Digtal Positoning of Saw Head

If you don't need position error correction, yes it can be a stepper motor, in which case the positioning would be controlled by number of steps (pulses generated) not time.

Depending on what's your budget for this, you can buy off the shelf CNC solutions, these are more than just a digital readout, they control your motors also.

Or you can buy a stepper motor and drive, you can't keep your old motor unles it is a stepping motor (make sure they match), use the software (generally supplied) and any PC to program distances, connect and program one start button.

If you need anything more complex than extend-retract, use a PLC and an OIT to transfer the whole setup thru the serial port. If you don't know how to do this, you need to hire someone to do it, send your machine to repair, or cope with the loss.

My best guess is that you really will need some sort of position feedback. There are many options for this which you should be able to implement aftermarket.

• LVDT (Linear Variable Displacement (Or distance) Transducer)
• Laser triangulation
• sting pot
• Vision system/bar-code reader
• ultrasonic transducers

There are other methods.
If you want the saw blade to be where you told it to go every time without making a cut where the computer told it to go, even though it skipped a count or for some reason is off by some distance you will need some sort of position feedback. Otherwise the system might be unreliable.
Maybe if you don't need a precise location of the blade each and every time, and high repeatability you can do it blindly.
Without knowing the process I cannot know for sure.

I do need precision to .5mm

If the encoder is belt driven, check the condition of the belt. Had a issue similar on a CNC plasma.

How much accuracy do you need? Resolution? Speed? How much head separation, or travel?

I need about .5mm accuracy.The max travel distance is 4 metres. I would like the speed to be around 1 metre / 5 seconds

I am with you there. GA.

I think you need a motion controller to control the motor on your head saw.

if you can send me micro controller specs then it was more easy to assist you.anyhow.mostly double head miter saw having the servo motors .which works on the pulse and direction.

as command ,so i suggest to to use Siemens logo which can generate the pulse and also there is pulse counter (to count the encoder pulse )but it will be with the electronic gear

(you will be unable to calibrate the pulse with mm ,just the values ) but you can run your machine with that.

Is it the encoder that generates the pulses that go back to the control board to be counted.?

'The computer and encoder do not work anymore.'

Will not the replacement, of the computer & the encoder, solve your problem? Why are you keen on some untried/untested complicated solutions? You will not, I trust, misinterpret this post.

For a local solution try Horner Ireland Ltd over in Cork. They do small controllers (£100-200) that you can program to your own requirements with free downloadable software. They also have some with pulse output (PWM set at equal mark space) that will count pulses directly into a stepper motor controller. It can be set up to cope with speed of cut, distance and cut depth. You will need to a) oversize your stepper motor, B) ramp up and down your speed of travel otherwise the stepper motor will slip c)always go back to a limit switch derived home position between each cut or you will get cumulative error. It is never going to be as accurate as you old feedback system but if you can tolerate wide tolerances it will do. You will still need a brake to prevent it from wandering during the cut. Stepper motors with brakes are less common than servos and will be expensive.

I don't know if it is, but it should be, the first rule of automated motion "Over coming inertia and getting a load moving is very easy. Over coming inertia and stopping the load where you want it to stop is very hard.

For a local solution try Horner Ireland Ltd over in Cork. They do small controllers (£100-200) that you can program to your own requirements with free downloadable software. They also have some with pulse output (PWM set at equal mark space) that will count pulses directly into a stepper motor controller. It can be set up to cope with speed of cut, distance and cut depth. You will need to a) oversize your stepper motor, B) ramp up and down your speed of travel otherwise the stepper motor will slip c)always go back to a limit switch derived home position between each cut or you will get cumulative error. It is never going to be as accurate as you old feedback system but if you can tolerate wide tolerances it will do. You will still need a brake to prevent it from wandering during the cut. Stepper motors with brakes are less common than servos and will be expensive.

I have contacted Horner in Cork. The would have the right gear I think. They said that I would need someone to program the controller in ladder language. Do you know anyone that can program in that language ?.

If the saw was doing the job, I have to agree with the repair approach. It is unlikely that two things fail at the same time. Do they have a common power supply that may have failed?

Encoders are easily replaced and are available from multiple suppliers.

The controller is a different matter. If it is old, direct replacements may not be available and you may want to upgrade anyway. Will the new controller have to be compatible with legacy manufacturing files? Or are you prepared to reprogram?

I dont need to be able to transfer data files anymore to the saw. I just want it for basic straight cutting to specific lengths that I would input manually via a keypad.

If the computer doesn't work how do you know the encoders bad? Is there specs on the encoder? What type of computer PC or PLC? What the problem with it? What about software?

Trying to reinvent the wheel can be a lot more costly then just buying one or repairing the one you have.

With a bit of digging, normally, used or surplus equipment is available. Buy 2 or 3, if price is agreeable. An encoder defective on the top of it? Nah, they are too simple to be defective, too generic to worry about their replacement.

To prod you, I met ancient PC board DOS controllers for CNC. Getting cleaned, cooled properly they provided solid yeoman's work without a complaint.

I like new and shiny, but not in this case.