Emco VMC100 specialities: Spindle and axes
31 Dec 2020 16:50 #193666
by atlantis
Emco VMC100 specialities: Spindle and axes was created by atlantis
My machine has some technical details that seem to be a bit special compared to others and I would like to ask for suggestions about how to implement them in LinuxCNC. These are the two of them that concern me at the moment:
Spindle
The spindle is driven by a 4000 rpm brushed dc servo motor. This is because the same motor does also power the tool changer tool carousel by disengaging from the spindle and engaging in the carousel and therefore it has to be able to move very precisely. Because I want the tool changer to be operational I can't just change to an ordinary ac motor and vfd. The dc drive responsible for the motor accepts step/dir signals much like a stepper drive, but I'm not sure how to configure it compared to the axes' steppers.
Axes
Every axis has two induction sensors:
- A first one that acts as an end switch on one side of the travel (there's none on the other side)
- A second one that indicates every full turn of the lead screw. As the steppers don't have encoders I think they did a kind of closed loop system this way.
I guess it shouldn't be a problem that there is only one end switch per axis but it seems that normally it would be expected that there is a reference switch in addition to the end switch. And how to make use of the one that indicates the leadscrew turns?
Many thanks to everyone who can contribute and a happy new year everyone!
Regards
Martin
Spindle
The spindle is driven by a 4000 rpm brushed dc servo motor. This is because the same motor does also power the tool changer tool carousel by disengaging from the spindle and engaging in the carousel and therefore it has to be able to move very precisely. Because I want the tool changer to be operational I can't just change to an ordinary ac motor and vfd. The dc drive responsible for the motor accepts step/dir signals much like a stepper drive, but I'm not sure how to configure it compared to the axes' steppers.
Axes
Every axis has two induction sensors:
- A first one that acts as an end switch on one side of the travel (there's none on the other side)
- A second one that indicates every full turn of the lead screw. As the steppers don't have encoders I think they did a kind of closed loop system this way.
I guess it shouldn't be a problem that there is only one end switch per axis but it seems that normally it would be expected that there is a reference switch in addition to the end switch. And how to make use of the one that indicates the leadscrew turns?
Many thanks to everyone who can contribute and a happy new year everyone!
Regards
Martin
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31 Dec 2020 23:43 #193693
by tommylight
The one pulse per turn is probably used for index homing, also can be used by LinuxCNC. It will use the switch to find the home and use the pulse for more precise homing.
Replied by tommylight on topic Emco VMC100 specialities: Spindle and axes
Some pictures might help.Spindle
The spindle is driven by a 4000 rpm brushed dc servo motor. This is because the same motor does also power the tool changer tool carousel by disengaging from the spindle and engaging in the carousel and therefore it has to be able to move very precisely. Because I want the tool changer to be operational I can't just change to an ordinary ac motor and vfd. The dc drive responsible for the motor accepts step/dir signals much like a stepper drive, but I'm not sure how to configure it compared to the axes' steppers.
One switch is enough as LinuxCNC can use that for homing and as a hard limit on one side, while the other side is limited in software.
Axes
Every axis has two induction sensors:
- A first one that acts as an end switch on one side of the travel (there's none on the other side)
- A second one that indicates every full turn of the lead screw. As the steppers don't have encoders I think they did a kind of closed loop system this way.
I guess it shouldn't be a problem that there is only one end switch per axis but it seems that normally it would be expected that there is a reference switch in addition to the end switch. And how to make use of the one that indicates the leadscrew turns?
The one pulse per turn is probably used for index homing, also can be used by LinuxCNC. It will use the switch to find the home and use the pulse for more precise homing.
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