Editing parts from assembly in STEP-format

[jehojakim]

Hi,

First of all, happy new year to you all, and of course special thanks to all the devs that made Freecad such a splendid program! Hope covid won't spoil this year too much...

On topic: I've ordered a Ratrig Killerbee CNC machine (it is a kit to be assembled). Ratrig (the firm) offers a drawing of the machine in Fusion-360 format, and from there I downloaded the .stp-format of it.

Besides the fact it is rather big (the saved .FCStd-file is 320MB), and my pc has a tough job playing around with it, this goes fine: I can see the assembly in the 3d-view, and can select the individual parts in both the 3d-view and the combo-view.

But I can't find a way to edit the individual parts (obviously, there are no Sketcher, Pad or such commands in the combo view). Also the constraints are not given in the combo-view, which again comes to no surprise.
Yet, because the file is for the 750*750 mm version of the machine, and I ordered the 1500*1500 mm version, I would like to be able to edit (some of the) parts.
Is there a way to do that?

My FreeCAD-version:

OS: openSUSE Tumbleweed (KDE//usr/share/xsessions/plasma5)
Word size of FreeCAD: 64-bit
Version: 0.20.26306 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 6701788)
Hash: 670178869ecdca52f7dcd332c513cb0c82b25cce
Python version: 3.9.7
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.3
Locale: Dutch/Netherlands (nl_NL)

[chrisb]

The Step file has no history, so no constraints or such. Thus you can not change the existing things, but you can use them in Part Booleans or just as they are as BaseFeatures in a PartDesign body and continue modeling with additional features.

[thomas-neemann]

...there are no Sketcher, Pad or such commands in the combo view)....

if the date is also available as inventor .ipt, the sketches could be included. these files can be imported with the add-on wb like invetor


edit

example

https://www.youtube.com/watch?v=q2jTAztKb_8

phpBB [video]

[jehojakim]

Thanks for your reply. But I'm afraid I'm not sure I understand what you mean, or, how I can applie it to my case. I've read the doc's on Boolean, but how can I use that procedure to the parts in the assembly, in order to get the correct dimensions?

As an example, I add one of the more than 1000 parts in the assembly.

[jehojakim]

...there are no Sketcher, Pad or such commands in the combo view)....

if the date is also available as inventor .ipt, the sketches could be included. these files can be imported with the add-on wb like invetor


edit

example

https://www.youtube.com/watch?v=q2jTAztKb_8

phpBB [video]

There is indeed a version called Inventor 2021. When downloaded, it comes as a zip-file, in which all the individual parts are .ipt-files. I followed your example video, which is somewhat fast, but clear; thanks.
When I import one of the .ipt-files with this new wb, using the "nativ" mode,I get the document name in the combo view, but no data except the label, and no object in the 3d-view.
In the other two modes I get the form in the 3d-view, and positional data in the data tab of the combo-view, but no dimensional data.

[thomas-neemann]

.... but no data except the label, and no object in the 3d-view.
...

that's a shame, I've already experienced something like that, apparently not files that are generated directly from inventor, but via converters.

here are examples of how to modify files in feecad srep


https://www.youtube.com/watch?v=_00RtoXmAXo

phpBB [video]

https://www.youtube.com/watch?v=ivZ3yb3I7Hs

phpBB [video]

https://www.youtube.com/watch?v=GpM3AMPXpDY

phpBB [video]

[jehojakim]

Thanks for your reply and videos.

But it virtually impossible to do applie that on the more than 1000 parts in the original drawing....

regards, jehojakim

[jmaustpc]

But it virtually impossible to do applie that on the more than 1000 parts in the original drawing....

You could split the assembly components into different files if the assembly is so big that it is too slow to work with. If the file is complex enough, you will eventually get to the point where you run out of memory in your computer.


You don't appear to understand that a STEP file is not an editable format, it just contains dumb solids, not directly editable components each if which are dumb not editable solids. However once the dumb solids are imported into FreeCAD, you can edit them by using one of the workbenches that work with solids. In Part WB that means use one of the solids in a boolean operation with any other solid that you add to the file, eg. If you want a hole through one the add an appropriate cylinder and use it to out the hole. In Partdesign WB, you would use the STEP file's solid as a base solid in a Body then attach a sketch to it then Pad a lump to it or pocket a hole in it.

This is what Chris told you above.

There are some defeaturing tools that can help in some limited cases.

[jehojakim]

You could split the assembly components into different files if the assembly is so big that it is too slow to work with. If the file is complex enough, you will eventually get to the point where you run out of memory in your computer.

While indeed some operations can be slow in this project, that is not the problem I meant to state here. With FreeCAD at the moment (the killerbee file open) using some 5.5 GB of the 64 available I don't think it will be running out of memory quickly, and the responsiveness is quite acceptable.

What I meant to say is about the labour converting all the 1000 items by hand into parts with the dimensional (constraint) data present. A amount of labour not feasible in my personal situation, and not worthwhile the goal.

So I hoped there would be a possibility to do that automagically, (after all, FreeCAD can show each part in the 3-d view window, with all correct dimensions), but there seems to be none.

You don't appear to understand that a STEP file is not an editable format, it just contains dumb solids, not directly editable components each if which are dumb not editable solids.

Well, I think I understand that. I'm less sure I understand the boolean operations suggested by Chris. I think I do understand what boolean operations in Freecad are and how to use them, but it is less clear to me how it helps me with my problem.

Unless I misunderstand this too, tackling the problem from within the Part Design WB seems redrawing the component based on the step-solid, measuring the all the distances in the step-solid first. Maybe I miss the point here completely, but otherwise it is a workflow that is practically impossible to apply to over 1000 parts...

Thanks for your replies!

best regards, jehojakim

[thomas-neemann]

So far I've only needed step files to reference or change parts of it. I haven't needed everything as Freecad geometry yet.