• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.
  • Guest,  We want to wish You and Your Family a Healthy, Happy Thanksgiving! Click the "X" at the top right corner to remove this notice)
  • PLEASE: Read the FORUM RULES BEFORE registering!

4

[How do I?] Safety interlock/shutoff help-slightly off topic

3
Like what you see?
Click here to donate to this forum and upgrade your account!
10

Olddaddy

H-M Supporter - Premium Member
H-M Supporter-Premium Member
Joined
Sep 23, 2015
Messages
109
Likes
46
#1
I am buildig a machine that has large rotating frames that could be hazardous to your health if you managed to insert yourself into their travel path. The machine is enclosed is a steel cage with a single opening gate at the front loading area. Large wooden molds are mounted in the secondary frame and it rotates within the larger primary frame. I want to install a safety interlock to prevent the machine operating when the gate is open, and shuts it down if the gate is opened while the machine is operating. In addition I want to wire in a rotating beacon, and an E-stop. My power source is 110 volts. I need some help to identify components and creating a wiring diagram. Anyone here who might be able to help me out? I have spec sheets for all the existing components, the motors etc. Any help greatly appreciated.
 

RJSakowski

H-M Supporter - Premium Member
H-M Supporter-Premium Member
Joined
Feb 1, 2015
Messages
2,773
Likes
2,844
#2
An E-stop usually uses a magnetic contactor in the main power circuit. When the E-stop is hit, the circuit for the contactor solenoid is broken and the contacts open.
 

Karl_T

Active User
Active Member
Joined
Oct 14, 2014
Messages
810
Likes
281
#4
Did this sort of work for many years....

You want to create a Master Control relay (MCR)

All control power for the entire machine goes through MCR. Break this NO relay and the machine is dead.

Now wire one self latching circuit to close this relay. I always label this machine reset.

Now put as many Estop buttons, door switches, etc. in the self latching circuit. Any of these opens; the machine dies.

Play with a relay till you see how to do this. The reset button just gives power to the coil. Then put power to one side of one NO contact. Run the other side through all your stop devices and back to the coil.

Karl
 

Olddaddy

H-M Supporter - Premium Member
H-M Supporter-Premium Member
Joined
Sep 23, 2015
Messages
109
Likes
46
#5
There are two Baldor CDP3440 3/4hp motors, one for each rotating frame. They are controlled by a pair of KB Electronics KBMC240D controllers.

Karl, if you would be willing to hand hold me through the process I can send you details of the existing wiring setup. Your info is great, but I barely speak the language.......
 

Karl_T

Active User
Active Member
Joined
Oct 14, 2014
Messages
810
Likes
281
#6
Industry would require motor contactors in front of those motor controllers... Some home shop types avoid this expense. Your call. Find a good way to make sure these motors die when the control signal is dropped. In industry, there is often a "machine stop" button that would stop the motors under control by commanding zero speed, in addition to the Estop button , doors ,etc. that kills power everywhere.

I am glad to give general advice. If this stuff is over your head, hire somebody that knows how to do this. Somebody's health or even life could depend on this being right.
 

markba633csi

Active Member
Active Member
Joined
Apr 30, 2015
Messages
1,327
Likes
539
#7
You could put a simple switch on your "gate" to disable the power, but if you want E-stops it gets more involved with relays and so forth as Karl was saying.
Mark
 

Keith Foor

Active Member
Active Member
Joined
Aug 4, 2015
Messages
278
Likes
203
#9
Couple questions.
First is if the machine is running and the power is cut to it, will it still have the inertia to keep moving and entrap someone dumb enough to open the gates and reach in at the wrong moment? Reason I ask is if that it the case then you need to do one of two things. Either build a braking system to stop the motion of the machine OR you will need to secure the gates when the unit is cycling.

Second, is the entire machine running on 110 or is that just the control voltage?
Getting the gates to have a interlock switch is fairly simple.
As long as the motor creating the dangerous motion is controlled by a contactor, and the machine will immediately come to a full stop if that contactor opens and the inertia situation is not a problem, then simply wire an industrial roller switch to the contactor coil and mount it in such a way that it will remove the power from the contactor any time that the gate is open.
But again, this is ONLY safe if there is no inertia in the machine that will allow the dangerous moving parts to continue moving after the power is cut.

