Help figuring this motor power out

[ack1]

Hey! I got a 2001 Multicam router. Its big with 2x3 meter workarea. Im currently running stock steppers and was thinking that id replace them for clearpaths or DMM-techs ac servos.
Going with Nema34's would mean drop in replacements.

I have never owned anything with servos so im a bit of a novice.
They say the clearpath HP models will have 8-15 times the power of similar sized steppers, but I dont really get it. Not for my application. But im no expert so help me here.

The machine runs r&p on Y and acme strew on X and Z. The acme screw has 25mm pitch so 1 turn equals 25mm travel. The motor is connected with a belt and 1:1.5 reduction.

Machine specs says cutting (and rapids) at 600IPM. So X motor does 900rpm at max travel speed, (900/1.5) 600rpm on screw wich gives 15240mm or 600ipm.

Looking at the torque curve for my current steppers. see attached(It states nm and rps in the pic) When i look at that i basically see about 250 watt in my rpm range. correct me if im wrong.

My stepper: @ 600rpm, about 4nm/556,4oz-in = 247watt @ 900rpm, about 3nm/424,8oz-in = 283watt.
DMMs AC servo: @ 600rpm, about 2,4nm/339,8oz-in = 150watt @ 900rpm, 2,4nm/339,8oz-in = 226watt
Clearpaths @600rpm, about 2.8nm/396,48 = 176watt @ 900rpm, 2,8nm/396,48oz-in = 264watt

Clearpath motors in example (CPM-SDHP-3432S-ELN) Rated at 2.8nm and 970rpm (1130 max).

Looking at the CPM-SDHP-3441S-ELN. The highest continuous torque nema34 if im not mistaken.
478.5oz-in of continuous torque and rated rpm of 730rpm(840rpm max) do 258w at rated speed,730rpms. And lesser when the rpms go down.

How could the clearpaths give 8-15x more power ? or even twice the power ? Should I take the peak values into consideration ? I seem to be able to make my steppers loose steps when I take big deep cuts at "high" rpms, a cut like that would cause the servos to need to be in peak range for longer than a second im assuming, and it just feels wrong to do calculations with consideration to the peak values?

If I rebuild/gear down (wich i prefer not to) and let the DMM's run 2000/3000 rpm then id get 500/750watt output. If im not confusing myself.

Im wrong somewhere or am i just missing something ? help me here! Is replacing my steppers not worth it unless i get DMMs with more gear reduction or go to bigger frame sizes ?

Ps.Ofcourse id like to have servos for the smooth quiet high resolution awesomness too, not just power.

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[ger21]

There's no attachment, but I find it hard to believe that you have steppers with 500+ oz of torque at 600 rpm. I don't think you can get anywhere near 280w from a stepper.

Which DMM servos are you referring to? It looks like you are looking at continuous torque, rather than the peak torque? If you are looking at a 750w servo, it's a 750 watt servo.

[ack1]

there, is the attachment visible now ?

I was looking at the 750watt ones. And yes they are 750 if 2.4nm and running 3000rpm so no confusion there. I think...

(2,4 x 141,6) x 3000 x 0,00074 = 754watt

[ack1]

Looking at this (see attached) it looks like if I had 325v drives it would be able to do 3nm at 40rps/2400rpm. Thats 750watt ?

I had leadshine 3 phase steppers once and just jogged them on the machine one time before that project was sold so i never properly tested them. But those drivers take 220 from the wall and (i might be wrong) but converting that to dc it shoud be able to put out over 300v. Wich just might be the case since those steppers will do 3k rpm. Seems like (if i am not missing stuff) that the leadshines will do pretty much 30-40% more than my current ones. 377watt at 4nm 900rpm. Tho its 75v vs 300+.

Thats what it looks like to me but as said i might be missing something or just have something wrong with the numbers, I dont know.

EDIT: Ps. my current steppers are Sanyo Denki SM series in case anyone was wondering.

