drive types for DMM dyn4

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20 Oct 2021 01:59 #223615 by PhilipME
Dynamic motor motion dyn 4 drive and AC servo motor

from www.dmm-tech.com/Dyn4_main.html


Type-B ( Modbus RS485 / Pulse / Analog / RS232 )

Type-C ( CAN / Pulse / Analog / RS232 )

What is the differance between those drives?


I am looking for 1500-1800 watt AC servo motor (3 phase) to drive a BT-30 spindle

Many thanks

Philip

 

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20 Oct 2021 10:53 #223652 by PKM
Replied by PKM on topic drive types for DMM dyn4
I'd prefer Type-B for Modbus control.
But if you have a spare analog output Type-A is OK too.
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20 Oct 2021 14:34 #223674 by spumco
Replied by spumco on topic drive types for DMM dyn4

What is the differance between those drives?



There is no output performance difference.  The only difference is in the communication protocol.  B and C add Modbus & CAN communications

If you plan on using the drive in step/direction or 0-10v analog, then get the A version.

Keep in mind that there have been numerous reports of issues using the DYN4 in analog position mode.  Step/dir works fine (I've got 3 installations working great), but there appears to be a 5ms delay from the motor encoder back to the controller (LCNC).  DMM uses a proprietary serial encoder signal from the motor to the DYN4, and then processes it and outputs a standard A-quad-B encoder signal for use by the external controller (LCNC).

This buffer/delay plays havoc with the servo loop unless you use external linear scales and program LCNC to ignore the DMM motor encoders.

I've seen no reports of serious problems with analog velocity mode, such as for a spindle motor, other than one or two unverified reports of motors not reaching top speed (can only get ~2700rpm vs 3kRPM nameplate, regardless of line voltage).

If your intention is to use the servo as a spindle because you also want homing capability (for an ATC), then there are less expensive/less complicated VFD's that can accomplish simple positioning (i.e Hitachi) using an induction motor with an encoder.

If you want a C-axis where the motor can hold a position (like a regular servo), then you might look in to the Delta drives/motors as an alternative.

If you want higher RPM and expect to have to over-drive your spindle because the DMM can only reach 3kRPM, you might consider an induction motor instead.  There are plenty of quality induction motors with a max RPM of >5kRPM.  Leeson, Baldor, Marathon and others all make VFD-ready motors with a CT ratio of 1000:1 or better that can hit 6kRPM no problem.  They are heavier and larger than an equivalent kw permanent magnet AC servo, but the increased rotor inertia of an induction motor can actually be an advantage in a spindle application.

 
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20 Oct 2021 16:48 #223685 by PhilipME
Replied by PhilipME on topic drive types for DMM dyn4
Thanks spumco, PKM 

Just to clarify, I am not planning to have ATC. as I have few tools to work with. Only looking for the simple function of driving the spindle.

I started with the induction motors, but I wanted some thing lighter in weight.

It seems that it will be easier and lower cost to deal with the weight issue of the induction motor than the servo motor option. 

Very informative feed back many thanks

 

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20 Oct 2021 22:11 #223713 by spumco
Replied by spumco on topic drive types for DMM dyn4
If you do go the induction motor route and don't feel like scrounging up a used motor, I spotted a vendor on ebay selling an aluminum-framed series of 'vector-ready' motors in the 0.5-3hp range.  They look decent, not Marathon/Baldor/Siemens quality, but should be OK for the majority of uses at that power level.

I'm not going to link to ebay here (don't know the policy), but if you search for "cobra line" in electric motors category it'll probably show up.  I believe the seller is 'motorconnection2017'

They look to be about 30% lighter than standard rolled-steel motors, and 50% lighter than cast-iron.  And they have an extended tailshaft for an encoder - big plus.
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21 Oct 2021 14:33 - 21 Oct 2021 18:20 #223818 by PhilipME
Replied by PhilipME on topic drive types for DMM dyn4
Yes

I searched ebay (cobra) and found many motors which seem very close to what Iam looking for.

I highly appreciate your help


Philip
Last edit: 21 Oct 2021 18:20 by PhilipME.

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22 Oct 2021 01:47 #223865 by JohnnyCNC
Replied by JohnnyCNC on topic drive types for DMM dyn4
I'm using a DYN4 with the 1.8kw motor running in velocity mode to drive my spindle.  I have it geared 1:1.8 giving me 5400 RPM at the spindle.  I am controlling it via +-10v using a Mesa 7i83 connected to a 5i25.  I added an index signal on the spindle and I am able to do rigid taping.  If I was doing it again I would probably try a 1:2 ratio for 6K RPM at the spindle.

John

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