# How to select stepper motor for a Z-axis application with Ballscrew

• Vatech
In summary, the weight of the Buildplatform for a MSLA printer is 2.29kg but may increase to 3.29kg due to a resistive force when detaching the printed model from the Fep film. The desired weight capacity for the platform is 6.6kg, and the ball screw being used has a 4mm travel per full rotation. The minimum holding torque of the stepper motor needed for the platform is 0.04Nm, taking into account acceleration and friction. It is also important to consider the detent torque and holding torque of the motor when choosing the appropriate one for the job.
Vatech
TL;DR Summary
it is needed to select stepper motor for a Z-axis application with Ballscrew.
we suppose as knowing data that the z axis is verstical and the load is 6.6kg.
I build a Z-axis (not the one displayed on image). The weight of the Buildplatform is 2.29kg and is going to be used on a MSLA printer, so the weight might get increased 1kg additionally, so 3.29kg. The problem is that when detached from the printed model from Fep film there is a resistive force, this needs tools and test to be calculated so this is unknown data for the time.
That’s why i would like to be able to lift double the weight , meaning 6.6kg.
The ball screw is a SFU1204 , meaning 4mm travel per full rotation. Friction

I sourced experimental a stepper that has 1.8N holding torque, but how could i calculated the minimum Holding torque of the stepper motor needed to lift up the platform?

Better check your inputs. I have seen ball screws with 4 mm lead, but never one with 0.4 mm lead.

When sizing a stepper motor for a slow speed drive, such as a 3D printer build stage, you can ignore acceleration. With a ball screw drive, include friction when moving up. Sources of friction include the ball screw bearings, the ball nut, and the stage bearings.

Assume zero friction when holding and when moving down. This will be somewhat conservative, but is good practice with the low friction of a ball screw drive.

jrmichler said:
Better check your inputs. I have seen ball screws with 4 mm lead, but never one with 0.4 mm lead.

When sizing a stepper motor for a slow speed drive, such as a 3D printer build stage, you can ignore acceleration. With a ball screw drive, include friction when moving up. Sources of friction include the ball screw bearings, the ball nut, and the stage bearings.

Assume zero friction when holding and when moving down. This will be somewhat conservative, but is good practice with the low friction of a ball screw drive.
Sorry for misstyping the 4mm

and this are the specs of my motor

By the above calculation is needed a Stepper with at least 0.04Nm Holding Torque? So in my case the 1.8Nm is a bit too much? OverEngineered?

Vatech said:
So in my case the 1.8Nm is a bit too much?
Maybe.
You have calculated the Running Torque to move the load.
You should also consider the Detent Torque, if any (not all stepper designs have any), and the Holding Torque.

Unless you plan to keep the motor energized to hold the load, it is the Detent Torque that will keep the load where you put it.

A quick explanation is at:
https://www.motioncontroltips.com/faq-whats-the-difference-between-detent-torque-and-holding-torque/

(above found with:
https://www.google.com/search?&q=stepper+motor+holding+torque)

Cheers,
Tom

## 1. What is the relationship between the stepper motor and the ballscrew in a Z-axis application?

The stepper motor and ballscrew work together to move the Z-axis in a linear motion. The stepper motor provides the torque and rotational movement, while the ballscrew converts that rotational motion into linear motion.

## 2. How do I determine the appropriate stepper motor size for my Z-axis application?

The size of the stepper motor needed for a Z-axis application depends on the weight and size of the load being moved, as well as the required speed and accuracy. It is important to consider the torque and step resolution of the motor when making a selection.

## 3. What is the difference between a single and dual shaft stepper motor for a Z-axis application?

A single shaft stepper motor has one output shaft, while a dual shaft stepper motor has two output shafts. The dual shaft motor allows for additional support and stability for the Z-axis, making it a better choice for heavier loads or more precise movements.

## 4. Can I use a stepper motor with a different step angle for my Z-axis application?

It is not recommended to use a stepper motor with a different step angle than what is recommended for your Z-axis application. This can affect the accuracy and precision of the movement, and may cause issues with the overall performance of the system.

## 5. How do I know if I need a geared or direct drive stepper motor for my Z-axis application?

The decision between a geared or direct drive stepper motor depends on the required torque and speed for the Z-axis movement. Geared motors provide higher torque, while direct drive motors offer higher speed and accuracy. It is important to consider the specific needs of your application when making a selection.

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