Fusion turning threading SFM calculation doesn't work

[RUSHdesign]

So, it appears that whatever you put in the SFM box for turning/threading is what it outputs when you post the file (as opposed to calculating an actual spindle speed).

In my case, I am shooting for 98 sfm which on my 1/4" part should giv eme a spindle speed around 1,500 rpm. Instead, it just uses the 98 I entered as the SFM as the output RPM. Not surprisingly, this doesn't work very well.

I am posting this with a Haas ST-10 post processor that I modified to work on my SL-10 by removing the C-axis gibberish. Otherwise it is exactly the same. I also tried posting with the generic FANUC turn post and I get the same RPM output.

I can obviously just put the RPM number I want in the SFM field, but this seems to defeat the purpose of having that field.

Can someone at Autodesk please fix this?

Thanks.

[angelo.juras · Accepted solution]

Hello @RUSHdesign - According to the code you attached, it looks correct to me.

G96 (Constant surface speed ON modal)

S98 M3 (S=Surface Speed)

This will maintain the SFM at 98 which will run at ~1497 RPM.

One thing to consider for threading is selecting Constant RPM (G97)

Then set your RPM at 1500. This is what I do.

G97

S1500 M3

This will actually run faster because the spindle will not have to constantly adjust up and down based on where the current X axis position is.

Hope this helps.

[RUSHdesign]

Hi Angelo,

Well, derp. Thanks for pointing this out.

This is my first real CNC lathe, so I am still getting used to the differences from milling.

Best,

Jon

[angelo.juras]

You are very welcome Jon @RUSHdesign