Hi,
Can you please suggest me some ways to add an extra axis to the KR700PA 's EOAT. It would be of great help.
Thanks in advance,
VJ
Hi,
Can you please suggest me some ways to add an extra axis to the KR700PA 's EOAT. It would be of great help.
Thanks in advance,
VJ
What controller and what version of KSS is this robot running?
Adding an external axis to a KRC2 controller is fairly straightforward (although for PA robots it's a bit more complex than for regular models). Adding an axis to a KRC4 is something I don't have any personal experience with.
The robot is still in design and development phase. So we haven't chosen the controllers yet. I was looking ways to add an external device like rotary actuator or a gear box to help the gripper achieve an extra degree of freedom. This is made to enable the robot to pick an inclined workpiece from the stack.
Ah, that makes things easier. It's always simplest to order a robot with external axes from the factory. Or, you could simply order a KR1000, with full six-axis articulation, and that would render the entire question moot.
KUKAbots integrate external axes quite well. But you need to be aware of the limitations. For example, if you have your TCP on a piece of hardware mounted to the external axis, moving that axis will not automatically alter the TCP. This might be a factor in your planning.
There are also "synchronous" and "asynchronous" external axes. Normally it is possible to switch an external axis between these modes. If an external axis is in "sync" mode, it will move simultaneously with the robot arm. If it is in "async" mode, the axis will not move when normal robot motions are executed, even if the point data includes values for that axis. When the axis is in "async" mode, it can still be moved separately from the robot arm by using special motion commands and wait commands.
When using an external axis, there can also be a question of braking. The external axis's brakes can be linked to the robot's brakes, opening and closing together. But if you want to use the external axis in Async mode, it may be advisable (or even necessary) to have the external axis's brakes wired and programmed separately.
KUKA sells a broad range of servo motors, all of which are compatible with KRC controllers. Once you have determined the speed/torque requirements of your external axis, it should be easy enough to have KUKA provide an estimate for adding that motor to your robot order. Make certain to specify that the quote includes complete integration of the axis, including sufficient cabling to run the distance -- resolver cables usually only run to the bottom of the robot, but the power cable will need to run the full distance to the controller cabinet. Make certain the cables are rated for that degree of flexion and use inside an end effector dress pack.
Once you have the hardware, it will be necessary to tune the mechanical parameters of the motor. This is fairly straightforward -- you will need to set the speed and torque limits of the motor to match the hardware you are having it move. And depending on gearing ratios and other factors, you will need to alter the configuration of the robot so that the motion of the hardware matches the program. For example, if you have the motor driving a ball screw, you will need to provide a ratio of motor shaft rotations to mm of linear motion.
Skyfire
Thank you very much. I really got a detailed idea. But I have this question. Other than the payload details and few details regarding the intented trajectory of the robot, I don't have much information. How do i start ot determine the right motor-gearbox combination. Can you suggest me some ideas to start up? I researched a lot and it seems I need to have some details on the input and output torque to choose motor-gearbox combinations. But how do I get to know those parameters from just the known details on payload.
Any suggestions would be of huge favor.
Thanks,
VJ
That... depends entirely on the nature of the payload, and on the tooling design. Inertia, leverage, CoG, all of these are highly variable and interact in various ways. This is why integration companies have entire departments of mechanical engineers to handle these questions.
There's also the question of how much reach the tool has to have, and what amount of space you have for it to work in. A larger tool will require a larger motor and/or gearbox combo, but also adds to the load the robot carries. Leverage also applies here: you can build a tool that can carry the payload on the end of a 2m long bar, only to find that that much leverage over-stresses the robot arm.
This isn't a "rule of thumb" question -- it's a subject for an entire end-to-end design engineering study.
Skyfire,
I have PM'ed the rough concept diagram.