Tool Nose Radius Comp

Quote:

Originally Posted by lukehonor

Hello All,

I'm having a problem implementing G41 and G42 when programming. I've always programmed without radius comp and lately I've been playing around with it.

When is the proper time to put in G40, G41, G42? Before the cut? Beginning of line when calling up tool?

Please help...:D

Thanks!

Screw Machine Shop - Screw Machine Parts and CNC Machining - Progressive Turnings -

As the thread is titled "Tool Nose Radius Comp" I assume we are talking about a lathe. A lathe, as opposed to a machining center, dose not rely on Tool Nose Radius Comp to "Size" the part, but it allows the component to be programmed using the dimensions directly from the part's drawing without having to calculate the true position of the tool with respect to the Tool Nose Radius. In my opinion, this is a very small consideration given the very inexpensive or free software available nowadays that will do this for you.

One consideration that you have to be mindful of when roughing a part, and when using Tool Nose Radius Comp, is that when the tool's direction is reversed to returned to the roughing start position, is that the direction of the Tool Nose Radius Comp also reverses. For example:

If the tool is on the right side of center line, machining towards the chuck, G42 would be used and the tool would be offset to the right, away from the center line. When the tool is moved back to the Z start point, the tool will be again offset to the right side of the programmed path, but this time its towards the center line, with disastrous results if the tool is not withdrawn sufficiently to avoid interference with the work, or the Tool Nose Radius Comp is not canceled or swapped for G41.

I'm not a fan of using Tool Nose Radius Comm on a lathe, as in my opinion, its easier to program the true location of the tool than it is to ensure that the G40 G41 and G42 are being used appropriately during roughing, and because its not necessary in the control of the size of the part, except in very particular instances.

If you're hell bent on using Tool Nose Comp, confine its use to the part, not when calling the tool. Apply the G41 or G42 in the block preceding the first cut line and cancel with G40 on a line after the last cut line in fresh air.

Regards,

Bill