newbie stuck trying to make pocket with complex face

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jswild
Posts: 12
Joined: Fri Mar 10, 2017 10:13 pm

newbie stuck trying to make pocket with complex face

Post by jswild »

Hi;
I'm brand new, but learning fairly quickly, I think. In my project I have created a 2x4 42 " long and now i want to carve out a piece of it to accept a piece of dowel. The slot for the dowel has to be sloped down. I've created an outline of the slot I want with two circles and a parallelogram drawn with sides tangent to the circles. You probably have to look at my project (attached) to understand what I mean.

The problem is, after I have finished the sketch of the slot and try to do a pocket operation, it says "Failed to validate broken face". So, I guess I have to assemble the parallelogram and the circle at its end into a single polygon defining a face. I tried Part | Loft, but it only tells me that I have to have at least two vertices, edges, wires or faces selected, but I think I have selected the whole sketch with its circles and the parallelogram. But Loft seems to be more than what I want anyway.

So I tried the wire assembly tool in Draft, but that doesn't seem to have changed anything, Pocket still can't validate the broken face.

Would one of you kind souls point me in the right direction? There may be a completely different way to get my slot done, I'm willing to abandon my current path for one that works.

Thanks,

Jim

Here's my technical data.

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.16.6706 (Git)
Build type: Release
Branch: releases/FreeCAD-0-16
Hash: f86a4e411ff7848dea98d7242f43b7774bee8fa0
Python version: 2.7.8
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17
Attachments
FreeCAD Stand.FCStd
(8.18 KiB) Downloaded 25 times
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NormandC
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Posts: 18587
Joined: Sat Feb 06, 2010 9:52 pm
Location: Québec, Canada

Re: newbie stuck trying to make pocket with complex face

Post by NormandC »

Hello Jim,

Welcome to the forum.

To create a pad or a pocket, internally FreeCAD needs to build a face from the profile contained in the sketch. To create a valid face, there must be an uninterrupted outer profile with no other geometry crossing it. The problem in your sketch is that the rectangle is crossed by the two circles.

What is the purpose of the two circles? Are they there only for positioning the rectangle? If so, you need to turn them into construction geometry. Construction geometry is ignored in face creation so this will fix this.

Select both circles, then click on Image Sketcher ConstructionMode.
jswild
Posts: 12
Joined: Fri Mar 10, 2017 10:13 pm

Re: newbie stuck trying to make pocket with complex face

Post by jswild »

Thanks for replying, Normand. The two circles represent the cross section of the dowel that will rest in the slot. The higher one at the right edge of the 2x4 is just a construction object as you suggest. The one at the end of the rectangle is both a construction object and a "real" object; that is, I need the semicircular end on the slot I am trying to make.

So, I thought I would make both circles into construction geometry and then add a semi-circle to the end of the rectangle overlaying the construction geometry. Will the internal squared off end of the rectangle (which appears as a diagonal of the circle) be a problem?

I would have gone ahead and tried all this instead of writing back to you except that I cannot change the circles to construction geometry. I have gone into the sketcher workbench, selected one of the circles and I can see the tool I want to use, but it is greyed out. Is that because I created everything in Part Design, not Sketcher? It isn't very much work so I could redo it in Sketcher.

Thanks,

Jim
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NormandC
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Joined: Sat Feb 06, 2010 9:52 pm
Location: Québec, Canada

Re: newbie stuck trying to make pocket with complex face

Post by NormandC »

jswild wrote:So, I thought I would make both circles into construction geometry and then add a semi-circle to the end of the rectangle overlaying the construction geometry. Will the internal squared off end of the rectangle (which appears as a diagonal of the circle) be a problem?
Yes, if you do not delete the line or turn it into construction geometry, because having a semi-circle and a line at the same time, FreeCAD cannot determine which is supposed to be used for the outline.
jswild wrote: I have gone into the sketcher workbench, selected one of the circles and I can see the tool I want to use, but it is greyed out. Is that because I created everything in Part Design, not Sketcher?
This is irrelevant. The PartDesign workbench includes all tools from the Sketcher for convenience, having one workbench or the other active makes no difference.

But to use Sketcher tools, you do need to be in the Sketch editing mode. Did you do that? Double-click on the sketch label in the model tree, or right-click on it and select "Edit sketch" in the contextual menu.
jswild
Posts: 12
Joined: Fri Mar 10, 2017 10:13 pm

Re: newbie stuck trying to make pocket with complex face

Post by jswild »

Everything worked! I now have my piece with the slot I need. I just have to create a second one just the same except with the slot angle up from the outside edge, but I can do that by just following the same method.

I'm very grateful, Normand.

Perhaps you could comment on my method of proceeding with the project. I intend to create each of the elements of the final project as a part in its own file then create a final file to import the parts into and assemble together. Something I read suggested doing this and making each part into a "simple object" (correct term?) before importing it into the assembly file. But maybe this method makes more sense when you have large projects which use the same parts many times. In my case, each part is different.

To give you an idea of what I am designing, it is a needlework stand. There will be two vertical pieces like the one you have seen parallel to each other and a 1 3/8" dowel fitted into the slots and extending about 3 feet off to one side. This dowel has two half inch dowels 15" long inserted perpendicularly into it and each of these has a small 1/4" dowel 1 1/2" long inserted perpendicularly into its end. The needlepoint frame sits on the two 1/2" dowels and is held from siding off by the two tiny dowels. To vary the angle at which the frame rests in front of the worker, the main dowel will rotate in the grooves. Its angle of rotation ill be controlled with a 6" diameter pulley fixed to the main dowel and positioned between the two main uprights. A chain on the pulley will be held by a hook lower down on the stand and, as the chain is hooked by different links along its length, the angle of the main dowel can be set. The base of the stand will be a board which cannot extend very far under the overhanging main dowel because it will not fit under my chair. Therefore, the stand itself, uprights and base and brace between the uprights has to be massive enough to keep the whole thing from tipping over under the weight of the needlework frame. So, I'm thinking of building it out of 2" thick lumber of some particularly dense hardwood, like wenge, or purpleheart.

Thanks for your kind introduction to the FreeCAD user forum.

Jim
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