Auto bed leveling servo issue

It's been working well for a while then after getting everything going great for few days and this happens, haven't found anything googling.
Sometimes the servo moves to set position, sometimes it doesn't, luckily I spot it in time to hit emergency stop. And now it's like every second time the servo is off by 5 to 10 degree, there for it will slip and crash the hotend in to the glass. Anyone ever came across this problem?

Edited 1 time(s). Last edit at 09/14/2015 04:31PM by deaconfrost.

is it a small R/C style of servo?

I found that having them close to stepper motors would cause erratic movement. jittery, inconsistent.

if you used a lot of force to push on the horn, you could have damaged the servo. you might try to gently pull out on the arm.
I had binding happen in the internal gears if I force on arms.

I'll check the gears and see if that's the case. But it was never hit before the first crash happened, and I stopped it as soon as it happened so no damaged was done to anything other than not sure about the servo gears, I have a metal version was a tail servo with a burned out board from a rc 450 size heli, I could use the gear from it

I didn't have to use much force on the arm, it slide in smoothly, if it is damaged now it would only be from hitting the bed, but usually if it's dagamed from arm crashing it would strip the gears, but there is no missing gear so no strip... hopefully not binding. Worst case I swap out the board to the metal gear case, since they the same model just metal version. Didn't want the take apart a new servo but I was planning on swapping out the gears at some stage, oh they are digital servos I use on rc helis but not cheap ones, reasonably good hitec servos

Would it have any difference using digital servo than analog servo or is it just because analog are cheaper, as I see everyone else seem to be using tower pro sg90 or similar which are all analog servos.

Edited 4 time(s). Last edit at 09/14/2015 05:31PM by deaconfrost.

checked the servo gears, today, they are perfect, no binding nor damaged, tested servo on the receiver, no problem with it..... problem must be somewhere else

is the servo near a stepper? like the extruder motor?

can you create a short wiring harness and put the servo near your controller board.
That would eliminate the long wires. If it runs smooth, then you are picking up noise from the wire bundle going to the head.

I will check the wires, I'm running bowden and the stepper is fairly far away. But thw wires do meet at some point, maybe I separate them and see how it goes.

Edited 1 time(s). Last edit at 09/16/2015 08:13PM by deaconfrost.

It could be a power issue. In particular, if you are powering the servo from a RAMPS board and not providing an external 5V power supply, the 5V rail may be dropping because the 5V regulator on the Arduino is overheating.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

If all fail I may look in to using a relay and a 5v psu so

That ks for the tip

you should be sure the 5V or 6V you're giving the servo is clean and strong. Most of the 5V you find around RAMPs on header pins is only able to do mA currents and won't handle the power needs of a servo.

in our kickstarter update #5, we talk about turning on and off servo power and logic to help servos stop jittering. It's a long read, but could be useful.
kick link

sending the PWM mosfet fan1 output to a voltage regulator, turning that on and off with analogWrite commands, and attach/detach the servo logic solved a lot for us.

I rerouted the wires and it seems all good now went through 4 prints without touching anything thanks for all the input everyone.

Tanks davew_tx I will have a read on that. Will be useful either way when I build my big printer