February 17, 2019, 08:04:03 AM
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 Welding With KR 16-2

Author Topic:  Welding With KR 16-2  (Read 139 times)

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February 06, 2019, 03:15:55 PM
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jorsborn


I have a KR 16-2 sitting in the corner collecting dust for about a year now. I also have a product which requires welding and is fairly low volume. Typically it would not be a worthwhile endeavor to automate the welding. However, the welding is the largest headache in the making of the project and is what pushes out my lead time the furthest. It's also the largest expense. My thought was to attempt to use the robot to eliminate/alleviate the headaches associated with the welding process. I realize there may be other headaches that this introduces but it can't hurt to automate if it's reasonable.

What I'd like to do is a poor man's robotic welding setup. I have a fixture for the welding of my product. I'd like to integrate that with my fixture table, strap a mig gun to the robot and program the robot to weld it. I would like to hear your suggestions on the easiest/cheapest way to accomplish this (or fail quick). Roughly speaking I envision that I could get away with making some sort of clamp to secure the MIG gun to the robot and control the contacts by wiring from an Ethercat IO module to the welder (Lincoln Power MIG 256). I would assume a proper welding unit would have IO to detect faults during the welding process which would allow the robot to stop what it is doing and raise an alarm. Perhaps there is a way to do this by monitoring the voltage? Anyways, I would just like to get some feedback.

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February 06, 2019, 04:37:50 PM
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SkyeFire

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What model controller?

What I/O options does the controller have on board?

If you want to integrate a "manual" MIG welder, and not go to one made for connecting to a robot, you'll have to nail down what controls you need.  At minimum, you'd probably have to hotwire a relay in place of the weld trigger.  But what about the gas-flow valve, the weld power settings, frequency, etc?

Monitoring the weld... well, you'd have to have a sensor of some kind, and convert that sensor to something the robot could detect.  As a very basic example, if you have a gas-flow sensor, you could probably wire that to a relay that would close one of the robot's I/O inputs, and write your program to kill the weld power if the gas stopped for any reason mid-weld.

If you don't have a MIG-welding software package on the robot, you'll have to write some of your own.  A basic welding program isn't hard, but will lack all the nice bells&whistles that the official KUKA option would have.

You'll need to look into using Trigger commands properly for performing I/O on-the-fly, hand-tweak your dwell times at the weld start/end, and set up interrupts to stop the robot if the welder fails, and to kill the welder power trigger if/when the robot stops for any reason.

February 06, 2019, 05:17:21 PM
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jorsborn


I suppose that would be important information. It's a recent controller... KRC4. The controller is outfitted with an Ethercat interface. I can't remember exactly which modules but I believe about 16 digital IO and at least 2 relay modules. Additional modules would be easy enough to add.

I didn't plan on adjusting any of the weld parameters (feed speed or voltage) available to me during the process. We currently don't adjust these when manually welding. Gas flow is controlled with the MIG gun trigger. I just glanced at second hand robotic welding units via eBay and they actually seem pretty reasonable though I am only seeing the power source so perhaps the additional accessories would add up to something more significant.

I don't have the welding package on the control so I guess I'd have to roll my own or investigate that cost from Kuka.

February 07, 2019, 06:14:27 PM
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SkyeFire

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The tricky bit, if buying the KUKA MIG-welding Tech Package, is that while it's very flexible, you still need to check carefully about compatibility before using it with "off-brand" hardware.  It's probably doable, but an once of prevention is worth a pound of cure.  I once had to re-write large chunks of LaserTech b/c the customer bought it, and somehow managed to buy all the wrong hardware to go with it (lack of due diligence).

If you have I/O, then worst-case, you might need to add some relays in between (or opto-isolators, which are essentially solid-state relays).  Depending on what you have for existing hardware you don't mind tinkering with, vs disposable budget, it might be worth putting off buying the more expensive options until you've given the DIY solution a whirl and gotten a feel for the potholes, speed bumps, and what's critical vs just nice-to-have.  If nothing else, it'll make you a much better-educated buyer, and that's always valuable.

After all, you can always spend more money later.   :yessir:



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