PDA

View Full Version : Proper handling of arcs?



Joe Petro
02-21-2006, 11:04 AM
I'm using TurboCad/AceConverter/TurboCNC.

When drawing circles or fillets, I usually explode once, and everything cuts fine.
Same for Bezier curves.

Lately, all circles and curves cut very slowly. They cut as a series of tiny straight lines, stopping at each one, sometimes for a second or two.

Needless to say, my cutting times have increased dramatically.

I noticed this when I built a newer computer for TurboCNC.
Dell PII 550 mhz 128mb RAM. DOS 7.1 is the only OS loaded, and TCNC is the only program.

I usually run 48 IPM..

It just seems that the program (TCNC) waits for the computer.

Anyone?

Thanks,
Joe Petro

kombayotch
03-09-2006, 11:57 PM
I have the same problem. Its painfully slow. Even when I leave the machine and comeback, it seems like it has accomplished nothing.

I was wondering if this is because of the computer or just the program itself. I am using an old 486, so I though that was the problem. But if you still have the same issue with a 550MHz machine... I'm running DOS 6.1 and TurboCNC is all that is running on it.

I find it goes faster if curves and circles are coded with G02 or G03 instead of a bunch or G01 lines (like, from CAM software). But it stops every quarter circle even then.

If this is what can be expected from TurboCNC, I'd love to know. Because, if so, I'm switching to something better. I love the simplicity of the program, but it just too slow.

ger21
03-10-2006, 09:23 AM
I'm using TurboCad/AceConverter/TurboCNC.

When drawing circles or fillets, I usually explode once, and everything cuts fine.
Same for Bezier curves.

Lately, all circles and curves cut very slowly. They cut as a series of tiny straight lines, stopping at each one, sometimes for a second or two.



If they are cutting as a series of straight lines, more than likely thats the way the g-code is written. You can minimize the starting and stopping by increasing the start speed, if your machine can handle it.

Bezier curves are almost always going to be a series of straight lines, unless they are converted to arcs before sending to ACE.

rippersoft
03-10-2006, 10:11 AM
Grab a beta copy of NCPlot and let it plot out your gcode. See what is really there. I have the same software setup, but run Pentiem 3 and DOS 6.22.

I have noticed that as I make changes to the drawing, the order of the file basically fractures so that when Ace converts it, the code is all over the place.

If you are cuting lettering, it might be better to use something like deskengrave. There are some general purpose programs for creating gcode for circles and hole patterns. May have been posted here.

Something else to look at is whether or not your last machine had any scripts, setups, or mods that optimized it for CNC. Also look at the differences between DOS 7.1 and the older version from your last system. TurboCNC has a port monitor and you can also get a standalone port monitor for the printer port.

Hope this helps a bit.

dkowalcz
03-22-2006, 11:17 AM
You've probably got this squared away already, but just to recap what Ger21 has mentioned, increasing the start vel for the motors is a great way to get around this.

Other schemes - you can get rid of the dwell by turning off backlash comp, and some users have increased acceleration to accomplish the same thing.

I'm working up a fix for this, as it's the #1 complaint I've gotten about the software, and there's no reason why it should be this way... Backlash comp is taken up as a rapid on the linear moves, so it should be done that way on the arcs as well.