Drawing the smoothest lines: How many segments?

[007lab]

How many line segments in a wavy polyline are too many before one blows up their cnc machine?

I'm trying to draw a wavy line about 15" long. It can't be faceted at all. Very organic looking.

So, I have two questions:
1-It's easiest for me to draw the shape I want with the spline tool. Do I need to convert this line to a polyline when I send the dwg file to the cnc? (The CNC runs on Millwright 6.)
2-When drawing a 15" wavy spline I can convert it to a polyline and then specify the precision from 0-99. Roughly what number along that range would remove faceting, but not bog down the program?

It would be a lot easier to test this out on my own if the shop wasn't 30 minutes away. So unfortunately I can't walk over to the machine and run a test cut.

I'm running autocad for mac 2015.

Here's where it's asking me about the precision:


Would adjusting anything in window #2 (below) improve how smooth the line is cut?


I'll be glad to hear about the easiest way to accomplish this task.

Thanks,
Lee

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[ger21]

How many line segments in a wavy polyline are too many before one blows up their cnc machine?

Depends on the machine.

With some machines, you won't have any trouble setting the precision to 99.
You might want to try using a lower precision, and the Curve Fit the polyline.

The display settings have no effect on output resolution.

[mmoe]

You may also want to call the shop and ask them what they require. If you were coming to me, I'd just tell you to leave it as splines. My software will create lines/arcs with the tolerance I specify off of the original spline curve, which will be far more optimized than anything you would do for me. With a tolerance setting of .01mm in the CAM software, you will not know it wasn't just the actual spline curve when cut. Others may only be able to import an older DXF and will need the spline broken down, but it would be best to do what the shop prefers.

[007lab]

I can convert to polyline without any troubles. Though, I tried the curve fit polyline thing just to see what happens. Unfortunately it changes the original shape quite a bit. I can't do that as I got my original shapes by tracing over a pdf of something I built years back by hand. I got such a good response from it I'd like to recreate it without all the extra work. So, I'm making router templates. I don't want to break out the files and sandpaper for these guys.

I have a feeling that my drawings are going to be ok, and that it's just that we haven't figured out the tolerances/settings in the CAM software to get it to do it's thing. It's running Millwright 6. I think I'm just going to send it to a shop and pay for it to be completed just so I can move one with project. The cnc in my friends shop is free for me to use. So eventually I need to work out the bugs with the software.

Thanks for your response!

[007lab]

It's my friends shop and cnc. It runs Millwright 6. He's still learning what it can do. I think he's had it for 1.5 years now. He can get it to do it's thing with his software. He's using turbo cad pro. Not sure why mine isn't working other than I was using turbocad deluxe 7, and it may be too basic a program to create such fine adjustments. So, I'm about to redraw everything in ACAD 2015 and I want to start out doing the right thing before having to redraw everything for what might be the 9th time.

Called a pro shop today and I'm going to see about their fees and if my existing files are ok, or what I need to do.

"With a tolerance setting of .01mm in the CAM software, you will not know it wasn't just the actual spline curve when cut." I sure appreciate accuracy! For this particular project I'm going for a loose +/- .0625". I work in a shop where the tolerance is +/- .003. Everything always fits. It's very nice. Mortises aren't so tight that they swell and break in warm moist climates.

[mmoe]

It's my friends shop and cnc. It runs Millwright 6. He's still learning what it can do. I think he's had it for 1.5 years now. He can get it to do it's thing with his software. He's using turbo cad pro. Not sure why mine isn't working other than I was using turbocad deluxe 7, and it may be too basic a program to create such fine adjustments. So, I'm about to redraw everything in ACAD 2015 and I want to start out doing the right thing before having to redraw everything for what might be the 9th time.

Called a pro shop today and I'm going to see about their fees and if my existing files are ok, or what I need to do.

"With a tolerance setting of .01mm in the CAM software, you will not know it wasn't just the actual spline curve when cut." I sure appreciate accuracy! For this particular project I'm going for a loose +/- .0625". I work in a shop where the tolerance is +/- .003. Everything always fits. It's very nice. Mortises aren't so tight that they swell and break in warm moist climates.

The tolerance setting in the CAM software can be set to exceed the machine's capability. The effect is that it will keep the tool closer to the drawing geometry, so the facets are reduced, or even eliminated if you set it fine enough. My machine has a practical resolution of closer to +/-.02mm, but you can tell a difference in the quality of the toolpath between setting the tolerance to .02mm and .01mm. I often set the tolerance to .001mm on certain 3d curves and it can really smooth the toolpath out, even if my machine can cut no where near that precisely.

I googled Millwright 6 and it looks like it requires pretty basic DXF files as you were planning to generate. There is a page on their website that gives recommendations for how to export the DXF best for their software. It will need to be an R14 or earlier version. Depending a little on the machine, it may not care how fine you break the splines up, or it may run really choppy. You may just have to give a couple files a shot and see what you get.

[007lab]

It also takes dwg files. He couldn't open the dxf files. I wonder if it reads them differently.

I just exported the turbocad file to dwg and opened it in ACAD 2015. It's faceted in the drawing. :/ I wonder why it looks smooth as butter in tcad but doesn't turn out that way. I'm attaching some screen shots of settings I have available in the original file. There aren't many. Perhaps tweaking one of these would help before I redraw everything?

[bhurts]

There are two settings in autocad that determine what things look like on screen. It's under settings. I'm not sure which tab under settings it is but it's probably the second or third. One of the settings is number of segments in a polyline curve but I can't remember the name of the other. It will be right above the polyline setting. The polyline setting can be as high as 8000 and the other 10000. Hope this helps.

Ben

[ger21]

I would just convert the spline in AutoCAD to the max precision, and export as v12 .dxf

That should give you more than acceptable results.

[007lab]

Regarding the spline-

Do you ever mess with the Degree setting under "Misc." in the properties inspector?

[ger21]

No. Depending on the type of spline, it's often a read only variable.

[007lab]

"Read Only"- does that mean it only affects how one views it on the screen?

[ger21]

No, it means you can't change it.

[007lab]

I see. TY. Studying up as much as I possibly can. If I can't find an explanation or video for something I then consult the forums.

Watching this free set of videos of Autocad for Mac. They're the most helpful I've found:

[victorofga]

cadprograms are using bspline.. I think it doesn't worth to convert either segments or arcs..

newest cadprograms all prepared for higher versions of dxf, which one already can contain splines..

even latest CorelDraw, already using spline beside Bezier..

as Gerry pointed out, there are settings for video, means how it will be displayed, but that setings has no effect on the actual calculation.. it just helps the computer using less video power..

[stucapco]

I would draw over the top of it. Once its acceptable segments will match, over all look will improve, no problem shooting it out to your post processor. I do this all the time in autocad. Just makes life easier.