Anyone with good Autocad experience?

[Danne]

So I had some watch strap templates laser cut. But something is wrong with the transition between lines and arcs. And it doesn't matter how I do it. Two circles and join and trim, a line and an arc, a polyline that transition into an arc (without snapping) there is a little step at the transition between lines and arcs. And this is visible in preview also, and if I print on paper (Except with like 0.05 in lineweight, because of resolution) Most templates came out really good anyway, this was the worst part, it do look worse than it is because the protective film is a little melted, it's like a 0.2mm step.

The geometry for the lines add up perfect if you look at X/Y on both the lines and arc in my included photos (Keep in mind that start and end is different depending on where I started drawing the line)

Edited January 5, 2023 by Danne

[kgg]

1 hour ago, Danne said:

But something is wrong with the transition between lines and arcs.

It appears that you are doing the arc from the vertical line to the tip of the arc. Have you tried creating the arc from the tip to the vertical line. I don't use your software but use Fusion 360 which is similar. What I would suggest try is to draw a horizontal line halfway between the top of the vertical lines and where the tip of the arc is going to be so as to keep the bend of the arc on the same horizontal line. This also maybe a cause by the laser not being tweaked as good as it needs to be. Just a thought.

kgg

[Danne]

3 minutes ago, kgg said:

It appears that you are doing the arc from the vertical line to the tip of the arc. Have you tried creating the arc from the tip to the vertical line. I don't use your software but use Fusion 360 which is similar. What I would suggest try is to draw a horizontal line halfway between the top of the vertical lines and where the tip of the arc is going to be so as to keep the bend of the arc on the same horizontal line. This also maybe a cause by the laser not being tweaked as good as it needs to be. Just a thought.

kgg

I get what you mean, like the radii would be too large, but on this one I used two circles (see my photo) and I have recreated it and checked  the geometry after trimming and everything is spot on dimension wise. I have drawn many arcs and lines in cad during my years as a lathe programmer, sometimes for more advanced projects, other times when a circle meet a line at an angle and I was to lazy for trigonometry, and never had any problems like this.

[kgg]

15 minutes ago, Danne said:

and never had any problems like this.

I just used my software and doing this using circles gives excellent transition from the vertical lines but using the arc feature can be a problem without using a horizontal guide line to remove a very slight bulge just above the vertical line. I have seen this type of thing occur with my 3 D printers and too solve the problem the printer software needed some tweaking before it gave a nice smooth transition.

kgg

[Danne]

1 minute ago, kgg said:

I just used my software and doing this using circles gives excellent transition from the vertical lines but using the arc feature can be a problem without using a horizontal guide line to remove a very slight bulge just above the vertical line. I have seen this type of thing occur with my 3 D printers and too solve the problem the printer software needed some tweaking before it gave a nice smooth transition.

kgg

Yes, I know what you mean when using the arc function. I find this way quickest and easiest to get the same shape on my points on straps. And it's a good way to avoid that problem you talked about.

I don't think this is a problem with machines, I used a laser cutting service with good reputation, and I mean they have nice fancy industrial laser cutters with servo motors. And I can also see the problem when I print it on paper. I'm not that keen on doing a reinstall of Autocad either, it's always settings you have to do, and you don't remember since it was a long time ago I installed it. Just things that should be simple like plotter calibration, I remember I struggled with that, I forgot to choose the correct calibration file somewhere and it refused to print to correct dimensions length wise lol.

[kgg]

20 minutes ago, Danne said:

Yes, I know what you mean when using the arc function. I find this way quickest and easiest to get the same shape on my points on straps. And it's a good way to avoid that problem you talked about.

I don't think this is a problem with machines, I used a laser cutting service with good reputation, and I mean they have nice fancy industrial laser cutters with servo motors. And I can also see the problem when I print it on paper. I'm not that keen on doing a reinstall of Autocad either, it's always settings you have to do, and you don't remember since it was a long time ago I installed it. Just things that should be simple like plotter calibration, I remember I struggled with that, I forgot to choose the correct calibration file somewhere and it refused to print to correct dimensions length wise lol.

Any software or hardware upgrade is always a royal pain. I just had to change out my C drive and even with a image of the old C drive it was a pain as I also decided to increase the systems memory as well. It's the little things that will get you every time.

kgg

[Danne]

2 minutes ago, kgg said:

Any software or hardware upgrade is always a royal pain. I just had to change out my C drive and even with a image of the old C drive it was a pain as I also decided to increase the systems memory as well. It's the little things that will get you every time.

kgg

Yes exactly. And even though I try to save text documents with instructions for settings, it's always something you forget, and you spend hours trying to remember or google to figure out how to do it (even if it's something simple, if you haven't done it in a long time, then it's easy to forget)

[MikeRock]

Are you talking the difference between a secant intersection and a tangent intersection?

[Danne]

32 minutes ago, MikeRock said:

Are you talking the difference between a secant intersection and a tangent intersection?

This is 100% tangent. But it doesn't show it that way when I preview a print or laser cut.

[Danne]

(I just exploded it and moved the arc section) R22.2 and exactly the same as the two circles beside.

[MikeRock]

Can you just hit the cut out pattern with a bit of 220 grit paper and eliminate that little step?  I can't even see it on the clear plastic pieces.

[Danne]

1 hour ago, MikeRock said:

Can you just hit the cut out pattern with a bit of 220 grit paper and eliminate that little step?  I can't even see it on the clear plastic pieces.

Yes, it's no problem with the templates, I will have to sand the inner edges of the larger parts anyway (they will be used to flush cut straps with padding also, so I have to remove the sharp edge)

And the exterior patterns are cut to the finished dimension, and I will still sand them so they become a little bit more narrow to make room for edge paint.

But I still need to solve this problem, I'm a perfectionist and this doesn't work long term.

[MikeRock]

"But I still need to solve this problem, I'm a perfectionist and this doesn't work long term."

Ah yes......my whole engineering career in those few words... 

God bless