What is a slide screw? An easy-to-understand explanation of its types, uses, and the difference between it and a ball screw

Slide screws are mechanical components that convert rotary motion into linear motion and are also known as feed screws or lead screws. While they have a simple structure and high load capacity, caution is required in terms of efficiency and wear. Slide screws are often compared to ball screws, so it is important to understand the design and manufacturing criteria.

In this article, we will explain the basics of slide screws, their types and uses, how they differ from ball screws, and design considerations from the perspective of precision machining.

What is a sliding screw?

A slide screw is a component that converts rotational motion into linear motion by utilizing the friction caused by direct contact between threads.Because there are no rolling elements between the nut and the screw shaft, the structure is simple, the manufacturing costs of ball screws that achieve the same function are low, and they have the advantage of being self-retaining (self-locking mechanism) due to the friction in the threads.However, the thread efficiency of slide screws is low at around 30%, and they tend to wear out easily, which can be an issue.

In recent years, they have been widely adopted in fields that require quietness and cleanability, such as food machinery and medical equipment. Previously, they were avoided due to issues with wear and lubrication, but with the combination of resin nuts and self-lubricating materials, as well as advances in high-precision grinding and proprietary heat treatment technology,As wear resistance and corrosion resistance have been improved, the range of applications is expanding.

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The difference between slide screws and ball screws

Slide screws and ball screws are often compared because they have the same feed screw mechanism.Here we will explain the differences between each.

1. Efficiency gap
2. Lifespan and maintainability
3. Cost

Efficiency difference

Differences in efficiency are directly related to torque design and motor capacity selection, making them an important criterion for decision-making during design.Slide screws and ball screws have very different mechanical efficiencies.

Slide screws are suitable for applications such as jacks and vices that hold loads, and can maintain their position even when the power is cut off, while ball screws are suitable for motor drives and other applications where energy efficiency is important.

Lifespan and maintainability

An important selection criterion for a screw mechanism is whether it can withstand long-term use.In particular, ease of maintenance and replacement is directly linked to equipment downtime and lifecycle costs.

Slide screw
Although they are prone to frictional wear, their simple structure makes them easy to repair or replace when they wear out. Because their lifespan varies greatly depending on how well they are lubricated, slide screws can be advantageous in applications where ease of maintenance is important.

Ball screw
There is little wear due to rolling, resulting in a long life. However, regular lubrication and cleaning are essential.

Cost

If cost is a concern,Lead screws are a common choice.

Slide screw
The structure is simple and easy to process, making it suitable for low manufacturing costs, small-lot production, and the prototype stage.

Ball screw
High cost due to the need for precision machining and rolling element assembly

Types and characteristics of sliding screws

There are several types of lead screws, each suitable for different applications.Here we will summarize the most common types.

1. 台形ねじ
2. Square thread
3. Round screw

台形ねじ

This is the most commonly used feed screw with a trapezoidal cross section. It has a good balance of strength and manufacturability, and is standardized in JIS standards. It is widely used in lifting devices and feed mechanisms of machine tools.Although it has greater friction than square screws, it has advantages in terms of mass production and cost.

Square thread

A screw with a square cross section that has less friction loss and is more efficient than a trapezoidal thread. It is suitable for press machines that transmit heavy loads, but because it is difficult and expensive to process, trapezoidal threads are often used instead in modern times.They tend to be limited to specialised uses.

Round screw

A screw with rounded threads, it is resistant to impacts and wears well because it is difficult for foreign objects to get caught in it. It is also easy to clean because it does not easily collect dirt. It is not often used as a feed screw, but is used in food machinery, light bulb sockets, hose connections, etc.They are used for special applications where hygiene and repeated donning and doffing are required.

Examples of sliding screw applications

Slide screws are widely used in a variety of applications, from industrial fields to everyday components.We will introduce some representative applications.

1. Mechanical parts
2. lift device
3. Industrial machinery

Mechanical parts

It is used for parts that require precision but prioritize simple structure, such as vices and positioning of medical equipment.In particular, small diameter sliding screws and products with high precision positioning functions that minimize backlash when the screw is moved are suitable for devices that require fine control in limited spaces.

lift device

It is widely used in devices that hold loads, such as jacks and lifters.Its self-retaining properties make it effective in locations where safety is a priority. Furthermore, by selecting a resin nut, it is possible to reduce weight while suppressing wear, giving you greater freedom in design.

Industrial machinery

It is used as a feed mechanism for machine tools and transport devices.The advantage is that it is possible to build a low-cost, robust system while paying attention to wear. Evaluation standards vary depending on the device and manufacturer, but if durability tests can confirm continuous operation of more than tens of kilometers under a load of about tens of Newtons, it can be said to be at a level that can be safely introduced into industrial machinery that is assumed to operate for long periods of time.

Points to note when processing and designing sliding screws

When designing and manufacturing a sliding screw, attention must be paid to several aspects, including wear, dimensional accuracy, and torque design.The lifespan and performance of the entire mechanism are greatly affected by the selection of appropriate design and reliable processing techniques.

1. Wear and Lubrication Management
2. Dimensional tolerance settings
3. Strength and torque design

Wear and Lubrication Management

Slide screws tend to wear easily due to friction caused by the nut and threads rubbing directly against each other.Selection of the appropriate lubricant and regular maintenance are essential.

In recent years, there has been an increase in the use of plastic nuts and self-lubricating materials such as PPS, PA66, and PE, which can reduce noise and costs while suppressing wear.

Dimensional tolerance settings

The performance of a sliding screw is directly linked to the precision of engagement with the nut.In particular, for small diameter products, stable processing with minute dimensions such as outer diameter φ0.5 to φ12.0 and pitch 0.15 mm to 3.0 mm may be required.

If we have a production system that can process parts with high precision roundness and surface roughness through grinding and heat treatment, you can safely order parts with highly complex designs.

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Strength and torque design

Slide screws have lower screw efficiency than ball screws, so there are cases where a large torque is required.It is essential to design the drive motor capacity and shaft strength so that they are neither too strong nor too weak.

For example, by using high-rigidity hardened materials or stainless steel, it is possible to manufacture sliding screws that can withstand a load of over 1500 N in destructive tests. Such high-rigidity sliding screws will be more reliable under high-load conditions, such as in robot arms and precision transport equipment.

Summary | Understand the types and characteristics of sliding screws and use them to create optimal designs

Slide screws come in multiple shapes, and it is important to select the appropriate one depending on the application. Although they are inferior to ball screws in terms of efficiency and lifespan, their major advantages are their simple structure and low cost. When designing, it is necessary to carefully consider factors such as wear, dimensional accuracy, and torque settings.

Sanwa Needle Bearings offers small diameter, high precision sliding screws with outer diameters of φ0.55 to φ12.0, a variety of resin nut materials such as PPS, PA66, and PE, and proprietary technology that can achieve high precision positioning with backlash of less than 2 μm.We perform thread grinding using special machines developed in-house, so please feel free to contact us if you have any problems with design or outsourcing.