have thought?
RE: Detailing Complex Geometry
Matt, if you produce Class II or III devices, I'd like to know how your regulatory department controls electronic files if you are not compliant with 21 CFR part 11.
thanks,
Phil
RE: Detailing Complex Geometry
If a company can machine to a solid model they will, even if you can cut enough sections and show enough points to create a cutter path they will never be used, no machinist is going to start trying to create new geometry from a 2D drawing when they have perfectly workable 3D data.
Other than adding many hours to the job and the possibility of the drawings being misinterpreted what use are they? Of course you need to show tolerances.
RE: Detailing Complex Geometry
Chris
SolidWorks 07 3.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 03-26-07)
RE: Detailing Complex Geometry
RE: Detailing Complex Geometry
Our rating is for diaganosis. I'll apologize for not immediately knowing the actual standard we hold to. However, the solid model is as much part of the control as the drawing. At the risk of making a general comment, I will say that many engineers these days are actually uncomfortable with drawings all together since the design intent is captured best by the solid model itself, and the drawing is only an interpretation of that solid model, thus creating a second layer where mistakes can/will occur.
Beyond this, I can't answer further if you need factual specifics. (I guess I can say that I do not believe that the FDA has any drawing standards at all.) From my experience, it's up to the company to determine their own system, and the FDA simply checks that system against a very specific publically available audit check list.
Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
http://sw.fcsuper.com/index.php
RE: Detailing Complex Geometry
I've also seen a lot of poor control of model & electronic drawing files.
The latter problem can probably be solved with either PDM/PLM or just good practices & procedures but I'm not sure about the former. The only really good configuration control system I've ever seen relied on signed hard copies of drawings(which did get scanned afterwards) but this seems archaic.
I would have thought that for an application like medical you'd have to have these areas covered. I would think that having a drawing, be it a partial one, was one tool to help with this.
ajack1, not everyone can fully check against the model. Also sometimes it's useful to have the option of just checking certain critical dims without having to put the part on a CMM machine. For this you either need an annotated model to reference or a drawing. Otherwise you’d have to interrogate the model which can be time consuming.
RE: Detailing Complex Geometry
I still cannot believe companies can waste this amount of time and money and still be in business.
RE: Detailing Complex Geometry
I also agree with KENAT.
Chris
SolidWorks 07 3.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 03-26-07)
RE: Detailing Complex Geometry
As for a poorly constructed model, that is another issue, and should be addressed by training and company standards along with vigorous checking of the models before release.
I am not familiar with FDA requirements, but do know that FAA requirements now allow a completely digital definition for aircraft.
RE: Detailing Complex Geometry
ewh, I was talking about editing of the model, this combined with poor file storage/config control practices can lead to problems. However, of course the same thing can happen if you lose the master drawing in old school systems so it's not specifically just a 3D issue. Although I’d think re-creating a drawing (and associated model if applicable) from a print may be easier then doing it to a dumb model. Given that drawing check has more or less gone the way of the Dodo in the 2D world, do places that rely on MBD really spend significant time auditing models? From my experience this could be even more time consuming than checking drawings.
As regards checking certain critical dims without CMM, many if not most of the 'complex shape' items I've looked at in detail still have interfaces (especially mounting points) somewhere with not so complex shaped items and it can be useful to check these interfaces with non CMM inspection methods. I’m not suggesting you try and check the complex shapes with it but for instance it may be you have a part on which you want 100% inspection of the mounting hole interface, which can be achieved with Vernier etc, while only every 10th, 50th or 100th… needs the complex area inspected.
I know plenty of people are making MBD work and presumably more efficiently than just using the model to feed 2D drawings or they wouldn’t still be doing it. However, I’d really like to understand how they make certain aspects of it work. I wasn’t saying the OP shouldn’t go MBD, in fact I was the first one who brought it up, I just think there are issues to address and I’m not sure I even know all the issues, let alone the solutions so was hoping posters that use MBD could elaborate, both for the OP benefit and for others (including me).
RE: Detailing Complex Geometry
RE: Detailing Complex Geometry
Most of the parts we make do not have "simple" interfaces that lend themselves to non-CMM inspection, but I do agree with where you are coming from.
RE: Detailing Complex Geometry
My current place barely has the configuration control standards adequate for the drawings which are fed from models. I can only imagine the mess it would be if the model were the master. In fact our sister site does use the model for some complex castings etc and have had configuration control issues.
I used to work in Aerospace/Defence in the UK. Our confguration control for the printed out, signed off drawings was probably the best I've ever seen, and I've done work with major US contractors. However the control there for the original CAD data was almost non existent.
My current commercial place in the US treats the CAD data as master and relies on 2D drawings fed by 3D models. However while they do manage the data it's not very rigourous and in my opinion no where near rigorous enough to support MBD.
I may post on the other thread to pose the config control questions but better go do some work first.