Now, how to address it if there is inertia.
pneumatic cylinders.
Assuming that this machine will somehow already require shop air, this is the thing to go with.
You can either use a cylinder with an air valve controlled by the motor contactor power and a gate position switch to hold the door closed (but not to CLOSE the door which would create a new hazard) or you can have a gate switch trip a valve controlling a cylinder to both cut power and you apply a wood block brake to the moving part stopping it's motion. Of course the brake thing can break stuff if it's able to stop things immediately (which it would have to for safety reasons) and there is enough inertia to carry the machine through a cycle after it's started and you are trying to stop that inertia with the brake system.
So the option that the gate has a cylinder attached to it that is pressurized when the cycle starts that is also configured to not allow the cycle to start without the gate being closed to begin with is the best option.
To do this you would need a cylinder that would create enough force that it can't be overcome by hand plus a safety margin, that was controlled by a valve the would fully release the pressure and vent the output port to open air when open so the gate could be slid open against the cylinder when it was not engaged.

Pictures of this build project would be great at this point because I am only guessing about how this thing looks and that my idea will work.
 

Blackjackjacques

H-M Supporter - Premium Member
H-M Supporter-Premium Member
Joined
May 20, 2017
Messages
37
Likes
15
#11
Are you sure your motor controller is not a KBMD rather than a KBMC? My search returned only KBMC - a simple DC controller with reversing.

I just provided the simple control logic - typically 120V - but you can configure as you need and even run it at 24 VDC if you need - just size your devices accordingly.

Braking before you open the doors or braking while the doors are open, etc changes the problem a bit. You can either brake the hard way with mechanical means such as a brake pad arrangement like in your car, or you can momentarily plug reverse by reversing motor direction for some interval and driven by a time delay device as suggested by Mr. Dawson. I don't know what having shop air buys you other than to make the project more complicated than you need, and introduce additional dependencies - for instance, if you rely on shop air to provide braking similar to air brakes on trains, then you need to ensure you have air pressure available before you can even actuate power to the motor, etc.

Probably the best way in your case is to have a spring-loaded mechanical braking system that is always engaged unless power to the motor is available - that is, have a solenoid parallel with the motor control circuit to engage the brakes upon loss of power - whether that loss is because someone inadvertently opened the gates or a command to STOP instruction.
 
Last edited:

woodchucker

Active Member
Active Member
Joined
Nov 25, 2015
Messages
1,024
Likes
645
#12
I am buildig a machine that has large rotating frames that could be hazardous to your health if you managed to insert yourself into their travel path. The machine is enclosed is a steel cage with a single opening gate at the front loading area. Large wooden molds are mounted in the secondary frame and it rotates within the larger primary frame. I want to install a safety interlock to prevent the machine operating when the gate is open, and shuts it down if the gate is opened while the machine is operating. In addition I want to wire in a rotating beacon, and an E-stop. My power source is 110 volts. I need some help to identify components and creating a wiring diagram. Anyone here who might be able to help me out? I have spec sheets for all the existing components, the motors etc. Any help greatly appreciated.
Grizzly sells a contactor with emergency stop for real cheap, I got mine on sale for 6.95. I looked at the wiring. Very easy to add more micro switches in line for your door, which would be low voltage to break the magnetic contact. you would need an extra normally open switch or get the dual open/closed switch and serially wire it into the existing switch.
 

Keith Foor

Active Member
Active Member
Joined
Aug 4, 2015
Messages
278
Likes
203
#13
One thing I forgot to mention with the air cylinders.
IF you run an air safety system, you will also need an air pressure switch that is wired in the control voltage line so that if there is no air pressure that the machine will not run.
 

Olddaddy

H-M Supporter - Premium Member
H-M Supporter-Premium Member
Joined
Sep 23, 2015
Messages
109
Likes
46
#14
I was able to find someone to help me in the tech support group of the company I am buying the controllers from. He has worked out a simple disconnect that will stop the motors if they are running, apply a brake and also prevent start up if the motor is not running when the gate is opened. It has a key that must be in place, locking the gate to prevent someone closing the gate inadvertenly and then starting the motor. I will post pics when the machine is finished so you can see what it all means.
 
[6]
5 [7]