Linear servos

[chantecler 15]

Dear colleagues,

I have an applclation in which we want to replace an old rotational servo for a linear one. The application, of course, is suitable for such a replacement.

I have done some motion projects using rotational servos but this time I am very confused about the different kind of linear servos (trhusters, linear stages, cylinders, linear motors, etc.) so I am asking you some guidence about where to utilize each one of them as well as its advantages and disadvantages.

An explanation or a link to a source of information will be appreciated.

Thank you

[kaiser_will 65]

Your question about different types of linear servos I cannot answer.  This specification is probably more suited to a mechanical engineer.

But for the controls-side, and integration with Allen-Bradley since you are in this forum, I can speak about.  Linear servos will be very similar to rotational servos with the difference being limit control (to refrain from bottoming-out an axis, running to the physical ends).  Selecting a linear motion solution that has proven history of integration with A-B PLCs is the key.

Festo has a line of linear servos and a proven history of integration with A-B.

https://www.festo.com/net/SupportPortal/Files/365747/13106434%20-%20Integrating%20Rockwell%20Automation%20with%20Festo%20(2.2015).pdf

A-B also has their own line of linear servos, or linear thrusters as they call them.

http://ab.rockwellautomation.com/Motion-Control/Actuator/Integrated-Linear-Thrusters#overview

Tolomatic would be my 3rd choice for linear motion and A-B success.

http://www.tolomatic.com/products/electric-linear-motion

A-B has a software package for their motion solution products, Motion Analyzer.  The instructions for this package are vague.  I developed a simple Work Instruction for our mechanical engineers to install the package and get their first mockup configured for testing.  Motion Analyzer has saved our bacon before by flushing out gaps between motor/gearbox specifications.

http://ab.rockwellautomation.com/Motion-Control/Motion-Analyzer-Software

Work Instruction - Allen-Bradley Motion Analyzer Software.doc

[chantecler 15]

Thank you, I am going to study the material and the information from the links.

[Joe E. 259]

We used to have about 15 machines with linear servo motors from a couple of different manufacturers.  They also had 3 different drive packages from Allen-Bradley, Kollmorgen, and Anorad.  All were controlled by PLC-5 processors using digital I/O signals to tell the drive which sequence to run. 

We're down to having one left that we upgraded from a PLC-5 with Allen-Bradley Ultra series drive to a CompactLogix and a Kinetix 6500.  The programming was very straightforward.  Rockwell had a motor file for the Anorad linear motor that Studio 5000 was able to read to set up its basic parameters.  We worked with a local Rockwell R&D engineer who helped us at no charge.  The autotune process got us close to where we needed to be, then a little tweaking gave us a very solid machine.  It runs faster and smoother than any of the other machines ever did and we have far better control of positions, accel/decel, speeds, etc. 

 

We have another series of machines from Korea that each have a linear axis moved by a regular rotational servo motor with a timing belt.  These are Festo servo drives controlled by Siemens S7-300 processors, which I would not recommend to anyone.  If the Festo drives are easier to deal with in AB than they are in Siemens (they'd almost have to be), they may be an option as well.

Size/mass/resistance/speed/precision of movement/etc. will be big driving factors for your selection.

[chantecler 15]

Just to thank Will and Joe for their help and useful information.

Happy Holydays

Bye