Cheapskates moving down tower on their own

[apostoly]

I haven't put power to the machine just yet, but 2 of the 3 cheepskates are moving down a little bit by them selves when raised up on the tower.
(The arms and hotend are attached by the way.)

Could this be most likely because i might not have tightened the belts hard enough or could it be that the stepper motors are faulty ?

[dtgriscom]

I haven't put power to the machine just yet, but 2 of the 3 cheepskates are moving down a little bit by them selves when raised up on the tower.
(The arms and hotend are attached by the way.)

Could this be most likely because i might not have tightened the belts hard enough or could it be that the stepper motors are faulty ?

You mean that if you push one Cheapskate up a significant distance and then let go, it may slide itself back down a centimeter or two?

That happens on my RMv2, especially if that Cheapskate's arms are mostly straight down to the platform. I can hear the stepper motor's "tick"s while this happens. I attribute it to stickiness in the other two sets of arms' u-joints: you have to move a significant distance before the joints actually flex, and that restoring torque pulls the Cheapskate back down.

I don't know if this is a problem in practice. I've done a few decent prints with it that way, but it is something I want to fix in the long run.


Dan

[apostoly]

I haven't put power to the machine just yet, but 2 of the 3 cheepskates are moving down a little bit by them selves when raised up on the tower.
(The arms and hotend are attached by the way.)

Could this be most likely because i might not have tightened the belts hard enough or could it be that the stepper motors are faulty ?

You mean that if you push one Cheapskate up a significant distance and then let go, it may slide itself back down a centimeter or two?

That happens on my RMv2, especially if that Cheapskate's arms are mostly straight down to the platform. I can hear the stepper motor's "tick"s while this happens. I attribute it to stickiness in the other two sets of arms' u-joints: you have to move a significant distance before the joints actually flex, and that restoring torque pulls the Cheapskate back down.

I don't know if this is a problem in practice. I've done a few decent prints with it that way, but it is something I want to fix in the long run.


Dan

Yea pretty much spot on, but this is happening on the z axis more than the other the other two

it just doesn't feel right to me, but if that's how its supposed to be, then who am i to complain haha

[dtgriscom]

Yea pretty much spot on, but this is happening on the z axis more than the other the other two

I'm guessing that the z axis' u-joints aren't as sticky as the other two axes.

it just doesn't feel right to me, but if that's how its supposed to be, then who am i to complain haha

Note that I did NOT say this is how it's supposed to be. I've tolerated mine (see here), but it doesn't feel right to me either.


Dan

[mhackney]

Firstly, without being energized, the carriages can move down due to gravity. The difference between towers you are seeing could be from one of several reasons:

the carriages are too loose or too tight - when adjust properly
the belts are not all tensioned properly

I suspect both of these may be the issue, it won't be faulty steppers.

My Rostock has a water cooled 4 nozzle Kraken installed, so the business end is heavier than most. My carriages do not move due to gravity when not energized but are easy to move up/down by pushing them.

[apostoly]

Yea pretty much spot on, but this is happening on the z axis more than the other the other two

I'm guessing that the z axis' u-joints aren't as sticky as the other two axes.

it just doesn't feel right to me, but if that's how its supposed to be, then who am i to complain haha

Note that I did NOT say this is how it's supposed to be. I've tolerated mine (see here), but it doesn't feel right to me either.


Dan

the cheapskate actually moves a good inch or two downwards at times, youre right, the u joints do feel abit lighter on the Z axes.

i still think i need to tighten my belts on that axis abit, see if that does anything

[apostoly]

Firstly, without being energized, the carriages can move down due to gravity. The difference between towers you are seeing could be from one of several reasons:

the carriages are too loose or too tight - when adjust properly
the belts are not all tensioned properly

I suspect both of these may be the issue, it won't be faulty steppers.

My Rostock has a water cooled 4 nozzle Kraken installed, so the business end is heavier than most. My carriages do not move due to gravity when not energized but are easy to move up/down by pushing them.

So if i had to tighten the carriages, could i do it with the belt installed,or would i have to take it all apart?

Ill start off by tightening the belts first before moving onto tightening the carriages?

[dtgriscom]

The difference between towers you are seeing could be from one of several reasons:

the carriages are too loose or too tight - when adjust properly
the belts are not all tensioned properly

I suspect both of these may be the issue, it won't be faulty steppers.

I agree that it isn't the steppers, but I'm pretty sure the primary cause is the u-joints being sticky. A loose belt might let its Cheapskate move freely up and down a mm or two, but not an inch (assuming the belt isn't completely floppy). A loose Cheapskate wouldn't be enough to let things start sliding down (they add very little friction), and if it somehow did it wouldn't stop sliding after an inch or two.

So if i had to tighten the carriages, could i do it with the belt installed,or would i have to take it all apart?

You can adjust the carriages without disassembling anything, and should recheck them now and then. Take one in your hand and lightly twist and push it in all directions; although there may be a slight bit of "give" you shouldn't see any actual looseness or feel a "tick" as the bearings load and unload.


Dan

[apostoly]

The difference between towers you are seeing could be from one of several reasons:

the carriages are too loose or too tight - when adjust properly
the belts are not all tensioned properly

I suspect both of these may be the issue, it won't be faulty steppers.

I agree that it isn't the steppers, but I'm pretty sure the primary cause is the u-joints being sticky. A loose belt might let its Cheapskate move freely up and down a mm or two, but not an inch (assuming the belt isn't completely floppy). A loose Cheapskate wouldn't be enough to let things start sliding down (they add very little friction), and if it somehow did it wouldn't stop sliding after an inch or two.

So if i had to tighten the carriages, could i do it with the belt installed,or would i have to take it all apart?

You can adjust the carriages without disassembling anything, and should recheck them now and then. Take one in your hand and lightly twist and push it in all directions; although there may be a slight bit of "give" you shouldn't see any actual looseness or feel a "tick" as the bearings load and unload.


Dan

I will give it a shot tomorrow after work, ill try tightening everything just a tad and see if it makes a diff without creating resistance on the bearings

Thanks Boys

[Captain Starfish]

I'd say that sounds about perfectly set up.

If the motors are off, you push the carriages up to the top and they stay there then they are too tight.

If they slowly creep down when released BUT there's no lateral or rotational play in them, they are spot on.

I had mine like this, it got too much of a PITA with the hot-end dropping back on the job after an end-of-print retract and melting, etc, etc so I overtightened my carriages just a whisker so they held in place.

[Polygonhell]

You really just want to take the slop out if the carriages, if you over tighten them you'll distort the extrusion, if the wheels are going round from top to bottom and there isn't any slop I wouldn't touch them.
The belt tension will impact this, but be careful not to over tighten them, the reason the carriages get harder to move with higher belt tension is mostly lateral load on the motor bearings, and they aren't designed for a lot of that.

Having said that mine don't droop, with the power off.

[apostoly]

You really just want to take the slop out if the carriages, if you over tighten them you'll distort the extrusion, if the wheels are going round from top to bottom and there isn't any slop I wouldn't touch them.
The belt tension will impact this, but be careful not to over tighten them, the reason the carriages get harder to move with higher belt tension is mostly lateral load on the motor bearings, and they aren't designed for a lot of that.

Having said that mine don't droop, with the power off.

from what everyone is saying, it sounds like i have everything set up correctly as i have absolutely no movements in my carriages and both bearings seem to be turning at all times.(need to double check all of them but i am pretty sure)

I'm thinking whatever changes i make are going to have to be extremely minimal just to get it from drooping that much