Just curious if anyone has. I am currently designing my own e-stop for my phoenix cnc router.

Would fear for my life when the owner of the mill finds out I've milled a ridge in the top of the table count as 'for personal safety'?

never for personal safety.... crap I dont even have estops on my machines;) I only use the estops at work to shut off the drives before I shut down the machines.
most of them are enclosed.

Jon

depends what you mean as personal safety? Ive used it a few times while destroying tools and jobs (as you do). Also use it when working on or in machines to avoid any disasterous outcomes.

I am surprised the safety police have not come running already about this thread. It seems as though many people believe that there should be absolutely no chance of being hurt no matter what they do.

E-Stops are good, they are highly visible and, if placed in a good spot, easy to HIT when needed. On my hobby machine, I have used it a couple of times to prevent the machine from doing something I didn't think it should - mostly during initial testing after construction.

On industrial machines, I don't recall hitting E-Stops for much of anything. It was always easier to hit Feed-Hold and or Reset to stop the machine and deal with the problems in that manor.

As for hitting E-Stop to prevent harm to myself, never. If I am near something that can hurt me (on my machine or on most industrial machines), chances are you can't get to the E-Stop button anyway.

If you look at industrial machines, the E-Stop is usually located outside the work area where, from operating the machine, you can see & hit the E-Stop. From that position, it is rare you could hurt yourself - you are not in the work area where things can hurt you. During setup, when your hands are inside the work area where there are moving parts and such, there is generally no E-stop that you can get at - doesn't make much sense for personal safety does it. So, my observation is that E-Stops are put on machinery not to protect the operator from harm, but to protect the machine from harm.

Kind of put's things into perspective as to what (rather than who) is being protected by the machinery builders and safety police.

The E-Stop is noted for being the hardest button to find on a machine ;)
Here is the NFPA79 regulations for Industrial Machinery, all equipment manufacturers in N.A. at least are supposed to conform.
Al

I grew up in a shop on a lathe that turned ø12"-18" shafts up to 9 feet long, and vertical machines with up to ø108" tables.
Big parts, big machines.
It's unfortunate that the machine manufacturers at that time (late eighties) chose to make the e-stop shut down EVERYTHING.
A broken clamp let a part come loose from a vertical turning center that a friend of mine was running, and he hit the e-stop.
After what seemed like minutes, but was probably less than five seconds, the table was still spinning at 200-300 RPM, (the e-stop killed the hydraulics, which provided braking for the table.) and the appx 1.5-ton part came out of the machine, killing my friend.

I hate the e-stop button, and would really prefer to see machine tools with a "stop" button that is as easy to find (and hit) in an emergency.

Granted, there should always be a perfect setup, and perfect tooling, perfect toolpaths, etc. And the operator should always be familiar enough with the control to know where all the buttons are.
But in the middle of a two-hour rough turning cycle (on the tenth part in the order), it's not always feasible for the operator to be right next to the control in the unlikely event that there will be an emergency!

Anyway, that's my two cent's worth.

Feel free to raise a glass in a toast to a fallen fellow machinist...

Here's to you, Joe.

I'm Sorry to hear about your friend. I think I would have gone after the manufacturors of the machine with a vengence.

I work in very heavy industry. When commisioning equipment, we always run the machine up to its full design limits (such as speed or load, what ever is appropriate) and E-Stop it BEFORE we turn it over to production. This way we detect things like you have described and get them dealt with before the machine is in opperation producing a product.

I have seen many machines that had E-Stops that most certainly protected the opperator. For example some equipment I commisioned a couple years ago had a cable running the length of the machine, about waist high, right in front of where the opperator worked. If the opperator got caught and was being pulled in, the cable stopped the machine within a few hundred milliseconds. Of course the opperator would probably still have a miner injury, but at least he wouldn't be dead.

Have I ever hit an E-Stop to protect myself? Hell yes! I hit an E-Stop the other day that probably protected a whole crowd of people. I'm currently doing maintenance on a production machine that is about a quarter of a mile long and three stories high. I was in a position to see the product (Steel strip about eight feet wide traveling at about 800 feet per minute) that runs through this machine broke. I hit the nearest E-Stop as the loose end was making its way to about half way through the machine. If it had gonne much further, it would have really created a lot of havoc in an area where a lot of people work.

When things start comming apart or going wrong with this kind of machinery, being a couple hundred feet away isn't even safe!

