Last night I tried an experiment.
I have a master sketch for the top half of an instrument case and have padded it and pocketed grooves for the front and rear panels.
The top and bottom halves of the case are similar but not identical. I have abandoned my original idea of essentially copying the top, inverting it and making the necessary changes as a bit more complicated than I would like in this beginner's document.
I have read where you should complete a sketch before you start using it, and I can see how geometric changes could break things based on it, but I wondered if it was safe add the lines for the bottom half of the case provided I didn't alter the existing top sketch. I could then proceed to model the bottom half, and all the information would be there to model the front and rear panels without using Mirror which I would like to leave out of this document.
I finished the sketch and looked at the existing model only to find that the first pad that formed the case top was undamaged, but the sketch on a datum plane referenced to the XZ plane for the pocket for the front slot has been destroyed, as has the sketch for the rear pocket which is also on a datum plane referenced to the XZ plane.
My questions are:
1 Is this to be expected? (in which case I can use this as an example of what can happen when you make changes to a sketch that has been used).
2 Is it likely to be something I did, although I am sure I didn't alter the already used part of the sketch other than to add coincident constraints where the old and new meet? (in which case I might be able to explain the cause of the damage, or just forget about it)
3 Is it something that shouldn't happen? (in which case I will have to leave the problem to a developer)
I'm not asking for advice on how to fix the problem I have created because that is out of the scope of my document.
I could delete what I have done on the first part of the sketch and develop the top again on the new master sketch, and then develop the bottom, but a beginner won't want to start again.
If what I have done is wrong, I will go back to my previous version where the top is good and add a second master sketch for the bottom half. This way a beginner can keep going forward even if it isn't the best way to do things.
I am (stupidly) thinking of a follow-up document that starts from the beginning again and explaining better ways to do things as I learn them. (I'm also vaguely thinking of an even more advanced document but I have to make this one successful first.)
One other thing I will mention is that I purposely left one vertex not coincidentally constrained by auto constraints, but so close that it wasn't noticeable. I was going to show and fix this as the last DOF.
When I got to one DOF, I found that it wasn't my deliberate mistake (it had been fixed???), but a line on the opposite side of the sketch I was sure I had made parallel to another line, wasn't.
It is possible I failed to select that line when I selected three others and applied a parallel constraint, but I did not fix my deliberate mistake.
I now have to go and pack my car and trailer ready to go to an antique machinery rally tomorrow. I will be back to this early next week.
OS: Windows 10 (10.0)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.17352 (Git)
Build type: Release
Python version: 3.6.8
Qt version: 5.12.1
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/Australia (en_AU)
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