Movement frequency is an important operating condition when selecting a linear guide block, but it should never be used as the only selection criterion.
Two machines may both operate at 40 cycles per minute, yet one may travel only 50 mm per cycle while the other travels 300 mm. Their accumulated travel distance, heat generation, lubrication demand and required guide life will be completely different.
The correct selection method is to evaluate the complete motion profile: stroke, cycle definition, velocity, acceleration, load direction, moment load, daily operating time, required service life, preload, accuracy and working environment.
What Does Movement Frequency Actually Mean?
Movement frequency describes how often an axis repeats its motion, but the term may be defined differently by different machine builders.
| Parameter | Meaning | What to Confirm |
|---|---|---|
| Stroke | One-way travel distance of the moving table | Whether the stated value is one-way travel or total forward-and-return travel |
| One complete cycle | One forward movement plus one return movement | Whether the controller counts a complete cycle or each individual stroke |
| CPM | Complete cycles per minute | Cycle definition, dwell time and whether the axis moves continuously |
| Reversal frequency | Number of direction changes per minute | A complete reciprocating cycle normally creates two reversals |
| Duty cycle | Percentage of total time during which the axis is moving | Moving time, dwell time, shifts per day and working days per year |
Before calculating guide life, confirm how the machine manufacturer defines one cycle. If one movement is incorrectly counted as a complete forward-and-return cycle, the estimated travel distance can be wrong by a factor of two.
Calculate Travel Distance Instead of Looking Only at CPM
For a reciprocating axis in which one complete cycle includes one forward stroke and one return stroke:
When the stroke is entered in meters, the result is meters per minute.
Example: Same Frequency, Six Times the Annual Travel
Consider two axes that both operate at 40 complete cycles per minute, 16 hours per day and 250 working days per year.
| Motion Profile | Stroke | Travel per Minute | Annual Travel |
|---|---|---|---|
| Axis A | 50 mm | 4 m/min | 960 km/year |
| Axis B | 300 mm | 24 m/min | 5,760 km/year |
Although the two axes have exactly the same movement frequency, Axis B accumulates six times the travel distance. It therefore requires a much higher guide life or more frequent replacement.
This is why fixed frequency categories such as "below 30 CPM" or "above 60 CPM" are not sufficient for linear guide block selection.
Include Acceleration and Direction Reversal Loads
High-frequency reciprocating equipment repeatedly accelerates, decelerates and reverses direction. The additional inertia force should be calculated rather than assumed from CPM alone.
- Fa = inertia force in newtons
- m = total moving mass in kilograms
- a = linear acceleration in meters per second squared
The total moving mass should include the workpiece, fixture, table, brackets, tooling, cable chain and other accessories that move with the carriage.
For a vertical axis, gravity must also be included:
Upward acceleration normally increases the guide and drive load. Downward acceleration may reduce the gravity component temporarily, but braking, emergency stops and direction reversal can still produce high peak loads.
Do Not Ignore Offset Loads and Moments
If the load center is above, beside or in front of the guide block, it produces an overturning moment:
- M = moment load
- F = applied force
- h = perpendicular distance from the force to the guide mounting plane
In high-acceleration equipment, the inertia force acts through the center of gravity. A tall carriage, cantilevered tool or offset workpiece can therefore create a substantial pitch, yaw or roll moment during every reversal.
Increasing the distance between two rails or between two blocks often reduces the load concentration more effectively than simply selecting a wider rail.
For a more detailed load-distribution method, see How to Select Linear Guide Rail and Carriage Load Capacity .
Calculate the Required Linear Guide Life
Movement frequency affects guide selection mainly because it changes the accumulated travel distance and the number of acceleration and deceleration events.
For a ball-type linear guide whose catalog dynamic load rating is defined using a 50 km nominal-life reference, a simplified life calculation is:
- L10 = nominal travel life
- C = basic dynamic load rating of one block
- Pm = equivalent mean load acting on that block
If the block load changes during acceleration, constant-speed travel, processing, deceleration and return travel, use an equivalent mean load rather than a simple arithmetic average.
This cubic mean applies to ball-type rolling guides. Roller-type guides may use a different life exponent and model-specific calculation method, so the selected series catalog should be followed.