The equipment and machinery I deal with has the potential to kill, injure, or scare the hell out of dozens of people at a time. I have seen E-Stops save a lot of people not just property.

Ghyman, I am very sorry to hear of the death of a friend.

I am not convinced however that e-stop is bad based on that problem. I have seen many situations where it did good. I personally work in very large machining. My machine, a horizontal Ingersoll, has nearly 30 feet of "X" travel. It has multiple interchangable spindle units. One day I accidentaly cycled started my machine while in a very bad situation--kind of hard to explain the real situation--. (The remote pendant can start the machine). Without the E-stop I would have been toast my friend. Now, this may be an rare situation but for me, it only took that one time. I'm not saying anything is 100% but I personally think it serves more good than bad.

Just my two cents
-AJames

In most countrys there are regulations in place for commercial machinery as far as E-stops, but the thing that really bugs me, fortunately it is rare, there are still manufacturers that shut the whole machine down with e-stop, including the CNC control :mad:
There is absolutly no need for this which makes trouble shooting a nightmare, when I install a system, I not only leave the CNC unit on, which reduces the work of re-zeroing the machine but I also leave the inputs active, they are mostly low voltage anyway, this way, on a CNC machine at least the input logic can be seen in its active state.
I just shut of the supply to the CNC outputs and supply to contactors, motors, and all moving parts, as per the code.
Al.

In most countrys there are regulations in place for commercial machinery as far as E-stops, but the thing that really bugs me, fortunately it is rare, there are still manufacturers that shut the whole machine down with e-stop, including the CNC control :mad:
There is absolutly no need for this which makes trouble shooting a nightmare, when I install a system, I not only leave the CNC unit on, which reduces the work of re-zeroing the machine but I also leave the inputs active, they are mostly low voltage anyway, this way, on a CNC machine at least the input logic can be seen in its active state.
I just shut of the supply to the CNC outputs and supply to contactors, motors, and all moving parts, as per the code.
Al.

Thats the way my RYE machine is at work. If I hit the E-Stop, I pretty much have to restart the whole machine. If something minor happens I usually just hit the cycle stop. But if its something major I hit the E-Stop because cycle stop don't stop the bit. Fortunatly I have only had to use it a few times though.

Although I can't say that I specifically remember having to ever hit the E-stop in a panic for personal safety (I probably have) I have worn them out using it mostly for set-up/maintenance safety (the machines I work with (Amada) allow me to do this without shutting down). Anytime my personal safety is in jeopardy, i.e. when any part of my person is in harms way, I make sure the E-stop button is depressed and locked to prevent the machine (or somebody else) from making any kind of dangerous move. It just makes me feel better.....I kinda like my matching set of fingers.

As a person who has little trust for electronics, I hit the estop when I do most anything on the machine. So, when I stand on my little step stool to change the tool on my Bridgeport Clone, I hit the estop. I think of it as a safety interlock.

I have an Elrod Z-axis and have mounted the estop switch on the front of it. Since it is the only button on the machine (everything else is done from the gui), it is quite prominent.

Just today, as I was brushing chips away and standing on the far side of the table while the machine was running, it occurred to me that I might want to hook up an RF remote control for the estop. The only issue is that to make it fail safe, it should continuously transmit a signal saying don't stop. But then the batteries wouldn't last as long and when the battery quit, the machine would shutdown.

So then I could add a low battery alarm to the remote. That begins to become a lot of engineering for a small problem. I could just mount additional estop buttons on each side of the machine.

Ken

Just today, as I was brushing chips away and standing on the far side of the table while the machine was running, it occurred to me that I might want to hook up an RF remote control for the estop.

I think that's an overkill. Why don't you wire more e-stops in series to the existing one (provided it's N.C., which it should)? You can have one in every side, even a bar around the base you can step on.

only to protect the pump/jet

I used the e-stop the other day, quite funny actually.
I was drilling some 6" deep 1" holes on the haas in some aluminum with an indexable spade drill, this haas we didnt have the thru spindle coolant so I had to turn it down a little. I turned it down to 1600rpm but it ended up being in high gear still.
I got about 4" down into the hole after running one or two, the spindle load was evenly 80% untill boom, it just stalls, I panick, must have been 4 seconds before I hit the emergency stop button. lol I stood there and thought about it and it was quite funny.

turns out I turned it down to 1400rpm and it was in low range and had no problems.

