Cutting an arc

[khaos]

I want to make an arc 8 foot long and 2" 'deep' So the code for this looks like

CG, ,19.844759,0.020793,574.745911,-47.979000,T,-1

Now what I would like to understand more is the code itself.

In this code I see
diameter is blank
Xendpoint is 19.844759
Yendpoint is 0.020793
*X-center-offset(I) is 574.745911
*Y-center-offset(J) is -47.979000
True T (cut on the line)
direction? -1 (Anticlockwise?)

I am assuming that the center offsets are the virtual center of a giant circle containing this arc on its circumference.

Since this arc bows left the -47 is confusing. How do I use the info to create my own arc?

If say I wanted an 8' arc with a depth of 3 inches?

Thanks in advance,

[donek]

This command does not work based on those parameters. You would have to calculate the radius/diameter of the circle based on your cord length and depth. Then you would have to write the g-code based on that radius/diameter and the position on your table that you want it to be placed.

[donek]

Check this for the derivation of the circle radius
http://mathforum.org/library/drmath/view/55146.html

[donek]

CG is a g-code circle. The shopbot help provides a good explanation, but you can also look at g-code tutorials as well. The only real difference is that g-code separates clockwise and counter clockwise circles into two different commands where shopbot adds a direction variable. I usually find this guy pretty helpful, although I have not read this particular article.
http://www.cnccookbook.com/CCCNCGCodeArcsG02G03.htm

[MogulTx]

18872


I hope the dxf for the arc you are looking for is successfully attached. I drew it up in my design program. You will potentially want to rotate it and perform other changes....

But this should get you a little further down the road. If you need it sent to your PM, let me know.

[adrianm]

Click on the Command Reference on the Help menu in SB3 and you will get a document explaining all the parameters of the CG command and others.

[khaos]

Thanks all. I have looked at the command reference and still don't quite get it. I know aspire makes a lot of commands more complicated than needed. Like many M3s could be MX,MY, or MZ. Is that the case here? Is there a better way to make this arc.

Mogul Thank you so much for your extended effort and attachment. You rock. I am sorry I was not clear about my question.

When I create the arc and tell aspire to cut the profile the command in the sbp are as follows. The real work is done by the CG command. I am just trying to 'get' the command based on the generated code.

'Toolpath Name = Short Part Profile - End Mill (0.5 inch)
'SHOPBOT FILE IN INCHES
IF %(25)=1 THEN GOTO UNIT_ERROR 'check to see software is set to standard
C#,90 'Lookup offset values
'
'Turning router ON
SO,1,1
PAUSE 2
'
MS,1.66,0.50
JZ,3.376000
J2,0.000000,0.000000
J3,19.844759,95.978790,3.375000
M3,19.844759,95.978790,0.000000
CG, ,19.844759,0.020793,574.745911,-47.979000,T,-1
J3,19.844759,0.020793,3.375000
JZ,3.376000
'
'Turning router OFF
SO,1,0
J2,0.000000,0.000000
END
'
UNIT_ERROR:
C#,91 'Run file explaining unit error
END

If I move it over so the bow of the curve sits on the x=0 the code generated is
CG, ,2.249133,0.020797,574.745911,-47.978996,T,-1

[adrianm]

If you're trying to code this hand by you might be better off using the CA or CC command.

[khaos]

I have been looking at both the site Sean suggests and the CA command. The end game being able to do this on the fly. Its really just a curiosity but it is what it is. :cool:

[khaos]

Going to the machine no. Looks like CA might be the exact thing I am looking for. :)

[khaos]

Sean, That G-Wizard tool looks neat. Too bad its just a rental and not real ownership. :'(

[bleeth]

The spreadsheet at the bottom of this page is great for circles and arcs as well as some other nice tools:
http://www.woodweb.com/knowledge_base/_Spreadsheet_Calculation_Program.html

[scottp55]

Dave, I wasn't really interested in the arc per se, But that knowledge base? totally missed it somehow,Got lost in the glue section for an hour! THANKS!

[khaos]

OK. CA IS exactly what I was looking for! :D

Thank You, Thank You, Thank You!