problem with disappearing pads

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tmoore
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Location: Bordeaux, France
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problem with disappearing pads

Post by tmoore »

Hello,
I've created a simple sketch, padded it, created another sketch based on a face from the first pad, then padded the second sketch. The second pad seems to be invisible unless it overlaps some geometry from the first pad. I've seen another manifestation of the problem in which creating the second pad causes the first one to disappear. Am I doing anything obviously wrong?

Thanks,
Tim

OS: "Fedora release 19 (Schrödinger’s Cat)"
Platform: 64-bit
Version: 0.14.3398 (Git)
Branch: master
Hash: 95bda087643493a7e31e9cf507f1041fd446c4c7
Python version: 2.7.5
Qt version: 4.8.5
Coin version: 2.5.0
SoQt version: 1.5.0
OCC version: 6.7.0
Attachments
sketch-bug.fcstd
(7.53 KiB) Downloaded 83 times
triplus
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Re: problem with disappearing pads

Post by triplus »

Technically speaking if i am not mistaken FreeCAD could allow you to do that but it was intentionally done like this. I am not 100% sure why but my basic understanding/explanation of what you are asking would be:

Simply put you are modelling single part and for that to happen there has to be "connection" between all features you add to form a single part. If there is no connection you basically end up with two or more separate parts and placing individual parts in 3D space with relations to one another is the task for forthcoming Assembly Workbench. For now if you want two separate parts you have to do them manually and position them in 3D space manually too. Without relations.
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bejant
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Re: problem with disappearing pads

Post by bejant »

Greetings tmoore,
To add to triplus' explanation:
The problem is that there is nothing contiguous between Pad and Sketch001. In other words, Sketch 001 is off in space; here's a view of both Sketches looking down from the top:
20140409c_tmoore.jpg
20140409c_tmoore.jpg (5.08 KiB) Viewed 3847 times

Try this:
Select Pad001 in the tree view and delete it.
Select Pad from the tree view and make it visible by pressing Spacebar.
Select the top face of Pad and it will turn green.
Select the Map Sketch to Face Tool:
Image
From the popup menu select "Sketch001", then click OK or Close.
Double-click Sketch001 to edit it (or right-click, then select Edit)
Change the Vertical Distance Constraint to something like 5 mm by double-clicking on it in the 3d window or the constraints window,
Now a portion of the circle is over Pad,
From the Tasks tab select Pad, you'll end up with something like this:
20140409d_tmoore.jpg
20140409d_tmoore.jpg (6.24 KiB) Viewed 3847 times
OS: Windows XP
Platform: 32-bit
Version: 0.14.2370 (Git)
Branch: master
Hash: a836759ebd91404954a778ff8885e152611576e1
Python version: 2.6.2
Qt version: 4.5.2
Coin version: 3.1.0
SoQt version: 1.4.1
OCC version: 6.5.1
Attachments
20140409b_tmoore.FCStd
(13.37 KiB) Downloaded 84 times
tmoore
Posts: 8
Joined: Sat Mar 01, 2014 11:44 pm
Location: Bordeaux, France
Contact:

Re: problem with disappearing pads

Post by tmoore »

Fair enough, though not very intuitive. I was trying to create some reference geometry on which to base other sketches and thought it would be easier to eventually cut it away if it was detached from the model.

Is there a plan to get datum planes into 0.14, even without the rest of the assembly stuff?

Tim
triplus
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Re: problem with disappearing pads

Post by triplus »

Is there a plan to get datum planes into 0.14, even without the rest of the assembly stuff?
In my opinion if FreeCAD 0.14 would happen without including Assembly Workbench that would already happen.
Fair enough, though not very intuitive. I was trying to create some reference geometry on which to base other sketches and thought it would be easier to eventually cut it away if it was detached from the model.
Well i would say this is possible in some limited scenarios ATM but for now focus on producing individual parts that are later manually and without reference positioned in 3D space to form assembly with other parts.
jmaustpc
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Location: Australia

Re: problem with disappearing pads

Post by jmaustpc »

Tim
Just to be clear, PartDesign workbench is originally intended, and designed, to make one single solid. This does not apply to all FreeCAD. Just PartDesign WorkBench. One of the other's might have said that already, I might have missed it. The idea is that the Assembly workbench will (when it exists) then be used to assemble these single solids into a complete model. There are now exceptions to this behaviour. :)

Jim
tmoore
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Location: Bordeaux, France
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Re: problem with disappearing pads

Post by tmoore »

jmaustpc wrote:Tim
Just to be clear, PartDesign workbench is originally intended, and designed, to make one single solid. This does not apply to all FreeCAD. Just PartDesign WorkBench. One of the other's might have said that already, I might have missed it. The idea is that the Assembly workbench will (when it exists) then be used to assemble these single solids into a complete model. There are now exceptions to this behaviour. :)
Jim
I understand that eventually the part made with PartDesign is intended to be a single solid, but it is awkward that this needs to be true at all stages of the construction of the part.

If I understand the documentation of http://www.freecadweb.org/wiki/index.ph ... r_External, it shows a case where an external edge is brought into a sketch from an object that is clearly separated from the body that contains the face on which the sketch is based. I can believe that the behavior might be different between objects severed by a pocket operation from the "principal body" and those created de novo by a pad operation, but I would think that users would find the distinction quite confusing.

Tim
jmaustpc
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Location: Australia

Re: problem with disappearing pads

Post by jmaustpc »

tmoore wrote:If I understand the documentation of http://www.freecadweb.org/wiki/index.ph ... r_External, it shows a case where an external edge is brought into a sketch from an object that is clearly separated from the body that contains the face on which the sketch is based. I can believe that the behavior might be different between objects severed by a pocket operation from the "principal body" and those created de novo by a pad operation, but I would think that users would find the distinction quite confusing.
That wiki page needs a bit of attention, its not totally accurate. It was not written by one of the main developers.

If you stick to the rule that PartDesign must make one single solid you should avoid most problems. If you want something else, then usually its best to look at how that could be accomplished with a different workbench or combinations of workbenches.

For example you can use construction lines in Draft WB to position solids with Draft Move and snapping but it will not be parametric.
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