Sketch Won't Create A Hole

[ChipsNChips]

Info: FreeCAD 0.20.1 under Windows 10.

I have a disk shaped model with one threaded hole in the center and a round groove on one side.

ToolCarouselBaseGrooveTool02.jpg (231.84 KiB) Viewed 872 times

I want to add six holes to make spokes to save plastic when I print it. So I have created a sketch with two straight sides and an arc. They are all joined with 0.5" radius fillets.

ToolCarouselBaseGrooveTool03.jpg (283.18 KiB) Viewed 872 times

The two fillets at the top and right were added as fillets. So I am reasonably sure they are OK. The fillet at the bottom-left was constructed as an arc. The coordinates for the straight lines were calculated separately (to five decimal places) and they were the first elements to be drawn and constrained. One is horizontal and the other is at 60 degrees. I did not deliberately over constrain them. I drew lines from the ends of the two lines and constrained them perpendicular to them. Then I found the intersection of those two lines and that became the center of my arc. Using that center I drew the arc from one line end to the other - or so I hope. The end points did change color when I clicked on them. But when I exit the Sketcher and try to use the sketch to make a hole, it does not work.

I had previously tried to construct that third fillet with the fillet tool, but that was a no go. Probably because the lines did not meet. Is there a way to make an arc tangent to both of those lines after using the three point arc tool to attach it to them?

I do not know how to find out if two lines actually meet - their end points being coincident or not. Nor could I see a way to add a fillet to two lines that did not actually meet.

My file is too large to attach. Here is a link to it.

https://www.dropbox.com/s/wjyyzz6ffde2s ... FCStd?dl=0

[Bance]

Click the reversed button or change the value in the properties tab.

When looking at a sketch as drawn, Pad is out of the screen, Pocket is into the screen.

It is not a good idea to model threads, they are computationally intensive, the file you posted is too large because of it (at least for posting to the forum switch it off.)

Like I said, forget what you think you know about CAD, calculating

The coordinates for the straight lines were calculated separately (to five decimal places) and they were the first elements to be drawn and constrained.

a thing like this is completely redundant.

[Shalmeneser]

1) Info: FreeCAD 0.20.1 under Windows 10.
2) The fillet at the bottom-left was constructed as an arc.
3) The coordinates for the straight lines were calculated separately (to five decimal places) and they were the first elements to be drawn and constrained.
4) One is horizontal and the other is at 60 degrees. I did not deliberately over constrain them.
5) But when I exit the Sketcher and try to use the sketch to make a hole, it does not work.
6) I had previously tried to construct that third fillet with the fillet tool, but that was a no go. Probably because the lines did not meet. Is there a way to make an arc tangent to both of those lines after using the three point arc tool to attach it to them?
7) My file is too large to attach. Here is a link to it.

1) FULL info is not this : follow link in the red banner
7) Your file should not be so heavy. Your Hole has a problem.
the hole depth should be minimal (I think threading void add weigth) :

Code: Select all

pad.length

2) Why not fillet tool ?
3) Sketcher is your friend. It can do calculus for you. 5 decimals is too much.
4) Why not constrain them ? Trying to fully constrain a sketch can give clues to construction problem of this sketch.
5) I think the problem is coming from the Hole feature.
6) Sketcher_ConstrainTangent ?

Do you know TNP ? Do not sketch upon face ! Moreover if you are threading upstream !

[Shalmeneser]

Btw, You should never set dimensions relative to a fillet. You should be able to modify the fillet dimension without modifying anything else !

[ChipsNChips]

I did not set any dimensions relative to a fillet. The two lines were set relative to the origin and at the desired angles. The arc was drawn between the two lines and using the origin as it's center. So I am curious as to where you see this.

If any of the dimensions on my model are set based on any of the fillets or on the shorter arc near the origin, I did not do it. Could FreeCAD have made such a change?

Btw, You should never set dimensions relative to a fillet. You should be able to modify the fillet dimension without modifying anything else !

[ChipsNChips]

In red below:

Click the reversed button or change the value in the properties tab.

I don't understand what this does. What "reversed button"? Where is it? And what value? Again, where is that "properties tab".

When looking at a sketch as drawn, Pad is out of the screen, Pocket is into the screen.

OK, so how does this apply to my situation. I was sketching on the X-Y plane, which coincides with the bottom of my part. Shouldn't it cut a hole from that position?

It is not a good idea to model threads, they are computationally intensive, the file you posted is too large because of it (at least for posting to the forum switch it off.)

Yes, I found that out after adding that single thread. I am glad I didn't add a dozen.