Example: Five-Year Life Requirement
The earlier 300 mm stroke example accumulates approximately 5,760 km per year. For five years of operation:
Before applying vibration, reliability, lubrication or environmental correction factors, the approximate required dynamic-rating-to-load ratio is:
This means a block selected only because its dynamic rating is two or three times the working load may not provide the required travel life in a continuously operating reciprocating axis.
Check Static Safety Separately
Dynamic life does not confirm resistance to a sudden stop, impact or stationary peak load. Static safety should be checked separately:
- fs = static safety factor
- C0 = basic static load rating
- P0 = maximum load acting on the most heavily loaded block
The required minimum safety factor depends on vibration, impact, acceleration, mounting accuracy and the consequence of failure. Use the value specified for the selected guide series rather than applying one universal number.
Select the Block Structure According to the Complete Motion Condition
Once the travel life and block load have been calculated, choose the block structure according to installation space, rigidity, moment resistance and moving mass.
| DLY Series | Structure | Selection Direction |
|---|---|---|
| HD Series | Standard heavy-load ball guide block | General CNC and automation axes requiring balanced load capacity, rigidity and smooth reciprocating motion |
| ED Series | Low-profile ball guide block | Compact automation equipment where lower installation height and reduced carriage structure size are important |
| RD Series | Roller-type guide block | Heavy load, stronger cutting force, high moment load or applications requiring lower elastic deformation |
| MD / Miniature Series | Miniature ball guide block | Small instruments and compact mechanisms with limited load, narrow installation space and low moving mass |
View the available DLY linear guide block series for square, flange, low-profile, roller and miniature block options.
Match the Block Length and Quantity to the Moment Load
Standard-length and long guide blocks of the same rail size do not provide identical moment capacity.
A longer block increases the contact length along the rail and normally provides stronger pitch and yaw moment resistance. It may be useful for a single-rail system, a cantilevered load or a carriage with a limited distance between blocks.
However, using one long block does not always provide the same stability as using two blocks with adequate spacing. Where machine space allows, two rails with two blocks on each rail provide more stable load distribution for wide tables and high-acceleration equipment.
| Machine Structure | Block Arrangement to Consider |
|---|---|
| Narrow, balanced carriage with low moment | One rail with two blocks may be acceptable after roll-moment and mounting-rigidity checks |
| Wide moving table | Two parallel rails with multiple blocks for better roll-moment resistance |
| Cantilevered tool or offset payload | Increase rail spacing, block spacing or block length before simply increasing rail width |
| Heavy cutting or pressing axis | Larger ball guide or roller guide with a rigid dual-rail mounting structure |
Select Preload Carefully for High-Frequency Motion
Preload reduces internal clearance and improves guide rigidity, but higher preload also increases rolling resistance, drive force and heat generation.
For a light-load, high-speed pick-and-place axis, excessive preload may increase motor load without providing a useful improvement in machine performance.
For a machine-tool axis exposed to cutting force or vibration, a higher preload may be necessary to control elastic displacement and maintain positioning stability.
| Requirement | Preload Direction |
|---|---|
| Light load and high speed | Prefer lower running resistance unless rigidity calculations require more preload |
| Frequent acceleration and reversal | Balance rigidity against motor load, temperature rise and smoothness |
| Cutting force or vibration | Consider higher preload after checking mounting-surface rigidity and drive capacity |
| Very smooth manual movement | Avoid unnecessary preload that makes the carriage feel tight |
See What Is Linear Guide Preload and How Should It Be Selected? for a more detailed comparison of preload levels.
High-Frequency Short Stroke Requires Special Lubrication Attention
A short-stroke axis may accumulate a large number of reversals while the rolling elements repeatedly operate over only a small section of the raceway.
If the stroke is too short to redistribute lubricant effectively, the contact area may have difficulty maintaining a stable lubricant film. This can increase the risk of local wear or fretting damage even when the total travel distance appears moderate.
Where the machine design permits, periodic longer travel can help redistribute lubricant across more of the raceway. The lubrication method and grease type should still be confirmed according to the selected guide model and operating environment.
