Disabling of door switches

Loomis · May 16, 2015

When we got a couple of Cincinnati machines a year or so ago the door safety switches were removed from the doors and just stuck into the switch. We haven't run the machines much but I was wondering how many here do this. I have reconnected the switch on the lathe but not the mill. I know it's a safety thing and an OSHA inspector might frown on it.

Grumpy365 · May 16, 2015

Just from a liability stand point. There is no way in hell, I would even have power to it in the shop.

(If it was my personal shop, then it isn't anyone else's business what I do with my equipment )

Mike1974 · May 16, 2015

I think it is fairly common, this topic (on machine 'safeties') has been discussed numerous times. I personally hate them, but I understand what they are there for (read: dumbasses). Someone here on the forum said something like this, "safety switches and the like do not prevent accidents, they just make better idiots". The point being no matter what safeguards are in place, someone will manage to defeat them without actually trying and injure themselves.
I heard, just recently, that somewhere a guy was running a wood chipper wearing like a flannel shirt (unbuttoned I assume) or some kind of really loose clothing or something similar. I remember it was something like "are you fu*&ing kidding me? what a moron". Anyways it pulled him in and killed him. I don't remember the details, but it was basically his fault. Just a common sense thing. I guess now they are looking at revising the safety shutoff or e-stop on those machines now.

gregormarwick · May 16, 2015

Loomis said:
...OSHA inspector might frown on it.

Over here they (HSE is our OSHA) can fine you heavily. It happened to a local shop a couple of years ago to the tune of £20,000. I suspect it might not have been their first infraction though.

Setup keys to temporarily override the interlocks are, for better or worse, commonplace, but I have no idea how acceptable or unnaceptable they are to the powers that be.

Peter from Holland · May 16, 2015

Safety is a never ending story
The more safetymeasures you take the more relaxed peopla get at their machine The more relaxed people are the more dangerous it gets
In Holland we have a kind of roundabout at Nijmegen Its a paved circle about 100 to 150mtr diam and just stoplights when you enter or leave
No signs no lines nothing Just a emty space
You would expect a lott of accident to happen, but no You get so focused by seeing all that potentional danger that almost no accidents happen

A almost accident is the best learning experience With that many safetyprecautions you get fewer almost accidents So fewer very valuable learning moments
The problem is you cannot predict if it is gonna be a almost or a real accident

Peter from Holland

Mike1974 · May 16, 2015

The whole cnc machine safeties are kind of "meh" IMO. Each machine manufacturer has different standards and practices for what the safety interlocks are. At least I understand this from some readers here. Certain machines will not run the spindle/chuck PERIOD with the doors open. The newer Haas has a setup mode and/or a 'maintenance' mode, controlled by 2 keys (like a car key), on the control panel. With them both set to "unlocked" I can open the door and run the spindle at 750 rpm. Not sure what all the configurations are as you can have one key locked and one unlocked, which would (I assume) change how the machine reacts with the doors open. Anyways, can I not hurt myself with a tool running at 750rpm?? Apparently not to Haas' thinking. :confused:

I can also jog the axis around with the spindle running so I could mill into my hand if I put it on the table! :dunce:

Philabuster · May 16, 2015

"Safety Third"

--Mike Rowe

https://www.youtube.com/watch?v=Ap3peqZ0RlA

CNC Hacker · May 16, 2015

I find door safety switches very aggravating and would prefer they didn't exist. That said....my shop got hit for this a few months ago. OSHA frowns upon it is an understatement. It is at the discretion of the inspector as to how much to fine you. We were told the maximum fine is $70,000 "per occurrence" (read: per machine!). This would come into effect if they deduce that it's part of the shop culture to disable the switches, not just one guy doing it to his machine. Our initial fine overall was something like $28K although I heard they were able to negotiate that down by making quick fixes.

So I would say that living with the annoyance is far better than risking your shop getting shut down over it. Funny thing is, they say nothing about the older machines pre-safeties. We have several big VTLs that have homemade sheet metal walls we use as the guard. Running a 3,000 pound part at 200 RPM with 0.5" chips flying out is no problem tho! :-P

Metalcutter · May 16, 2015

I find it necessary to get into the machine to see what the cutting tool is actually doing, or where it is in relation to where you want it. Have you ever tried to reference a .013" circuit board drill without seeing the spinning drill touch the top of the work?

