Need info on using PLC for Sawmill setworks

[kamenges]

Originally posted by milldrone:

...that have enough precision for motion control.

You know, we've never really asked him what his precision requirements are. So it's hard to know if he has any shot at all with what he has. He certainly won't have a system that would be accepted in industry but if he is cutting up logs in the back yard he may be fine.

Keith

 

[Lucky55]

What is a Good PLC and Human interface to buy that can be used to learn and then moved to motion control for a Hyd. Motor?

Leland

 

[milldrone]

You know, we've never really asked him what his precision requirements are.
Keith

Keith,

This is just a guess from what I have seen on other homebrew woodmizer clones. He probably has a tape measure next to a reference point and either the tape measure moves or the reference point moves with a height change. Depending on parallax correction his precision is some where around 1/16th of an inch. He may or may not have a solenoid valve controlling the motor. The ones I have seen used a tandem center log splitter valve. The problem is he almost certainly has an constant flow hydraulic system. This makes teasing the positioning motor to move slowly an issue. My suggestion to solve this part of the problem is to create a hydraulic subsystem just for the positioning circuit.

What is a Good PLC and Human interface to buy that can be used to learn and then moved to motion control for a Hyd. Motor?

Leland

If your not going to use the software for anything else. I believe the software is going to be the biggest problem.

 

[Lucky55]

Does anyone know how the Log-Master Photo Setworks works with Photoelectric emitter & receiver? I think they have holes drilled thru a plate to give a NO/NC signal for different settings.

Leland

 

[milldrone]

Does anyone know how the Log-Master Photo Setworks works with Photoelectric emitter & receiver? I think they have holes drilled thru a plate to give a NO/NC signal for different settings.

Leland

I googled for about 5 minutes and couldn't find any details on the logmaster setup. Classically for positioning with a hoist screw, one would use an encoder coupled to the hoist screw. The encoder would be connected to a high speed counter. Encoders generally have photo eyes inside that are "masked" inside by a disk with holes or clear sections.

 

[Lucky55]

I called Log-Master and they said it does work with a photoelectric emitter & receiver. They have different log scales setup with different scale holes drilled example one for 1 inch & 2 inch board cuts.

Leland

 

[milldrone]

I called Log-Master and they said it does work with a photoelectric emitter & receiver. They have different log scales setup with different scale holes drilled example one for 1 inch & 2 inch board cuts.

Leland

Do you have any links to the above?

 

[milldrone]

Leland,

Is this where the plate with holes is positioned on the machine?

 

[Lucky55]

They said it was like a manual log scale so I think it has several rows of holes drilled at different scales (example 1 inch, 2 inch spacing) on a vertical mounted flat bar. I think it has a different photoelectic unit for each scale. I don't think it is on the low end unit they sell. I don't know how big the holes are to let the light signal pass. That looks like a sprocket. He did not say that it uses a sprocket.

The upgrade high end setworks they sell does use a PLC. This is the standard unit, but not on the manual mill.

 

[milldrone]

Leland,

To control the hydraulic motor so that it does not overshoot or undershoot we need to slow and speed up the oil going to the motor. Describe what happens when the oil flow is blocked. Like if you run the carriage to the end of the travel and continue to go in the same direction. I'm presuming you have a handle connected to a hydraulic control valve that controls carriage travel. Does the Prime mover (gas motor) pull down?

edit: can you change cutting speed on the fly? Like in ease into the cut?


I drew red circles on the control valves. I'm presuming you have tandem center valves. In the tandem center valves see how there is a connection to go to the next valve. In the closed center valve there is just a tee in the pump line.

 

[milldrone]

They said it was like a manual log scale so I think it has several rows of holes drilled at different scales (example 1 inch, 2 inch spacing) on a vertical mounted flat bar. I think it has a different photoelectic unit for each scale. I don't think it is on the low end unit they sell. I don't know how big the holes are to let the light signal pass. That looks like a sprocket. He did not say that it uses a sprocket.

The upgrade high end setworks they sell does use a PLC. This is the standard unit, but not on the manual mill.

A large amount of the problem is the hydraulics, I hope you can answer the earlier questions.

I'm going to presume that This is the operating scenario you would like.

1. Load log
2. Jog saw head (height) to opening face position. This would be an infinitely variable position (not dependent on a hole in a plate)
3. Saw opening face.
3a. Do you need to raise saw on return?(a little)?
4. Decide on next cut What thickness. Push the button for the thickness into the control.
5. Have different thicknesses for say 5/4 alder and 5/4 shagbark hickory, but still use the same set button. Ect. ect.
6. Allow for different saw set or swage (different saw mfgr)
7. On last cut, run seworks to top for next log.

 

[Lucky55]

The mill I am wanting to put this on is a older Cook's AC-36. It has a engine driven open center hyd. system. I could use flow control to slow down the movement of the head. The valve I have is;
Solenoid Valve D03 C6 Tandem 12 volt



Examples of use:
Tandem Valves - Used for the head travel up and down. These valves don’t allow any drift when power it cut off. Therefore, it will allow precise stopping points with no drift
Features:

• Voltage - 12 volt
• Spool Type - C6
• Max GPM - 16
• 5000psi. max

It had manual Sectional Control Valves on it for all functions.

 

[Lucky55]

I am just wanting to have something that would be a electronic version of a manual log scale for now. I can always go to a PLC for control after I learn Ladder Logic programming and motion control down the road. It just as much a challenge and learning exercise for me.

 

[milldrone]

These valves don’t allow any drift when power it cut off. Therefore, it will allow precise stopping points with no drift

If this were a hydraulic forum I would debate you on this point. Definitely not what I have witnessed. But for your use It will probably work.

I could use flow control to slow down the movement of the head.

In your situation two of the D03 valves (both controlling the same height mechanism ) might give you the best you can hope for (given your constant volume pump). One would be set up for full speed, one for creep speed.

The valve I have is;
Solenoid Valve D03 C6 Tandem 12 volt

The tandem center gives it away. Do they give a rating for back pressure on the "T" port?

Edit: I could not find any details on the height mechanism. Is it a screw or a cylinder?

 

[Lucky55]

Thanks for all your help!
I know what I am trying to do is not like a high end comercial mill. The setworks Cook's sells uses this valve with a M/90 Micro PLC. I will install the valve and just control it with a dpdt toggle switch and see what happens. I will let you know how it goes.