Some Qs on Imported CAD Files

[Tool-n-Around]

Hi fellas. It's been a while. I've been happily motoring along with CB and more recently bought some CAD software (Alibre Design) to solid model my projects. As you may recall, I primarily use CB to machine polystyrene foam patterns for lost foam casting, primarily automotive parts.

Attached is a Camotics simulation picture of my first CAD modeled part. It’s an automotive intake manifold flange. I saved the solid model as an STL file for use in CB and that file is 15MB. When I import it into CB and set up several scanline 3D Mops to machine it, it becomes a 75MB CB file so I assume too large to upload here. The actual part is roughly 20”L x 3.5”W x 1.25”H. I simulated in Camotics and it looks ok. I haven’t tried to optimize the run time. This model is not filleted. The filleted version is even larger but I figured it wasn’t necessary since I use a 1/4D ball end mill as the cutter and it happens naturally without the filleted model.

To date I’ve done most of my CAD within CB and not imported objects. What is the preferred type of CAD file to import and use within CB? For the STL file, I have a bunch of options about the faceting parameters, surface deviation, and coordinate system as described here in the Alibre documentation. I have no idea what is necessary/adequate for my use in CB and probably chose excessive parameters. Any rules of thumb or advice in this regard?

https://help.alibre.com/articles/#!alibre-help-v25/stl-export-settings

Ultimately, it seems this part would run much faster as a 2.5D part excluding the angled bosses, followed by some 3D MOPS for those bosses, but even with the run time, just running it as one surface would be quite attractive. Run time isn't me-time when you’re only making one or two parts :-)

Best,
Kelly

[dave benson]

Kelly

An STL model surface is made up of  many small triangles, more triangles
give a more faithful representation, however they make for large files.
There are programs out there like Meshlab that you can use use to simplify
the mesh (decimation is one methods) but not the only one, there are many more.
You may already have the tools in Alibre, the surface deviation doesn’t need to be
that small.
 Typically, you can reduce the file size by many times.
You don’t need a stl file to have a resolution any greater than the resolution
you can achieve with the tools (the diameters) you have selected.
I make and export stl files with freecad or fusion and before I export the model I check
it’s size and water tightness and use the inbuilt tools to reduce the size of the model.
Great job on the Willy’s by the way.

Dave

[Tool-n-Around]

An STL model surface is made up of  many small triangles, more triangles give a more faithful representation, however they make for large files.

Part of the question was rather STL was the best import format. I only selected it because I had used them before with success and I dont know any better. It doesnt seem like 15MB is excessive when the smart phone pictures these days are 5MB . Would you consider 75MB large for a CB program on a part that size with three scanline 3D MOPs.........one roughing and two finish? Other than being able to post the file here, it's not that big of a deal but if it can be 10x smaller, why not? Doesnt seem like the CB file is ever going to get smaller than the STL file it contains.

There are programs out there like Meshlab that you can use use to simplify the mesh (decimation is one methods) but not the only one, there are many more. You may already have the tools in Alibre, the surface deviation doesn’t need to be that small.  Typically, you can reduce the file size by many times.

The only Alibre tools I'm aware of are the STL parameters described at the link in the previous post.

You don’t need a stl file to have a resolution any greater than the resolution you can achieve with the tools (the diameters) you have selected.

I guess I'm just going to have to scratch my head a little more to see if I can decipher what that may mean to the three settings for the STL export and experiment a bit. I suspect it was excessive but cant say.

Great job on the Willy’s by the way.

Thanks Dave. It was a fun project.

Best,
Kelly

[dh42]

Hello

I saved the solid model as an STL file for use in CB and that file is 15MB. When I import it into CB and set up several scanline 3D Mops to machine it, it becomes a 75MB CB file so I assume too large to upload here.

Mops does not take a lot of space in the .cb file, it is the STL that is saved into the .cb file that take space because it is saved as ASCII mode contrary to Alibre (and most of 3D software) that save the STL as binary file.

An example, I exported the same STL file (from SW)

Bin format: 196 KB

ASCII format: 1.07 MB so 5.66 time the size of the Binary file.

And the ASCII file zipped: 89KB

++
David

[dave benson]

Hi Kelly

There are some threads here about this subject (file exchange formats), it’s a tin of worms.
We can import .dxf, .stl and step files.

For what you want to do it’s not worth the effort to use step files, as they require you to know
a fair bit about (exchange formats) to get a reasonable result. I use them because I’m making
engineered components in 2.5D, ‘3D’ won’t cut it for the accuracy required.
The step file format has an Industry standard. NIST.

I don’t know about Alibre, It has a somewhat checkered history, that software has been bought
and sold a few times, but even things like Freecad have an export preferences page and many tools to work
with repair and reduce the file size as part of the Mesh workbench. The STL format is old but it’s it’s an open
standard, newer programs are transitioning to AMF (the 3D printing crowd are all over it) which is better in every way.

In short use a stl and dig around in Alibre to find the working with mesh’s doc.
Some programs like Prusa slicer (free) will automatically on loading the file repair it
and on occasions I’ve had a stl file that I could not fix and running through the slicer
it was repaired. Alibre may already do this, I don’t know.
It’ll be a matter of trial-and-error finding what works best for you, just reduce the stl
triangle count until it’s not usable in CB (you’ll get to much faceting) especially for waterline tool paths
and then start raising the count until the file is ok for CB. I’ve included a pic hopefully showing what I
meant about the resolution you can expect with a 6mm and 4mm tool, as there is no point having a model
with huge resolution if the tools won’t allow you to achieve it.

Dave

[dave benson]

more pics

[Tool-n-Around]

I was off gallavanting about England for a week but back on the pitch now!

...For what you want to do it’s not worth the effort to use step files...........The STL format is old but it’s it’s an open standard, newer programs are transitioning to AMF (the 3D printing crowd are all over it) which is better in every way.

Will check that out.

I don’t know about Alibre, It has a somewhat checkered history, that software has been bought and sold a few times,.....

Old stuff I read said it was it could be a bit buggy bit buggy. I have several friend that use it and recommended it. I tried the demos of a few others and it seemed pretty good to me and has a pretty good user forum. As a hobbyist and less frequent user the perpetual license and (lower) cost of ownership ownership made it look like a good value for me comparedto packages that were $1000s to buy and maintain.

In short use a stl and dig around in Alibre to find the working with mesh’s doc. Some programs like Prusa slicer (free) will automatically on loading the file repair it and on occasions I’ve had a stl file that I could not fix and running through the slicer it was repaired. Alibre may already do this, I don’t know. It’ll be a matter of trial-and-error finding what works best for you, just reduce the stl triangle count until it’s not usable in CB .....

I'll experiment.

Thanks again.

Best,
Kelly