electronic lead screw

[Briney Eye]

Clearly my perspective is wrong then, I am thinking here if wear forces on the brass (mine) 1/2 nuts & on smallish HSS threading tool that has to put up with lateral carriage forces and the rotational force of stock being cut/threaded. Wonder what that would be for 2'' dia, CS1020 steel, 20 thou cut for 8 tpi?!

Well, if I understand Machinery's Handbook (which I probably don't), 0.02 depth and 0.02 feed rate at 100fpm (carbon steel) is removing right at 0.5 cubic inches of metal per minute, and that translates into about 0.4hp at the motor if you're using a sharp tool on a belt drive machine.

Addendum: With an electronic leadscrew that will be divided between the spindle motor and the feed motor.

 

[Briney Eye]

No probably no diff cos with 1.8° steppers, 400 is 1/2 stepping, 800 is 1/4 stepping, but u will see diff say at full tilt, 1/16th steps vs 1/2. (Should also see a torque diff between full steps & 1/8th stepping rate too).

The motor that I'm using is actually from www.omc-stepperonline.com, since it was shorter than the one that I got from Banggood and would fit in the available space. I just noticed that they now have a 3.5Nm NEMA24 motor that should fit. I would have to upgrade my power supply, which would probably mean moving to a larger enclosure as well.

 

[Reddinr]

Is there a method or calculator online that can help estimate the feed screw HP requirements? The force on the tool will be in two axes I think; the radial force that tends to push the tool down and the longitudinal force that pushes the tool away from the headstock. Only the longitudinal portion of that force would contribute much to the HP / torque needs of the lead-screw motor, correct? I suppose there is some effect of the radial force too that could increase the frictional force between the ways and the saddle. This would seem to be tool profile dependent too I would think.

 

[Briney Eye]

Is there a method or calculator online that can help estimate the feed screw HP requirements? The force on the tool will be in two axes I think; the radial force that tends to push the tool down and the longitudinal force that pushes the tool away from the headstock. Only the longitudinal portion of that force would contribute much to the HP / torque needs of the lead-screw motor, correct? I suppose there is some effect of the radial force too that could increase the frictional force between the ways and the saddle. This would seem to be tool profile dependent too I would think.

I strongly suggest getting a copy of Machinery's Handbook if you don't already have one and reading the section on Machinery Power. That's where I pulled the info from. The power is going to be shared between turning the spindle and moving the tool. I'm going to try to measure the power drawn by each during turning and facing cuts and observe the correlation.

 

[Briney Eye]

Is there a method or calculator online that can help estimate the feed screw HP requirements? The force on the tool will be in two axes I think; the radial force that tends to push the tool down and the longitudinal force that pushes the tool away from the headstock. Only the longitudinal portion of that force would contribute much to the HP / torque needs of the lead-screw motor, correct? I suppose there is some effect of the radial force too that could increase the frictional force between the ways and the saddle. This would seem to be tool profile dependent too I would think.

Look at the calculators at kennametal.com. You still need Machinery's Handbook.

 

[Briney Eye]

Clearly my perspective is wrong then, I am thinking here if wear forces on the brass (mine) 1/2 nuts & on smallish HSS threading tool that has to put up with lateral carriage forces and the rotational force of stock being cut/threaded. Wonder what that would be for 2'' dia, CS1020 steel, 20 thou cut for 8 tpi?!

Ha! Kennametal has a calculator! For 1018 steel, Brinnell hardness of 195, cutting depth .02, feed rate .02, 100sfm, direct belt drive gives 0.35hp at the tool, 0.39hp at the motor, 9.62 foot pounds of torque. So my 0.4hp estimate was pretty darned close.

I've ordered the 3.5Nm motor from stepperonline after looking at these numbers. I think I can rearrange things and squeeze a 350W supply into my enclosure.

Oh, it works in Firefox but not in Chrome.

 

[Qtron]

Ha! Kennametal has a calculator! For 1018 steel, Brinnell hardness of 195, cutting depth .02, feed rate .02, 100sfm, direct belt drive gives 0.35hp at the tool, 0.39hp at the motor, 9.62 foot pounds of torque. So my 0.4hp estimate was pretty darned close.

I've ordered the 3.5Nm motor from stepperonline after looking at these numbers. I think I can rearrange things and squeeze a 350W supply into my enclosure.

Oh, it works in Firefox but not in Chrome.

- Not sure how CS1020 compares w 1018 BH 195..

( i used a simple calc, http://www.discount-tools.com/sfm.htm), so @ 100sfm, stock 2" dia = 191 RPM, if i understand your fig's. correctly then.
So thats 0.35HP rotational power on the tool .. amazing what such a small cross-section of HSS puts up with!! The next Q would be the leadscrew h.p. required and axial forces in that same set of figures..

Thankyou Very Much for your clear insight, time etc, & i /others look fwd to final results, both with the force gauge measurements results, the final gearing, & the average & peak power supply requirements too.

I guess there will be a compromise in the end, re how fast & deep cuts can be made in worst case materials vs lathe tolerance to such. I just dont wanna put your previously quoted 1100 lb axial force on my 8 TPI leadscrew, bearings, 1/2 nuts, regardless of job demands! (maybe i already unwittingly have).
Have bookmarked the Kennametal Calc., Thanks

 

[Qtron]

The motor that I'm using is actually from www.omc-stepperonline.com, since it was shorter than the one that I got from Banggood and would fit in the available space. I just noticed that they now have a 3.5Nm NEMA24 motor that should fit. I would have to upgrade my power supply, which would probably mean moving to a larger enclosure as well.

i got bit by a local supplier of steppers, 3 duds sitting here basically useless. The new business owners cant rebate me, but admit they were impossible to drive, & no longer sell them.
Reason is because the Inductive reactance, is way too hi, & the mechanical resonance was aweful to boot.
The Inter-winding capacitance was also hi.

The new ones from Stepperonline are 1/3 of the orig at XL~2,5 ohms.
XL=2pi x freq x L, so the higher the stepper rate, the greater the inductive reactance, or more simply, the impedance at that frequency.
Anything over 180 RPM at full step rate, & those ****ty motors clagged out.
The new ones driven at full step, (so non-sinusoidally driven), stall after 1500 rpm, a big difference. Thats, no mechanical load, No mid band resonance tuning, which evidenced itself at about 950 rpm, from memory.
Alos,
Sometimes a heavy steel disc (damper) is clamped onto the stepper shaft to dampen the resonance, the downside is the accel/decel rate needs to be tempered accordingly. It also helps if a heavy-ish steel plate is fixed securely to the steeper body to help dampen this resonance.
BTW, A rubber mount method should never be used!

 

[Qtron]

Baby steps, but it‘s alive!

Is that a galvanised steel mounting plate the goodies are bolted to, GreatOldOne?

 

[Qtron]

.. NOT using ratios from stepper to leadscrew..

i presume a grunty servo or perhaps a closed loop Nema 34 stepper is required then? i like your trick of stabilising the encoder with the now obsolete gear arm (sorry the correct term evades me). And in my shop everything is so tight - a protruding motor would be a real issue, well done!