That said, I did buy a small inspection "telescope" to help me see how the chips were flowing.

An on purpose, especially designed for this difficulty may be all that is needed.

I also thought it would be cool to have an X&Y microscope on a pedestal, like the submarines have.
You could pull it down and do the inspection right on the machine, where it needs to be done.

Think about it...

Regards,

Stanley Dornfeld

CW Steel · May 16, 2015

Depends on the skill level of the operator. If you have unskilled part loading button pushers then the interlock might be a good idea. With skilled operators IMO the interlocks are kind of an insult. What about open bed cnc machines with no doors should OSHA require a laser or light curtain?

cncFireman · May 16, 2015

I worked for a fairly large company that had all the interlocks bypassed. Well one day one of the operators polishing a shaft (that had some legs on it) with emery cloth got pulled in. She was lucky to live and got messed up pretty good. Osha was not happy I had to go around and fix any issues and reinstall all locks. Well one month or so after our last inspection with osha and all the locks were unbolted again.

yardbird · May 16, 2015

My MTB has a M-code to disable the door locks, puts the machine in service mode. Chances are they aren't the only one, getting them or any MTB to tell you how to override door safeties without a waiver of responsibility but I bet most all have something like this by now, if not certainly a parameter change will fix it. You're probably ten times more likely to get hurt or killed on the way to work then by a disabled door lock. If you can't tell im the guy at the machine, no I don't run it with the door open but some setup stuff is way less of a headache.

Brent

gregormarwick · May 16, 2015

yardbird said:
My MTB has a M-code to disable the door locks, puts the machine in service mode. Chances are they aren't the only one...

Here in the UK (and all of Europe I think) machines must meet CE specifications.

That entails that all doors must be fully interlocked, but can retain some basic level of functionality with the doors open. We have machines from several different MTB's, but the lathes for the most part will let you jog, and rapid at a reduced rate, and run the spindle at a low speed.

The machining centres won't let you run the spindle, but will let you jog while holding a deadman switch on the pendant.

Neither will allow a toolchange with the doors open, amongst other things.

yardbird · May 16, 2015

gregormarwick said:
Neither will allow a toolchange with the doors open, amongst other things.

Yeah it is a limited RPM depending on the gear range your in. How can someone get hung up in a tool change if you have to be outside to hit the button?

Its always been a grip of mine on a newer lathe you couldn't polish a 1/2 thousandth off a dia or dedurr the start of threads or rotate the turret, run the conveyor, turn the freaking coolant on for a wash out hose. Couple keep relays and a M code has me past everything but the conveyor and its not too big of a deal.

Believe me I do completely understand the need for these kind interlocks, its the same reason I write "do not drink" on my tapping fluid squirt bottle. It just makes everything a PITA when setting up, I suppose if you could see through the glass I'd help, lots of times I couldn't and had to run/setup the POS with door shut.

Brent

james siffel · May 17, 2015

OSHA: Lloyd Industries in Montgomery Township fined more than $800K

I like my fingers. I saw this place and ran the other way!

rwbaldwin · May 17, 2015

OSHA have taken a page out of the EPA playbook and are looking to give themself new powers.

We regularly get missives from OSHA telling us what is best practice and what we should be doing as manufacturers (we make production/assembly line stations). I'm sure Haas, etc, get the same.

We are now expected to detect tampering with safety circuits and force a service visit.

Their latest big idea that won't go away is a 'black box' for machines. They have no idea how this might work - just that they work like it. It begs the question - who regulates these people.

SteveEx30 · May 17, 2015

I witnessed a terrible accident several years ago and since then I strongly believe that switch should be there. Take the extra few minutes it takes to Pause your program and check for blending, or whatever other reason you need to stick your head inside. After what I saw, it really isn't worth it... I have all the confidence in the world in my programs, and I still FeedHold or Pause before I open the doors.

IAMATT · May 17, 2015

Oh my aching ass!! Door switches are the most annoying things in the world. On a VMC or TC they only aggrivate and destroy tools. On the plus side they keep the floor clean. Sure there are stories but i can tell you that i havent owned a machine in 25 years that had working door switches and i plan to keep it that way.

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