Circle Calc Program

[Al_The_Man]

This may have been posted before, but some may find it usefull assistance for milling a circle with auto 'loop in' loop out'
http://www.kentechinc.com/tip7.html
Al.

[Geof]

I looked at your link and my first thought was that it makes complicated what is really simple. My second thought on reading through it and seeing G42 was that it is not a good example. G42 is Cutter Compensation Right which means you are conventional milling (that is if you are using a conventional cutter). When you are inside a hole this means tool deflection tends to pull the tool oversize, to a larger radius. This is okay if you make sure if your finishing allowance in the roughing cut is larger than the deflection.

Using G41 gives climb milling which deflects the tool to a smaller radius. Often when using G41 it is not even necessary to leave a finish allowance; the tool deflection provides it. Also I find the residual tool marks are often barely noticeable even when just going straight in and out.

[Al_The_Man]

All Righty Then......

[BlueChip]

Al ... thanks for the mention.

Just to clarify ...

Hey Geof ... isn't the purpose of the page to teach the whole idea of ramp in / ramp out ? So is it really a "bad example"? Hopefully it's plain enough that if you went the other direction ( CCW ) in the example, you would be climb milling and simply use G41 for cutter comp.

I'm not sure I would ever agree with your point of using the "tool deflection" as your finish allowance for obvious reasons ... and for closer tolerance work, the tool marks of coming straight in and out will certainly effect the "roundness" of the hole.

[Geof]

Originally Posted by BlueChip Al ... thanks for the mention. Just to clarify ... Hey Geof ... isn't the purpose of the page to teach the whole idea of ramp in / ramp out ? So is it really a "bad example"? Hopefully it's plain enough that if you went the other direction ( CCW ) in the example, you would be climb milling and simply use G41 for cutter comp. I'm not sure I would ever agree with your point of using the "tool deflection" as your finish allowance for obvious reasons ... and for closer tolerance work, the tool marks of coming straight in and out will certainly effect the "roundness" of the hole.

The "bad example" comment was aimed at the G42 because going this way accentuates tool marks because it puts the deflection into the part not away from it.

And I don't know what your "obvious reasons" are for not using tool deflection as the finish allowance. If you want to get to a final size within a certain tolerance and with a certain finish why does it matter how you get there?

[broby]

Hello Everyone,
I have used the attached spreadsheet to simplify the process of milling circles with arc in/out.
It uses G41 (climb milling).
Very straight forward to use, enter the information at the top and then highlight the result and copy and paste into your program.
Obviously, this program does not contain all the required code for spindle start up, coolant, positioning at the centre of the hole etc... just the milling of the ID of the hole.
Just my 0.02c worth... use (or abuse) at your own risk.
BTW the values in the spreadsheet are metric and the DA value is what I use on our Okuma Mill. it is the "D" offset value for the "Active" tool in the spindle, unlock the spreadsheet (no password req, protection only used to stop anyone from accidently deleting the formulae!) and change this value as required.
Cheers
Brian.