I reviewed TwinCAT 3 in February of 2013 and it was a mixed bag. I lauded the amazing performance but warned about the reliability problems. I think it’s time to revisit the topic.

Things have improved greatly. When I wrote that review we had 2 production systems running TwinCAT 3 (the 32-bit version). We’re now up to 5 production systems with another on the way, all running version 3.1.4016.5 (which is a 64-bit version). The product has been more stable with each release. First we tried switching to a Beckhoff industrial PC, but we still experienced two blue screen crashes. We’ve then turned off anti-virus and disabled automatic windows updates. So far I haven’t seen another blue screen on that system, for about two months.

Manually installing windows updates isn’t a big deal, but it’s unfortunate to be running a PC-based control system with no anti-virus. Our industrial PCs are blocked from going online, and each one is behind a firewall that separates it from our corporate network, but it’s still a risk I don’t want to take. Industrial Control vendors continually tell us their products aren’t supported if you run anti-virus, and I don’t see how anyone can make statements like that in this day and age.

The performance of the runtime (ladder logic) and EtherCAT I/O is still absolutely amazing.

While the IDE is much better than the TwinCAT 2 system, the editor is still quite slow (even on a Core-i7 with a solid state drive).

The Scope is now integrated right into the IDE, and I can’t give that tool enough accolades. I recently had to use Rockwell’s integrated scope for ControlLogix 5000 and it’s pitiful in comparison to the TwinCAT 3 scope.

The TwinSAFE safety PLC editor is light years beyond the TwinCAT 2 editor, but it’s still clunky. It particularly sucks when you install a new revision of TwinCAT 3 and it has to upgrade the safety project to whatever new file format it has. We recently did this, then had to add a new 4-input safety card to the design, and it wouldn’t build the safety project because of a collision on the connection ID. It took us a couple hours of fiddling and we eventually had to manually set the connection ID to a valid value to get it to work. On another occasion, after a version upgrade, I had to go in and add missing lines in the safety program save file because it didn’t seem to upgrade the file format properly (I did this by comparing the save file to another one created in the new version).

The process of upgrading to a new TwinCAT 3 version often involves subtle problems. The rather infamous 3.1.4013 version actually broke the persistent variable feature, so if you restarted your controller, all the persistent variables would be lost. They quickly released a fix, but not before we experienced a bit of pain when I tried it on one of our systems. I’m really stunned that a bug this big and this obvious could actually be released. It’s almost as if Beckhoff doesn’t have a dedicated software testing department performing regression tests before new versions are released, but certainly nobody would develop commercial software like this without a software testing department, would they? That’s a frightening thought.

I ended my previous review by saying I couldn’t recommend TwinCAT 3 at this time. I’m prepared to change my tune a bit. I think TwinCAT 3 is now solid enough for a production environment, but I caution that it’s still a little rough around the edges.

Edit: Note that I’ve since added a TwinCAT 3 Tutorial section to this site.

Edit: Note that I have posted an updated TwinCAT 3 Review in 2014.

So back in 2010 I wrote about my first impression of TwinCAT 2 and later that same year I wondered if automation programmers would accept TwinCAT 3. I was lucky enough to be involved in the TwinCAT 3 beta, and now that the 32-bit version of TwinCAT 3 is available for general release we’ve deployed 2 production systems based on TwinCAT 3, and will likely deploy more in the future. What follows are my impressions of the current state of TwinCAT 3 based on our experiences with those 2 systems.

I think the best way I can describe TwinCAT 3 to the non-initiated is by comparing it with Allen-Bradley’s ControlLogix platform with their RSLogix 5000 programming environment. I say that because I’m familiar with that platform, and so are most of my North American readers (I assume). It speaks well of Allen-Bradley that they are the de-facto default control system platform around here.

We often fall back on car analogies, and I don’t want to break with tradition. If ControlLogix is the Ford Taurus of control systems (common, reliable, with lots of performance for most tasks, lots of room, and fairly maintenance free) then TwinCAT 3 is something like the Rally Fighter. That is, it’s road legal, fairly rare, requires lots of TLC and understanding and may not be as reliable, but will take you places you’ll never get to go in a Ford Taurus.

When it comes to speed, TwinCAT 3 with Beckhoff’s EtherCAT I/O is a beast. I can’t stress this enough. We’re running both production systems of TwinCAT 3 with both a 0.5 millisecond logic scan time and a 0.5 millisecond I/O bus scan time and we’re only using about 10% to 15% of the available horsepower of each system. You can see and react to things in the TwinCAT 3 system that you’ll just miss in a ControlLogix processor. For instance in one case we’re driving an output off of an absolute encoder and the repeatability of turning on that output is much better than anything we’ve seen with any other controller.

Furthermore, data accessibility is light years beyond any traditional PLC. In one test I moved a 400 kB block of data from the real-time (ladder logic program) to a .NET program running under windows on the same PC and all I can say is that it’s nearly instantaneous. That’s an advantage of having the HMI and real-time executing on the same physical hardware.

That’s not even getting into the new C++ integration (which I haven’t used).

Any TwinCAT 3 vs. ControlLogix system comparison will also certainly favor the Beckhoff solution when it comes to price. At least I can’t seen any case yet where that’s not true by a significant margin. I can’t say exact prices, obviously, but I’m confident that’s generally a true statement.

Does that mean I think the competition is a hands-down blow-out in favor of TwinCAT 3? No. In fact if you’re considering trying TwinCAT 3 I can’t even go so far as to give you my blessing right now. It has problems.

TwinCAT 3 crashes with a blue screen. Regularly. There, I said it. That’s the dirty secret. Everyone’s fears about PC-based control on the factory floor were around stability and in our experience TwinCAT 3 isn’t stable yet. This is odd to me because we have another system with TwinCAT 2 and it’s solid as a rock. Unfortunately our TwinCAT 3 system crashes with a blue screen regularly, and the crash report always shows that it’s some kind of memory violation in their Tc*.sys files, which are the system files responsible for running their real-time system under ring 0 of the OS (as far as I understand). I’ve never even seen blue screens with Windows 7 until trying out TwinCAT 3. There are actually two different times that it crashes: (1) randomly, and (2) when I try to do an online change.

Beckhoff’s response was that we were running it on 3rd party hardware. They loaned us a Beckhoff industrial PC to try. We tried it for a week and we didn’t see any random crashes, but it still crashed the real-time when I tried to do an online change, and it also crashed the IDE almost every time I recompiled the program. In fact that’s the reason we had to stop the test with Beckhoff’s hardware after only one week. I needed to compile a change and couldn’t get it to compile. It did work on our 3rd party PC (an HP desktop PC).

Now, I don’t think these are insurmountable problems. Beckhoff is still coming out with new versions on a regular basis. Their new support for 64-bit windows operating systems is on the horizon. TwinCAT 2 seems stable and I’m sure TwinCAT 3 will get there eventually. However, for the moment, if you’re considering the plunge, I suggest waiting about a year before bothering to check it out. If you just need the speed, consider TwinCAT 2, as even though it doesn’t take advantage of multiple cores it will likely do what you need and is a much more mature product at this point.