Arcs Drawing as Crude Lines

Arcs Drawing as Crude Lines

Postby conundrumdg » Sun May 22, 2016 10:32 pm

If I draw a page of circles they come out just fine but if I stretch them then the G-Code turns into lines and the oval becomes a series of lines and is no longer an arc. I am using the latest Aspire 8.024 and have been for about 2 years. I never noticed this before but I've recently upgraded my CNC and moved from Mach3 to UCCNC. I am still using the Mach2/3 Arcs (inch) post processor as I always have. I thought it might be UCCNC but when I look at the G-Code it appears that it's Aspire that is the issue. All my fonts now are coming out blocky as well. For example, the outside of the letter "O" is drawn with about 9 G1 commands which draw straight lines. The preview in Aspire looks perfect - it's just the rendering that is bad. I may have inadvertently changed something somewhere but I can't see what that might be.
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Re: Arcs Drawing as Crude Lines

Postby ger21 » Sun May 22, 2016 10:59 pm

A stretched circle becomes an ellipse, and there are no g-codes for elliptical arcs.
What you might want to try, is arc fitting on your stretched circles, which should then give you all tangent arcs, instead of straight lines.
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Re: Arcs Drawing as Crude Lines

Postby Makingtoothpicks » Mon May 23, 2016 1:55 am

I am not any kind of expert. I had a similar problem with small text cutting in small straight lines
I was informed by some of the experts in the UCCNC forum to change 2 numbers in the settings
in configurations Max Linear error change to .001 and corner error .001 save settings and restart.
Hope this helps.
Don
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Re: Arcs Drawing as Crude Lines

Postby TReischl » Mon May 23, 2016 4:27 pm

I have tried duplicating your problem and have had no luck.

Drew a circle. Stretched it. Created G code for Mach, lots of small linear moves which is normal. Not just nine. . . .

One thing you wrote is that the preview looks correct in Aspire but the g code only has 9 lines or so to go around a circle. I CAN duplicate that by using the "curve fit to vectors" from the Edit menu. Are you using that to attempt to control the number of arcs output? If so, why?
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Re: Arcs Drawing as Crude Lines

Postby dhellew2 » Tue May 24, 2016 3:37 am

Sometimes I receive dxf files that are made of straight segmented lines to create the circle or curve. When possible I convert them to a bezier curve which eliminates the problem.

When the line segment/circle/curve cannot be converted, I draw a circle over the top of the segmented one, stretch the new bezier circle to the exact same shape and size, then delete the original... works perfectly, and does not take much time.

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Re: Arcs Drawing as Crude Lines

Postby conundrumdg » Sat May 28, 2016 9:08 pm

Makingtoothpicks wrote:I am not any kind of expert. I had a similar problem with small text cutting in small straight lines
I was informed by some of the experts in the UCCNC forum to change 2 numbers in the settings
in configurations Max Linear error change to .001 and corner error .001 save settings and restart.
Hope this helps.
Don


Awesome! That little configuration change did the trick and now it's all formed perfectly. Should put this out for all UCCNC users! Thank you so much.
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Re: Arcs Drawing as Crude Lines

Postby Makingtoothpicks » Sat May 28, 2016 9:19 pm

Follow the UCCNC forum on cnczone. They list updates and other info there.
Not much happens there but I check once a week for any changes. The
people on that forum are like the ones here very helpful and keep up with
the developer.

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Re: Arcs Drawing as Crude Lines

Postby Toneski » Wed Jul 06, 2016 7:43 am

Hi conundrumdg,

I've hit this very problem this morning.

All my characters (certainly when they are 2"+ high) are drawn with straight line segments. Normally (like when the text is 1/2" or less tall), you dont see it, but at 2" you certainly do. Plus it makes the mill jerk as each line segment is traced out in the material.

After further investigation, you can get round it, but in my view its definitely a bug within VCarve and aspire (it sounds like aspire shares the same code base). The annoying thing is that while the 2d preview is perfect, the cut in the material is not. I've use openscam to examine the gcode output and you can clearly see the problem (see pic 1).
letter_d_zoom_BAD.PNG
accender of the letter D - showing lines used to make the shape.

The fix is to convert the text to curves (right click with the text selected - Convert to curves), then vcarve as though it was text. The output is shown in (pic 2).
letter_d_zoom_GOOD.PNG
same letter - now converted to curves.

Its annoying in as much as the text cannot now be easily edited as its a collection of curves now - not ascii text. I suggest, copying the text with its attributes to a spare bit of your design (outside the working area) - you can always drag the copy back should you need to change it.

Its a shame that a piece of software thats used to make signs can't handle large text correctly. Still - at least there is a fix...
Hope this helps

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Re: Arcs Drawing as Crude Lines

Postby martin54 » Wed Jul 06, 2016 8:52 am

True type fonts aren't optimised for cutting on any type of machine & there are many that are made up the way you describe or with loops & cross overs that cause problems for any type of cutting, cut on a vinyl plotter using signmaking software you would get the same results. Using a different font is normally the best thing to do, signmaking fonts won't cause these sorts of problems as they are designed to be cut as well as printed but they tend to be a bit more expensive than those that are not.
Rather than copy & move to a different part of your work space you could simply copy the text to a new layer & switch that layer off so it cant be seen, that way you haven't got to worry about trying to position it correctly if you need to make alterations.
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Re: Arcs Drawing as Crude Lines

Postby Adrian » Wed Jul 06, 2016 1:00 pm

It's not a bug in the Vectric software. It's either an incorrect setting in the Post Processor (as was the case in the original question) or it's how the letter has been made by the font maker as Martin says.

If the vector doesn't contain arcs then the Vectric software won't output arcs for it which is exactly what should happen.
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