CAD software for geers? (mechanical engineer types, that is)

I'm trying to find some design software that's cheap enough for the RepRap project, yet useable for engineering types like myself. I keep running into issues with all the free/cheap versions, most of them won't import STL's, and I find Blender incomprehensible; whereas I can pick up something like Alibre and start designing immediately.

I finally got CoCreate up and running (by logging into a completely different network, via Jet Fuel Coffee!), and it won't import STL files either. It's interesting, there seem to be two camps of 3d design software, STL compatible ones, and not. All the ones I want to use are not STL compatible. Interesting. Possibly because STL is such a bad format for solids...

What I've found so far is:
STL Import - AOI, Blender, Meshlab, RepRap Host, Skeinforge

STL Export, but not import - CoCreate PE, Alibre, Sketchup (free version with CADspan's plugins)

Still trying to figure out BRLCad, it might work. Can't tell yet.

I still have not found a way that works to import STL's into Sketchup, but I can now produce them using CADspan's free tools; I think I'll try printing something from Sketchup. So far I've been using Blender for simple scaling, rotating and positioning, but I can't seem to do any useful modeling in it; probably because I come from a CAD background, as opposed to a 3d modeling background. Just found a Blender tutorial that Beaglefury posted, that might be the way to go...

Wade

Edited 1 time(s). Last edit at 12/12/2008 07:01PM by Wade Bortz.

Wade,

I just downloaded this [www.sycode.com] Its a .stl importer for Alibre and you get 10 free .stl imports before you have to either delete the program or buy it. between the 2 of us we should be able to cover the darwin parts. YOu pick 10 you want to convert and I will do the next 10. I know this does not solve the long term problem but it will get the darwin parts into alibre for editing which we can then export to .stl from alibre.

Edited 1 time(s). Last edit at 12/12/2008 10:17PM by SCphotog.

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Charles Gantt.
Build blog [themakersworkbench.com] <---- my personal site
Build worklong [www.thebestcasescenario.com]

On a side note I downloaded the Darwin parts from Sourceforge and I can open them all in Alibre and edit and export to .stl I also downloaded the alibre to google sketchup exporter. This could be handy too.

Yeah, that could work, but I count 54 unique Darwin STL's (cartesian bot plus 1 extruder), not counting jigs. That'll require 6 people that only make one mistake each. Plus I'm then screwed if I ever want to import an STL in the distant future, like, say, next week. So then I pay the 200 Euros for the converter, but then I have to pay $1500 for the software (for the first year only), and so on...

And really, this is exactly the situation I'm trying to avoid - I don't want to invest a lot of effort into a single CAD package, only to have the rug pulled out from under me when the license expires, or they change their mind about their licensing scheme.

If I was charging my professional rate, I wouldn't mind dropping $10K or so on software tools, but so far this project is definitely on the non profit side of things, so I need to find something that works, and is cheap.

Learning Blender seems to be the way to go at the moment; it's slow and painful (for me at least), and maybe doesn't make fiscal sense in the short term, but it certainly makes sense in the long term. If it works, that is. I haven't seen many engineering designs produced with Blender, yet.

OK, I had to delete a few paragraphs of carping about the high cost of design software, but hey, software guys want to eat too. I just paid top dollar for a new laptop, and I paid extra for a good design. Why am I so opposed to paying for design software?

All this complaining just because I wanted to change the length of a simple STL file. I think I could have redesigned it from scratch by now, several times over. I'd best get busy.

Wade

I opened the darwin files that are in the source forge download in alibre with out the converter.

Sorry, my bad, I also deleted the part where I asked you were able to load the STL's, as opposed to the STEP files. I also was able to load the cartesian bot files, which eD was kind enough to export from Solid Edge into STEP format, which I agree, Alibre will load. STL's are the problem though.

I want to edit the screw-holder.stl file, which is part of the thermoplastic extruder 1.03 release, and it only seems to exist in STL format. Yeah, I can use the 1 in 10 converter, but I'm looking for a long term solution here.

Wade

The extruder was designed by Adrian in AOI so the only files available are AOI and STL I believe. The shapes are fairly simple so I find it easier to remodel things in CoCreate than to modify the originals in AOI.

The STEP files for the bot seem to load into CoCreate OK.

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[www.hydraraptor.blogspot.com]

I suspect some CAD programs don't allow STL import because they need a higher level model to represent objects than a simple triangle mesh provides. For example in CoCreate you can select features like holes and faces and change them. I would think it is easy to convert from a cylinder say to a triangle mesh but harder to convert a mass of triangles into a cylinder.