Jon

I recently had a machine that was not only E-stoped but locked & taged out tear a good part of my hand off because the previous idiot who worked on the machine left an uninteruptable power source inside the control cabinet and the E-stop circuit was not properly designed.. Do not take chances & always remember...the previous idiot probably did everything wrong..

I recently had a machine that was not only E-stoped but locked & taged out tear a good part of my hand off .... the previous idiot probably did everything wrong..

Sounds like in your case, it was more than one idiot that did everything wrong! The designer and the guy before you!

We bought our first cnc about 11 years ago, (milltronics) and while my dad was out of the shop I decided to backup the programs on disk. I think it was two months old at the time and had glitched a few times before in the Z axis but we didn't know any better.

Anyway, about half way through saving the files to disk, (I was watching it count on the screen) the Y axis takes off!! I hit the E-stop at LEAST 6 TIMES and it kept speeding up!! I mean fast too, I would estimate it was going 500-600ipm when it blew the leadscrew out of the casting right next to me. I was sooo sick to my stomach, lol, I looked at the other guy in the shop and asked if he saw me hit E-stop and he just shook his head yes because I was swearing the entire time it was 'spooling up'. I muttered something and asked him to relate the story to my dad, I went home and went to bed.

Milltronics in the infinite wisdom explained to me, (true or not, I don't know but I talked to their engineer) that the E-stop on our machine told the computer to trigger something else to disengage the power to the drives. In other words since that inbetween part is what failed, had it not shot out the casting it would have continued going faster until the capacitor dumped it juice. They then said it was operator error... Ummmm, I was saving a program to disk, how could it be operator error?! I had to laugh though because they fixed it for free, (operator error, riiiight) and about a year later it did the EXACT same thing.

I don't trust E-stops anymore than I trust the engineers that designed em'. I've had to use it a couple times for broken tooling or the time I forgot to put clamps on my mold base and parked it on the floor, lol but I hope if I ever do need to use one, it actually works.

Anyone else heard of this or know why an E-stop doesn't just cut power?? I don't understand the concept if its basically just a 'suggestion button' for the drives to shut off. What IF the computer is the part thats going nuts to begin with?!

I've had a simular failure on a Bridgeport EZtrack (2 axis) - no damaage to anything mind! indexing just between drilled holes when for some unexplained reason both axis started moving quite slowly together - I remember the feed hold button didn't stop anything - its a few years back now but as far as I recall - sorry I canna remember for sure - the Estop did nothing either ! never trust it anymore - not such a bad thing!! only done it once in 7 years on same m/c

Pat

Anyway, about half way through saving the files to disk, (I was watching it count on the screen) the Y axis takes off!! I hit the E-stop at LEAST 6 TIMES and it kept speeding up!!

snip

Milltronics in the infinite wisdom explained to me, (true or not, I don't know but I talked to their engineer) that the E-stop on our machine told the computer to trigger something else to disengage the power to the drives.

snip

Anyone else heard of this or know why an E-stop doesn't just cut power?? I don't understand the concept if its basically just a 'suggestion button' for the drives to shut off. What IF the computer is the part thats going nuts to begin with?!

That's a very interesting situation. I'm wrestling with this very problem right now in my own design. My assumption was that I would use the estop to disable the drives as opposed to removing power from the drives. In the case of a big heavy machine, removing power from the drives is a bad thing, since there will be nothing to stop the machine. I know a lot of people just run estop into the computer and hope it knows what to do. I know with EMC, "getting the machine out of estop" is a big first step, so I'm concerned that removing power from the drives with estop is too drastic. But I think anyone that relys on the computer to always respond properly to estop is fooling themselves.

I use the E- Stop all the time, every job, every day. The problem I have is Optical Designers (bless them) sometimes don't understand the co- efficients they put into the equations and so I have to alter them one by one to get the correct surface form. One wrong co- efficient can give the machine an excuse to send the tool somewhere I don't want it to be.

I won't risk a Single Point Diamond tool rotating at 5000 RPM hitting a jig and snapping off.. sods law states that it would head directly for the only person in the lab, ie me!

Every time I start the beast, I have my hand firmly over the E- Stop and am extremely stressed.

estop are meant to stop the drive with out power down when you power down you loose you zero position on all axis when I prove or run a new program I use the dry-run which over ride rapid moves to feed rate on controller also keeping machine in single block check distant to go before turning feed from 0 imp to what ever also there are no tools in spindle that’s the best way I know of but as far a machine taking of like you say it did I never seen that but I guess it could happen

I think that's the safest way- dry running with manualy seleceted Rapid Overide. However on this particular machine there's no Manual Rapid Overide- I have to physicaly alter the program to obtain this, so I constantly havbe my hand over the E-Stop.

