What Is the Hidden Function of Air Slides That Could Revolutionize Your Production Line?

Production managers struggle with space limitations and contamination issues in modern manufacturing. Traditional linear actuators create bottlenecks and maintenance headaches that cost thousands in downtime.

The function of an air slide is to provide precise linear motion using compressed air in a compact, sealed design that eliminates exposed moving parts while integrating guides for smooth operation and contamination resistance.

Three months ago, I got a desperate call from Maria, a production engineer at a Spanish pharmaceutical company. Her packaging line was failing FDA inspections¹ because traditional cylinders were contaminating sterile products. We installed our rodless air slides, and she passed her next inspection with zero contamination issues. The sealed design changed everything for her operation.

Table of Contents

• What Is the Primary Function of an Air Slide?
• How Do Air Slides Provide Linear Motion Without Exposed Rods?
• What Are the Key Functional Components of Air Slides?
• How Do Air Slides Handle Different Load Types and Orientations?
• What Control Functions Do Air Slides Provide?
• How Do Air Slides Function in Different Industrial Applications?
• What Safety Functions Do Air Slides Provide?
• How Do Air Slides Function Compared to Other Linear Actuators?
• What Maintenance Functions Are Required for Air Slides?
• Conclusion
• FAQs About Air Slide Functions

What Is the Primary Function of an Air Slide?

The primary function encompasses multiple operational aspects that make air slides essential for modern automation systems.

The primary function of an air slide is to convert compressed air pressure into precise linear motion while providing integrated guidance, contamination protection, and space-efficient operation for industrial automation applications.

Linear Motion Generation

Air slides convert pneumatic energy into controlled linear movement through internal piston action. The sealed cylinder contains compressed air that pushes against a piston surface to create force.

Force transmission occurs through magnetic coupling or mechanical linkage systems that transfer power from the internal piston to an external carriage without exposed moving parts.

Motion control enables precise positioning, variable speeds, and repeatable operation through integrated sensors and control systems that monitor and adjust performance.

Load handling capability allows air slides to move, position, and manipulate various objects with forces ranging from 100N to over 5000N depending on design specifications.

Space Optimization Function

Compact design eliminates the space requirements of traditional rod cylinders by integrating the actuator and guide system into a single unit that requires only stroke length plus minimal clearances.

Installation flexibility enables mounting in tight spaces where traditional cylinders cannot fit, improving machine design efficiency and production line layout optimization.

Multi-axis integration allows multiple air slides to work in coordinated systems for complex motion patterns while maintaining compact overall dimensions.

Modular construction enables custom configurations for specific applications without requiring complete system redesign or extensive modification work.

Contamination Prevention

Sealed operation protects internal components from dust, debris, moisture, and chemical contamination that would damage traditional exposed rod systems and cause premature failure.

Clean room compatibility makes air slides suitable for pharmaceutical, food processing, and electronics manufacturing where contamination control is critical for product quality.

Hygienic design features include smooth surfaces, minimal crevices, and materials that resist bacterial growth and facilitate cleaning in sanitary applications.

Environmental protection shields sensitive components from harsh operating conditions including temperature extremes, corrosive atmospheres, and high humidity environments.

Precision Control Function

Position accuracy enables precise placement of components, products, or tools within tolerances as tight as ±0.1mm depending on sensor systems and control methods used.

Speed control provides variable velocity profiles for different phases of operation, enabling smooth acceleration, constant velocity operation, and controlled deceleration as required.

Force regulation allows adjustment of applied forces to match application requirements, preventing damage to delicate components while ensuring adequate force for heavy-duty operations.

Repeatability ensures consistent performance across thousands of cycles, maintaining production quality and reducing variation in manufacturing processes.

How Do Air Slides Provide Linear Motion Without Exposed Rods?

The elimination of exposed rods represents a fundamental design innovation that solves multiple operational problems simultaneously.

Air slides provide linear motion without exposed rods through internal piston systems coupled to an external carriage via magnetic coupling, cable systems, or band mechanisms that transfer force through sealed cylinder walls.

Magnetic Coupling Systems

Magnetic force transfer uses powerful neodymium magnets³ embedded in both the internal piston and external carriage to create a magnetic field that passes through the non-magnetic cylinder wall.

Coupling efficiency typically achieves 85-95% force transmission from the pneumatic system to the external load, providing reliable power transfer without mechanical contact or wear.

Overload protection occurs automatically when applied forces exceed magnetic coupling capacity, preventing damage to internal components while maintaining system integrity.

