Helix Hell

[chutch]

I am having difficulty getting my cutter compensation to work correctly in a cam Helix The Helix changes pitch at one point and it really freaks out the Fanuc 0M control. It gives me circles like in the Post "Automatic Cutter Compensation problems" on this site.

I started using I,J and then switched to R and then converted the whole thing to X,Y,Z points. I haven't had sucess yet unless I re-write it to show the moves without G41.

I'll attach what I've Got now.

This is On a Hardinge VMC 600 with a Fanuc 0M control Vertical Machine


Hutch

[crazythunder]

Probably going to need to change it to segments some controllers can not do helixes very well and can only do standard 3 axis move not 3 axis arc moves.

[Kiwi]

Using G41/42 with short segments around arcs can cause the controller to stall.
Most likely the change of the helix pitch is the error point.
If the segments at the change point are made longer may overcome your problem. This may make your part out of specs.
You may need to create a actual tool path to overcome your problems.

[oldjohn]

Chooks: THELIX.DLL and SPIRAL.DLL can do that in Mastercam.

[chutch]

Thanks,

I do not have MasterCAM. I am still overshooting and can't get rid of it.

[gar]

070924-0630 EST USA

chutch:

I can not understand this discussion so far.

Your first post indicates problems using arcs, but you provide a program illustration with straight line segments.

The simplest of operations for a CNC controller to handle are straight lines. You need to find the exact point in your attached program where the problem occurs. If there is not too much lookahead the point where the program appears to stop may be close to the actual problem.

Just providing us with a program with hundreds of points is not an effective way to find the problem.

Without cutter comp and straight lines there are probably no invalid motions except exceeding travel limits. With cutter comp there may be some rules on invalid motions at corners.

What is the code near the failure point, and what are the error messages?

What do you mean by overshoot? If it means that the machine runs your program but you do not get the desired result, then where the error occurs you have to look at your code and how cutter comp works and see what geometry this produces at the cutting point.

.

[Stu_M3]

One thing i have noticed is that your ramp onto the helix is not tangential at the start of the helix and your ramp on & at that point the short lines of which your spiral is composed form a "v" the maximum cutter rad at that point is .217
which may cause problems when using comp if your cutter of a greater rad.

[Kiwi]

chutch
What is the radius of the cutter you wish to use?
Are you using a CAD/CAM program to create the helix?
Sketch below shows problem point when using G41/G42 which stalls some controllers.

[oldjohn]

Do you think you can give me a list of values to fill the parameters in the attachment as well as centre coordinates and tool diameter. I can try to generate some code for you to use.

John

[Kiwi]

oldjohn
Does your helix code generator make allowance when using a ball-nose cutter?
Don't see where the cutter info is entered.

[oldjohn]

To Kiwi
That dialog box is only to create the drawing. Once you have the drawing you generate a toolpath and then the nc file. You can do it internal and external. It is better to use compensation in control.

John

[Kiwi]

Originally Posted by oldjohn It is better to use compensation in control.

When using tool compensation, this is when chutch is having problems.
He needs a actual toolpath.