Delta Motion Control question for Peter (and others)

[agarb]

I am working on a small press that will utilize a Delta controller and a double acting hydraulic cylinder.

The customer needs very precise control of the actual force applied to the product.

Peter, have you had any success using a small load cell inline with the cylinder rod and controlling based on the load cell reading instead of dual pressure transducers?

Perhaps one of these in the stud-mount version:
http://www.stellartech.com/products/techsheets-load/min840.pdf

I have been unable to find a load cell signal conditioner that has an update rate faster than 70 milliseconds.

 

[keshik]

I don't have the answer for this, but another good place to ask would be on Delta's forums themselves: http://forum.deltamotion.com/

 

[Highland Controls]

I believe a load cell can be used with a Delta controller. Also, Interface Force has a signal conditioner with a 6kHz bandwidth. I usually use the SGA.

 

[ndzied1]

We do a job using a load cell on a cylinder into an AP2 module on an RMC75. The application runs at 180 - 200 parts per minute so it is very fast. This is the load cell we use:
http://www.interfaceforce.com/index.php?1000-Fatigue-Rated-LowProfile-Load-Cell&mod=product&show=1

I can't say that we are actually getting to a NIST traceable force at that rate because our goal is not force put a property of the workpiece achieved by hitting it with a certain force. However, the results are very repeatable.

 

[agarb]

We do a job using a load cell on a cylinder into an AP2 module on an RMC75. The application runs at 180 - 200 parts per minute so it is very fast. This is the load cell we use:
http://www.interfaceforce.com/index.php?1000-Fatigue-Rated-LowProfile-Load-Cell&mod=product&show=1

I can't say that we are actually getting to a NIST traceable force at that rate because our goal is not force put a property of the workpiece achieved by hitting it with a certain force. However, the results are very repeatable.

Good info! Thanks.

Do you know which of their signal conditioners you were using?

I will call Interface Force and have them recommend a solution.

The challenge on this project is we need very minimal force (about 1% of full scale) initially until the parts are fully heated. And then we go to a higher force.

My goal at this point is to install a load cell with dual pressure transducers as a fallback.

 

[agarb]

Just seen where Highland Controls says the SGA is the one they use from Interforce. I'll check it out.

I did find that Phoenix Contact has one with a selectable 30, 1000, or 5000 Hz filter.

 

[ndzied1]

We had Interface include a 0-10V signal conditioner right into the load cell. It has been a while and I don't have the specs on it handy right now.

 

[Peter Nachtwey]

I am working on a small press that will utilize a Delta controller and a double acting hydraulic cylinder.

The customer needs very precise control of the actual force applied to the product.

Peter, have you had any success using a small load cell inline with the cylinder rod and controlling based on the load cell reading instead of dual pressure transducers?

Yes, that is the preferred way of measuring force in lab or test environments. In industrial environments load cells have a half life of about 2 milliseconds.

Perhaps one of these in the stud-mount version:
http://www.stellartech.com/products/techsheets-load/min840.pdf

I am at home now but look on our forum about third party products we recommend.
http://forum.deltamotion.com/
Jacob does a lot of the customer support now. I still geek out on my own special projects.

I have been unable to find a load cell signal conditioner that has an update rate faster than 70 milliseconds.

I know there are some list with 4-8KHz response which is what we recommend.

 

[ndzied1]

Yes, that is the preferred way of measuring force in lab or test environments. In industrial environments load cells have a half life of about 2 milliseconds.

The load cells I referenced get hit about 22 million to 44 million times a year in an industrial environment (depending on how many shifts they are running). They are rated for 100 million cycles and we are not running them to their limit every cycle so they actually survive well past the 100 million cycles rated.

But you do pay for it

 

[agarb]

Thanks for all the responses.

Peter - This is more of a low cycle lab press than industrial application so if the load cell will survive just 10% as long as ndzied1's...

If I used an RM75E-AA1 with (2) EXP-AP2 would it be possible to wire in two pressure transducers to one AP2 and the load cell to the other AP2? Then if it was determined that a failure occurred, switch to pressure transducers instead of load cell? Switchover would be via PLC message to RMC.

Also MTS distributor was in here the other day bragging about "new" Ethernet ip position sensors. Will those eventually be supported as feedback devices (maybe they already are?) or are they non-synchronous, too slow, or some other reason why they would not be able to work?

 

[Peter Nachtwey]

T.
If I used an RM75E-AA1 with (2) EXP-AP2 would it be possible to wire in two pressure transducers to one AP2 and the load cell to the other AP2?

Yes

Then if it was determined that a failure occurred, switch to pressure transducers instead of load cell? Switchover would be via PLC message to RMC.

Yes, the RMC can do the switch over on-the-fly without waiting for the PLC.
See this link
http://www.deltamotion.com/support/..._Features/Custom_Feedback/Custom_Feedback.htm
I would still make the load cell the primary force feed back device.

Also MTS distributor was in here the other day bragging about "new" Ethernet ip position sensors. Will those eventually be supported as feedback devices (maybe they already are?) or are they non-synchronous, too slow, or some other reason why they would not be able to work?

Salesmen don't know squat. The Ethernet/IP transducers are fine for level control and connecting directly to a Rockwell PLC or Ethernet/IP equipped HMI , but for motion control the sampling is not synchronous to the motion controller. One of the things we do is use a FPGA to read all the feedback devices in parallel at the same time with NO software. There is NO sample jitter due to interrupt and non deterministic software. The allows us to easily compare positions between axes. It also makes calculating velocities and accelerations easier. It is harder to compare position between axes if the sames are taken at different times.

I like 5,2 or 1 micron SSI rods. Our controller will send the clock pulse out to all the rods at the same time and clock in the data at the same time. We put a priority on being synchronous and deterministic.

 

[agarb]

Peter-

Thanks for the link to custom feedback. Looks very good.

You confirmed what I suspected with regards to the ethernet ip transducers.