Encoder Pendant for manual motion control of hydralic pistons.

I need to locate an encoder pendant for manual control of four hydraulic pistons. During tooling alignmant the operator needs to have fine manual control of the piston position. I'm envisioning a pendant where the operator can select which piston to move, then modify the piston setpont by turning the encoder knob on the pendant. Controlling the positions right now is currently done with a set of jog forward/reverse buttons that increment/decrement the position command for each piston. Using an encoder pendant would give the operator some control over piston velocity by simply turning the knob slower or faster.

Any favored sources? Reliablilty? Harrowing stories or good experiences?

Haven't come across any that have a select dial but I do have similar operation I'm currently using a pendant to control a parker hydraulic valve however in my case the operator has a speed selector on the panerl door this controls how fast the blade is to move then he has an up down button to control the knife during the cut on a loin puller machine which essentailly is used to seperate the backfat from the loins. The selector button can probably be mounted on the pendant (3 position switch) the Pendant I'm using is An AB pendant rated nema 6p I would recommend having some form of display showing the height value for the benefict of your operator for consistency purposes

Do you mean a simple 0-10V potentiometer linked to the hydraulic servo system? or are you looking for a 'canned solution'

Cheers

the pendant is the 800c configured pendant you can get up to 12 buttons and the part number will include your button configurations of which there are several options

I don't have any specific experience with these but there are several options from Koyo part way down the page.


Keith

I should clarify how the example above is done essentially the pendant interfaces through an input card which tells the logix 5550 processor what speed setting is used then when the up down buttons are used the processor adapts the output to the pneumatic valve 0 to 10 volts the use of the controller has the side benefict of reducing resistance errors due to corrosion, poor connections etc.

cjd1965 said:

Do you mean a simple 0-10V potentiometer linked to the hydraulic servo system? or are you looking for a 'canned solution'

Cheers

Click to expand...

Not a pot. The encoder has a knob that is turned by the operator to manually generate pulses back to the PLC. The pendant encoder will be a virtual axis to which the selected hydraulic axis is electroncially geared. When the operator moves the encoder the piston will track. If the operator turns the knob fast, the piston will move fast. If he movies it one or two 'clicks' very slowly then he can have very fine position control.

I see.

You want something that has rotary contacts every few degrees to provide a pulse train that speeds up or slows down the system depending on the speed of the rotation?

What about a spring return to centre switch, and use a timer in the PLC to say if the switch is ON, every x millseconds send a pulse, and if the switch is held on for say 5 seconds, half the pulse time so you get twice the pulses in the same time period?

Maybe have a 'timeout' facility or a pulse counter to restrict how long the switch can be active for in a single turn of the selector

Cheers

mordred said:

I should clarify how the example above is done essentially the pendant interfaces through an input card which tells the logix 5550 processor what speed setting is used then when the up down buttons are used the processor adapts the output to the pneumatic valve 0 to 10 volts the use of the controller has the side benefict of reducing resistance errors due to corrosion, poor connections etc.

Click to expand...

I'm interested in hearing more. Does your pendant setup then have a speed selector?

Here is the situation: I can easily set up a speed adjustment at the HMI, but the HMI is several feet away and down some stairs - the operator is on a work platform of a very tall 12,000 ton press during setup. I could have three preset speeds, but the encoder just seems to be more versatile. Right now its frustrating to them because they punch the jog button and sometimes overshoot the mark. Jogging is open loop right now but I intend to make it closed loop.

Safety is another issue - the simplest solution is a pendant with a three position enable switch so that the operator has to keep both hands on the pendant.

Hi I think this is exactly what you are asking about

http://homanndesigns.com/store/index.php?main_page=product_info&products_id=29

http://homanndesigns.com/store/index.php?main_page=product_info&cPath=15&products_id=28

essentially correct we have a speed selector switch its a 3 position so we merely increment and decrement a value that is used for the rate control then the operators can control their position movement according to whats confortable for them Unfortunateley this system is still under a service plan so I cannot post the code for it. The advantage comes in that we only require a regular input card rather than an analog input then run the pneumatic valve via the analog output. This educes possible noise or resistance issues.