Edited 1 time(s). Last edit at 12/13/2008 09:38AM by nophead.

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[www.hydraraptor.blogspot.com]

Yeah, going from a solid model to STL is like going from STL to Gcode - you can't really go back the other way. I assumed I could at least import the STL and use it as a reference shape, or even just as a fixed polygon mesh that I could then edit, join and intersect.

I know I've done that almost a decade ago with PTC, but it was tricky. And expensive. My client would send me fancy industrial designed hollow shells of polygon meshes (STL or STEP, usually), and I'd sit down and design the mechanical guts inside the shell to make the device actually work. I'd usually start by making the polygon shell a solid, then convert it back to a shell with a non-zero thickness, slice it on a "parting" plane, and then extrude any internal details from the parting plane up to the shell, and so on.

The kicker is I can edit the STL's in Blender, and that's what I have been doing for the last few months, but at that point I'm editing polygon meshes, not a parametric solid model.

CoCreate does seem to be the best available solution; I just can't access their license server from any of the networks on this side of town; seems to be a problem with my ISP. Which makes me very nervous about doing a lot of work in it; I just helped my girlfriend go through the pain of converting her thesis from Open Office to MS Word - all those formatting options and tables that are supposed to transfer across don't quite work as they should. I've already got a stack of modified STL's that are useless unless I continue using Blender or find a cad package that can import STL's.

And that's the thing I'm trying to avoid here; doing a lot of pointless re-work redesigning designs that have already been designed once, but in a different package.

Which is why Adrian is pushing AoI - it's not perfect, but at least we all can use it.

I think the basic problem here is that I want some perfect design software, and I want it for free. Not going to happen, at least not yet.

Thanks for cluing me in on the AOI extruder files, Nophead. Right now, STL is the only common format that we're using across the entire RepRap project, which is why I was so keen to find some CAD software that could deal with it.

I think it's time for me to stop whining and start designing.

Wade

Edited 1 time(s). Last edit at 12/13/2008 01:31PM by Wade Bortz.

OK, sometimes I think I have these forum discussions simply to straighten out my own thoughts; putting fingers to keyboard helps organize things back in the wetware.

I've been editing meshes, which is like editing G-codes; possible, but a pain in the rear, and is really a backwards way of doing things.

What I should be doing is changing the underlying ideas of the design; which means I need to work with solid modeling concepts. Either use the original AOI files in AOI via boolean operations, or the Solid Edge files in Solid Edge, or redesign from scratch in another CAD package as Nophead suggested.

While it's possible to import STL's and mess with those, I essentially loose the original design intent and am working with a surface representation of the original design. In some cases that's actually preferable, but for the most part I think I need to stay away from STL's except as a way to pass the final shape information to Skeinforge.

STEP files seem to convey a bit more information about the design intent; they're at least easier to import into the solid modeling packages. I haven't tried editing them much yet though; I suspect a fair amount of information is lost in that conversion as well.

Thanks for the help guys; I have a tendency to go charging off full tilt in the wrong direction, so I wanted to make sure I was at least pointed in the right direction this time.

Wade

If someone can get me some measurements of the plastic components of both versions of the extruder I will be more than happy to help model some and output to STEP files. This would help take some of the load off of Wade. I am also willing to model any of the reprap related plastic parts and output to STEP files as long as someone supplies me with measurements.

Hello Wade, I have also posted this in another part of the forum as I would appreciate feedback on this issue of 3D modelling. I understand that most in the RepRap community have an engineering bias and therefore have little problem with most CAD packages. I come from the arts/applied arts/design direction where CAD is not the intuitive medium that inspires and motivates to learn and to work digitally in 3D. Speaking for myself it was hard work to get to grips with AutoCAD. Rhino was easier but I had to come with fully fledged designs worked through drawings and rough models.

I thought you would be interested in the 3D conceptualisation software we are developing as we are adding import .stl to the package which we will test thoroughly forst before making it available to our 'stakeholders'. It already has export .stl and we are testing colour for printing in colour. To make it a great application for artists, designeres we are exploiting the benefits that haptics (virtual touch/force feedback) gives to work more fluidly in 3D.
If you are willing to comment on what we have achieved so far please have a look at the short video at [www.anarkikangels.co.uk].
Cheers.