I have seen an 8kg lump of Germanium leave the chuck at 6000 RPM- it was the most almighty BANG- it went off like a grenade! Thank goodness for polycarb safety screens!

When I E-Stop, I don't lose any zero positions and all other variables stay ok so it's the easiest option for me really :)

Geeze, Im gonna keep this in mind when I start designing my cnc router table. Your all getting me a bit worried, sounds like a lot of lucky scrapes!

estop are meant to stop the drive with out power down when you power down you loose you zero position on all axis when I prove or run a new program I use the dry-run which over ride rapid moves to feed rate on controller also keeping machine in single block check distant to go before turning feed from 0 imp to what ever also there are no tools in spindle that’s the best way I know of but as far a machine taking of like you say it did I never seen that but I guess it could happen

I any shop I've worked in this is the standard method in CNC Program Proove Out. E-Stop is usually used before Powering Down a CNC after all Axies are away from their respected home positions and maintenancing. On most machines E-Stop isn't going to save anything unless your right next to it. Slow Rapids, IPM Override, Feed Hold, Optional Stop, Single Block, and Distance to Go ;) . Mostly stay alert when proving out someone elses program or using a machine you aren't familure with. I some rare cases when a program is loaded via RS232 there is a small chance that even one sepuence block could be missing. Only seen this happen twice in a shop that did a lot of welding. ;)

I've wasted time thinking about E-Stops. I might as well share the thoughts.
I would have someone who knows this stuff to make one E-Stop that you could tape to your skin and have some way of adjusting the sensitivity of the thing so that as you're learning the new machine and becoming more comfortable you can reduce the sensitivity. Galvonometer?
The second is what I call the Optional A-Hole switch. After your company, or you, if you sign the checks, spend a gazillion bucks on the new piece of equipment that travels near the speed of light in rapid mode there should be an optional piece of equipment that you can insert. The first time I crashed my new mill I had the distinct impression that my sphincter reacted much faster than my hand hitting the E-Stop.
Joe

It's the only why to quickly and safely stop all machine functions (i.e. drives, spindle, and every thing else) nto only that it's supposedly the largest button on the panel.

There are some controls where the e-stop is essentially the same as Feed Hold. The problem with that desgin is when the control locks up, especially with the increasing number of PC based controls, there is no e-stop anymore. Runaway axes like the Milltronics described above happen on other controls as well and a "software" e-stop is unresponsive.

On machines like VMCs, the e-stop must cut power to all axis drive motors and bring the spindle speed to zero as fast as possible. The machine has to stop moving and stop applying power to it's outputs like axes, spindle, hydraulics, coolant pumps, pallet changers, tool changers, and chip conveyers.

On hobby size machines, the e-stop may prevent damage or getting a hand pinched. On larger machines, it can save life and limb along with expensive parts.

There are some controls where the e-stop is essentially the same as Feed Hold. The problem with that desgin is when the control locks up, especially with the increasing number of PC based controls, there is no e-stop anymore. Runaway axes like the Milltronics described above happen on other controls as well and a "software" e-stop is unresponsive.
That's the point I'm worried about. Sure, it would be nice to be able to panic and hit the e-stop, then realize nothing was wrong and start right back up again. But on the other hand, I really want to be able to shut the thing down if there is a big problem. So maybe we need a big honkin' red switch for e-stop, and the "I'm just a weenie" sized switch for all the other times.

The E-Stop is noted for being the hardest button to find on a machine ;)

Al


in a panic situation , after flying leaps across a shop floor ,it very well might be,
and the guys face is normally more red :drowning: :drowning: than the button (chair)

we have two old mori's that drop the spindle about .15 when the estop is hit , sort of defeits the purpose

perhaps some should get eye bolts implanted into there skulls and have clip on kill cables to be attached to these eye bolts , like snow mobiles

perhaps some should get eye bolts implanted into there skulls so they can clip in kill cables to them , like snow mobile kill switches

I'm in the process of setting up a new machine right now. If I arrange the power feed so that there is a kill switch that will simultaneously kill power to the gecko boards, kills the 5VDC feed to the BOB and kills power to the router will this be a safe arangement for a e-stop? Or does it have to be wired in so that it kills power in some gentler kinder way?