Like I said, forget what you think you know about CAD, calculating

The coordinates for the straight lines were calculated separately (to five decimal places) and they were the first elements to be drawn and constrained.

a thing like this is completely redundant.

OK, if calculating the position of those lines is COMPLETELY REDUNDANT, then please explain just how I should have found the constraints for them. I wanted 0 and 60 degrees. I wanted them parallel to two radials from the origin. I wanted them to leave a 3/4" central hub AFTER adding the 1/2" fillet between them. And they needed to end 2.5" from the origin were they meet the arc with that radius. I can draw them in a rough manner as FreeCAD seems to want us to do. That is no problem: less than 10 seconds of work. Then I can apply restraints. But WHAT constraints do you suggest and in what order so they wind up meeting the above conditions?

It is easy to say that I am doing it wrong. I already know that. It is easy to say that I must change my thinking. Again, I know that and am trying to do so. I selected what I thought would be an easy first project so I could start learning. I expected all of this before I selected FreeCAD for my 3D CAD. But some actual details as to how to do this particular task would really be appreciated.

[GeneFC]

Your sketch may not be the ultimate in efficiency, but it will work fine for this purpose.

The only thing you need to do is what Bance said.

Reverse the direction of the pocket. Depending on your settings you may need to increase the depth of the pocket or change to through all.

Do a polar array on the pocket you just created and you should be done.

I know the rules, and a fair amount of the time I still need to reverse the direction of pockets and pads. It is not always easy to picture exactly what will happen, especially when working in planes other than x-y.

Gene

[ChipsNChips]

In RED below:

1) Info: FreeCAD 0.20.1 under Windows 10.
2) The fillet at the bottom-left was constructed as an arc.
3) The coordinates for the straight lines were calculated separately (to five decimal places) and they were the first elements to be drawn and constrained.
4) One is horizontal and the other is at 60 degrees. I did not deliberately over constrain them.
5) But when I exit the Sketcher and try to use the sketch to make a hole, it does not work.
6) I had previously tried to construct that third fillet with the fillet tool, but that was a no go. Probably because the lines did not meet. Is there a way to make an arc tangent to both of those lines after using the three point arc tool to attach it to them?
7) My file is too large to attach. Here is a link to it.

1) FULL info is not this : follow link in the red banner

OK.

Code: Select all

OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.20.1.29410 (Git)
Build type: Release
Branch: releases/FreeCAD-0-20
Hash: f5d13554ecc7a456fb6e970568ae5c74ba727563
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.3
Locale: English/United States (en_US)
Installed mods: 
  * Help 1.0.3
  * lattice2 1.0.0

I hope that is enough. Or am I missing something else?

7) Your file should not be so heavy. Your Hole has a problem.
the hole depth should be minimal (I think threading void add weigth) :

Code: Select all

pad.length

I am going to back up and start again at a point where the center hole has not been added. Then I will leave the thread for the last feature that I add. Lesson learned. Second lesson: I need a faster computer.

2) Why not fillet tool ?

I had tried the fillet tool after drawing the two lines. It does not seem to work if the lines do not meet. So I thought that an arc would work: apparently not. If I don't get a better suggestion, I am going to try starting with the two lines meeting at a point and also meeting the outside arc. I hope that will work better.

3) Sketcher is your friend. It can do calculus for you. 5 decimals is too much.
4) Why not constrain them ? Trying to fully constrain a sketch can give clues to construction problem of this sketch.

I checked after adding each and did have both line and the outside arc fully constrained. Later, after adding the fillets FastCAD was reporting that the sketch was over constrained. I still do not understand how that happened.

5) I think the problem is coming from the Hole feature.

How could that be? OK, perhaps I will eliminate that hole before I try again with the pie shaped holes.

6) Sketcher_ConstrainTangent ?

I will check this out before starting again on the model.

Do you know TNP ? Do not sketch upon face ! Moreover if you are threading upstream !

I have read about the TNP problem. I don't understand why FreeCAD does not have Construction Planes like Fusion360 uses. I am not a programmer, but to me it seems that they help a lot with this. Anyway, so far, all my sketches have been on one of the three planes: X-Y, X-Z, or Y-Z. I planned on that before starting on this model.

I do not totally understand you comment about threading upstream. My present intention is to leave the thread for the last feature that I will add. I hope that helps.

[GeneFC]

In RED below:

Please stop with the red.

It is very hard to read.

Gene

[chrisb]

In RED below:

Follow the IMPORTANT link above and read how and what to quote.