@Jeremy_G_WeisTek_Eng is there much advantage to that? So far I’ve always run the spindle at the same speed throughout a whole job. In what circumstance should it be altered?
I’m assuming, it would be for different material profiles such as soft woods to hard woods and soft metals etc. Different rpms chip better and or worse with different materials. You don’t want to just make dust.
That will heat your tool up to much and you will have a much greater chance of snapping your bit.
Plus you get the add bonus of the system guessing your rpm which should be realistically closer than you would get from just running your spindle from a pot etc.
And I’m sure there would be a way for the system with a small amount of added hardware and a marker point to monitor if your spindle had lost revs or stalled all together. Mine has done that resulting in breaking bits.
@Jeremy_G_WeisTek_Eng I understand why you use different speeds generally. But I just set the speed I want for the job I’m doing and hit start manually. Since it doesn’t change during a single job, I don’t really sure why I need the gcode to control it.
@Daniel_Would
Until you start machining steels the discussion of speeds, and feeds is pretty academic stuff. Once you start cutting steel though it gets real fast.
The number for tool steels cutting mild steel is ~100 SFPM
Here’s the formula for calculating surface speed (This is the precise formula – there is a simplified one which gives less accurate results but lots use it because it generally works)
PI = 3.1415927
DIA = diameter of tool
RPM = Spindle speed in Revolutions Per Minute
SFPM = Surface Feet Per Minute
(PI X DIA X RPM) / 12 = SFPM
That formula is difficult if you have a cutter and want to figure out what speed to run it at. This is less elegant but gives you the answer straight away because you solve for the unknown.
RPM = ((12 / PI) X SFPM) / DIA
I’ve no idea how to figure any of this out in metric. They must have some way they do it though.
Found in a blog online???
RPM = (1000 x Surface metres per minute) divided by (pi x diameter in mms)
There the target is ~30 MPM Between feet and meters I think I’ll stick with feet. They’re a finer pitch. I’ve known this stuff to get picky at times too.
