Looking for advice about buying a used Kuka for milling.

Lower hours the better, backlash will be your biggest enemy when milling so an older worn robot will obviously not be as ideal

If you are vat registered you can import without having to pay the vat, you just declare it in your return, I have not done it myself yet if I'm doubt check gov website or ask accountant.

0. Set up safety around the robot, or update your life insurance.

1. DO NOT buy a Volkswagen version if you can avoid it -- the (V)KRCs are heavily modified from "stock" and are a real pain to work with. And you find a lot of used ones floating around the Euro 2ndhand market. Audi, BMW, and some other customers had their own more-lightly customized versions of the KRC -- "plain vanilla" is the best option, but there's likely to be lots of "customer specific" KRCs packing the market. Likewise, avoid any heavily-customized KRCs -- you'll sometimes come across units that have been heavily modified for very custom setups, and unless you really know what you're doing, getting those to work can be a crapshoot.

2. Avoid anything older than a KRC2 ed2005. KSS 5.4 to KSS 5.6. Honestly, if you can get a used KRC4, go for that instead -- KRC2s are getting progressively harder to find parts&service for.

3. Avoid mix&matching if at all possible -- get your robot&controller together, and try to insist on a powerup and jog test before putting money down. Trying to match up a random KRC with a random KR can be made to work, but may involve hardware issues.

4. Check on what I/O the robot has on board. A refurb KRC will probably be stripped down to factory stock, and as such will only have the built-in DeviceNet connector (X801) on the MFC card. That's entirely usable, but you need to be aware of what the robot does and does not have.

5. Make sure the robot comes with the X11 safety connector or parts for same (or the equivalent connector for customer-customized versions). If it doesn't, you'll need to budget buying the correct Harting connector to pin out the safety contacts

6. Make sure your CAD/CAM tool chain will support post-processing to the robot. There are postprocessors that will output simple .SRC and .DAT files that any KUKAbot should be able to use, but some toolchains rely on having special option packages installed in the robot, and your used robot probably won't have them.

7. Be aware that no robot is as rigid as a mill, and has a lot more backlash on every axis (amplified over a much larger working envelope). This gets even worse when you start adding external axes. Robots are good at repeatability, not accuracy.

8. MAKE A BACKUP!!! Before doing ANYTHING ELSE, pull the hard drive and make a full clone of it using CloneZilla, Acronis, something. In fact, copy the hard drive onto a new drive, and make sure the robot can boot from the new drive. Used robots never come with the re-install media, and old hard drives fail eventually. If your HD fails, you'll have no chance to re-build the robot without a full-drive clone backup.

9. Spare parts. If you get a chance at buying a "matched set" of KRCs, consider it -- it may well be cheaper to buy a "spare" KRC to use as a source of spare parts than to buy spare parts on the open market. And KUKA doesn't make spares for KRC2s anymore, so the parts will only become more scarce over time.

Fully agree with going for KRC4, imo krc2 will only cause you pain and cost you more in the long run (a krc4 cabinet to upgrade the robot will cost you £15k+ IF the robot is upgradable)

Bear in mind anything 8.5 below will be running win7, this is now at the end of support life BUT a KRC4 can be upgraded to win10 and 8.6 for approximately £5k, a KRC2 will be running the very ancient unsupported xp and is not upgradable beyond buying a whole new cabinet and spares are getting scarce.

As sky fire alluded to, many used dealers will mix and match robots and controls to find working bits, this can lead to some issues down the road even with KRC4 systems.

Also be aware that robots may seem cheap at first look, but there is a huge learning curve and costs you may not initially consider, such as install, safety cells and software. And often what seems cheap to start will can end up costing a lot more than you expect it too, especially with unknown used robots.

Hope this helps

Quote

Bear in mind anything 8.5 below will be running win7

KSS8.3 runs on Win7.

KSS8.2 runs on XP...

Ah yes, iv never ran a Krc4 below 8.3, from a milling robot point of view, kuka.cnc 2.1 will run on 8.3 only (Not 8.5) and kuka.cnc 3.0 will run on 8.6

Hey marbles, how did it go? Did you get the KR 210 with KRC2?

Now I'm facing the same question - I'm about to buy the same machine for myself, quite tight on budget, and there are two options for me now (for the same price):

KR90 R2900 EXTRA HA (KRC4) (2015) - made as a complete package (already with ATC spindle, additional table etc), machine is in very good condition.

VKR210 R2700 (KRC2) (2009) + KL1500 (linear track) - complete package, low grade spindle (I'm about to upgrade it), history with no heavy usage - all motors and gearboxes are original, actually it's pack of two same VKR210 for redundancy + the linear track. Looks to be in very good condition too, but a bit older.

What should I be aware of? I'm going to do all my programming offline using Grasshopper (Rhino) and the linear track is a huge advantage for me.

I'm a bit afraid of KRC2, should I be so afraid? I'm a Mac user, so Grasshopper is my go-to solution for generating code. I'm not prepared to write KRL on a regular basis.

