Regarding Z Axis delta servo motor stall / overload protection

[M.Abid]

Hi guys, my question is about a z-axis servo motor that is a 1 kW delta servo motor with a 6 kW HSD spindle.

What occurred was that I wanted to cut 18mm mdf, but I accidentally entered 185mm, which is 18.5mm, in the final cut depth field on the Artcam program.
and I start the machine to cut the piece, the z axis motor pushing down to achieve the 185mm cutting depth.
The spindle collet makes contact with the mdf sheet and grinds, causing smoke to appear.
When I am aware, I push the e-stop button, but everything said above happens first.
My concern is that the servo drive will protect the servo motor from this type of condition when the motor is pushing itself but there is resistance.
and also for will the vfd also protect the spindle from this when the spindle shaft is start jamming because of this type of mistakes.

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[joeavaerage]

Hi,
I use 750W Delta B2 series servos, and yes they do protect themselves. As part of the programming you can set the maximum current, which is in effect the the same
as a maximum torque limit. If I recall correctly the default factory setting is 100% of rated current and short term overload of 300%.

This means that your servo has plenty boogie. Whats the bet that you bend/break/wreck the Z axis long before you stall the servo.

Just as an example: my Z axis servo is direct connected to a 5mm pitch 32mm diameter ballscrew. The peak overload is 7.1Nm and thus if
the Z axis is physically stopped, say a collison, the stall thrust is 8.9kN, or 890kg force. Something is likely to bend or break before the servo faults out.

You might think well I'll back off the peak torque, I mean....it is programmable right? Yes it is and you could back off but that will degrade the acceleration
your axis can achieve also. By-in-large you want the highest acceleration you can get for the fastest and best possible tool path following, but that also means
potentially damaging thrust under fault conditions, one comes with the other.

Craig

[M.Abid]

Hi,
I use 750W Delta B2 series servos, and yes they do protect themselves. As part of the programming you can set the maximum current, which is in effect the the same
as a maximum torque limit. If I recall correctly the default factory setting is 100% of rated current and short term overload of 300%.

This means that your servo has plenty boogie. Whats the bet that you bend/break/wreck the Z axis long before you stall the servo.

Just as an example: my Z axis servo is direct connected to a 5mm pitch 32mm diameter ballscrew. The peak overload is 7.1Nm and thus if
the Z axis is physically stopped, say a collison, the stall thrust is 8.9kN, or 890kg force. Something is likely to bend or break before the servo faults out.

You might think well I'll back off the peak torque, I mean....it is programmable right? Yes it is and you could back off but that will degrade the acceleration
your axis can achieve also. By-in-large you want the highest acceleration you can get for the fastest and best possible tool path following, but that also means
potentially damaging thrust under fault conditions, one comes with the other.

Craig

I appreciate your response, friend.

Did you want to say that the drive's protection makes the servo motor fine? Additionally, this machine includes thick ball screws.
You give an example, but it seems a little technical to me; could you kindly explain in plain

[joeavaerage]

Hi,
the bottom line is that the servo is (electrically) well protected but the stall force that the servo can apply is likely to break your machine, the servo will almost certainly
survive but its likely to bend or break something else.

My machine can happily push nearly a ton in a fault situation before the servo trips out.

Craig

[servtech]

Hi guys, my question is about a z-axis servo motor that is a 1 kW delta servo motor with a 6 kW HSD spindle.

What occurred was that I wanted to cut 18mm mdf, but I accidentally entered 185mm, which is 18.5mm, in the final cut depth field on the Artcam program.
and I start the machine to cut the piece, the z axis motor pushing down to achieve the 185mm cutting depth.
The spindle collet makes contact with the mdf sheet and grinds, causing smoke to appear.
When I am aware, I push the e-stop button, but everything said above happens first.
My concern is that the servo drive will protect the servo motor from this type of condition when the motor is pushing itself but there is resistance.
and also for will the vfd also protect the spindle from this when the spindle shaft is start jamming because of this type of mistakes.

The drives will normally protect themselves from overcurrent in this case. However, the mechanical parts may be damaged. Machine geometry or even the spindle bearings.

Back out of the "collision" and check the machine function and accuracy.

[M.Abid]

Hi,
the bottom line is that the servo is (electrically) well protected but the stall force that the servo can apply is likely to break your machine, the servo will almost certainly
survive but its likely to bend or break something else.

My machine can happily push nearly a ton in a fault situation before the servo trips out.

Craig

True, I forgot to mention that before pressing the e-stop button, I noticed that the z axis was not moving upward after jogging the z axis before pressing the e-stop button, so I restarted.
the machine, but the z axis still does not move and does not come out after a second restart of the z moving upward. Will this indicate that the drive tripped and trigger fault code.

Another thought was that the machine's maker might take the type of scenario into account and reduce the specifications to save the machine.

Currently, nothing that can be seen on the machine appears to be damaged, and there is any way to tell if the ball screw is bent or not.

[joeavaerage]

Hi,
if there is a fault of that description then open the cabinet and look at the Z axis servo drive, if its faulted it will
have something like
"ALM 08" or "ALM 09" or something like that.

