Need info on using PLC for Sawmill setworks

I am just starting to learn about PLC. I want to use a PLC with Human Machine Interface and Rotary Encoder to control the Bandsaw Mill Head for Motion Control and Cut Depth.

I think the the PLC would need two Relay outputs to control a Hyd. Control valve. What inputs would the PLC need for a Red Lion rotary encoder? I think I would also need some D1 inputs for the push buttons.

Would a person setup a counter to do this?

I would like 12 programable control point with a zero & home setting. For example cutting different board thickness.

Thanks,

You would probably be looking at a high speed counter. You'll want to find a PLC that has a set of high speed inputs. Some cheaper PLCs have a couple high speed inputs in the first section, the rest being normal.

I have done lots of these

First you should use a sevo quality valve.
Second, you should use a Temposonic or Balluff rod for position feed back.
A PLC doesn't have a fast enough counter to count the time between the start and stop pulses.
A PLC must use analog feed back or have a hydraulic motion controller card.
Your application is a easy one if you use the right equipment .

What output does the PLC need to control the Hyd. Servo valve?

Servo Solenoid valves require +/- 10 volts.
True servo valves require current. The range varies but is usually in the range of +/- 40 ma to +/- 60 ma.

Check these guys out
http://www.motrona.com/
They make a nice converter card for handling your high speed pulses. Software is easy to use and configure as well

That isn't a hydraulic controller. These are hydraulic motion controllers

Enough nonsense. Those are motor controllers. They don't take into account that the gains are different in each direction because there is a piston rod. The PID for a motion controller is just that, a PID. That is good for controlling a motor where the dominate pole is the inertia of the motor and the load but a hydraulic system is a mass between to springs. The motor controllers fail here. PLCs fail here to because they are designed to control temperature systems with time constant in minutes not systems with a natural frequency and damping factor.

ELake20 said:

Check these guys out
http://www.motrona.com/
They make a nice converter card for handling your high speed pulses. Software is easy to use and configure as well

Click to expand...

If you are serious you get a 1756-HYD02 or 1756-M02AS or a Delta Computer Systems RMC150 or RMC75. Everyone on this forum knows I am biased but I doubt anyone will dispute what I say below.

http://www.ab.com/en/epub/catalogs/12762/2181376/2416247/360807/1837520/print.html
Look at the bottom of the webpage.
Or
http://www.deltamotion.com/

You can try to go cheap, waste your time and have poor performance and accuracy or you can get the best and something that is supported. I bet over 80% of the hydraulic actuators in sawmills are either Rockwell or Delta RMCs.

Your application is so simple that you should be able to get a RMC75E and a Red Lion display and make a 21st century setworks. If you must be AB we can work with PVs too. I would buy Temposonic rods with SSI for position feed back. The Red Lion or AB PV interfaces to the RMC using Ethernet and can have programmable buttons that can change if you change dimensions with species change.
http://www.mtssensors.com/products/index.html
The Temposonic rods are normally inserted into the back of the cylinder and measure the distance between the end of the cylinder to the piston.

If you can control hydraulic or pneumatics then controlling a small motor system is easy.

http://www.mtssensors.com/news/r-series-sensor-balloon-domonstration/index.html

There is no way you can do that with a PLC even if you are experienced.
The really cool part is that one of our engineer programmed that system from 3000 miles away over the internet.

Peter Nachtwey
President
Delta Computer Systems, Inc.

My Bandsaw Head is controled with a Hyd Motor that is geared do thru roller chain and sprockets gearing to raise and lower the sawhead. It has a total of 36 inches up up and down travel.

Lucky55 said:

My Bandsaw Head is controled with a Hyd Motor that is geared do thru roller chain and sprockets gearing to raise and lower the sawhead. It has a total of 36 inches up up and down travel.

Click to expand...

Then you use the 1756-m02as or the rmc75 with SSI. SSI can be rotary too. There are many companies that make rotary SSI encoders. The best part is that they are absolute so no homing is required. The SSI encoder will need to be multiple turn encoders. These cost a little more but again, no homing is required.

Unitronics M90/M91

Has anyone used the Unitronics M90/M91 PLC?

Lucky55 said:

My Bandsaw Head is controled with a Hyd Motor that is geared do thru roller chain and sprockets gearing to raise and lower the sawhead. It has a total of 36 inches up up and down travel.

Click to expand...

This sounds like a woodmizer or woodmizer clone. Is there a reason you do not want to use an already prepackaged solution?

They won't sell for a Homebuilt Bandsaw MIll.

Lucky55 said:

They won't sell for a Homebuilt Bandsaw MIll.

Click to expand...

Ahh! By the way I have no experience with Unitronics.

I'm guessing you have some other handicaps that have not been mentioned.

What kind of power (electrical) is available for the project?

What kind of hydraulic pump do you have, constant volume or pressure compensated?

And maybe the most important, budget?

The Unit has 12 VDC Power. I do have a 12VDC to 24VDC converter if needed. The Hyd. pump is a Belt Driven Gear Pump constant volume at set engine RPM. Max budget set at $1,500.00

I have worked on SCADA 485, AI, AO, DI, & DO but have never been involved with motion control.

I want to try and learn PLC's

Lucky55 said:

The Unit has 12 VDC Power. I do have a 12VDC to 24VDC converter if needed. The Hyd. pump is a Belt Driven Gear Pump constant volume at set engine RPM. Max budget set at $1,500.00

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I had suspected the above would be the answers.

The control electronics can be damaged by the electrical spikes during engine starting.

I'm not aware of a hydraulic control valve that is compatible with what I will call "tandem center" hydraulics and capable of positioning. There are two basic types of control valves that have enough precision for motion control. These are on the low end ($) proportional and on the high end ($) servo. Both require pressure compensated pumps. The proportional valve has moderate (hydraulic) dirt tolerance. The servo has zero (hydraulic) dirt tolerance. I would recommend a separate hydraulic system for your motion control. If you have learned what you now know about hydraulics from your gear pump system, understanding how a pressure compensated system works may seem very foreign to you.

Unless someone else knows different, I believe the $1500 will not get you any better performance than you are now seeing manually. My gut feel is that somewhere around $4500-$6000 will get you a system that has better performance than what you presently own.

Lucky55 said:

I have worked on SCADA 485, AI, AO, DI, & DO but have never been involved with motion control.

I want to try and learn PLC's

Click to expand...

I would suggest learning the PLC part first, the motion second.