Why should I care what version of Windows is running on the machine? I'm not going to bother with package updates as they are both unsupported, am I? What am I missing here? (I haven't used Windows for 20 years, so if there's anything I need to know, say so).

What about rigidity and backslash? Will I benefit from a higher payload?

Is it a good idea to have a redundant machine or is it not worth the extra money and space?

Thanks to all of you, also in return, for all the valuable information in this thread and on the forum in general.

Definitly do not take the vkrc2. Its outdated and additionally a special version for VW that is quite different than a standard krc. People who can support with vkrc is quite limited compared to standard krc. Also machines coming from VW are usually pretty worn out. Nothing you would want for milling.

Fubini

Hi Fubini, thanks for your reply. I still don't understand what it means to be "oudated" in relation to a machine that is only expected to move on the basis of the commands it receives. What kind of updates are we talking about? A richer set of commands? Like what? Faster or more accurate movements?

I own an ordinary CNC machine, and I can't imagine any reasonable software update. Sure, I'm hungry for any updates regarding the software that helps me generate toolpaths etc, but it's not the machine business as I think of it. Am I wrong? Is the robot machine doing more business here that I should be looking after?

I'm just trying to understand. I'm about to spend a lot of my personal money on something that's not a business yet, it's just going to be my sandbox to play in and try to create something that I can build a business around.

Quote from bn1-cz

A richer set of commands? Like what? Faster or more accurate movements?

Yes. For example spline was created later on. Spline motion usually is faster and has a higher precision in path guided motions.

Also VKRCs usually are not equipped with absolute accuracy because VW never uses and therefore never orders it from KUKA. For KRC4 this might be available and increases robot accuracy. So you should check whether the system you are buying has the absolute accuracy package which is no general package that can be installed on any robot but is a set of specially defined machine data exactly made for a specific robot (a single serial number) to make it high precision. Btw. the HA in the robot name states High Accuracy and usually then comes with the absolute accuracy package. Also some other mechanical parts of HA robots are chosen special to allow this higher accuracy.

Also the programming interface for VKRC and KRC are very different. Even though in the end both systems run with KRL code. But getting this externally generated KRL code to run on a VKRC is more difficult than on a KRC. I can not say for sure whether Grasshopper even supports VKRC. Interfaces of VKRC are very much pimped to exactly fit into VW plants and VW way of thinking. In general KRC is a more open and as most people say simpler to handle and flexible system. Even though you plan not to do much on the robot side without touching and at least having a small grasp of the robot system will not work.

Also no matter what machine you have eventually something will get damaged. Spare parts for KRC4 are still available. For VKRC2 it might get difficult to get them and then they also are already old and might not run as long as well.

Fubini

So you are saying that buying the older machine is not a good idea at all? I'm thinking that way because the package includes two complete milling units (two drives, two pedants, ...), so I could use it as a replacement machine or for spare parts.

Writing code is my daily bread, so I can do it, I can definitely create some automated code post-processing by myself, but I would prefer to avoid it as this activity is my side hustle to produce something in physical space.

I'm about to mill some low poly sculptures and some chairs and benches out of a single piece of wood. I don't need a higher precision for joints etc. I expect to continue using my CNC machine for this type of work.

Quote from bn1-cz

So you are saying that buying the older machine is not a good idea at all?

Exactly I would not.

But ultimately its your decision. I remember some older threads in this forum where people did exactly this: Bought an old VKRC for milling because those are the cheapest ones available and then coming to this forum and complaining the system is not what they expected. Maybe use the forum search to get an idea of the problems that came in these threads up in the past.

No offense CNC machines and robots are totally different beasts. When executing jobs the are totally different. Robots suffer from other effects than CNC machines due to the different mechanical construction. They are a lot more prone the effects like elasticity/singularities/backlash. Effects you would have to learn to handle in your process. These effects get worse over the lifecycle of a robot.

Fubini

Quote from marbles

As it happened the sticker on the controller states it as a (v)KRC2ED05 from 2010 but for whatever reason I have not had the issues commonly found by others working with the VW variant ...

The sticker is the same for all versions. Doubt you have the VW version. Anyway, think if you use offline path planner you also can use VW version, as the low level commands (like lin {x 0, y 0,z 100,a 0, b 0, c 0} ) can be used on both versions.

OK, I get it. So the main risk for me is not being able to control it properly due to the specific SW version etc. That's scary enough for me, so before I buy anything I try to arrange some time with the sellers to stay at their place and play around with the machine to see if I'm able to control it in the intended way.

Thank you all here, I'll keep updating later for anyone who is going to find themselves in a similar situation.

Guys, thanks for all the information. I went for the KRC 4. It was not an easy decision for me as the price difference between the two was quite significant.

Quote from bn1-cz

Guys, thanks for all the information. I went for the KRC 4. It was not an easy decision for me as the price difference between the two was quite significant.

I can just about guarantee you'll find it cheaper over the long run, despite being more expensive up front. It should certainly be less frustrating and have less downtime.