How to synchronize multiple motors / What products to use

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How to synchronize multiple motors / What products to use

Postby om_tech_support_JT » Mon Sep 09, 2013 1:53 pm

Q: I am working on a bottling and labelling application. We are using two DC motors to run a dual belt conveyor. The dual belts carry the bottle through a coding station and it is critical that the speed of the belts match because if one belt is going faster (or slower) the bottle will rotate and it will cause an error. Right now, my DC motor speeds are not synchronizing well enough, so I'm looking for other options. What do you have to offer for my requirements, and how can I achieve this?

1. 10in-lb torque @ 150 RPM
2. Master/salve ? need to make sure dual belts run at the same speed
3. Need to run continuously
4. Needs encoder pulse output to feed into PLC for real-time position/speed verification
5. Ethercat
6. 24VDC preferred

A: I have some suggestions which I will list below. We have no problem with the 10 in-lb torque requirement. We have several products that could work and several ways that we can synchronize speeds. Continuous duty rating is no problem for us even for our stepper motors. Certain products already offer built-in encoders, resolvers, hall effect sensors, or voltage generators to close the loop. Output pulses can be connected to the PLC from our driver for position/speed verification.

With regards to Ethercat protocol, we'll need a FLEX, Modbus/RS-485 network compatible product plus a Ethercat converter which converts Ethercat protocol to RS-485 protocol. "FLEX" products are products that accept Modbus/RS-485 communication as well as stored data capabilities.

For more information regarding our Ethercat converter, please click the link below: ... ochure.pdf

For our FLEX product series offerings, literature downloads, and training videos, please click the link below: ... index.html

1. CONTINUOUS DUTY BRUSHLESS MOTOR SYSTEMS: Use 2pcs new BLE FLEX series motor and driver package models and 1) wire one external potentiometer to both drivers, or 2) have something supply the same analog voltage to both drivers, or 3) preset speeds digitally with the optional OPX-2A module or MEXE02 software, then turn on an input (direct or remote via Modbus) on both drivers at the same time. It does have a speed output of 30 pulses/rev that it can feed back to the PLC for speed/position verification. The BLE FLEX series has not been released as of today. If you're interested in this product now, please contact our technical support group.

2. HIGH DUTY STEPPER MOTOR SYSTEMS: Use 1pc SCX11 universal controller connected in parallel to 2pcs AR pulse input series closed-loop / high efficiency pulse input models, then connect its simulated encoder pulses back to the PLC for verification. The SCX11 pulse signal is strong enough to synchronize 4 drivers. While our documentation does not support this method, our engineers have successfully tested and synchronized 4pcs drivers with 1pc SCX11 controller. However, due to lack of test data, we cannot guarantee that this method will work for every customer. For example, it probably won't work for long distances (between driver and controller). We actually offer a "pulse splitter module" (VCS04) as an accessory that can also work here if needed. It's designed to split one single pulse signal to two. However, the SCX11 controller only communicates via USB, RS-232, and CANopen networks.

For information regarding our SCX11 universal motion controllers, please click the link below: ... ochure.pdf

For information regarding our AR series high efficiency stepper motor and 24VDC driver series, please click the link below: ... ut-dc.html

If USB, RS-232, or CANopen is not possible, then I would suggest to use a CRK FLEX series driver to run the 1st motor, then use its pulse/direction output function provide pulses to the 2nd CRK pulse input driver. However, the pulse output is line driver, and the pulse input is TTL/photocoupler. While we've successfully tested and synchronized multiple CRK systems, this method is also not supported by our documentation.

For the continuous duty requirement, we can oversize bigger CRK series encoder motors, and reduce the motor current to reduce heat, which allows the motor to increase its duty cycle. It's suggested to keep the motor case temperature at below 100 deg C to prevent reduction in expected life. Normal motor case temperature should be around 60 deg C.

We end up with 1pc CRK Flex series encoder stepper motor and stored data type driver package model, and 1pc CRK series encoder stepper motor and pulse input type driver package model (+ 1pc Ethercat to RS-485 converter).

For information regarding our CRK FLEX series, please click the link below: ... er-dc.html

For information regarding our CRK pulse input series, please click the link below: ... ut-dc.html

If oversizing the motor is not preferred, we can use 1pc SCX11 univeral controller to output pulses in parallel to 2pcs new RK II FLEX series encoder stepper motor and AC input driver package models. This way, we can offer high duty cycles with a smaller motor plus be able to use the Ethercat converter as well as feed the encoder pulses back to the PLC for position/speed verification. The RK II series has not been officially released in the US as of today, but please contact our technical support group if interested.

3. OTHER: There are also dual-output gear reducers in the market that converts one motor output into two. However, we have limited knowledge in these gear drives since we don't manufacture them.

If you have any questions, please feel free to contact our technical support group @ 800-468-3982 or [email protected].

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