For high-cycle applications, check:
- Lubricant type and viscosity
- Grease replenishment interval
- Grease nipple direction and maintenance access
- Whether centralized lubrication is required
- Seal resistance at the required speed
- Temperature near the guide block
- Compatibility with coolant, water, dust or cleaning chemicals
Selection Directions for Different Motion Patterns
| Motion Pattern | Main Risk | Selection Focus |
|---|---|---|
| High CPM, short stroke and light load | Frequent reversals, lubrication-film difficulty and seal resistance | Ball guide with suitable low-friction preload, correct grease and periodic lubrication verification |
| High acceleration and rapid direction changes | Inertia load, moment load, mounting-bolt stress and vibration | Calculate m × a, reduce moving mass and use adequate rail and block spacing |
| Moderate CPM with long stroke | High annual travel distance and limited fatigue life | Calculate annual kilometers and select C according to the required operating life |
| Low CPM with heavy cutting or pressing force | Static load, impact, elastic deformation and moment load | Heavy-load ball guide or roller guide; frequency is not the primary deciding factor |
| Continuous multi-shift operation | Lubrication depletion, temperature rise and accumulated life | Confirm maintenance interval, lubrication access, rated life and stable operating temperature |
| Dusty, wet or chip-producing environment | Seal wear, lubricant contamination and raceway damage | Select suitable seals, scrapers, covers, surface treatment and maintenance method |
Verify the Guide System Under the Real Motion Cycle
A calculation should be followed by a controlled operating test, especially when the machine uses high acceleration, short cycle times or unusual mounting orientation.
During commissioning, check:
- Move the carriage manually or at low speed through the full stroke and check for local tightness.
- Confirm that the two rails remain parallel and that mounting bolts are tightened according to the intended sequence.
- Run the axis at reduced speed before increasing to the production motion profile.
- Compare motor current during acceleration, constant-speed travel and direction reversal.
- Check block temperature after the system reaches a stable operating condition.
- Listen for circulation noise, impact at reversal points or changes in sound near the rail ends.
- Inspect seals and raceways for abnormal grease leakage or contamination.
- Record a baseline for motor load, temperature, noise and positioning repeatability for future maintenance comparison.
If the block becomes noticeably tighter as speed increases, do not immediately replace it with a larger model. First check rail alignment, mounting-surface accuracy, preload, seal resistance, lubrication quantity and structural deformation.
Information Needed for Accurate Linear Guide Block Selection
To select a linear guide block for repeated movement, provide the complete operating condition rather than only the CPM value.
- One-way stroke length
- Definition of one cycle
- Cycles per minute
- Maximum and average linear speed
- Acceleration and deceleration
- Daily operating hours and annual working days
- Total moving mass
- External cutting, pressing or process force
- Center-of-gravity position
- Rail spacing and block spacing
- Horizontal, vertical, inverted or side mounting
- Required accuracy and rigidity
- Required service life
- Dust, chips, coolant, water, temperature and maintenance conditions
Frequently Asked Questions
Is 60 cycles per minute considered high frequency?
Not by itself. A 20 mm stroke at 60 CPM and a 500 mm stroke at 60 CPM have very different travel distance, speed and life requirements. Acceleration, load and daily operating time must also be known.
Does a higher movement frequency require a larger guide rail?
Not automatically. A larger guide may be required when the calculated load, moment, rigidity or travel-life requirement exceeds the smaller model's capacity. Increasing guide size unnecessarily may add weight, cost and running resistance.
Is a roller guide always better for continuous operation?
No. Roller guides are valuable when higher load capacity and rigidity are required. A ball guide may be more appropriate for light, fast equipment where smooth movement, compact size and lower resistance are more important.
Can a round-shaft aluminum slider be selected according to low CPM?
Low CPM alone is not enough. Round-shaft slider systems are normally considered according to load, shaft deflection, rigidity, accuracy, cost and mounting structure. A low-frequency machine with heavy moment load may still require a profile linear guide.
Why does a short-stroke guide block wear even when annual travel is not high?
Very short repetitive strokes may keep the rolling elements working over a limited raceway area and make lubricant redistribution more difficult. Load, preload, vibration and contamination can further increase local wear.
Contact DLY
Send DLY your stroke, cycle definition, CPM, speed, acceleration, moving mass, load direction, rail layout, required service life, accuracy and working environment. We can help compare HD, ED, RD and miniature linear guide block options according to the complete motion condition.
Email: dlyexport2@dlybearing.com | WhatsApp: +86 16605788856
