B axis brake - Leave the amp on?

We have The Money Pit (an Excello 408) wired so that the B axis amp is off and the brake is on by default.

As well - the pressure switch on the brake has to be "made" for the amp to even pull the ENABLE contactor in. I think that this was how it was set-up to begin with, but not 100% sure anymore. ???

But when dooing heavy werk - especially any real distance from center, it is somewhat easy to overpower the brake, and then the control sees the OUT OF POSITION value go out of the preset allowance, and then the brake is released, and in a cpl seconds _ once pressure builds, the amp kicks in and tries to correct it. (durring the cut!)

Currently, my amp needs tweaked, and when it engages it lunges a bit at first. All of these issues together add up to a heapin' helpin' of dissatisfaction!

It was believed that we would not want the amp live while the brake is holding, as it could/would overheat from fighting agginst the brake constantly. But just powering off the brake the B can drift a bit sometimes before the brake catches it. (.05* max)

Just for that fact alone I want to rewire and re-program it so that the amp stays on untill a few seconds after the brake seats.

Can any of you comment on how your machine is set-up?

This is essentially a HBM application, but HMC and maybe even A axis on a VMC info could be mentioned. Older - less smart drives/controlers may be more relivent?

This is on a retrofit, and we can make it doo whatever we want...

It would be swell to have the "lockdown" of a 1* index table AND the manouverability of a B axis.


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I am Ox and I approve this h'yah post!

Is there any reason why you wouldn't open the thing up and inspect the brake surface condition (or the actuator) so the brake doesn't slip?

We had this issue on some old 810 Siemens drives with the brake not getting engaged before the drive shut down and the axis moving. We did as you are thinking, added a timer to the logic to keep the drive on for a second or two after the brake went on. Never had an issue with the drive or motor. I can see issues if you leave the amp on all the time with the brake engaged, but not for a second or two.

HuFlungDung said:

Is there any reason why you wouldn't open the thing up and inspect the brake surface condition (or the actuator) so the brake doesn't slip?

Click to expand...

No - but I don't believe there is anything wrong with it.
When we first hooked up the machine, I was able to tell some movement there. I just don't think that it is big enough for the task at hand.


???



Thanks Tony.


I highly expect most all of the operators do not know the answers to those questions as for the most part, that is just part of the MTB's layout, and nothing that we can generally manipulate. (unless for some reason we have an issue with it)

I have two 4 axis VMC's that I have no idea of the same answers to.



If someone out there has experience with a full 4th on a 408, or similar machine, I would love to hear their experience with the brake trq!



We are thinking about making the motor live, but not allowing a G0 move until we see a brake full open signal. (simple logic) Then trying to code it so that a G1 move needs to see that the brake is just not on. (valve shifted, but not wait for the full open signal (it takes prolly 5 seconds to build pressure the opposite directions. Too small'a lines?)) And then let the motor try to hold position the rest of the time. Not 100% sure how to code that tho?

Then monitor the 4th axis motor regularly for a while and see what we git....

???

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I am Ox and I approve this h'yah post!