This has happened to me a couple of times now.
I finish the rough cutting of a Lithophane project.
The Sharks then decides to lower the Z axis by something between 3 and 5 mm.
Because I used the centre as XYZ0 I didn't realise the Z axis had shifted and continued with the finish cut, left the machine to work then returned to fins it had cut right through the material.
I thought I had done something wrong in the toolpath calculations and called myself all the names under the sun.
I shifted XYZ0 to bottom left corner.
This time it was worse than ever, the Z axis had dropped about 10mm when I returned to XYZ0
I hit the panic button immediately and reset the XYZ0.
Instead of running the finishing toolpath, I loaded another part of the project, hit run the file and BANG the router dived straight down through the material.
Hit the panic button again and reset the XYZ0 with the same result, a great big hole in my material.
When I try to lift the router on the Z axis it stops halfway up and chatters like it has hit the top.
This has happened a couple of times before but with a bit of going up and down the router eventually returns to the top of the cradle.
Not this time, it will not go past halfway up but will happily try to go past the bottom of the cradle.
I read somewhere that the software has a limit built into it, it looks like that has shifted.
How do you change that limit?
Cheers
Wolffie
Loss of Z axis
Moderators: ddw, al wolford, sbk, Bob, Kayvon
Re: Loss of Z axis
Wolffie
I seem to remember if it is hot here in the USA it should be getting cooler were you are. And is the hummidity also droping. My real question is if this is your all new AL machine have you grounded it. If you are using a dust boot do you have a bare ground wire inside the air hose. ( the ground wire in the dust boot should not conect to the shark) With the original Shark and the all plastic frame static electric does not become a problem until you have a dust boot. With an all metal machine it can be a much biger problem. If you follow the ShopBot message board there was a very good articale about grounding on there forum.
If you turn off your router and dust collection and do an air cut does the problems still happen ???
I seem to remember if it is hot here in the USA it should be getting cooler were you are. And is the hummidity also droping. My real question is if this is your all new AL machine have you grounded it. If you are using a dust boot do you have a bare ground wire inside the air hose. ( the ground wire in the dust boot should not conect to the shark) With the original Shark and the all plastic frame static electric does not become a problem until you have a dust boot. With an all metal machine it can be a much biger problem. If you follow the ShopBot message board there was a very good articale about grounding on there forum.
If you turn off your router and dust collection and do an air cut does the problems still happen ???
drueth
Shark Pro Plus HD
new to CNC 12/2012
Shark Pro Plus HD
new to CNC 12/2012
Re: Loss of Z axis
Hello Woffie
Here are a few thoughts regarding your z axis.
If you hear the stepper motor making pulsing noises as if it has run up against a stop, the motor is getting some type of pulsing move signal from the controller/driver.
If the software hit a limit, the motor would be silent but held in place so it can not be easily turned. When power is removed from the motor entirely, you can turn the shaft by hand. That should happen only with the controller turned off.
One of the issues with the z axis is that it must lift the weight of the router when it retracts. The other axis do not have that issue, the load is the same regardless of direction. On the x and y , you have the inertia load of moving the router up to speed, but not also lifting the weight of the router.
The z is different in that when moving the z down (plunge) the weight of the router helps it start moving. When going up, the router weight works against it.
also, when plunging, the motor will move at the plunge rate selected for the tool, on a simple "straight up" retract it may try and move at the full speed and acceleration rate that the controller thinks the axis is capable of. This creates a situation where the stepper motor has to work a lot harder in retract than it does in plunge. (both the weight of the moving z parts and the power to accelerate that weight faster)
If you try and accelerate a stepper motor too quickly, it can "stall" in which case it stops turning, but you still hear the pulsing of the motor that is now happening too quickly for the motor to respond to. The rate of acceleration is usually set in the controller. Additionally, the gcode generated with standard tooling in vectric tend to be pretty aggressive (for the shark) with its speeds.
I would check for any binding in your z axis, and if it is running freely, your software/controller may be on the borderline of asking it to retract faster than it can. You can get intermittent problems where you lose steps on retract, but don't notice it unless it stalls completely and sits there and pulses. All subsequent cuts will be deeper by the number of steps it lost in retract.
I am not sure if the acceleration rate for the z can be adjusted by the user in the shark software. On my machine I can fine tune it directly in Mach3 and it does make a difference. (especially if you have a heavy router or a spindle) I believe the older controllers (prior to the 2.0) used a lower voltage to the motors and hence developed less power, so you may not have the motor power to lift the z axis quickly. One solution is increase the motor power, the other is slow down the acceleration rate so you are not trying to retract faster than the motor can keep up with.
Hope this helps.
Bob
Here are a few thoughts regarding your z axis.
If you hear the stepper motor making pulsing noises as if it has run up against a stop, the motor is getting some type of pulsing move signal from the controller/driver.
If the software hit a limit, the motor would be silent but held in place so it can not be easily turned. When power is removed from the motor entirely, you can turn the shaft by hand. That should happen only with the controller turned off.
One of the issues with the z axis is that it must lift the weight of the router when it retracts. The other axis do not have that issue, the load is the same regardless of direction. On the x and y , you have the inertia load of moving the router up to speed, but not also lifting the weight of the router.
The z is different in that when moving the z down (plunge) the weight of the router helps it start moving. When going up, the router weight works against it.
also, when plunging, the motor will move at the plunge rate selected for the tool, on a simple "straight up" retract it may try and move at the full speed and acceleration rate that the controller thinks the axis is capable of. This creates a situation where the stepper motor has to work a lot harder in retract than it does in plunge. (both the weight of the moving z parts and the power to accelerate that weight faster)
If you try and accelerate a stepper motor too quickly, it can "stall" in which case it stops turning, but you still hear the pulsing of the motor that is now happening too quickly for the motor to respond to. The rate of acceleration is usually set in the controller. Additionally, the gcode generated with standard tooling in vectric tend to be pretty aggressive (for the shark) with its speeds.
