I wonder if some people might be risking more trying to avert risk and so maybe shouldn't be risking building a ATC to begin with much less be trying to make that risky upgrade less risky by risking hurting themselves than just using a risky machine straight from the factory

I think your risk assessment process is completely reasonable. I think you reuploading this to cover off other s=aspects of safety is commendable. I'm a massive fan of the way you work and think you are a star. Thanks mate.

I think some misinterpret for humor, some don't exactly misinterpret but see the POSSIBILITY of misunderstanding and want to clarify, some misunderstand, some just take things the wrong way.

I call the hand on the table the 'texting while driving' effect: we can only really pay full attention to one thing at a time. The rest of our behavior (here, where you put your hand) defaults to habit. This is why we want safety systems to prevent something we would never do ***if we were paying full attention to that*** as opposed to paying attention to e.g. the part we're machining, a funny noise the spindle just made, etc.

Or maybe there is genuine, possibly misplaced, concern for James' safety. It's not liability, it's health and safety. In this case I don't think he's at risk. As someone that has spent at least 1/2 a lifetime designing safety systems I see both sides of the discussion, even yours. James, like usual, has his end covered for what his needs are. He's not building and selling. He's the owner operator.

Not a problem. I can still launch parallels out of the lathe chuck. :)

I wonder if the controversy would have arisen if James had used the words "Quick Stop" or "All Stop" instead of "Emergency Stop"?

The most important safety rule: sure, you won't do something dumb when you're awake and paying attention to that one aspect. However, people get tired and most importantly try to do more than one thing at a time. You know what happens when you text while driving, followed by resolving to never do that again? Expect to be focusing on something else, then using the controls without thinking about it. Or, you drop something on the keyboard or switches.

Thanks for sharing. Are you removing power from the inverter during an emergency stop, or just removing the run or asserting the trip input?

Some people use both an interrupt to the run command and remove power to the inverter via a timer (to allow the spindle to spool down otherwise it could damage the inverter) by switching off the contactor to the inverter. But I only interrupt the run command. Inverters don’t like being powered up and down repeatedly so it comes down to your personal choices. I’ve built several machines since 2008 and this has been my preferred method along with cutting main power to the steppers. Enjoying the series so keep it up. Best regards from the UK 🇬🇧 (the mycncuk forum over here is very active if you would like further suggestions. Some members build machines for their business so good to tap into!)

Thanks for re-commenting. Unfortunately, there isn't a way for me to update the video content without creating a new video, leaving the old comments behind.

You say that the VFD might be a single point if failure. Can you explain that more? I don't really understand; if the entire safety circuit is NC, then the VFD failing won't stop the e-stop from working. Is the concern contact-welding on that relay? That's the only thing I can think of that would cause it to fail dangerous.

@@evbunke2 There's a number of different scenarios so I'll cover a few different examples but please don't take this as an exhaustive list: (It also depends on exactly what components you're using) 1a) As you suggest contacts can weld and the mitigation for this is to double up on the contacts as safety relays do. It's important to note that if you have a multi-pole (three phase?) contactor and you connect the poles in series, this doesn't mitigate this issue as there's only one electromagnet which operates them all. If one pole is jammed, it can hold all of them closed. 1b) As an extension of 1a let's say you use two separate contactors in series so that if either contactors are welded the other will still disconnect the load. This lacks monitoring so you won't notice that the first one has welded and that you again have the single point of failure. This is why monitoring is important in safety relays - The mitigation is to use a normally closed pole from each of the contactors to form part of your reset circuit, so you can only reset when both contactors are in their open position. (or closed, for this monitor circuit) 2a) The e-stop wire could be cut, this is why we use a normally closed e-stop as you suggest. 2b) The e-stop wires are shorted together, this would prevent a normally closed e-stop from functioning and this is the reason why safety relays have dual e-stop circuits. Essentially they have two normally closed loops which must not be shorted together - Shorting them together is detected as a fault. 3) The VFD software failing - This could be caused by a programming or hardware error which causes the program to hang or otherwise stop responding while still operating the spindle. The mitigation for this could be a watchdog which monitors the microcontroller. 4) A hardware failure somewhere along the "fault input" or speed control signal path. As far as the VFD is concerned, the main point of the "Safe Torque Off" feature of a VFD is that it's a certified implementation which is specifically designed to not have a single point of failure within the VFD and to allow monitoring to detect such failures just as I mentioned in example 1 & 2. It is not designed to provide electrical isolation, it is simply there to ensure that the motor can be reliably stopped when needed. This quote sums it up: "ABB’s Safe Torque Off has a certified SIL 3 / PL e safety rating and complies with EN/IEC 61800-5-2 which is the standard that defines the Safe Torque Off feature. Finally, it is important to remember that Safe Torque Off DOES NOT provide electrical isolation. The motor must be electrically isolated by cutting the supply to the inverter and by local isolation to the motor before any access to the motor power connections." This of course applies across the whole system, in a CNC machine this primarily means that the axis drive motors and spindle motor must all have a way of stopping them in an emergency and that no single component failure will impede this. The more you can interlink into this system, the better.

@@yngndrw. I agree, this man knows what he is talking about. This is the way we wire e-stops in the industrial world.

@@yngndrw. I agree with you. I understand all that you are talking about. But I just want to chip in (not for you, you already know this but for others) that emergency stop buttons could be ok with just one contact. It depends on the level of safety that ones wants to reach. With one contact in ES button level it is Suitable up to category 1, PL c (EN ISO 13849-1), SIL 1 (EN 62061). With dual contacts in ES one can reach higher level like category 4, PL e, SIL 3. Also sometimes a real safety relay is not needed, it could be done anyway. But once you get used to them they are nice to use. Being over on the EU side we usually use Phoenix brands. But there are a lot of other brands.

Thats not a bad idea.

@@Clough42 I'm not sure what happened to the rest of the comment. There "should/could" be a spindle air cutoff sensor connected to estop, preventing spindle rotation when no spindle air.

I could be wrong, but I think the e-stop instructs the VFD to bring the spindle to a stop. In a previous video he configured the VFD to start/stop the spindle at certain rates. So, I believe the VFD may be handling braking rather than just letting it idle down.

@@CL-gq3no that is correct, but it will throw an over-voltage error when stopping with large tools. At least mine does.

@@CL-gq3no A braking resistor will allow the VFD to to stop the spindle/motor faster without putting the VFD into an over-voltage error condition.

I have no doubt you have heard this. In fact it's the first Google result. I'll defer to the Fluke 87 manual. Check out page 15. dam-assets.fluke.com/s3fs-public/87______umeng0800.pdf

Twist the connector 15 degrees to the left before pulling it out of the wall. :)

Depends on how you define better. A speed sensor would be new hardware that doesn't exist in the system today to solve what is not really a very big problem. This VFD does have a delay configuration, but I think it also delays the switch on startup, so you could move the problem to the other end, leaving the ATC active for a moment during start. Interestingly, the ATC activation does appear to lock the spindle while pressure is applied. I have no intention of testing to see what happens at speed. :)

@@Clough42 Ah, I see. Something to think about if you ever need to replace/upgrade the VFD I guess. Thanks for your reply!

The electricians turned up to tell him he wasn't being safe enough.

Yeah. I've heard of ring mains, but I don't know anything about them.

www.te.com/usa-en/products/connectors/circular-connectors/intersection/circular-plastic-connectors.html?tab=pgp-story

The horror