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Author Topic: Gear Reduction question.  (Read 4005 times)

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Re: Gear Reduction question.
« Reply #20 on: November 16, 2017, 05:01:48 PM »
So looking into the servo options. I have some experience retrofitting a laser system with ClearPath motors and looking at there SD Nema-34 motor the torque spec looks like
its peak is at the RPM were I'll be happy with the speed of the machine. This is roughly the same cost as adding the Hi-torque steppers and additional bits. Here is the data from there site.
I like that these motors are so quiet too.

https://www.teknic.com/model-info/CPM-SDSK-3441S-RLN/

Re: Gear Reduction question.
« Reply #21 on: November 16, 2017, 05:44:42 PM »
Hi,
I think the 1.8kW DMM servos will eat those Clearpath types, to start with the DMM types are powered by 230V or 320VDC link voltage and 11.5Nm works
out to over 1800 oz.in, through a 10:1 gearbox you're talking serious grunt.

Craig
My wife left with my best friend...
     and I miss him!

Offline ger21

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Re: Gear Reduction question.
« Reply #22 on: November 16, 2017, 06:36:33 PM »
Quote
I think the 1.8kW DMM servos will eat those Clearpath types, to start with the DMM types are powered by 230V

Yes, an AC servo will easily outperform a Clearpath, and they cost about the same.
A lot of people seem to be jumping on the Clearpath bandwagon lately. They are great, if you want a drop in replacement for a stepper motor. But if starting new, AC servos provide far more power.

Be careful with the voltage on the DMM;s, though. I just got one back today from being repaired. It blew as soon as I powered it up, apparently from overvoltage. They claim they should be safe up to about 260V, they tell you not to provide over 240V. I have about 245V here at home. I'm going to get a transformer to lower the voltage down before I fire it back up.
Gerry

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Re: Gear Reduction question.
« Reply #23 on: November 16, 2017, 07:24:46 PM »
Hi ger21,
with due respect 1.8kW servo and driver for $700 is very cheap. That they may be a bit suspect under modest overvoltage conditions is hardly suprising.

The real test is how they perform/survive emergency de-acceleration when they 'generate' and will if uncontrolled push the DClink voltage sky-high and blow
something.

Craig
My wife left with my best friend...
     and I miss him!
Re: Gear Reduction question.
« Reply #24 on: November 17, 2017, 09:19:33 AM »
Budget limitations at this point means that any change to the motor configuration would need to be "plug and Play"  meaning no changes to the controller
step and direction and Nema-34 frame size only. The Clear Path servo motor may be the only viable option to gain the extra torque. I agree looking at the specs the DMM
servo would be the better option but at this time I'm either going with the Clear Path servo motor or 2 hi-torque steppers. I measured the tonnage last night with a load cell and I'm at exactly 1-ton and need to be at least 2.5 ton to get the desired results and material thickness range. That's with one Chinese 1600oz stepper at 6:1 gear reduction and I needed to slow slow slow it way down to get that 1.0ton load pressure. looks like the torque range is peak till about 125rpm at 12nm on those CP servos. I'm going to get a quote from them later today.
Re: Gear Reduction question.
« Reply #25 on: November 17, 2017, 12:00:43 PM »
Hi,
those CP servos are good for 500 oz.in if you expect to run them at their peak torque they will fault out within seconds.

Fundemental fact about motors: torque s proportional to current. Therefore to run those servos at three times rated torque (1500 oz.in) will require three times
rated current.....and that level of current might be sustained for 10 seconds but not much more.

Those DMM servos require Step/Dir signals only, they have their own 230V power supply, they require less of your controller than the CPs. Don't see that you should
have to do anything to your controller at all.

Craig
My wife left with my best friend...
     and I miss him!
Re: Gear Reduction question.
« Reply #26 on: November 17, 2017, 12:42:08 PM »
Worth giving those DMM's a look.
The concept of this machine is to mimic (as close as you can) a hydraulic piston operated press.
The peak current (max load) comes into play at the coining stage when your piston or in my case the screw runs
into the bottom of the die. Stalling at this point cannot happen , The idea would be to hit max peak and stop. Then
that is what the machine would be rated for tonnage. That little 1600oz stepper stopped and stalled at 1.0ton. Not nearly
good enough.  If the DMM servo's frame is equivalent in size to Nema-34 I will definitely consider them.

Quick look at the 1.8kw motor and the frame size is 130mm , I would have to really hack the frame up to shoehorn that motor in.


« Last Edit: November 17, 2017, 12:54:50 PM by ddefocy »
Re: Gear Reduction question.
« Reply #27 on: November 17, 2017, 12:58:40 PM »
Hi,
best rated torque for 80mm frame (34 size) DMM servo is 2.4 Nm, not enough.

The 11.5 Nm (rated) DMM is 130mm frame, quite a bit bigger.

Large torque requires a large rotor diameter...

Craig
My wife left with my best friend...
     and I miss him!
Re: Gear Reduction question.
« Reply #28 on: November 17, 2017, 01:11:32 PM »
Hi,
don't know if you've had much to do with AC servos but almost all of the offer 'torque mode' usually with analogue input.

You dial up 8V and the servo will produce 8/10 x 11.5 (Rated torque)=9.2Nm through your reduction and screw to give 1.3 t say. Doesn't matter if it
stalls it still produces the force that you wanted. If you want more force....turn up the knob a bit more.

Caig
My wife left with my best friend...
     and I miss him!

Offline ger21

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Re: Gear Reduction question.
« Reply #29 on: November 17, 2017, 07:31:51 PM »
Hi ger21,
with due respect 1.8kW servo and driver for $700 is very cheap. That they may be a bit suspect under modest overvoltage conditions is hardly suprising.


The one I have is actually 400w, and the fact that it's very cheap is the main reason I bought it.  ;D

I wanted to do some testing with it, before I buy the two more that I need. I was a bit disappointed that it blew up the second I applied power to it. But they fixed it for free, so I'll have another go at it when I lower my voltage.
Gerry

2010 Screenset
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JointCAM Dovetail and Box Joint software
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