[Jim Dawson]

I replaced the servos on a 2x3M MultiCam router with ClearPath CPM-SDHP-3432D-ELN motors. The installation went well and the customer is happy with the result.

The motor tuning and setup was easy to do. Support from ClearPath was very good.

4 Controller Cable CPM-CABLE-CTRL-MM660
4 DC Power Cable CPM-CABLE-PWR-MM660
1 USB Cable CPM-CABLE-USB-120
4 ClearPath Integrated Servo Motor CPM-SDHP-3432D-ELN

And this power supply
Automation Technology Inc
Unregulated Linear 1440W/72VDC/20A Toroidal PSU (KL-7220)

[ack1]

I take it the customer had something like 1:10 gearboxes on his machine ? and how did you tune the dual servos for the gantry ? Two computers simultaneously ?

Been thinking about this power factor thingy. I guess the most demanding moment is accelerating while cutter is in the material. That where its gonna lose steps if ever. So I guess that the peak values can be used for that situation, giving more headroom. For example the DMMs do 7.1nm/1000 oz-in at 3000 rpms wich equates to 2.2kw output power for that brief period. Kinda a big deal.

But then again the continous torque need to be able to sustain the speed.
If im not mistaken..
The steppers have 4+nm under 600rpms wheres DMMs have 2.4 but since im runnig max 900 rpms now, i guess with the DMMs i could gear it 3 times higher giving me 3 times the torque.
Running 2700rpms at 600ipm feedrate and higher rapids still.

The peak power in combination with the higher reduction would crush current setup. This is where someone comes and corrects my math making my evening a waste of time.

If i dont want to rebuild anything then a 3:1 nema34 gearbox would be the easiest but extra cost and kinda wonky doing gearbox to belt reduction eh ?

[Jim Dawson]

If I recall correctly, the gantry gearboxes were 3:1. The NEMA 34 motor shafts were directly inserted into the gearboxes and secured with a coupling clamp, no timing belts. Y axis leadscrew 1.5:1 timing belt, and the Z axis leadscrew maybe 2:1 timing belt.

To tune, I just let the motor do an auto tune, one at a time. The movement is very short, maybe 50mm maximum, and for the most part about 5mm. Only that motor powered. Not the best method, but it worked OK.

Once the axis has accelerated to speed, it takes very little power to maintain that speed. Only friction losses and cutting pressure if you are cutting on that move. The largest power requirement would be acceleration to rapid speed.

[ack1]

If it did have 3:1 then I guess there would be alot of unused power left. Lets say it had 1" diameter pinion on the rack(i bet its closer to 2") , thats 3.14" travel per rotation. At 4000 rpms /3 = 1333 at the pinion, thats almost 4200 IPM. (And 8373IPM with a 2" pinion)
If it was 6:1 it would have twice the torque and still be able to run 2100IPM.(and 4186IPM with a 2" pinion. Anyway, would probably work just fine. Im just thinking out loud.

Good idea on tuning with just one motor powered, i bet that would be fine.

If i went with lower rpms clearpaths i wouldnt need gearboxes. It aint the same power output as with higher rpms and gearing (the DMMs with bigger drive) but very easy and convenient.

Still not sure im havent made a mistake somwhere in all these motor power calculations, hoping someone will either confirm or correct them.

[Jim Dawson]

I'm not sure how ClearPath is calculating 8-15 times more power, a bit optimistic I would say. I will say that in the machine that I retrofitted works fine and rapids at about 1000 IPM. I think your calculations are correct, but the machine will only rarely use anywhere near full power and speed. If you are operating a commercial enterprise where time is money, then go with the higher power DMM and run the machine at max performance. I do commercial work with my router and find that 500 IPM rapids is fine, most of the runs are several hours so I can just walk away from it and let it run. Consider that when cutting the machine will almost never reach anywhere close to maximum speed.

Like mine, your real limitation is the spindle power, you can only push the tool bit through the material just so fast.