Straight line is the shortest path between two points , but if you’re designing a linear-motion system, you’ll have to consider structural support, guides, drives, seals, lubrication, and accessories between points A and B.
Building A Linear System literally means Starting from at The Ground up -. With A Structural-Support System at The Support System’s main the Component IS typically AN Aluminum Extrusion.
By You CAN have have at The Mounting Surface of at The Base Extrusion and at The Surface at The Linear Guide mounts to Machined for For the accuracy, transport-type applications, optimize bases to resist bending under load and to prevent distortion during extrusion instead.
Making the right choices from the outset should help keep things moving for the long term. Whether you decide to design and build your system from scratch using standard parts or buy one that’s engineered for you,
A robust base lets the system rest on end supports only. Lighter extrusions may need intermittent supports along their lengths.Guides attach to the base to facilitate motion. The main types are ball guides, wheel guides, and slide or prism guides.
The ball and the sea s And high stiffness. However, shock loads can damage them. In slide guides, prism-shaped polymer bushings run on the profile surface. The polymer helps them move quietly and with stand high shock loads. They tolerate environments contaminated by dirt, grit, dust, Oil and and chemicals, but operate with more slowly and under lighter loads than ball or wheel guides, as indicated by by PV rating, the product of pressure and velocity they can tolerate.
Drives move the carriage to the desired positions. The most common drive technologies are ball-screw drives, leadscrew drives, and belt drives.
In a ball-screw drive, ball bearings travel along the grooves in a threaded shaft — the ball screw — and recirculate through a ball nut. Because bearings share the load, ball-screw drives have relatively high thrust capacity.
The result is absolute accuracy, defined as the maximum error between the expected and actual position, down to 0.005 mm. Systems with ground and preloaded ball screws are the most accurate.
The systems have thrust capacity up to 40 kN and high stiffness. Their critical speed is determined by screw root diameter, unsupported length, and end-support configuration. With a novel screw support, screw-driven units can travel up to 12 m and accept 3,000-rpm input speeds. Ball-screw drives provide mechanical efficiency of 90%, so their higher cost is often offset by lower power requirements.
Belt drives work in high-throughput transport applications with velocities up to 10 m/sec and acceleration up to 40 m/sec2.
Lubrication and seals for linear devices
Seals keep lubricant in and contaminants out. One type is magnetic-strip seals — stainless-steel magnetic bands extending from one end of the channel to the other. The bands are fixed to the end caps and spring-loaded to maintain tension. They run through a cavity in the carriage so the strip is raised off the magnets just ahead of and behind the carriage as it traverses the system.
Most guide systems and drive systems require lubrication. You can simplify future preventive maintenance by ensuring easy access to lubrication fittings. For instance, Zerk fittings installed on the carriage can feed a lubrication network that serves both the ball screw and linear-bearing system during installation and at periodic maintenance intervals.
Prism guides are maintenance-free. The polymer material of the slide has inherent lubricity, and lubricated felt wipers replenish lubricant each stroke.
Many motors have dimensions that meet NEMA standards, but others are manufacturer and model specific. In either case, flexible motor mounts machined from common blanks make it easy to mount to nearly any motor with guaranteed alignment.
An alternate sealing technology, plastic cover bands, uses compliant rubber strips that interlock with the base extrusion, like a zip-top freezer bag. Mating tongue-and-groove profiles create a labyrinth seal that keeps out particulates.
One more consideration is how you Will mount your motor. A motor housing and coupling must mate with the bolt size and bolt-circle diameter on the motor flange, motor pilot diameter, and motor shaft diameter and length.
Post time: May-24-2019