cutting large arc's

[peterklos]

Hi I have problems cutting large arcs ( 1 metre +) and hope some one can help me . My problem is when I cut large arcs the arc surface has slight wavy edges on the arc circumference, this presents a problem as I am trying to mate several pieces of wood together.
I built my own CNC which is very ridged and is driven by large steppers and run via CNCplayer software (real time DOS so no windows lag) I also designed and made the 8 amps stepper drivers. I draw the patterns on Auto Cad which is then converted to cnc player.

The drawn arc on the screen is perfect and is made up of many nodes. When running the CNC the steppers execute the node then stop this happens on every node. So the x and y axis is stopping and starting many times which I assume may be the problem.

I have tried for hours to resolve but with no luck , can some one suggest what I am doing wrong . I cant work out if it is the soft ware , my amps or the drawing from Auto cad.
Regards Peter

[ger21]

You need to use either G2 or G3 in your code instead of what I assume to be all G1's.

Gerry

[mikeschn]

I second that. Some CAM packages generate a series of lines to represent a circle, and others generate a bona-fide circle! You want the later!!!

Mike...

Originally posted by ger21 You need to use either G2 or G3 in your code instead of what I assume to be all G1's. Gerry

[Urgundiz]

Peterklos,

I'm interested in those 8A drivers you've designed.. if possible, could you post a schematic when your arc problems are resolved?

thanks in advance

/U

[limbo]

Probably cncplayer has no constant velocity contouring, just like turbocnc. In that case the steppers ramp up and down between every node in a curve. In autocad you don't want to see many nodes in a circle, just the centre and four points on the circle. If you have that, the conversion program should translate it as a G02 or G03, not many lines. A G02 or G03 will not cause the up- and downramping.

John

PS. Quick and dirty, if you really need the parts made, just temporarily set the max. stepper speed equal to the start speed in the cncplayer motion settings. Slow but should work.

[balsaman]

Try converting the geometry in ace converter, you should get arcs, and not a zillion lines.


Eric

[ger21]

Eric, if you reread his post it sounds like his drawing is made up of straight segments, not just his g-code.

Gerry

[peterklos]

RE stepper drivers -(Urgundiz)
HI all my circuits are on bits of paper I will draw on protel ( or similar) and send to you .

They use descreate FETs in the output as I was sick of blowing up L6203's , You can push them past 8 amps with no problems . just heat . I use choppers with load resistors to increase slew rates , Load resistors are made up of old room heater elements

[peterklos]

Many Thanks
I guess CNCplayer does not have constant velocity contoring. ( will check with cnc player( cnc player still works in progress)
Just to confirm my process . I draw the file in Auto cad and save in DXF . I then convert the DXF file to a PLT file in cncplayer and run the job with cncplayer via PLT file. I dont ever use any G codes

regards Peter

[balsaman]

I am thinking the drawn acrs on his screen is refering to the cncplayer screen....I was hoping he could verify the dxf by converting it with ace.

E

[peterklos]

many thanks Balsa Man I have tried ACE converter and I experience the same problems. You are correct re the screen drawings they are on the CNCplayer screen.
peter

[alarants]

I am using also cncplayer and doing exactly as peterklos. But constantly getting error message "Stop in cycle". Probably some elementary thing but can't find out. Any idea would be appreciated?