Linear Guide Guide

Linear Guide overview

Linear Guides are a block and rail system that helps support the motion of an application.

How linear Guides Work

There are two parts to the Linear Guide System: the Linear Block and the Linear Rail. The linear block moves along the linear rail along the plane the rail is positioned for. The block moves forward and backward along the straight linear rail. Linear blocks connect to the moving components by mounting to the block to support the motion for the specified component. The motion is created along the rail through recirculating ball bearings within the block that is contacted on the rail.

Basic Types of Linear Guides

Two basic types of linear guides are predominantly used in industry today. These types are: sliding contact linear motion bearing and rolling element linear motion bearing guides. The main distinction between the two is how the motion of the linear block occurs along the linear rail.

Sliding contact



The sliding contact is considered the oldest type of linear guide used within industry. This may be because of its simplicity and low in manufacturing that companies still use this "old technology." A huge drawback with the sliding contact is its high coefficient of friction compared to its other types. With such a high coefficient of friction it becomes difficult for companies to use this type of guide for applications with high precision or high speed. This huge setback makes it hard to predict and design an exact lifetime for the linear guides.

Rolling Element



This type of linear guide is known to be the most commonly used type for most applications. Ball bearings, or rollers, are elements usually used within these blocks to create the rolling motion of the block. The coefficient of friction is therefore already decreased from the original sliding contact block just because of the rolling action. These types of blocks are easier to control increasing accuracy, precision, and speed for the guide. There are a wide variety of options to customize this block, another reason why it is generally a better choice over the sliding contact block.

Industries that Use Linear Guides

A wide variety of industries use and order linear guides for their own applications…


Applications that Use Linear Guides



Linear guides are used to move a machine table in either the X or Y direction. Applications which require high precision use linear guides due to their high accuracy and precision capabilities.



In the application to the left, each table uses linear guides for positioning. Machine tool applications use linear guides because of their ability to manage temperature rise and high speed changes.



Linear guides are used to transport heavy product with ease.



In this application, the linear guides were used to help create the motion of a robot pick-and-place machine.


Select a Linear Guide

As with any large investment, there are a few factors that should be considered when selecting a linear guide for your application. Following this flow chart will help guide you in choosing the perfect Linear guide through our website. Necessary equations are found within this guide for lifetime, max torque, etc.


Note 1: There might be limitations on the mounting space of the linear guide because of structural restrictions on the machine.

Note 2: In the case of a ball screw drive, it is advisable to choose a linear guide with its model number the same, as or closest to the ball screw shaft diameter.

Note 3: Applied load per ball slide herein shall be calculated simply by dividing total applied load by the number of ball slides.

Advantages/Disadvantages of a Linear Guide

Advantages Disadvantages
Durable; can withstand a wide range of loads depending on the application. Not as effective for vertical applications.
Little friction between block and rail with the ball bearings for high accuracy of block.
Equal loading in four directions and a sufficient preload that provides high rigidity to the linear guide.

Troubleshooting a Linear Guide

There are a few things to look for in your linear guide that want to avoid. Regularly machinery such as corrosion of the rail, indentations in the rail, or wear can occur within the linear guide. These different damages can occur because of poor care of the system, excessive misalignment, contaminating the rail with the wrong product, or poor lubrication. An easy way to troubleshoot these types of problems is to always clean and care for the blocks and the rails, and make sure the installation is followed as stated in the manuals.

The Cost of Linear Guides

The cost of linear guides is dependent upon size and material of the linear guides. For applications with higher load capacity, you will generally need a bigger linear block. In this case the wider the block or the longer the rail needed will increase the price of the linear guide. For more specific pricing inquiries please contact the factory to assist you in pricing.

Required Maintenance for a Linear Guide
Most linear guides are equipped with a lubrication mechanism within the block. This is a great advantage because it essentially decreases the maintenance required for the user of linear guide. The main requirement is to just refill the grease lubrication when needed and the block will have a longer lifetime. Although the lubrication does help decrease maintenance, linear guides still need to be dusted and cleaned from unwanted debris that would cause the linear guide to deteriorate.

