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Isaac
10-01-2014, 06:16 PM
I have a small aluminium framed machine that was previously using a small 200 watt spindle. I changed to a 1.5kw spindle and after a few weeks its started making a rough noise on the Z axis. Thing is, is if I increase the speed/acceleration it sounds normal and like the spindle is no issue for it but I'm worried it will kill another driver chip(when doing 3d work) like a I did a few weeks back. Would springs on the Z axis rails help(pushing back against the Z axis) alleviate the weight problem. If I use my hand to lift the spindle a touch they sound returns to normal.

Thanks, any idea would be great!

Isaac

irving2008
11-01-2014, 07:04 AM
"Doctor, I have a pain, what could be wrong with me?"
"a pimple or cancer, take your pick"


* What's the machine,
* how is the z-axis driven (e.g. belt/pulley sizes, ballscrew/pitch, leadscrew/pitch?),
* what is the z-axis motor (NEMA size, torque, current rating.)
* what voltage/driver board/PSU
* What velocity/acceleration (original/new)
* what's the weight of the two spindles
* anything else that might be relevant

JAZZCNC
11-01-2014, 10:39 AM
I'll Take a wild guess it's 3020/6040 or some rubbish from Devon.!!

Springs cost pennys so try them is the easy answer to that question. They will help not indure but you obviously have issues so a better solution is to heal problem not cover it up with parcel tape.!

Give the details irving asked and we can advise more specific.!

Isaac
11-01-2014, 12:16 PM
I'll Take a wild guess it's 3020/6040 or some rubbish from Devon.!!

Springs cost pennys so try them is the easy answer to that question. They will help not indure but you obviously have issues so a better solution is to heal problem not cover it up with parcel tape.!

Give the details irving asked and we can advise more specific.!

Hi. it is a 3040. It uses leadscrews and nema24 motors. I will check the power from the supply shortly and see what its pushing out. The electronics are all original. It is about 3.5 years old now and is in the process of being upgrades(ran out of cash while building my 1200x600 laser). :)
I will check the rest of the details shortly and let you know.

Thanks. Isaac

Isaac
11-01-2014, 06:56 PM
Hi. it is a 3040. It uses leadscrews and nema24 motors. I will check the power from the supply shortly and see what its pushing out. The electronics are all original. It is about 3.5 years old now and is in the process of being upgrades(ran out of cash while building my 1200x600 laser). :)
I will check the rest of the details shortly and let you know.

Thanks. Isaac

The steppers are 2.5a, 1.8degree steppers. Voltage is 24v I believe, cant find my multimeter to check.

Original accel was 80, Velocity 400 (MM for units)
New better sounding values are 120/500

Spindle is about 6kg, old one probably less than 1kg.

Thanks

JAZZCNC
11-01-2014, 07:42 PM
The steppers are 2.5a, 1.8degree steppers. Voltage is 24v I believe, cant find my multimeter to check.

Original accel was 80, Velocity 400 (MM for units)
New better sounding values are 120/500

Spindle is about 6kg, old one probably less than 1kg.

Thanks

To get around this correctly will be uneconomical because you'll probably need to replace most of the electronics including motor. Only you can decide if the machine is worth the cost and trouble.?

I would just devise some counter weight like the springs idea has it will be a lot cheaper and probably easier.

EddyCurrent
11-01-2014, 08:05 PM
Would you put a tractor engine in a mini ? put the old spindle back in and either use it like that or sell the whole machine to be replaced with something larger.

irving2008
11-01-2014, 08:11 PM
That machine has 1204 trapezoidal lead screws with Delrin or bronze nuts so very inefficient. The stepper motors are probably 1.1 or 1.5Nm. I'd hazard a guess the Z-axis stepper is struggling with that additional weight. You either need to counterbalance it, or upgrade the stepper/driver combo or replace the leadscrew with a ballscrew.

As Jazz says, you're on a hiding to nothing....

Isaac
11-01-2014, 08:33 PM
Would you put a tractor engine in a mini ? put the old spindle back in and either use it like that or sell the whole machine to be replaced with something larger.

