Stepper motors have different torque-speed characteristics depending on whether the motor is starting/stopping or already running. These characteristics are depicted in two curves on the motor’s torque-speed chart, and it’s important to understand the differences between these curves and what each one means for the motor’s operation. But a stepper motor can also produce torque […]
FAQs + basics
Part 2 – What is racking in gantry systems, and how can it be avoided?
In Part 1 of this post, we looked at various methods of driving the X axes in gantry systems and how the drive method can influence the gantry’s tendency to experience racking. Another factor that can cause racking in gantry systems is lack of mounting accuracy and parallelism between the two X axes. Racking is the common name […]
What is racking in gantry systems, and how can it be avoided? (Part 1)
Gantries differ from other types of multi-axis systems (such as Cartesian robots and XY tables) by using two base (X) axes in parallel, with a perpendicular (Y) axis connecting them. While this dual X-axis arrangement provides a wide, stable footprint and allows gantry systems to deliver high load capacity, long travel lengths, and good rigidity, […]
Mechanical properties of materials: stiffness and deflection
In a previous post, we looked at the stress-strain curve and its relationship to various aspects of material strength — tensile strength, yield strength, and fracture mechanics strength, for example. And while we often think of materials and structures in terms of strength, technically, “strength” is a measure of how much force a material can […]
What causes synchronous belt noise and how can it be reduced?
Synchronous belts are common in motion systems, providing smoother operation and better high-speed performance than chains and lacking the problems of slipping and stretching that can plague V-belts in precision applications. But one downfall of synchronous, or toothed, belts is the noise they produce. Although quieter than a chain drive, a synchronous belt can still generate noise […]
How can lead screw backlash be reduced?
Backlash is an inherent property of lead screw assemblies due to the sliding motion between the screw and the nut. For some applications, a certain amount of backlash, or “play,” can be tolerated, but applications such as positioning, dispensing, or assembly often require a level of precision and repeatability that can’t be achieved if backlash […]
What’s the difference between ball screw critical speed and characteristic speed?
Ball screw drives incorporate two primary moving components: the rotating screw shaft and the nut that traverses the screw. (The radial bearings that support the screw shaft play a minor role for the purposes of this discussion.) This means that to accurately determine the maximum allowable speed of a ball screw assembly, there are two […]
Motion basics: Difference between Cartesian and polar coordinate systems
Coordinate systems provide a way to define a point in space in either one, two, or three dimensions. The most prevalent coordinate system used in linear motion applications is the Cartesian system. Cartesian coordinates define a position as the linear distance from the origin in two or three mutually perpendicular axes. The origin is the […]
What types of motion can you create with multi-axis linear systems?
For many tasks, multi-axis linear systems — Cartesian robots, X-Y tables, and gantry systems — travel in straight lines to achieve quick point-to-point movements. But some applications, such as dispensing and cutting, require the system to follow a circular path or a complex shape that can’t be created by simple lines and arcs. Fortunately, modern […]
What is a follower nut, and what role does it play in lead screw operation?
Although the idea of a “follower nut” may seem to indicate that the nut serves a passive role in lead screw operation, it actually plays an important part in monitoring the condition and life of the screw assembly. The wear characteristics of a lead screw nut make the expected service life of the assembly difficult […]