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Re: [Feature Request] Radial array/polar pattern in Sketcher

Posted: Sat Jul 02, 2022 3:28 pm
by Darktrax
My apologies that I reply to a thread that is months old.

I do perceive the need for a polar array feature withing the sketcher, if only to greatly ease the need to be making many separate repeats of a feature that will be given form when the sketch is padded.

Something as simple as a set of equally sized bolt holes around a common centre. One can laboriously define each hole, and position them. To some degree, one can save effort by making copies, and constraining symmetries. We know that once in the sketch, they instantly appear in the pad.

I am sure there are other ways, but I ran into a tangle of pockets (not wholly successful), and then I tried to make a boolean subtraction of a polar array of cylinders (to make holes), and then I decided I just did not know enough about how best to drive FreeCAD.

Appreciate the power of such a feature when one needs the polar pattern to be rotated some angle about the normal axis. or alter the polar radius. Positioning the holes individually is a chore, even with as few as three or four. The whole reason we have sketches is to be able to put stuff in them instead of having to make external temporary separate objects for boolean operations.

Draft Workbench has such a tool. Is this something one should use the Draft Workbench for?

Re: [Feature Request] Radial array/polar pattern in Sketcher

Posted: Sat Jul 02, 2022 4:00 pm
by Bance
Darktrax wrote: Sat Jul 02, 2022 3:28 pm Something as simple as a set of equally sized bolt holes around a common centre.
Make a sketch of one hole then pocket/hole it and use a polar pattern to repeat it.

Re: [Feature Request] Radial array/polar pattern in Sketcher

Posted: Sat Jul 02, 2022 5:35 pm
by drmacro
Darktrax wrote: Sat Jul 02, 2022 3:28 pm ...
Something as simple as a set of equally sized bolt holes around a common centre. One can laboriously define each hole, and position them. To some degree, one can save effort by making copies, and constraining symmetries. We know that once in the sketch, they instantly appear in the pad.
...
In a sketch, it is far more efficient to create the lowest denominator of any symmetry. It is not only easier to view the sketch, but the constraint scheme is easier and faster. It also makes the sketch easier to maintain and update.

Once one part of the symmetry is sketched and then a Pad/Pocket/etc. is perfomed, then the Polar Pattern can be used.

chrisb recounted a lecture from his past: "Concerning usage of simple sketches, there was the 7-7-7 rule from an old Pro/E teacher, saying a sketch should either have 7 elements or have 7 dimensions or take 7 minutes to build."

;)

Re: [Feature Request] Radial array/polar pattern in Sketcher

Posted: Sat Aug 27, 2022 4:57 pm
by steve123
In my experience, from a performance perspective, it is much more efficient to create a large array of elements in a sketch and then pad or pocket them than it is to create a smaller number and use the pattern tools.

For example, pocketing 144 holes into a slab takes less than a second to render when the 144 holes are defined in a sketch. If I create a part with 12 holes, pocket it and then use the multi transform tool to apply a mirror and polar pattern, it takes a several seconds to render the result. The problem gets worse when the "hole" is not a simple cylinder; for instance, a slot. This type of feature, in my experience, can take a minute or longer to render using the pattern tools rendering this method almost unusable.

Re: [Feature Request] Radial array/polar pattern in Sketcher

Posted: Sat Aug 27, 2022 5:12 pm
by user1234
steve123 wrote: Sat Aug 27, 2022 4:57 pm In my experience, from a performance perspective, it is much more efficient to create a large array of elements in a sketch and then pad or pocket them than it is to create a smaller number and use the pattern tools.
Then update FreeCAD. Here with PartDesign Pattern 144 holes <0.5s. Besides that, it makes no sense (hidden arrays are bad practice).

Greetings
user1234

Re: [Feature Request] Radial array/polar pattern in Sketcher

Posted: Sat Aug 27, 2022 5:54 pm
by steve123
Another issue I have run into is that the pattern tools often fail to fuse the resulting geometry properly due to a bug in OCC that does not handle coincident faces.

Re: [Feature Request] Radial array/polar pattern in Sketcher

Posted: Sat Aug 27, 2022 5:56 pm
by user1234
steve123 wrote: Sat Aug 27, 2022 5:54 pm Another issue I have run into is that the pattern tools often fail to fuse the resulting geometry properly due to a bug in OCC that does not handle coincident faces.
Without a file and a good description (see red banner above) this statement is invalid. Most of the time it is an user error.

Greetings
user1234

Re: [Feature Request] Radial array/polar pattern in Sketcher

Posted: Sat Aug 27, 2022 6:01 pm
by steve123
Here is an example of the fuse problem.

This takes about 18.5 seconds to render if there is a change to the hole geometry.

Re: [Feature Request] Radial array/polar pattern in Sketcher

Posted: Sat Aug 27, 2022 6:04 pm
by steve123
Here is the file if you would like to have a look.

Re: [Feature Request] Radial array/polar pattern in Sketcher

Posted: Sat Aug 27, 2022 6:05 pm
by steve123
The bug in OCC is known.