In linear and sliding motion mechanisms, a linear shaft rod plays a crucial role. Without a linear shaft, we wouldn’t complete a sliding mechanism with linear power transmission.
But, the manufacturing and choosing of the appropriate linear shaft can get tricky. Linear shafts can have different structures and be made of various materials, depending on the properties needed.
So, we’ve decided to put together this in-depth guide to a linear shaft to help you stay in the loop and make an informed decision.
What Is a Linear Shaft?
The linear shaft in power transmission applications is a long, rod-shaped tool used for support in linear motion, especially sliding motion. With a linear shaft, the motion can be guided and fine-tuned.
The load and specific requirements determine the size and precision of the linear shaft. Linear shafts made with tight precision tolerances are more durable and resistant to wear and tear.
How Do Linear Shafts Work?
In linear power transmission mechanisms, the shaft works together with an actuator, support rail, bushings (ball bearings), etc. In linear power transmission, the actuator typically does all the sliding work, while the rail, bushings, and linear shafts provide support.
Linear shafts have to be mounted before they’re used. There are two main ways of linear shaft mounting – continuous support and end-supported. Linear shafts with continuous support are typically used for heavier loads, while those supported at both ends are used for smaller weight loads.
What Is the Function of a Linear Shaft?
The function of a linear shaft is to provide support in linear motion. The term can be slightly misleading since the shaft isn’t doing anything other than staying static for support. There’s an actuator doing the work for the slide motion to take place up and down the linear shaft.
Simply put, any type of sliding or transmission mechanism needs to use either a linear shaft, a post or a rotary shaft. The kind you use depends on the application.
What Are the Materials Linear Shafts Are Made Of?
The majority of linear shafts are made of aluminum, steel alloys, stainless steel, carbon steel, plastics, or other composites.
For instance, stainless steel is often used for applications when the linear shaft must resist rust and corrosion. Another great material for a corrosion-resistant linear shaft is aluminum. On the other hand, you can use alloy steel if your goal is durability, toughness, and stability.
And finally, if you need something more lightweight that uses less energy, you can choose between various composite materials made of bonded carbon fibers. However, these lack the toughness of alloy steel.
It’s important to note that linear shafts are usually coated with different materials to improve their hardness or durability. Depending on the requirements and their applications, linear shafts can be hardened with:
- Ceramic coating– used to give the linear shaft water-resistant properties;
- Chromium coating– for corrosion resistance and decreasing friction;
- Anodizing coating– used mainly for hardening aluminum linear shafts;
- Black oxide coating– used to give steel or stainless steel linear shafts a superior ion corrosion protection;
That’s not an extensive list of coatings. There are many more surface finishers out there, such as electroplating, powder coating, PVD coating, etc.
The Advantages of Linear Shafts
Here are some of the advantages and benefits of linear shafts for different applications:
- A wide range of appropriate materials to choose from;
- Applicable in many different industries;
- Possibility to manufacture with different diameters, strengths, materials, etc.;
- Option for tapped, threaded, standard (full), or hollow shafts;
- Superior bearing and support for different machines and mechanisms;
The Hardness of Linear Shafts
The hardness of a linear shaft can be measured with different tests or ways:
- The Rockwell Hardness: by pressing a diamond or steel cone-shaped object against the material in question – in this case, the linear shaft – we can check the indentation and determine the hardness. Typically, linear shafts have a Rockwell hardness range of 50 to 59, 60 to 69, and 70 to 79;
- The Knoop Hardness: another test that can measure the hardness of the linear shaft material by checking its resistance to indentation;
- The Brinell Hardness: the material of the linear shaft is tested by placing huge loads of over 3 tons on it;
The Applications of Linear Shafts
A linear shaft as support for linear power transmission has applications in many industries, most notably in:
- Medical – for the sliding motion mechanism of MRIs, dental chairs, instrument adjustments, scan heads, surgical tables, and more;
- Automotive – anywhere where linear power for sliding is needed, such as car seat mechanisms and similar;
- Aerospace – used in many mechanisms such as the plane/passenger seat adjustment;
- Packaging/printing – many printing and food packaging machines use linear motion shafts in their production;
The above is not a complete list of linear shaft applications. They’re practically used anywhere we need linear sliding power transmission.
Do DEK Offer Customized Linear Shafts?
Yes! We here at DEK offer customized linear shafts with no MOQs. Our state-of-the-art 5-Axis CNC machining, centerless grinding, milling, and lathes allow us to provide low-volume manufacturing services as well as mass production of linear shafts.
We work with any pure or alloy materials, composite materials, and different types of appropriate plastics. DEK can take care of the entire production – prototyping, machining, surface finish and coating, and testing.
And, most importantly, we offer ultra-precision machined parts with tolerances as tight as ±0.0001mm (+/-.00005″). Knowing how vital precision is in manufacturing a linear shaft, our tight tolerances will offer you the security you need.
To Sum Up
The strength, precision, and accuracy of the linear shaft are vital for determining its quality and durability. As a part that’s constantly exposed to motion and grinding, tight tolerances regarding diameter, surface finish, straightness, and roundness are necessary.
We here at DEK manage to meet these tight tolerance requirements with the help of the most cutting-edge technology such as 3, 4, and 5-Axis CNC machining, precision grinding, 3D printing, etc. You can use our on-demand, no MOQ service and place a customized linear shaft order. You can always contact our engineers for technical support so you have clarity about each step and functionality.