[cnc1000]

I'm retrofitting this mill with Geckos. I'm down to a problem with the pneumatic brake system. They use 24V solenoids. I can apply the brake, but it never lets go. I energize the solenoid, it clamps the brake on, and just stays. I think it was working fine before the operation. It should pressurize the ram and then exhaust it out after the 24v is removed, right? Am I missing something here?
cnc1000

[gus]

I think it is a two way cylinder, you want to put power to another cylinder to disengage it

[cnc1000]

Looked at it some more and found a single pneumatic schematic that was a little help. Not much. The speed up/down pneumatics use a double acting valve, with a center-off position. Energize one ram for up. As soon as you take away the 24v, it should revert to center off by a spring. Same for the down ram. The brake only has a single 24v coil. When you energize it, it forces air into the ram. When you take the 24v away, a spring is supposed to return it to off and vent the air away. Problem is, the brake just turns on and stays on. More work today.....

[John Bennett]

The system engages the brake when 24 volts is supplied to the solenoid valve, this allows air pressure to flow to pneumatic piston to engage brake. Remove the 24vdc from solenoid and the valve should block air pressure going to cylinder and allow air from cylinder to vent, causing brake cylinder to retract.
Things to check for release of brake. When brake is applied, remove power wire off solenoid and see if brake releases . Next remove air line between valve and cylinder. Does brake release. Grasp piston end and see if you can manually retract cylinder to release brake.

If system was left for a long time you might want to add a bit of air tool lub into air line to lubricate .

[cnc1000]

Hi,
Yes, the system was dormant for years. Air tool oil would be a great idea. However, I fiddled with it some today and it turns out that the operation is exactly backwards from what I'd expect. If there is no air to the system, there is no brake. If there is air to the system, the brake defaults to ON. In order to turn the spindle motor on, I have to actually send 24V to the solenoid, and that releases the brake. Go figure. I'm retrofitting it anyway, so I can account for that. I'm probably going to use a set of contacts on the emergency stop button to engage the brake when the motor is shut down. Seems odd that it's made that way, but I guess it is.

[John Bennett]

Normally the brake on /off is linked to the mr/mf relay. On the top of the spindle relay, there are low voltage contacts that are used to connect or disconnect brake so that when spindle is on, brake is off and visa versa. You could do this with a PLC but the easiest would be to use the low voltage contacts.

[cnc1000]

Ah. I see. Well, I rewired that function up inside the front control panel. Using an output from the Emergency Shutdown button, I wired that over to the brake, so any time the ES is smacked, the power drops and the brake comes on. I'll plan on using those little microswitches on the direction contactors to send emergency shutdown signals to the breakout board. I succeeded in getting all of the head functions running, today. I can start and run in either direction, ramp the speed up and down, and actuate the brake. Woo hoo! It was helpful to just rip out all of the wires in the front panel, test continuity on all of the switches in all positions, and then just do my own wiring. Now to wire in the motion controls.

I'm not sure about the lube feature. Is that supposed to be on all the time or what?

[gus]

lube was wired to run when spindle is running on interacts, not sure on boss.

[John Bennett]

On the boss machine, lub is on when the spindle is active. There is a float level switch in the lub oil tank that will not allow the spindle to start if the level is low. The control of the pump is switched on by the MR/MF low voltage contacts.

[jonesturf]

I just did mine today. It was hung up like yours. Added air tool lube and cycled it a bunch and it finally started working. Seemed like the pneumatic valve even hung up. Once it freed itself it was good to go. Had to cycle the solenoid a bunch to get it to finally work.

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