I have a part (Leg_Base_Right) that I have built with the Part Design WB and I need to place a pocket on a face. Because of the Topo Naming problem, I have learned to stick with using datum planes vice using faces for sketch supports. The problem in this case is that I cannot seem to get the datum plane to line up with the face. Here is an image of the misalignment and a close up:
The angle seems to be off by 1.4 degrees (based on when I just adjust the angle by hand) which does not seem to correlate to anything. The angle is an expression pulling the angle from Sketch016 where I have the offset angle being calculated by the solver and stored as a reference constraint. Because of that, I assumed that the angle of the datum plane would always line up without failure. Here is an image of Sketch016.
The 23.2 degree angle in red in the sketch is the "offset_angle" and then the 0.328 is the "center_support_offset_x" and the -2.4206 is the "center_support_offset_y". All of the properties for the datum plane are:
I have been messing with this all night and cannot figure out why the plane does not line up with the part face.
I have also attached the FCStd file here.
@chrisb: I had posted a different question about the cyclic dep issue in the expression engine. To try to systematically remove that I took out the intermediate storage and calculation of things in the spreadsheet so there should be no more cyclic issues.
Thanks for any help on this. This is driving me crazy.
File originally started in the 0.20 weekly's but has been most recently saved in the current stable 0.19.1 for MacOS and I am using MacOS 11.2.3
Cannot Get Datum Plane To Line Up
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Cannot Get Datum Plane To Line Up
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- TableSave.FCStd
- (251.69 KiB) Downloaded 34 times
Re: Cannot Get Datum Plane To Line Up
90deg - 68.2deg = 21.8 deg (face I am assuming you are trying to align to?)
<<Sketch016>>.Constraints.offset_angle = 23.2deg (datum plane angle)
no wonder than 23.2deg - 21.8deg = 1.4deg misalignment ???
unless I got what you are trying to do entirely wrong?
<<Sketch016>>.Constraints.offset_angle = 23.2deg (datum plane angle)
no wonder than 23.2deg - 21.8deg = 1.4deg misalignment ???
unless I got what you are trying to do entirely wrong?
Re: Cannot Get Datum Plane To Line Up
Umm. Yea... you are correct.
Thanks for that.
Thanks for that.
Re: Cannot Get Datum Plane To Line Up
This is better done with an appropriate attachment.
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- TableSave_cb.FCStd
- (197.81 KiB) Downloaded 35 times
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- SnipScreenshot-661889.png (10.99 KiB) Viewed 921 times
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
Re: Cannot Get Datum Plane To Line Up
using the same mapping mode for the sketch directly, without additional (not needed) plane?
Re: Cannot Get Datum Plane To Line Up
@chrisb: Thanks for the pointer. I will check out that document. Looks like it has a lot of gold in it. Does what your suggesting compensate for the Topo naming issue that I was trying to avoid? I have tried to avoid this by only ever attaching to the base coordinate system for the part and never referencing anything other than a sketch.
Re: Cannot Get Datum Plane To Line Up
To a good extent, yes, but if you add or delete geometric elements in the sketch it may still fail. So your approach is indeed even more stable.
Bambuko is right with omitting the DatumPlane. I use DatumPlanes only if I attach more than one sketch to them.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
Re: Cannot Get Datum Plane To Line Up
Hi justacec, Greetings to the Community!
I was reading the section of this forum and I came across the problem, after careful analysis of the references (I do not go into the merits of the correctness of the modeling workflow) I noticed an incorrect definition of the angle that determines the inclination of DatumPlane001 on the face assigned.
The following images demonstrate the error.
Beware it is very difficult for FreeCad to make mistakes in these trivial geometric calculations rather it is easier for us to make mistakes, after all he does what we tell him to do (almost never the opposite), so I always recommend not giving up but checking carefully (maybe sipping a cup of tea) inputs, this is what makes us grow technically and appreciate this wonderful software more and more.
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- errata_Constraints.png (239.9 KiB) Viewed 826 times
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- correct_Constraints.png (133.41 KiB) Viewed 826 times