Cutting Circles? Help please!

[sawdust-and-noise@sympatico.ca]

I'm having problems cutting circles (Drawing in AutoCad, Post in Rams 1.6). The following are two of the circle cut instructions generated. The first functions correctly - it plunges buzzes arround and then pulls up, the second plunges and then immediately pulls up again (no circle). In reading the documentation on "CG" it seems that both should work. HELP!?

First circle,
J3,15.125 ,18 ,0.5
M3,15.125 ,18 ,-0.76000005
CG,,14.875 ,17.75 ,-0.2500,0.0000,,1
CG,,14.625 ,18 ,-0.0000,0.2500,,1
CG,,14.875 ,18.25 ,0.2500,-0.0000,,1
CG,,15.125 ,18 ,-0.0000,-0.2500,,1
J3,15.125,18.0, 0.5

Second circle
J3,13.125 ,16 ,0.5
M3,13.125 ,16 ,-0.76000005
CG,,13.12440014,16.01639938,-0.2508,-0.0010,,1
M3, 13.125 , 16 , -0.76000005
J3,13.125,16.0, 0.5

[sea_nc@bellsouth.net]

Guy,
It looks like the problem is in the Xendpoint and Yendpoint specified in the second circle CG code. Specifically the code for the second circle is asking the machine to:
1) Move to the start point (X=13.125,Y=16)
2) Plunge from Z height of 0.5 to depth of -.76
3) Cut a tiny arc clockwise from the starting point of 13.125,16 to an ending point of 13.1244,16.016 (a distance of only about 1/64inch)
4) Move back (at depth) from arc end point of 13.1244,16.016 to arc starting point of 13.125,16
5) Pull up
On a running machine with a whirling bit that would look like it merely plunged down and pulled back out.
David

[sawdust-and-noise@sympatico.ca]

David;

Thanks for your answer but it seems to raise more questions than to solve the problem.

The bit is starting at position 13.125,16 and moves CLOCKWISE to position 13.1244,16.016 (a position slightly to the left and above the starting point).

.............x <- ends here (13.1244, 16.016)

...............x <- starts here (13.125, 16)
...............|
...............V <- clockwise be thisaway, Help!

[Ted Hall, ShopBot]

Hi Guy,

The second circle works for me both in Preview Mode and on the tool. I'm thinking there are 1 of 3 possible problems:
1. You may not be using version 2.28 or 2.29 of the software ? (We did have some earlier problems with CG.)
2. Your circle segment resolution may have gotten set too high. It is the 5th parameter of VU and should be .05 or less.
3. There may be something else funny in the file, and it is just getting expressed in this line ... if #1 or #2 don't fix it, send along the Part file and your PROBLEM.LOG file.

[Guy Hilliard]

Thanks Ted U got it in 1. I had version 2.25m. The file cuts perfectly now.

[sea_nc@bellsouth.net]

Guy and Ted,
The file does work fine in version 2.28, and I would have known that if I had run it *before* proposing an answer based on the numbers alone! In this case the numbers didn't support my answer either, because, as you correctly pointed out, an ending position of 13.1244,16.016 will always be slightly to the left and above the starting point of 13.125,16. I definitely got this one wrong -- my apologies for the extra confusion that it caused. I'm glad you were able to resolve this one.
David

[pedro]

Off-shaped Circles.

Hello:
I am gettig off shaped circles out of my PRT96.
Just installed version 2.35, and I use Vector cad to output sbp. files.
Everything rusn fine, but when it comes to cutting, the circles come out off-shaped, Why is this happennig?
VU values for my PRT96 are
X AND Y VALUES: 5.56972
Z: 44.5579
ACC: 78.7406
Are there any adjustments to correct the problem?
Thanks

[gerald_d]

Pedro, what is "Off-shaped"? Is your problem on both x & y directions? What size circles are you cutting and how far "off" are they?

[tlempicke]

Most likely your machine needs to be re-calibrated. Really easy to do - its built right in to the Shopbot software.

Go to Utils > Calibrate X and Y axis.

If you have one of the cheapy laser pointers this is duck soup. Just tape it to the Z axis and lay a yardstick on the table. If you want to get really anal (Like we do) put a piece of sharpened steel rod in the chuck and use a machinists steel rule. We have also used a dial indicator but the advantage of having thousandths to read is lost by the disadvantage of having less than one inch of travel.

Remeber that the Shopbot is going to think in decimal inches, so don't forget to convert.

Before you actually calibrate practice a time or two. Move the Z axis up a couple of inches and run through the program. It gives you a choice to bail out at the end without saving the results.

[pedro]

Hello gerald
When I say off sahape, I mean oval like circles,
sometimes the ends do not meet.
I will Try Tom's suggestion to see if it works.
Thank you guys for answering.