press brake cell

Are you using a KUKA robot? This is the KUKA sub-forum.

Quote from javaman

krc2 robot

Oh. That could be a problem. I'm not sure KUKA offers software support for any KRC2s anymore, so unless your robot already has the BendTech option installed, you could be stuck.

Quote from javaman

robodk supports bending or other external software ?

No idea.

I think the biggest issue will be achieving synchronized motion. That would usually require an external resolver, which is not something any software is going to help with.

Then, you need software in the robot to take the resolver input and generate the synchronized motion, which for KUKAs would probably require ConveyorTech or RSI, at minimum. Or hacking on the Function Generator, which every KRC has, but is not documented.

What are you trying to accomplish? it might be possible to achieve something roughly like BendTech motion by programming a fixed arc motion at a fixed speed, and relying on the press to bend the metal at a consistent speed.

Quote from javaman

What technique this bending cell uses ?

Fixed predefined speeds and motion?

Having never worked on one of those, I can't say, but the video's mention of "interrupt-free job change", along with the way the robot and press cooperate, strongly suggests to me that they're using KUKA BendTech (or something equivalent). It would be the smart way to go.

Using fixed predefined motions is not impossible, but is likely to be difficult, and take a fair amount of work to tune in for each piece being bent. In an ideal case, the robot would not need to follow the part as it's being bent, and only need to pick&place the parts before and after bending. A middle case might be to use an end effector with a lot of compliance (say, vacuum cups with deep bellows) to let the robot "follow" the part as it bends (using predefined motion), and letting the compliance make up for the inevitable inaccuracies in the non-coordinated motion.

Quote from javaman

How can modify motion of robot real time with the input from linear scale ? RSIXML ?

If feedback linear scale output to other-external plc-controller how can control the robot

motion in realtime from this plc-controller ?

The answer to "realtime control" is almost always RSI. Using RSI over Fieldbus from an I/O module or PLC will probably be simpler than trying to use RSIXML over ethernet. Also, RSIXML requires a dedicated ethernet card in the KRC2, which might be difficult to find these days.

That said, RSI is extremely powerful, but not easy. Getting a motion-control profile programmed and tuned to work properly will require substantial amounts of time and test runs. I ended up needing to learn the basics of PID control theory in order to make it work.

I'm using a Fanuc crx20iA on a 4ft press brake. All we have ever used for motions is a combo of (place, release & retract arm, form, regrip, retract press ram). This has worked for us relatively well. Depending on metal gauge there may be a spring back that will trigger a force warning, which we have countered with a thicker foam material in the robot arm gripper. No further programming required.

Quote from javaman

Can i read a linear scale ( incremental quadrature signals ) from krc2

i suppose so, it should be only a matter of picking correct IOs.

suppose you have the value (you can use one of counters for test)...

how do you plan on using it? RSI?

Quote from javaman

Can i read a linear scale ( incremental quadrature signals ) from krc2 and do the pid loop of press brake's ram movement in robot controller or need external plc-controller to read the scale and control the robot?

Quadrature? So, just two pulse signals 90deg out of phase?

This should be doable in RSI, but it would be necessary to create an object chain in your RSI application to create an Integer variable and increment/decrement it based on the encoder pulse train. I don't know of any RSI object that natively supports quadrature encoders?

the whole point of measuring press position is to let the robot follow the press. because robot is agile and has position control...

i must be missing something because it sounds like you are turning this around and - letting press follow the robot? how agile the press is? and how do you plan on making PID loop control press stroke position when the only control on the press is manual pressure adjustment?

Hello javaman how did you solve this? I have the same task now, but with a new robot