Alaric said:

Not a pot. The encoder has a knob that is turned by the operator to manually generate pulses back to the PLC. The pendant encoder will be a virtual axis to which the selected hydraulic axis is electroncially geared. When the operator moves the encoder the piston will track. If the operator turns the knob fast, the piston will move fast. If he movies it one or two 'clicks' very slowly then he can have very fine position control.

Click to expand...

Alaric
so what you are doing is "replacing" the installed / fixed position sensing / ram speed control with an encoder on a pendant. Ram speed control and final position is dialed in by the operator by rotating the encoder and final position is guaged by operator eyeball.

Sounds pretty slick and should make life a lot easier when adjusting for different die height and other setup work etc etc.

The only question I have is that while control is on the pendant is how you are going to ensure there is no movement when someone bumps or drops the pendant?? Somewhere (was it you??) two hand control was mentioned - that may be the solution to this.

Dan Bentler

You need a handwheel like a CNC machine has. I have used some from a company call Dado. They were a 100ppr encoder with detents. We would give the operator a X1 X10 X100 so they had some different speed selections. This of corse was just different gear ratios. I will look and see if I can find some more info on them.

Edit

It was a company called Daido and the one I used was OLM-01-2DZ1-11A and it was $95 in 2002. I did a quick search and could not find it but it may still be out there.

We had a machine with a panel mounted encoder for manual control and it was very effective.
I did have to modify the original code a little bit, though. The original programmer did not limit the accel rate or distance and the operator could make a real mess if he slipped and spun the knob too far or too fast. I added logic to limit the velocity and total distance.

I have not seen one made into a pendant but I would think you could roll your own enclosure quite easily.

CharlesM said:

You need a handwheel like a CNC machine has. I have used some from a company call Dado. They were a 100ppr encoder with detents. We would give the operator a X1 X10 X100 so they had some different speed selections.

Click to expand...

CNCs are where I got the idea from - thanks again for the suggestions.

leitmotif said:

Alaric
so what you are doing is "replacing" the installed / fixed position sensing / ram speed control with an encoder on a pendant. Ram speed control and final position is dialed in by the operator by rotating the encoder and final position is guaged by operator eyeball.

Sounds pretty slick and should make life a lot easier when adjusting for different die height and other setup work etc etc.

Click to expand...

Yes Dan, thats the general idea. Right now I'm in the process of designing new controls for the machine and some feedback that came up in our design review was this issue from the operators. Pressing the jog buttons opens a bang-bang solenoid valve to move the piston, its damn near impossible to hit the desired position when trying to align the tooling.

The new design I have puts those bang-bang valves in the garbage can and has manual jogging managed by the proportional valves and closed loop control, in essence jogging will not be conventional jogging but a manually adjustable position command from the pendant. I haven't decided yet between using a Delta RMC or a couple of HYD02 modules in the CLX chassis (I guess either way they're made by Delta). The operators really liked the idea of something similar to the MPGs on some of our CNCs.

The only question I have is that while control is on the pendant is how you are going to ensure there is no movement when someone bumps or drops the pendant?? Somewhere (was it you??) two hand control was mentioned - that may be the solution to this.

Click to expand...

You hit the nail on the head Dan. That is one of my concerns as well. Thats why a three position enable switch is an attractive option to me, the operator has to depress the enable button to the middle position with one hand, then turn the encoder with the other hand - should be safer than the current jog method. The setups are performed only by specifically trained operators but I still want it to be safe - so I'm wide open to suggestions.


Oakie, the idea of making it panel mounted might just be a good one. A remote panel could be placed on the work platform far enough away that I know the operator's hands are out of the way but not so far as to be inconvenient.



Thanks everyone for your input so far, I'm still interested in hearing ideas.