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John252058

Using linear encoder for position feedback to control stepper drive and motor

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I need help with picking the proper hardware and how to accomplish, I'm green but will learn.

I have a milling machine that needs a new feed drive and motor. It drives the 3 axis through a common drive powered by 1 drive and motor. The drive uses clutches to direct the power to the appropriate axis.

Which of the HMI/PLC combo units would be suitable to control the drive using 3 Hiedenhain LS803 linear encoder as feedback for positioning on each axis. I want to enter a target position on the HMI then move the appropriate axis at a specific feed rate, when approaching the target position  the motor ramp down then stop at the target position accurately.

I've choosen Copley Controls Stepnet Plus TEL-090-10 drive for Nanotec ST8918L6708-B stepper motor.

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After some discussion with the local Unitronics supplier I've decided on the V350-35-TR34 / V350-J-TR34.

The technical folks at Unitronics suggested moving away from the Hiedenhain LS 803 because of the 5v signal, my choice here is the Sick encoder TTK70-AXA0-K02.

I had to buy a new laptop so I can download and learn the Visilogic software.

The stepper drive choosen is the Copley Controls STP-075-10 Data Sheet and Nanotec stepper motor                 pdf                

Any help or suggestions would be appreciated.

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The Sick Encoder you specified has a serial SSI output.  You'll have to develop a protocol to talk to it and verify electrical compatibility with Unitronics' com ports.

 

The stepper drive looks like a nice one with internal 5V pull-up inputs.  You can use the NPN high speed outputs of the PLC to push it.

 

Look at the protocol and the stepper examples once you get Visilogic installed.

 

Joe T.

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I also looked at Newall's SHG-PV Linear Encoder which may be more suited for my application. I can't seem to find any examples of writing protocol to read the 24v signal.

Also does anyone have issues with running Visilogic in Windows 8.1, my new laptop only has Visilogic and Copley CM.2 running and is shutting down sometimes along with being very slow sometimes.

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The SHG-PV encoder will be much easier to implement.   Look at the Help for hardware configuration for a HSC to read a high speed quadrature input.  Unitronics refers to this as a shaft encoder.

 

 

I'm running Win 8.1 on my desktop machine and it seems to be working OK with Visilogic.  I also have a tablet with 8.1 and it's much more doggy.  I have a feeling that the video processor in the more compact devices doesn't have the RAM to work really well.

 

Joe T.

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On 11/30/2014 at 10:44 PM, John252058 said:

.... I want to enter a target position on the HMI then move the appropriate axis at a specific feed rate, when approaching the target position  the motor ramp down then stop at the target position accurately.

In this configuration, you can only make linear moves. That is, it is impossible to ensure the simultaneous movement of two axes. Today, such modernization is not acceptable.

As for me, it is better to put separate drives (stepper motor or servo with Step Dir) on the axle and manage them with one of the available CNC controllers.
If there is a desire to use Unitronics then the simplest solution is the Arduino-GRBL controller.

It's easy to create a transmitter of commands based on the Vision panel.
I created simple positioners for two axes with this principle - everything works. You just need to send to controller G-code commands correctly.
And GRBL can control stepper motors in 3D and transfer position to the panel for display.

Using of linear encoders for coordinate reference requires a "real" CNC controller with high-frequency inputs (500kHz or more) or modern "Two positioning loop" servo drive. They are quite expensive and require significant skills for mounting and programming.

If you only need linear motion without replacing the engine to another one, use the Lenze 8400 high line+encoder or other CAN-open drive and operate it using the Vision panel via CAN.

 

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