Environmental Aspects for a Linear Guide
The environment of a linear guide in use is dependent upon the application of the linear guide. Certain precautions should be taken for different environments. Linear Guides should have a clean, debris free environment because of its re-circulating rolling elements. These rolling elements may lose its lubrication when interfering with dirt on the rail. Although a clean environment cannot be sustained in some applications at all times, an upgraded lubrication option can be added to a linear guide to help increase lifetime of the guide in a dirtier environment.

History of Linear Guides

Linear Guide Invention & Evolution
The invention of the linear guide occurred in 1932 when it was patented by a company based out of France. Steel was the first type of material used in the rolling elements because of its accurate and smooth linear movement. However, while this may be true, a US company named Thomson first commercialized the rolling element in their ball screws with the first recirculation ball type in the year 1946. Years following, companies have been innovating and evolving the linear guide into the product it is today.

Formulas for a Linear Guide


A. Calculation of the load that is acting on a ball slide You need to calculate two cases of load conditions: one is for when the linear guides are loaded (moving outward), and the other is for when returning unloaded (moving backward).

1. When the linear guide is loaded: (moving outward)

Similarly,
Fr2 = -497 (N)
Fr3 = 1997 (N)
Fr4 = 967 (N)
1) When no load is applied to the linear guide (moving backward)

Similarly,
Fr2 = 123 (N)
Fr3 = 177 (N)
Fr4 = 147 (N)
Table below shows the above results

Linear Guide Glossary

Accuracy
Based on the running accuracy of ball slides that travel on the rails, the required motion accuracy is expressed in a particular accuracy grade, like P5 or PN.

Applied Loads
These are the loads applied to the linear guides, which usually consist of self-weight of a table, weight of transported objects, and/or forces that are working on a machine tool. The loads are normally applied vertically or laterally against motion axis.

Application
This is the information on the type of machine (application) like machine tools, transporting systems, or measurement apparatuses for which linear guides are to be used. Generally, such information is very useful to select the appropriate linear guides.

Ball Bearings
Steel circular balls that create the motion for the linear guide system through its re-circulation.

Dynamic Load Capacity
The amount of force the linear guide can withstand when the block is in motion.

Grease
The class of lubricants applied to smooth the movement of guides and moving parts of the ball screw. Grease forms an oil film on metal surface to reduce wear and friction, thereby prolonging the life and preventing rust. Linear slides require periodic maintenance of grease according to their use conditions.

Linear Guide Block
The block that moves along the track that supports the machine or application it is holding. It houses the lubrication and the re-circulating bearings within the block.

Linear Guide Rail
The track that the block moves on made of carbon steel. This track is a uniaxial track, meaning it travels only along one axis.

Load Moment
When the load acting upon the table extends beyond the table in the longitudinal, lateral or vertical direction, the linear slide receives a torsional force.

Machine Structure
This information covers the structure of machines and their relevant aspects of construction such as dimensions around the place where linear guides are mounted to, positions and directions of external forces, etc. This is compulsory information for selecting particular linear guides.

Pitch
The hole-to-hole distances found on the linear rails.

Required Life
Required life is expressed in a total travel distance (For example, 5000 km).

Service Life
The calculated time the linear guide can withstand before failure in hours.

Speed
This means a relative speed of the table (with the ball slides) against the rails. It is expressed as, for example, 100 m/min.

Static Load Capacity
The amount of force the linear guide can withstand when the block is not moving.

Stroke
This means a travel distance that a table mounted on ball slides is required to make.

Lifetime for a Linear Guide

Nominal Life (L) for a linear motion system with balls

Nominal Life (L) for a linear motion system with rollers
C = Basic dynamic - Load Rating; Pc = Calculated Load; fh = Hardness factor;
ft = Temperature Factor fc = Contact Factor; fw = Load Factor
Service Life (Lh) of linear guide in hours
ls = stroke length (mm); n1 = Number of reciprocating cycles per min (min-1)

FAQs

Q: What material is the rail made from for most of the Standard Linear Guides?
A: The material you will find most standard linear guides in is carbon steel.

