Stepper motors not homing

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AlexisT
Posts: 2
Joined: Fri Nov 25, 2016 2:43 am

Stepper motors not homing

Post by AlexisT » Mon Nov 23, 2020 7:38 am

Hi im wondering if i can get help.

I purchased the Geeetech delta g2s pro a few years ago had it setup and printing fine. For a year i haven't been using it and now getting it back out. As I got it setup again I came to do a homing sequence. Started out promising first axis homed the second one also and then the third moved just a bit then stopped it didn't go up at all to the sensor. after just to make sure the stepper was still working i tried jogging the printer in X Y and Z and all three motors seam to be working. I haven't tried printing like this because I feel like it would crash. So if theirs any information on what i could do or try it would be great. PS I'm really not good working with the firmware.

Thanks for the help

Prospectt
Posts: 1
Joined: Sat Jan 09, 2021 12:38 pm

Re: Stepper motors not homing

Post by Prospectt » Sat Jan 09, 2021 12:43 pm

AlexisT wrote:
Mon Nov 23, 2020 7:38 am
Hi im wondering if i can get help.

I purchased the Geeetech delta g2s pro a few years ago had it setup and printing fine. For a year i haven't been using it and now getting it back out. As I got it setup again I came to do a homing sequence. Started out promising first axis homed the second one also and then the third moved just a bit then stopped it didn't go up at all to the sensor. after just to make sure the stepper was still working i tried jogging the printer in X Y and Z and all three motors seam to be working. I haven't tried printing like this because I feel like it would crash. So if theirs any information on what i could do or try it would be great. PS I'm really not good working with the firmware.
alaskasworld
Thanks for the help
Stepper motors are deceptively simple. The simple view is that for every step you issue the stepper will rotate a predicable amount. Unfortunately the simple view is an illusion. There are real-world issues with starting torque, holding torque, acceleration profiles, winding currents and micro-stepping modes.

1. The big issue with stepper motors is torque. If a stepper is a rest and you issue a single step pulse, the stepper will move if the torque that it can generate is greater than what it takes to move the stepper's rotor and the attached load. Torque is determined by the design of the stepper motor, the current that your stepper driver supplies and the step mode that your driver is using.

2. Once you can issue a single step pulse, the next problem is figuring out how long you have to wait to issue the 2nd step pulse. You trying to figure out the maximum step rate without losing any steps. If the stepper stalls and hums or if the system continues to move (inertia) after the last step pulse, you are stepping too fast. You need to figure out this maximum step rate and cut it in 1/2. This is as fast as you can operate without using acceleration / deceleration ramps.

3. Next you will run into mechanical resonance. Stepper based systems can howl and scream at certain step rates and these are determined by a mess of physics. To keep the noise down you can change the step mode of your controller (micro-stepping) rates like 1/4 or 1/8 might help quiet the system down. However, this reduces the starting torque and you will need to re-evaluate the maximum step rate without acceleration (step 2). The other strategy is to run your system at higher step rates and you will need to figure out the acceleration/deceleration profiles to ensure that you do not lose position.

If you are using the stepper motor to move the door against gravity, you get into another stepper motor bit of physics, holding torque. Most stepper motors use permanent magnets and this results in a motor resisting rotation when the coils are not powered. Most stepper controllers, reduce the current through the coils when the stepper is not actively moving to reduce power usage. With no or low current it will be much easier for your load to move due to gravity.

AlexisT
Posts: 2
Joined: Fri Nov 25, 2016 2:43 am

Re: Stepper motors not homing

Post by AlexisT » Fri Jan 15, 2021 2:45 am

it could be a default stepper motor but I'm uploading a video to show the bug issue
Thank you for your help
Attachments
IMG_0227.zip
unzip folder for video
(10.18 MiB) Downloaded 469 times

Salterm36
Posts: 1
Joined: Tue Jul 27, 2021 7:44 pm

Re: Stepper motors not homing

Post by Salterm36 » Tue Jul 27, 2021 7:47 pm

A slightly less crude method would be to have a limit switch, and step it back until the limit switch is activated. But basically you can't do it just with the stepper motor, you need to add 'something' to let you know it's position.


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Russellsw
Posts: 1
Joined: Tue Dec 28, 2021 6:36 pm

Re: Stepper motors not homing

Post by Russellsw » Tue Dec 28, 2021 6:43 pm

Homing Sensor or switch is placed in a predetermined position to provide a reference point.

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ava121
Posts: 3
Joined: Thu Apr 15, 2021 5:04 pm

Re: Stepper motors not homing

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ducklife
Posts: 31
Joined: Wed Oct 21, 2020 11:19 am

Re: Stepper motors not homing

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