Old spindle died, which is why I bought the 1.5kw ready for the upgrade.

I will counterbalance it for now, only needs to last another 4-8 weeks while I order the rest of the parts and build it. Is there a method to choosing a spring or is it just trial and error. I reduced the accel to 50 today and it did a full 3d job just fine and the noise wasn't too bad but noticable. I also cut some Aluminium for the first time and I'm pretty please with the result. This machine will be my fulltime foam cutter once the new one is up and running.

Cheers for the help guys, Isaac

GEOFFREY
11-01-2014, 08:38 PM
As a very quick cheap short term fix you could try rigging a "bungee". G.

EddyCurrent
12-01-2014, 12:02 AM
Stand the machine vertical

JAZZCNC
12-01-2014, 01:02 AM
Stand the machine vertical

Nah couldn't handle that either. . Lol. . . . . . But on it's side at 15deg angle would maybe work.? . . . . And I'm being serious.!!

Isaac
12-01-2014, 01:10 AM
I'll try it tomorrow :) Will nip wickes see if they have any springs.

EddyCurrent
12-01-2014, 07:51 PM
Springs will change their 'pull' depending upon how far they are stretched whereas a counter weight over a pulley would be constant at any Z position. If the weight was dangled inside a tube, that would prevent it flapping about.

Jonathan
12-01-2014, 08:21 PM
Whichever way you tilt the machine, you're just going to transfer a component of the gravitational force on the Z-axis to one or more axes. If either X or Y uses a ballscrew, then you could re-orientate the machine to place the force on that axis, however that could cause problems if the stiffness of the machine frame in general is low, which seems likely.


Nah couldn't handle that either. . Lol. . . . . . But on it's side at 15deg angle would maybe work.? . . . . And I'm being serious.!!

If an axis is placed 15 degrees to vertical, the gravitational force will only be cos(15) times less (i.e. 3%) than if the axis was vertical. However I think by 'on it's side' you mean have Z 15 to horizontal and Y 15 from vertical? In which case you've just transferred almost 97% of the Z-axis weight to the Y-axis nut...


As a very quick cheap short term fix you could try rigging a "bungee". G.

Yes, a bungee cord attached to the ceiling would be nice and easy - assuming the machine is fixed to the bench!


Springs will change their 'pull' depending upon how far they are stretched whereas a counter weight over a pulley would be constant at any Z position. If the weight was dangled inside a tube, that would prevent it flapping about.

Whilst it does give an even force, the annoying thing with that approach is you're adding even more mass (about 5kg to cancel the new spindle) to the gantry [Edit: Not thinking.. this doesn't apply as you can attach the pulley to a stationary point, i.e. bench the machine is upon], so the X and Y axes are going to wear out even faster. You could start cascading pulleys to reduce the mass, but that introduces other problems...

Jonathan
12-01-2014, 08:25 PM
Delete please..

johnsattuk
12-01-2014, 08:34 PM
Springs will change their 'pull' depending upon how far they are stretched whereas a counter weight over a pulley would be constant at any Z position. If the weight was dangled inside a tube, that would prevent it flapping about.

One of the snags with counter weights is their mass, OK when static but any accelerating movements increase the forces required to move the spindle which may be counter productive.

I use gas struts which are more or less constant force with low mass. Can be a bit tricky finding the correct one, but there are adjustable ones which you can use, you start out with too high a force and let fluid out to get what is required.

EddyCurrent
12-01-2014, 08:53 PM
I would have thought gas struts would introduce too much damping to rapid movement ? unless there are different types.

johnsattuk
12-01-2014, 09:03 PM
Yes there are different types, damped ones are used on things like doors or boot/bonnet lids, fast moving ones are available, depends on the design of the piston and the oil charge. As an example very fast ones are used to drive the piston in an air gun.

Isaac
24-01-2014, 12:44 PM
Just thought I would update you. I put on a couple of springs and its seems much, much happier now, hopefully it will survive a little longer :) Thanks for the help!