Thanks

hello sdantonio.
i would guess and hope that your motors are sure to stop with the power shut of of the devices uou have mentioned.
which is the main goal of a kill switch , in this situation

hello sdantonio.
i would guess and hope that your motors are sure to stop with the power shut of of the devices uou have mentioned.
which is the main goal of a kill switch , in this situation

Yes, I would expect everything would shut off too. But I am also interested in everything shutting off safely (safe for the router table components that is).

That's the point I'm worried about. Sure, it would be nice to be able to panic and hit the e-stop, then realize nothing was wrong and start right back up again. But on the other hand, I really want to be able to shut the thing down if there is a big problem. So maybe we need a big honkin' red switch for e-stop, and the "I'm just a weenie" sized switch for all the other times.

If you've ever seen an operator, in a panic situation, hunt for the right button to stop the the machine, you'll agree that only one large button is really all that should be avail. in a panic situation

If you've ever seen an operator, in a panic situation, hunt for the right button to stop the the machine, you'll agree that only one large button is really all that should be avail. in a panic situation

The way I'm putting together my power supply is this: Once switch turns on the "power one" power supply. This supply powers up the three gecko's and the BOB, and through the gecko's, the motors. It also supplies power to the router itself. Then there is a little toggle switch that opens current flow from the power one to the gecko's to avoid and startup surges or anything like that.

If I have enough current in the circuit I may also put the computer on the same switch.

So basically, there is one big switch between the whole CNC unit and the wall.

That seems good. Is there any chance of a "coasting" situation? I realize that your typical "hobby type" machine may not incorperate a brake for axis motors etc., but...?

That seems good. Is there any chance of a "coasting" situation? I realize that your typical "hobby type" machine may not incorperate a brake for axis motors etc., but...?

I wouldn't think coasting would be a problem. Steppers are pretty much designed to be able to stop on a dime (under power) and have a relatively high inertia (while not under power). So I would think they would stop pretty quickly. But I have been wrong in the past and expect it may happen again. And at70 to 100 ipm I wouldn't quite describe the thing as flying. I would think the motor inertia and the leadscrew inertia would all stop the thing pretty quick.

I agree 70 - 100 ipm is'nt "fly'in" by any strech but still...? I guess my thought is in safety first. Do the steppers actually "brake" when powered down or do they "coast"???

... killing my friend.

But in the middle of a two-hour rough turning cycle (on the tenth part in the order), it's not always feasible for the operator to be right next to the control in the unlikely event that there will be an emergency!


I'm sorry about your friend.

I agree with you about not being able to babysit a machine at all times. In our shop I run two Haas TM-1 mills and a Mazak QT250. As a general rule I'm moving between two machines constantly with the remaining one running a longer cycle, I try to plan it that way so I can keep up with parts loading and still program etc.

Our machines stop immediately when you e-stop them, spindle and axis travel both. I've stopped it a couple of times when threading, tapping or moving into a first cut with the lathe tail stock extended, but I've yet to have to e-stop one for my own safety. I did however have to do so once for someone else's. I use to think the mill e-stop was in a poor location before that, but learned it was in a place where it couldn't be blocked by the operator's body if a second person had to come into the picture, or the operator could hit it as he tried to get out of harms way if needed. Guess I have to chock one up for an engineer on that one. From what you've said it seems that there may be more fore thought in how it shuts down a machine these days.

Scott

Do the steppers actually "brake" when powered down or do they "coast"???

I don't know. I was just assuming they would return to their power down state and the inertia would take care of breaking the motor. Of course inertial works both ways as it is just the resistance to change in the state of motion. But the inertia od the spining spindle is much less than that of the magnet. So it would actually be mre of a fixed magnet interaction that would slow it down.

It's unfortunate that the machine manufacturers at that time (late eighties) chose to make the e-stop shut down EVERYTHING.
A broken clamp let a part come loose from a vertical turning center that a friend of mine was running, and he hit the e-stop.
After what seemed like minutes, but was probably less than five seconds, the table was still spinning at 200-300 RPM, (the e-stop killed the hydraulics, which provided braking for the table.) and the appx 1.5-ton part came out of the machine, killing my friend.

Sorry to here about your friend:(
It seems like all to often I hear of situations like this where the E-stop causes unwanted results like these. It's bad enough when it's the fault of a machine tool that has poor maintanece or simply is broken, but when it's the fault of the machine design someone should be held accountable!