Quiz #1

  1. Anaheim Automation's linear guides are all made from Stainless Steel.
    1. True
    2. False
  2. In general, when comparing between TBI, CPC, and NSK, the lowest cost supplier is?
    1. TBI
    2. CPC
    3. NSK
    4. They are all the same price
  3. Anaheim Automation carries more than $50,000 in stock of linear guides.
    1. True
    2. False
  4. The supplier that has the highest quality is?
    1. TBI
    2. CPC
    3. NSK
    4. They are all the same quality
  5. In general, what is the best supplier to use for high volumes over 1000 pieces per year?
    1. CPC
    2. NSK
    3. TBI
    4. Our chances are the same with all of them
  6. Which supplier has the most experience with custom coatings?
    1. TBI
    2. CPC
    3. NSK
    4. They are all the same quality
  7. CPC and TBI Linear Guides are made in China
    1. True
    2. False
  8. CPC and NSK have stock in the United States
    1. True
    2. False
  9. The smaller linear guides get, the less expensive they are
    1. True
    2. False
  10. Linear guide blocks from one manufacturer can be used on another manufacturers rails
    1. True
    2. False

Quiz #2

  1. Linear guides are a block and rail system that helps support a curved-motion application.
    1. True
    2. False
  2. Which environments can linear guides be exposed to?
    1. Dusty
    2. Underwater
    3. Clean-room
    4. All of the above
  3. Linear guide dynamic load capacity refers to
    1. The amount of force the linear guide can handle when not moving
    2. The amount of force the linear guide can handle when moving
    3. The amount of force the block can handle when not mounted on the rail
    4. The amount of force the rail can handle when the block is not mounted
  4. Advantages of linear guides include
    1. Very effective for vertical applications
    2. Requires no maintenance even in environments with high amounts of debris
    3. Highly durable and can withstand a wide range of loads depending on the application
    4. They come in different colors
  5. A company based out of France patented the linear guide invention in 1932
    1. True
    2. False
  6. The hole-to-hole distance found on the rails is known as the
    1. Hole distance
    2. Pitch
    3. Catch
    4. Mount
  7. What type of linear guide is most commonly used and offered by companies such as NSK, TBI, and CPC?
    1. Sliding Contact
    2. Ceramic Bearing
    3. Rolling Element
    4. None of the above
  8. Which supplier offers a roller bearing linear guide?
    1. NSK
    2. TBI
    3. CPC
    4. LOL
  9. The technique used to join two linear rails together to form a longer rail.
    1. Arm joint
    2. Rail joint
    3. Block joint
    4. Butt joint
  10. Ball bearings can be easily replaced when removed or are lost.
    1. True
    2. False

Quiz #1 Answers

  1. b, false - only a few lines are made from stainless steel
  2. a - TBI has the lowest prices
  3. a - We carry at least $50k from both TBI and CPC
  4. c - NSK is by far the highest quality when compared to all but THK
  5. c - TBI has the best high volume prices
  6. c - NSK handles these situations very well
  7. b, false - they are made in Taiwan
  8. a - CPC has stock in Chino, California. NSK has stock in Indiana.
  9. b, false - they do get less expensive from 55, 45, 35, 20, 15.... Until you get to the miniature sizes, when the price goes up!
  10. b, false - they all have different designs.

Quiz #2 Answers

  1. b, false - Linear guides are meant for linear applications. Products such as "roller" guides can provide curved-motion support.
  2. d - Linear guides can be exposed to most environments when properly coated or customized.
  3. b - Dynamic load refers to force capacity while in motion.
  4. c - Linear guides are very durable.
  5. a, true - A company in France patented the linear guide in 1932
  6. b - The pitch is the term widely used that calls out the hole-to-hole distance on a rail
  7. c - The rolling element is most commonly used in the majority of applications.
  8. a - NSK offers a roller bearing linear guide that provides a larger load capacity compared to TBI and CPC.
  9. d - A butt joint is a technique used to combine two linear rails together.
  10. b, false - Blocks contain ball bearings made specifically for certain accuracies and preload and can be difficult to replace without the right size ball bearings and training.

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