If I'm not mistaken current overload alarms of that type are latched, that is to say the drive MUST be reset before normal operation can resume.
It maybe the machine maker has provided a button or other control to do this. If not you will have the turn the power off to the machine, wait 30 seconds or
so and then repower. A power cycle resets the servo drive.

Craig

[M.Abid]

The drives will normally protect themselves from overcurrent in this case. However, the mechanical parts may be damaged. Machine geometry or even the spindle bearings.

Back out of the "collision" and check the machine function and accuracy.

Thanks pal.
Some times unintentional thing happens which we don't want ever.
The machine looks works fine nothing sound/noise noticeably different from before.

[joeavaerage]

Hi,

Another thought was that the machine's maker might take the type of scenario into account and reduce the specifications to save the machine.

Yes they could do that but then the Z axis wouldn't work properly.

Imagine a car maker saying 'bad accidents only happen at over 10km an hour so we are going to build our cars to do 9.9km an hour'. Really safe just a bloody useless car!

Craig

[M.Abid]

Hi,
if there is a fault of that description then open the cabinet and look at the Z axis servo drive, if its faulted it will
have something like
"ALM 08" or "ALM 09" or something like that.

If I'm not mistaken current overload alarms of that type are latched, that is to say the drive MUST be reset before normal operation can resume.
It maybe the machine maker has provided a button or other control to do this. If not you will have the turn the power off to the machine, wait 30 seconds or
so and then repower. A power cycle resets the servo drive.

Craig

Yes the same thing came in my mind after turn off the machine and restarted.

I needed to check the code and open the cabinet. But I restarted in a hurry and with a little panic.

Will the drive's restored log include the most recent error code or alarm?

[joeavaerage]

Hi,

Will the drive's restored log include the most recent error code or alarm?

My Delta B2 drives store fault codes, maybe five or six of them. You just have to hope it does not send a email to your boss 'the bloody plonker crashed the machine'

Craig

[M.Abid]

Hi,



My Delta B2 drives store fault codes, maybe five or six of them. You just have to hope it does not send a email to your boss 'the bloody plonker crashed the machine'

Craig

how to find those codes i think look in to the manual the way

[joeavaerage]

Hi,
there are two ways to read the stored codes.

The first and preferred method is to use the Delta set-up and tuning software. That in turn requires that you have the proper cable to plug into the IEEE1394 programming
socket and that you have the Delta software on your PC. Thereafter you just get the drive on-line and read the parameters. Whether the machine maker left the software on the PC
is questionable.

The other method is to push buttons like programming a microwave. To be honest its very tedious and error prone, it more likely that you'll cock up the programming of the drive
than finding what you want. There are hundreds of parameters in at least four pages, if you cock it up you could stop the servo altogether. How would your boss feel about that?

Craig

[M.Abid]

Hi,
there are two ways to read the stored codes.

The first and preferred method is to use the Delta set-up and tuning software. That in turn requires that you have the proper cable to plug into the IEEE1394 programming
socket and that you have the Delta software on your PC. Thereafter you just get the drive on-line and read the parameters. Whether the machine maker left the software on the PC
is questionable.

The other method is to push buttons like programming a microwave. To be honest its very tedious and error prone, it more likely that you'll cock up the programming of the drive
than finding what you want. There are hundreds of parameters in at least four pages, if you cock it up you could stop the servo altogether. How would your boss feel about that?

Craig

I find a link https://trakmtsupport.dozuki.com/Gui...Servo+Drives/5

[joeavaerage]

Hi,
Yep, that's how its done if you don't have the proper comms cable and software. I would advise against it....its so easy to make a mistake and screw up some other
critical parameter. Your call. Get your bosses approval before hand or it could bite you BAD.

Craig

[mactec54]

Hi,
the bottom line is that the servo is (electrically) well protected but the stall force that the servo can apply is likely to break your machine, the servo will almost certainly
survive but its likely to bend or break something else.

My machine can happily push nearly a ton in a fault situation before the servo trips out.

Craig

It won't protect against this if the servo drive is set to 300% overload, this needs to be reduced to suit the machine mechanics, so it will survive, the motor / Drive and spindle will survive, you have to protect the mechanics of the machine, by setting max overload Parameters.

[joeavaerage]

Hi,
the maximum short term overload of a Delta B2 servo is 300% of rated current, and is the factory default. You can program it to be less if you wish, but in most cases
its left as is.

OP dove the spindle hard down into the material by mistake, everyones done it at some stage. It usually creates a hell of a bang, and not much in the way of servo or machine programming will save
that. Or if you do program it 'to be gentle if it crashes' then the Z axis is as slow as a wet week and likely to stall under regular cutting, not much cop.

Craig

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[M.Abid]

Hi,



My Delta B2 drives store fault codes, maybe five or six of them. You just have to hope it does not send a email to your boss 'the bloody plonker crashed the machine'

Craig

HI Pal
I checked the code which is the recent ONE which is L0003.