Loud groans from homing Z

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jtknives

JTknives
Been setting up all my controls and was working on the z axis. Standard stepper motor on a .125 /rev ball screw. Got it moving with a good speed and set up the z axis home switch. This is where the troubles seamed to start. I would home the z and it would shoot up to the home position perfectly and it would move back down alittle ways off of the home position. But when it would move back off the switch it would make this crazy loud growning wining noise and the stepper would vibrate bad. Only way I could get it to stop was change the acceleration to a low number like 30. In normal continuous jog mode this would show up if I crank the acelaration up past like 160 and over 500in max. What is causing this?
 
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machinedude

machinedude
sounds like your trying to get to much out of your steeper motor. the z axis is a bit different than the x and y axis in the sense your lifting the weight of your head up and down. the thing to remember is a stepper is a open loop system and when you throw momentum into the mix you can run into missed steps. often people add counterweights and gas struts on the z axis to balance out these problem areas. also a .125 lead on your screw is not very aggressive in terms of speed so the motor has to run faster to get better speeds but at the same time steppers loose a lot of power on the torque curve at a higher speed. typically a stepper system will only get about 75 to 125 imp on rapids and you might do a little better if the motors are over sized but I would not expect to much gain. all this would explain why you have better luck when your acceleration is set lower. I would also say if your speeds are slower on the z axis that would be normal in most cases. keep in mind this is just a very basic observation on my part based on the limited information provided in your post. I have no idea if this is your first build or 10th build?
 
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jtknives

JTknives
Yeah I have returned the stepper and buying a closed loop version that s stronger. I m running closed loop on the x and y so I thought I could get away with a standard stepper. But man that motor just sitting there not moving would hit 180 f.
 
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machinedude

machinedude
the hybrid steppers do a little better but they even lack on performance. an actual servo is the best in my opinion. I have dmm servo's and i'm only slowed down by the controller with a .200 lead on a ball screw. the servo's have the potential to do 1000 ipm but I max out at around 650 imp in my case. the first few builds I've done were stepper builds and everyone of those was disappointing for rapid rates. only down side to the servo system is the cost.

if your motor is getting that hot your most likely trying to get to much from it as well. something to keep in mind with the tuning on the new one. I would guess you might get double your speed with a hybrid but I have no personal experience with those honestly. I've only seen some reviews on-line.
 
J

jtknives

JTknives
Well I solved it. I bought a closed loop stepper and everything is roses now. It now moves at some alarming speeds. We will see how well it works when I get the torch mount on it. Thanks guys.
 
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