Defining the position of a slot

[Alodine]

I have a puzzlement.

My simple project is a rectsngular piece of plastic 1/4 inch thick. I need to cut some holes and slots in it. The holes and some slots come out fine. One curved slot is a prroblem.

The offending, curved slot cuts as seemingly random holes inside where the slot is defined. I went back to the sketch and noticed it was in orange (Magnitude defined, Position not defined). This is one of the insidious side effects of not fully defining a cut that the tutorials warned about.

So - I am trying to define the position of the slot. I cannot understand how to select the entire slot so as to define its end points. I can select the sides of the slot. I can select the arcs at the end of the slot. . . . but. I am stumped as to how to select the entire slot. I thought I had defined the end points as coincident with a reference circle but I guess that did not occur.

I have attached the part file and two explanatory pdfs for your info.

 

[HaroldL]

The offending, curved slot cuts as seemingly random holes inside where the slot is defined. I went back to the sketch and noticed it was in orange (Magnitude defined, Position not defined).

Fully constrain the two end ref .500 dia circles and that will fully define the slot.


Try adjusting the Facet Resolution in File Properties to smooth out the slot edges.

 

[Joseph_L]

The offending, curved slot cuts as seemingly random holes inside where the slot is defined. I went back to the sketch and noticed it was in orange (Magnitude defined, Position not defined). This is one of the insidious side effects of not fully defining a cut that the tutorials warned about.

I seeing your part, but I'm unable to see what is undesirable, it seems to be working as expected. I turned my graphics way down and made this image:



If you see the slot being made up of a bunch of straight lines, that slot is actually curved but graphics approximate curved surfaces with straight lines (Every CAD platform does this). As HaroldL pointed out, turning up your graphics settings does make it appear more curved.

Please let us know if there is a different issue I didn't find.

 

[Alodine]

Hello to you all.

Thank you for pointing out how to fully define the slot. It worked.

I see the graphics setting you mentioned and I am experimenting with it.

But - neither of those was the problem. See the atached picture of the project cut on my Tormach PC1100. Notice the two slots perfectly formed and the random holes forming what was meant to be the outer slot?

The end mill I used was a 0 .125 diameter. The two correct slots were defined as 0.132 wide while the outer slot was 0.126. The CAM program (Mesh Cam) could not deal with the narrow outer slot and decided to just poke a couple of holes in the defined slot area. No idea why it did that rather than give me a warning. Widening the outer slot solved the problem.

I create some of the oddest problems, don’t I? Hope they keep you interested.

 

[Joseph_L]

Hello to you all.

Thank you for pointing out how to fully define the slot. It worked.

I see the graphics setting you mentioned and I am experimenting with it.

But - neither of those was the problem. See the atached picture of the project cut on my Tormach PC1100. Notice the two slots perfectly formed and the random holes forming what was meant to be the outer slot?

The end mill I used was a 0 .125 diameter. The two correct slots were defined as 0.132 wide while the outer slot was 0.126. The CAM program (Mesh Cam) could not deal with the narrow outer slot and decided to just poke a couple of holes in the defined slot area. No idea why it did that rather than give me a warning. Widening the outer slot solved the problem.

I create some of the oddest problems, don’t I? Hope they keep you interested.

Thanks for the update Alodine. If widening the slot solved the problem, I'm wondering if that was a toolpath issue? I checked the model and the geometry had no reported problems. You're right, you found an interesting problem.

 

[dwc]

I would claim that that is a MeshCam problem.
Or maybe a problem of the file transfer to MeshCam.
I could understand it if MeshCam is really receiving a file with the arcs approximated as straight sections.

 

[DavidJ]

Are you transferring to MeshCAM using STL or STEP? - if STL, the STLE export settings will have an effect. STEP would probably be more straightforward.