what? 3D Builder shows STL dimensions. Sli3er too. Always. Maybe run
from that fabricator

On 12/31/19, fred via Discuss discuss@lists.openscad.org wrote:

From the reference of a machine shop constructing a part from a drawing, STL files are not suitable, especially if the parts are to be created by a CNC machine. Even though many programs provide bounding box dimensions, I know of no program that could, for example, provide the diameter of a hemisphere mounted on a truncated cone, if the source file is an STL.
By converting a file to .step or .stp or one of a few other machine-shop-friendly formats, the shop can use the file to program the CNC for production, rather than use valuable and expensive manual labor to examine every aspect of model provided in STL format.

On Tuesday, December 31, 2019, 11:59:21 PM EST, Serge <moneyforidea@gmail.com> wrote:  

what? 3D Builder shows STL dimensions. Sli3er too. Always. Maybe run
from that fabricator

On 12/31/19, fred via Discuss discuss@lists.openscad.org wrote:

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

Why are they not suitable for CNC? I can use PyCAM to mill 3D parts from an
STL. If they don't like the segmentation and want true curves then
converting STL to STP will not do that.

If they are doing manual fabrication then I can see STL is not good because
you can't drill polygonal holes, etc. So manual fabrication can never
exactly match an STL file.

On Wed, 1 Jan 2020 at 10:53, fred via Discuss discuss@lists.openscad.org
wrote:

I have a friend who worked in a machine shop and eventually (as a youth) became a shop owner. His experience in the industry lasted as many years as I've been alive. I learned quite a bit from him before he retired.
One aspect of the business is that if it's not within certain parameters, it's not a job to be taken. Qualified machinists have no problem getting work. They (he) won't necessarily take on a job that requires new investment in learning programs other than that which is currently in use at the shop.
If the OPs resource has requested .step or .stp files, that shop will not take an STL file in its stead. My answer provides a conversion process, to permit the OP to provide the required file format.
If the OP cared to cast about for a shop that can handle an STL file, I suspect he would not have posted the question.
Regarding my now-retired friend; his requirement was three-view drawings. If a computer file was provided in any format, it had to be DXF and had to be accompanied by at least a PDF or a printed set in order for the job to be accepted. This was because he created the g-code to run the CNC mill. He did not use any intermediate software, although that was attempted in the past. When one has decades of experience writing g-code, even a computer can't do it better!

On Wednesday, January 1, 2020, 6:04:57 AM EST, nop head <nop.head@gmail.com> wrote:  

Why are they not suitable for CNC? I can use PyCAM to mill 3D parts from an STL. If they don't like the segmentation and want true curves then converting STL to STP will not do that. 
If they are doing manual fabrication then I can see STL is not good because you can't drill polygonal holes, etc. So manual fabrication can never exactly match an STL file.
On Wed, 1 Jan 2020 at 10:53, fred via Discuss discuss@lists.openscad.org wrote:

From the reference of a machine shop constructing a part from a drawing, STL files are not suitable, especially if the parts are to be created by a CNC machine. Even though many programs provide bounding box dimensions, I know of no program that could, for example, provide the diameter of a hemisphere mounted on a truncated cone, if the source file is an STL.
By converting a file to .step or .stp or one of a few other machine-shop-friendly formats, the shop can use the file to program the CNC for production, rather than use valuable and expensive manual labor to examine every aspect of model provided in STL format.

On Tuesday, December 31, 2019, 11:59:21 PM EST, Serge <moneyforidea@gmail.com> wrote:  

what? 3D Builder shows STL dimensions. Sli3er too. Always. Maybe run
from that fabricator

On 12/31/19, fred via Discuss discuss@lists.openscad.org wrote:

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

STL. ...

But you know the dimensions and tolerances that you want.  They're not in
the STL.

--
Sent from: http://forum.openscad.org/

Well as there are no tolerances in OpenSCAD how can any file format
generated by it have tolerances?

On Fri, 17 Jan 2020 at 14:33, NateTG nate-openscadforum@pedantic.org
wrote:

Some step files can have tolerances - either global or on a per-part basis.

I guess a dividing line is the quality needed and how professional you need to be.  Military and heavy industrial uses, for example, often have very tight tolerances and if it’s out of spec it fails the quality control and you won’t be paid for the job.  Catia ($25000 /seat) can  include tolerances and step files like this, I think solid works as well.  My 30 year old CNC router is probably accurate to  0.5 millimeter or so (which is pretty sloppy) but I don’t need it to be more accurate than that for anything I’m doing.

A moot point for openscad, as it doesn’t have tolerances in the first place .

I use FreeCAD to convert STL to other formats (usually STEP). Check for
mesh errors and fix, convert the mesh to an object, convert the object to a
solid, export.

On Sat, Jan 18, 2020 at 6:42 AM Ezra Reynolds shadowwynd@gmail.com wrote: