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How to increase circle resolution?
« on: June 23, 2008, 11:03:29 PM »
I am using Mach3, lazy Cam, and Corel Draw.
When I cut out a small circle on my CNC, the circle has a very high resolution and it looks realitivily smooth.
As my circles become larger they become more choppy.

Is there any way I can smooth out my larger circle cutting?

I have tried every format to export my drawings and there is no change.

Any help would be great.

Jon

Offline Chip

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Re: How to increase circle resolution?
« Reply #1 on: June 24, 2008, 03:26:18 AM »
Hi, Jon

Read this post http://www.machsupport.com/forum/index.php/topic,5117.0.html

It will help to enplane what's going on.

Getting to late hear, Chip

Offline jimpinder

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Re: How to increase circle resolution?
« Reply #2 on: June 24, 2008, 07:27:37 AM »
Have you looked at your GCode in the program.

If you are cutting a circle, then the correct GCode command is G2 to cut clockwise, G3 to cut counter clockwise. This is a single code for the whole of the arc or circle, and it either specifies a radius (with an R command) or specifies the centre of a circle (with an I,J, or K command) Mach 3 understands these two commands and adjusts the speed of both axis smoothly and simultaneaously to produce a circle.

The only way you can get "choppy" circles is if your Coral Draw or Lazy cam is not producing a circle when you draw, but is making up what appears to be a circle from lots of little, straight lines - a G1 code.

If you are using Constant Velocity, then this will smooth out a lot of the changes, until the straight lines get too long, and then you will get a threepenny bit effect or a fifty pence effect (a multi sided round coin with smooth edges).

You GCode will tell you which this is. The post Chip has highlighted is identical to your query and comes up with the same reply - although I don't think it resolved it.

« Last Edit: June 24, 2008, 07:30:30 AM by jimpinder »
Not me driving the engine - I'm better looking.
Re: How to increase circle resolution?
« Reply #3 on: June 24, 2008, 05:41:01 PM »
Thanks for the help guys.

No, I don't have any G2 or G3 commands when my code is loaded into Mach.
Basically I have G1 code that creates little straight lines to cut out a choppy circle.  There is also no I, J, or K commands.

When I view or print my drawing on Corel draw it is perfect.  After I load it into Lazy cam and zoom in I can no longer see my perfect circle, it has now transformed into small segments of straight lines.

So what's next?  How do I correct this problem?

Any help is appreciated


Offline Chip

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Re: How to increase circle resolution?
« Reply #4 on: June 24, 2008, 06:20:54 PM »
Hi, Jon

It's the DXF exporter in Corel, In most cad programs you can select the "line segment length" for cir's, arc's or just export cir's, arc's in the DXF, I Think!.

I haven't used Corel maybe Corel has this option, In the Link I posted, It was suggested to import your dxf in a differant Cad and re-export it's dxf.

Better answers should follow, I hope.

Thanks, Chip

Offline jimpinder

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Re: How to increase circle resolution?
« Reply #5 on: June 25, 2008, 01:17:56 PM »
As you talking about circles, i.e. true circles, which could be rewritten into G2 or G3 commands, or are these just odd bits of curved lines.

The problem with many of the drawing packages is that they do not draw circles - so from that point of view Mach 3 out performs many of them

If it is a circle, you may be able to put in one line of code that cuts outs many, many lines. G2 or G3 command is basically  - move from herre to a new position and (on the way) describe a circle radius R.

e.g. G2 X7 Y10 R6  - If you were at 0,0 then go to X7 Y10, but on the way describe an arc of a circle radius 6

This on simple command might save you 100 lines of code if your arc had been made up of 100 straight lines.
« Last Edit: June 25, 2008, 01:38:31 PM by jimpinder »
Not me driving the engine - I'm better looking.
Re: How to increase circle resolution?
« Reply #6 on: June 25, 2008, 10:18:19 PM »
Well my test has been with an eight inch circle.  Usually I have arcs, and turns etc. in my drawings.

But here is what I have found.  It seems as if Corel Draw exports DXF files in a low res output.  Which really stinks.
I love Corel Draw and I am not in the mood to spend more money, nor do I want to try and learn a different Cad program.
Then I found a program called "DXF tool" for Corel draw, to export full res DXF files.  Price was a little much $50.
But after I downloaded the demo,  it said it would not support Corel Draw 12 on Vista.  $#$%^!!!   Wouldn't you know it, that is what I have. 
I find the solution and I can't use it.  Not too impressed.

There was another write up on the Corel Draw site, in which they were asked about the exporting of DXF files and the problems Cam programs were having with resolution.
Corel said that they knew of no problems and their tests said everything was fine.

So I need some sort of conversion program.........any one know of one?


Re: How to increase circle resolution?
« Reply #7 on: June 26, 2008, 08:14:14 AM »
Found a fix for Corel Draw resolution.

When a normal circle is exported from Corel to a DXF file it is divided into 63 line segments.  So smaller circles look ok, but the larger circles look choppy.

So.......In order to increase resolution in a large circle, you must first "convert it to curves" then add more nodes.  The more nodes you add the more resolution you curve will have.
Unfortunately this greatly increases the amount of G-code, but it's a sacrafice I'll make for now. 

I hope this helps someone.

Thanks.    Jon
 

Offline budman68

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Re: How to increase circle resolution?
« Reply #8 on: June 26, 2008, 12:00:37 PM »
Jon, have you tried ProgeCAD? It's just like autocad (and a little better IMHO) but completely free for private use only.

Might be worth learning to draw in it!

http://www.progecad.com/compra/index.asp?left=prodotti/eng_progecad2008smart&abspage=1&lang=eng
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Offline docltf

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Re: How to increase circle resolution?
« Reply #9 on: June 26, 2008, 05:25:49 PM »
Johnny

get a copy of cad std lite,it is a free program.import into cadstd lite and export export as a standard dxf.it will smooth your arcs up.

bill