I would check for any binding in your z axis, and if it is running freely, your software/controller may be on the borderline of asking it to retract faster than it can. You can get intermittent problems where you lose steps on retract, but don't notice it unless it stalls completely and sits there and pulses. All subsequent cuts will be deeper by the number of steps it lost in retract.
I am not sure if the acceleration rate for the z can be adjusted by the user in the shark software. On my machine I can fine tune it directly in Mach3 and it does make a difference. (especially if you have a heavy router or a spindle) I believe the older controllers (prior to the 2.0) used a lower voltage to the motors and hence developed less power, so you may not have the motor power to lift the z axis quickly. One solution is increase the motor power, the other is slow down the acceleration rate so you are not trying to retract faster than the motor can keep up with.
Hope this helps.
Bob
Re: Loss of Z axis
Thank you Bob.
The "pulsing" happens when I jog the Z axis.
It doesn't matter whether I use step, slow medium or fast up movement, it stops halfway up and refuses to go any further.
It has happened a couple of times before and I have been able to fix it by hand screwing it to the top.
This time, it was only roughcutting and that went fine but when I returned to XYZ0 it had dropped 10mm
I reset ZYZ0 and that's when everything went haywire
Cheers
Wolffie
The "pulsing" happens when I jog the Z axis.
It doesn't matter whether I use step, slow medium or fast up movement, it stops halfway up and refuses to go any further.
It has happened a couple of times before and I have been able to fix it by hand screwing it to the top.
This time, it was only roughcutting and that went fine but when I returned to XYZ0 it had dropped 10mm
I reset ZYZ0 and that's when everything went haywire
Cheers
Wolffie
Re: Loss of Z axis
I have a similar problem with my Z axis. Mine keeps getting higher and higher. It starts out cutting the wood then each time it raises it gets further away from the workpiece. Any help would be appreciated. Thank you.
Re: Loss of Z axis
RickSoul: I'd look for some interference on the Z lift. Could be some dust building up on the threads, a loose coupler between the motor and the threaded rod, etc. If something makes it get higher and higher, then something is keeping it from going down that the motor can't overcome and so the stepper loses track of where the Z is. Also, check that the bit you are using CAN actually reach the depth you want it to. If the Z bottoms out before the bit reaches the depth it is supposed to then again the Z stepper will lose track and the bit will be higher on the next toolpath.
Just some ideas. Can't know for sure without being there to inspect your machine.
Just some ideas. Can't know for sure without being there to inspect your machine.
Re: Loss of Z axis
It's actually the other way around.4DThinker wrote:RickSoul: I'd look for some interference on the Z lift. Could be some dust building up on the threads, a loose coupler between the motor and the threaded rod, etc. If something makes it get higher and higher, then something is keeping it from going down that the motor can't overcome and so the stepper loses track of where the Z is. Also, check that the bit you are using CAN actually reach the depth you want it to. If the Z bottoms out before the bit reaches the depth it is supposed to then again the Z stepper will lose track and the bit will be higher on the next toolpath.
Just some ideas. Can't know for sure without being there to inspect your machine.
It goes deeper not higher.
Thank goodness I have set the router so it can't reach the table only the spoilboard or I would have had another disaster on my hands
I have just taken the cradle apart to find whether it is rubbing somewhere.
Cheers
Wolffie
Re: Loss of Z axis
Hi Wolffie,
If you switch out the cables - put X on Z for example - do you still get that pulsing? If you plug Z into X do you still get that pulsing?
If you switch out the cables - put X on Z for example - do you still get that pulsing? If you plug Z into X do you still get that pulsing?
Re: Loss of Z axis
I don't know how and why but after taking the router cradle completely apart, cleaning and reassembling it, the problem seems to have resolved 
I am guessing something got stuck between the leadscrew and the drive nut.
Thank you for all the suggestions.
I left the project sitting on the table and my fingers are crossed that I can re-establish the starting point.
Cheers
Wolffie
I am guessing something got stuck between the leadscrew and the drive nut.
Thank you for all the suggestions.
I left the project sitting on the table and my fingers are crossed that I can re-establish the starting point.
Cheers
Wolffie
Re: Loss of Z axis
Well, I managed to finish the project yesterday without too much trouble.
Been working on a frame for it today.
Then I decided to turn on the machine to do a sign.
Now the confounded thing refuses to go down to the table
It will move up no problem but stops moving down at 3.570" from the top and makes the same rattling noise as the other day.
If I turn the screw by hand there is no resistance however, if I stop with the screw on top pointing south, it will do half a turn and start rattling again.
Handturning right to the bottom is no problem, it moves smoothly to the top then, going down, it stops at the same point.
I tried to swap cables but that made no difference
I have contacted NWA, hopefully they can offer a solution to the problem.
Wolffie (no cheers today)
Been working on a frame for it today.
Then I decided to turn on the machine to do a sign.
Now the confounded thing refuses to go down to the table
It will move up no problem but stops moving down at 3.570" from the top and makes the same rattling noise as the other day.
If I turn the screw by hand there is no resistance however, if I stop with the screw on top pointing south, it will do half a turn and start rattling again.
Handturning right to the bottom is no problem, it moves smoothly to the top then, going down, it stops at the same point.
I tried to swap cables but that made no difference
I have contacted NWA, hopefully they can offer a solution to the problem.
Wolffie (no cheers today)