Some basics about a proper e-stop:

I design industrial machine controls occasionally. E-stop design is one of the most crucial designs, due to the liability & just plain personal safety regardless of the liability; except if you are some foreign manufacturers. Yes, as mentioned above, there are applications where it is more dangerous to remove power from the servo(s), usually due to inertia or gravity issues. In such cases, brands that are the most trusted to bring motion to a stop in such a condition MUST be used. I have went so far as to include a timer to remove power from servos with a high-inertia load after sufficient time has expired to allow the servo to brake the inertia, just to increase the safety level of the e-stop function. Some machines should use brakes to stop axes with inherent drift pressures such as caused by gravity. Any such brake (involved in safety) MUST be of the type that uses energy to remove the braking action, for instance spring-tension-activated braking with electrical release.

It might not be as easy as you think to design a good e-stop:

Unfortunately, not all manufacturers take appropriate measures to guarantee a fail-safe e-stop. When the enable signal is shut-off, most servo or motor drives will only respond by entirely shutting down the outputs. So in many cases these drives must not have the enable shut-off on E-stop condition, in order to bring the inertia to a quick stop. Thus my timer solution as mentioned above, which should be implemented with a simple timer not dependant on a larger computer system, to increase reliability. It still is not a perfect solution. But I think that some companies will throw safety out the window when they realize that they are adding cost for a imperfect safety solution. At least that solution is very safe, at least in my opinion. And I would not trust the drive enable signal for e-stop, I add a contactor to remove the power from the drive unit.

Some possible reasons for the failures to design a good e-stop:

Some manufacturers have designed e-stop systems very poorly. Others may have had a good e-stop design in the early stages of machine design, and then did not re-evaluate the e-stop design when the machine had undergone major changes (in the mechanics or the control). Sometimes manufacturers run out of budget (time or labor) for re-design after changes and refuse to fund time or labor for the re-design. Others may be just sloppy - haphazard. These are the ones that deserve to be sued. I sometimes must compete (in bids) with this.

The real root of the problem:

I think that poor e-stop design is often affected by the safety standards in the country of design, and/or perhaps it is affected by the legal difficulty of suing a foreign company for a safety-related accident. Of course these issues are entirely dependant on the exact country of the manufacturer. In my opinion, this is one of the biggest factors in the decline of machinery manufacturing in the US! Many US manufacturers have gone out of business due to the liability, and the foreign companies can make the machines cheaper since they do not have to add expense for some safety issues; like a good e-stop system for instance. I am not supporting a relaxing of liability for e-stop accidents here, as much as arguing against free-trade agreements (such as NAFTA) with other countries. Obviously, judging by history, telling people to buy american won't be effective; people tend to buy the cheapest regardless. It's all about the bottom line, and some managers do not recognize many safety hazards as a threat to the bottom line when they look to buy a new machine; and some other managers just miss them. After all, most managers do not know what constitutes a good e-stop system, and only a few companies will have written standards in place that prospective machines must comply to. So cheap usually wins. I cannot and would not take such chances.

Wow! Thats quite a post for your first time and very well put I might add.

As I mentioned in an earlier post, there is guide lines laid out in standards like the NFPA79 for industrial machines. But I have found that in general, European machines have been ahead of N.Amer. in the terms of E-stop safety, The use of special Safety Relays has been in effect in Europe for some years and this practice is slowly become normal here. especially seen in the case of imported equipement from that part of the world.
There are many configurations of Safety relays to take in account the controlled machine shut down in case of e-stop.
They are not cheap, hence manufacturers reluctance to use them.
Al.

In multi-axis, servo controlled machines that we manufacture, we use STI safety relays with timers to allow for a controlled shutdown. Basically when an e-stop is pressed or an enclosure door is opened, servo drives are sent an immediate stop command, allowing them to decelerate to a stop under power. At the same time contacts on the VFD's control side are opened to decelerate the spindles to a stop. The timer is set to give everything time to stop, then power is removed from the VFD's and Servo drives.

To be a truly safe system, every component must have redundacy. For example, there are two contactors in series that drop out to remove power from the drives. That way, if the contacts weld shut on one of the contactors, the other one should still remove power.

On the control side, true safety relays look for a pair of contacts to be switched simultaneously in the door switches when the door is closed, or when the e-stop is pulled out in order to enable control power, usually a set of N/O and N/C contacts. The reason for this is if only a single contact is used, an open circuit or short to ground could bypass an e-stop function, and you would not know it until you needed it.

This is still not 100% safe, but about as close as you can get.