# Stepper motor

#### rahulmon

Joined Apr 7, 2015
11
Hi Guys,

I need to drive a column of approximate 5 kg at a speed of 1cm/s in vertical up and down direction using stepper motor (rotational motion to linear). I need help to select an appropriate stepper motor.

Thanks and regards,
rahul

#### MrChips

Joined Oct 2, 2009
19,160
That is a heavy load. You will need a rack and pinion gear or screw drive.

#### mcgyvr

Joined Oct 15, 2009
5,394

#### rahulmon

Joined Apr 7, 2015
11
Hi Guys,

Thanks for the quick reply. As i could see the calculations given in the above links are little complicated for me. May be because am not familiar with motor and mechanical driving sections. My aim is to drive a column of diameter nearly 2 inches and having weight less than 5 Kg at a speed of 1 cm/s. What i want to know is the maximum torque (the parameters needed to be considered) needed to drive such a column up and down using stepper motor, so that i can select a stepper motor and continue with mu=y design
Thanks

Joined Jul 18, 2013
18,872
I do not really use steppers if I can help it, but there is also a sizing program on the Kollmorgen site, if you can do without high accel/decel rates, this can lower the maximum torque rating of the motor considerably.
Max.

#### mcgyvr

Joined Oct 15, 2009
5,394
another..
http://www.jvl.dk/713/motorsizer
You are going to have to learn to do the calculations.
The information you are requesting cannot be given without knowing the mechanical design/aspects/friction/gearing,etc... of the design.
Thats something YOU must do.

You must also nail down your requirements.. "less than 5kg" implies .000001kg or 4.9999kg and anything in between.
And yes as max said.. Any requirements for acceleration times.. (aka how long till it gets to 1cm/s speeds)

or just pick up a cheap nema 17 to just go for it and adapt

#### rahulmon

Joined Apr 7, 2015
11
Hi,
The weight will be exactly 5 kg. The column will be of diameter 2 inch and it will be a hollow column. I would like to use rack and pinion mechanism. But i don't know what radius of the rack will be more efficient. My aim is to move the column up and down using this rack and pinion system in a speed of 1cm/sec. I prefer to use a stepper motor to drive this system. Any suggestions will be helpful.
Thanks

#### cmartinez

Joined Jan 17, 2007
6,380
Hi,
The weight will be exactly 5 kg. The column will be of diameter 2 inch and it will be a hollow column. I would like to use rack and pinion mechanism. But i don't know what radius of the rack will be more efficient. My aim is to move the column up and down using this rack and pinion system in a speed of 1cm/sec. I prefer to use a stepper motor to drive this system. Any suggestions will be helpful.
Thanks
My opinion is that if you must use a stepper, then you definitely need to use a ball-screw/nut with closed loop position monitoring. Plus a counterweight or break to prevent your mechanism from stalling when it's not energized.

#### rahulmon

Joined Apr 7, 2015
11
Hi,
Thank you for the suggestion. My aim is to find the appropriate stepper motor to meet my requirements. I want to control the system using microcontroller. I am working in micro controller based projects. I am new to this type of motors and mechanical design. That's why I posted it in here. Hope you understand .

Joined Jul 18, 2013
18,872
Do you have any of the mechanics worked out? Motor sizing will also depend on how and what you use to mechanically move the load, the mechanics are usually decided on first before any motor decision is made.
Max.

#### rahulmon

Joined Apr 7, 2015
11
Hi,
This is thee first time i am using a mechanical design. I would be using Rack and Pinion to drive the system.

#### cmartinez

Joined Jan 17, 2007
6,380
Hi,
This is thee first time i am using a mechanical design. I would be using Rack and Pinion to drive the system.
A rack and pinion vertically mounted to lift a weight? I would not recommend that. Can you change the design?
Otherwise I'd strongly suggest a counterweight to balance the load

#### rahulmon

Joined Apr 7, 2015
11
Hi,
The design can not be changed in the current implementation. The column will be locked in the position after movement. It will be moving inside another column.So mechanical balance is not a problem. My aim is to find out the motor torque needed to move the column up and down. The column weight will be 5 Kg.Length will be 30 inch. Rack and pinion design will be in such a way that to reduce the motor torque needed.

Joined Jul 18, 2013
18,872
Rack and pinion generally require a high degree of gearing due to the relatively high torque required, either that or a much larger motor increasing the relative cost of motor and drive.
I have used up to 100:1 planetary G.B. when using rack and pinion on some large applications.
It may be wise to look at a ratio that will still give you the IPS that is required for this project.
Max.

#### rahulmon

Joined Apr 7, 2015
11
Rack and pinion generally require a high degree of gearing due to the "relatively high torque required", either that or a much "larger motor" increasing the relative cost of motor and drive.
I have used up to 100:1 planetary G.B. when using rack and pinion on some large applications.
It may be wise to look at a ratio that will still give you the IPS that is required for this project.

I can change the design. But before changing design i need to find out the torque required to drive such a system and also the size of motor needed .

Thanks.

Joined Jul 18, 2013
18,872
To begin with you can determine the break-away torque, this is the initial effort to move the mechanism from a standstill, this can be done with either a sizing program such as Kollmorgen or measure with a spring scale or small torque wrench.
Then the final torque value is decided on based on accel/decel rates.
If these are trivial, the breakaway torque can be used for most part with some degree of allowance.
Max.

#### shortbus

Joined Sep 30, 2009
6,893
One thing that hasn't been mentioned in this thread is load holding. Does the 5KG load have to stop and stay at a certain level? You better use either a worm gear in the drive or a brake system.

To the O/P - T/S, do you know of this site? A lot of information there. http://www.engineersedge.com/

Joined Jul 18, 2013
18,872
One thing that hasn't been mentioned in this thread is load holding. Does the 5KG load have to stop and stay at a certain level?
This would be based on the break-away torque figure on the input shaft/device.
Max.