Am I on the right track?

Hi all,
I have a project that deals with dyeing clothes:
1)Operation will be started by a foot pedal or a 2 hand safety switch.
2)2 piston will lower spray nozzles a minimum of 6 inches
3)6 piston pumps will dispense 6 uniquely colored liquids (water) onto a garment. Each pump will be independently metered
Pumps will be dispensing 2 – 10 ounces of liquid (water) per cycle.
All 6 Pumps will start dispensing liquid at the same time
4) 2 Piston raises spray nozzles a minimum 6 inches to start position.

Ideal but not necessary: electric eye safety sensor will stop the piston from lowering onto an operators hand

So I think I will need:
1)PLC and Touch Screen
2)6 servo driven piston pumps
3)6 servo motors
4)2 servo or air pistons to move spray nozzle holder up and down (needs minimum of 6" of travel)
5)Foot pedal or 2 hand safety switch.
6) Anything else?

I will need:
1)Flexibility to turn on and off any number of the pumps
2)Flexibility to independently control the amount of liquid (water) dispensed by the pump
3)Flexibility to independently control the pistons that raise and lower the spray nozzles
4)Pumps will be dispensing 2 – 10 ounces of liquid (water) per cycle
5)Save and retrieve recipes (ideally store 50 recipes)

Am I selecting the adequate parts?
Are the servo driven piston pumps the way to go to dispense
2 to 10 ounces of water?
Are the servo motors easy to control for a newbie like me?

Any comments and experience with this kind of projects are welcome!

Good start, it really depends on your budget.
For your application, repeatablity, quality....etc is it an issue?
You really don't need a touchscreen, but again it depends on your budget.
For your detergent, I would tend to use dosing pumps in place of servo's.

So far the only quality restriction is that the ideal accuracy for the amount of liquid dispensed by the pumps should be +/- 0.5 oz. If this significantly affects the price I could consider higher tolerances.

Why you say I don't need a touch screen? How would I enter recipes, select the amount of liquid, start/stop the pumps, operate the air piston, etc.? Maybe I am missing something here.

What is the advantage of using dosing pumps instead of using piston pumps?

Thank you for you reply!

How would I enter recipes, select the amount of liquid, start/stop the pumps, operate the air piston, etc.?

Click to expand...

In the old days you would use thumbwheel switches to enter the setpoints, selector switches & pushbuttons for other inputs, and indicator lights, counters, and pixie tube displays for outputs. But one touchscreen in current times will be much cheaper and more versatile than all the individual components.

A metering pump does not require a servo motor and may be a cheaper method, if your most strict accuracy is only +/- 0.5 ounces out of 10 (.5/10 = 5% error, 95% accuracy). For 2 ounces it would be .5/2 = 25% error, 75% accuracy. On a metering pump, you give it a setpoint and it pumps until it calculates that it has pumped that much, based on its pumping rate.

On raising and lowering the spray nozzles, I would think that two air cylinders with 6" stroke lengths, controlled by a solenoid valve, would do that job. No need for servos here, unless the nozzles must stop at some in-between position.

Have you done a risk analysis.

I see you stating a light guard not needed, I would have thought some sort of guarding to protect spraying someones eyes, let alone the protection of hands.

A foot switch or two hand switch, if you have a foot switch then it means they can put both hands in?

Have you thought of a guard door that lowers, making safety switches which enables a start.

It is not my intention to disregard safety concerns.
I'm trying to make the best approach to the project, and everyone's opinions are greatly appreciated!

Elcan, and Peter,

I would have thought that the spray nozzles would have a maximum travel distance that made sure the nozzles did not come down far enough to impinge an operator's hands, even if he left them under it. If spraying dye on clothes, there is no need for the nozzles to touch the clothes. If they COULD come down far enough to touch, it means the dye job will not be very even, therefore a hard stop for maximum travel distance is a must. These dyes are probably safe for human contact - they have to be safe enough to wear against your skin every day.

Is spray nozzle height a parameter in the recipes? Does the nozzle height vary with the different patterns? If so, you will need some type of cylinder positioner, or a screw drive and controller.

At this point, you need to specify exactly what values and devices each recipe will control. I understand you will control the amount of dye from 5 different nozzles, but are you also controlling the height above the clothes? Are the clothes moving, or does the operator have to place each garment under the nozzles? What are the garments - shirts, pants, coats?