# Blog: General Motion Control

## A tale of two states and an ACME screw axis

An ACME screw story In our last posting we talked about the advantages and disadvantages of ball screws and ACME (lead) screws. In the next two postings I’ll share two stories, one about the Road Runner and the other about Wile E Coyote…If you’re just joining us and this makes little sense to you, you …

## ACME screws – a cost effective alternative to ball screws

In our last posting, we talked about the positional accuracy of a point of the moveable plate or work surface of our ball screw table with the terms roll, pitch, and yaw. The application that you’re trying to solve should be with the most cost-effective positioning solution.

## Linear Systems: Bearing Supports and End Fixity

Let’s start this discussion with the bearing supports for the ball screw. Let’s assume we have a ball screw that is 18” long and it provides 12” of travel. We have 3” on both ends that have been machined down past the root of the thread to form a smooth surface to install bearings that will support the screw. Let’s place the screw so it’s oriented left to right and our stepper motor and its coupling is on the left. We could install a number of bearing combinations on both ends of the ball screw that’s easier to define with a table:

## Linear Systems: Thread precision and mechanical backlash

In our last posting, we introduced leadscrews, ball screws and linear slides. We’re going to continue with that discussion by considering how accurately the threads are cut into the screw. Using the five-pitch screw as an example, we understand that five revolutions are supposed to move the plate one inch, but what happens if the thread is cut too long or too short. Five revolutions might move the plate 0.990” or 1.010”.

## Linear Systems: Lead screws, Ball screws and Linear Slides

With this posting, we’ll begin a discussion about leadscrew/ball screw/linear slide systems. Picture a screw with a nut on it. No, no not a Walnut.  Sighhhh. OK then, picture a right-hand threaded 1/4-20 screw with a 1/4-20 nut threaded on to the screw. A 1/4-20 screw has an outside diameter or major diameter of 0.25” and the thread of the screw has 20 turns per inch.

## Design Essentials: How to Size a Motor Properly to Avoid Oversizing

[vc_row][vc_column][vc_column_text]One of the challenges that face motion-control engineers is how to properly select a motor. If the motor is undersized or too small, it will not handle load. If the motor is oversized or too large, the motor will be too expensive in terms of purchase point and operation. Accurately sizing the motor can help …

## Fundamentals of Motion Control

[vc_row][vc_column][vc_column_text]Recently I came across a simple infographic from Power Jack Motion that did a nice job of visualizing the difference between alternating current (ac) and direct current (dc) motors. This article will follow and present the information contained therein. What is Motion Control, Anyway? Motion Control is a sub-field of automation encompassing the systems or …

## Motor Stalls in Stepper Systems

In our last posting we established a number of good things about stepper motors and their controls: Small changes in the winding current can be controlled by using bipolar chopper drive. Torque is in a fairly linear relationship with the winding current

## Understanding how torque is produced II

In our last posting we showed that the holding torque a step motor develops follows a sine wave as the shaft is moved from its stable position. This posting we’ll take a look at the torque that is produced by micro stepping (uStep) the step motor. We now know, through the past several blogs, that …

## Bipolar chopper drive circuit IV: understanding how torque is produced

With this posting we’ll take a look at the torque that is produced by step motor.We now know, through the past several blogs, that we can control the current in the motor’s winding in very small increments by using a bipolar chopper drive. We also know that the current in one phase follows a sine …