Temperature stability varies with magnet grade selection, with standard grades operating to 80°C and high-temperature grades handling up to 150°C for demanding applications.

Cable Force Transfer

Steel cable systems connect internal pistons to external carriages through sealed cable exits that maintain pressure integrity while allowing motion transmission.

Cable materials include stainless steel for corrosion resistance and aircraft cable for flexibility, with selection based on force requirements and environmental conditions.

Pulley systems may redirect cable forces and provide mechanical advantage, enabling higher force output or different motion directions as required by specific applications.

Sealing challenges require specialized dynamic seals that accommodate cable movement while preventing air leakage and contamination entry into the cylinder.

Band Mechanism Systems

Flexible steel bands transfer force through slots in the cylinder wall, providing the highest force capacity and best contamination resistance for harsh industrial environments.

Band materials range from carbon steel to stainless steel and specialized alloys, selected based on strength requirements, corrosion resistance, and environmental compatibility.

Slot sealing systems prevent air leakage while allowing band movement, using advanced seal designs that minimize friction while maintaining pressure integrity.

Contamination tolerance exceeds other coupling methods since bands can push through debris and continue operating in dusty or dirty conditions.

Mechanical Linkage Options

Direct mechanical connections provide positive force transfer without slippage, offering maximum force transmission capability for heavy-duty applications requiring absolute reliability.

Linkage designs include rack-and-pinion systems, lever mechanisms, and gear trains that can provide mechanical advantage or motion transformation as needed.

Sealing complexity increases with mechanical penetrations through cylinder walls, requiring multiple dynamic seals and careful design to maintain system integrity.

Maintenance requirements are higher due to mechanical wear and lubrication needs, but the systems provide unmatched force transmission and reliability.

What Are the Key Functional Components of Air Slides?

Understanding component functions helps optimize air slide selection and maintain reliable operation throughout the system lifecycle.

Key functional components include the cylinder body for pressure containment, internal piston for force generation, external carriage for load handling, integrated guides for smooth motion, and control systems for operation management.

Cylinder Body Functions

Pressure containment creates the working chamber where compressed air generates force, with wall thickness and material selection based on operating pressure and safety requirements.

Internal surface finish affects seal performance and component life, with honed bores providing optimal conditions for smooth operation and extended service intervals.

Port configuration enables air supply and exhaust connections, with port sizing and location affecting flow capacity and system response characteristics.

Mounting interfaces provide secure attachment points that handle operational forces and moments without compromising cylinder integrity or performance.

Internal Piston Assembly

Force conversion transforms air pressure into linear force according to F = P × A, where piston area determines maximum force output at given pressure levels.

Seal integration maintains pressure separation between cylinder chambers while minimizing friction and ensuring smooth motion throughout the stroke length.

Coupling interface connects to the force transfer mechanism, whether magnetic elements, cable attachments, or mechanical linkages depending on system design.

Mass optimization reduces moving weight to enable faster acceleration and higher operating speeds while maintaining structural integrity under load.

External Carriage System

Load interface provides mounting points and surfaces for attaching application-specific tooling, fixtures, or components that require linear motion.

Guide integration ensures smooth, precise motion while handling side loads, moments, and off-center loading conditions that would bind traditional cylinders.

Sensor mounting enables position feedback, limit detection, and process monitoring through various sensor types integrated into the carriage structure.

Adjustment features allow fine-tuning of position, alignment, and operating parameters to optimize performance for specific application requirements.

Integrated Guide Systems

Linear bearings provide smooth motion with minimal friction, using ball bearings for precision applications or roller bearings for heavy-duty service.

Load capacity handles radial forces, moments, and combined loading conditions that exceed the capability of traditional cylinder designs.

Precision maintenance ensures consistent accuracy over extended service life through proper lubrication, contamination protection, and wear compensation.

Stiffness characteristics affect system dynamics and positioning accuracy, with guide design optimized for specific load and precision requirements.

Control and Sensing Components

Position sensors detect carriage location using magnetic, optical, or mechanical sensing principles to provide feedback for closed-loop control systems.

Limit switches provide end-of-stroke detection and safety interlocks to prevent overtravel and protect system components from damage.

Flow control valves regulate air flow rates to control speed and acceleration characteristics, with separate controls for extend and retract motions.

Pressure regulation maintains consistent operating pressure for repeatable force output and stable performance across varying supply conditions.

How Do Air Slides Handle Different Load Types and Orientations?

Load handling capability determines air slide suitability for various applications and operating conditions encountered in industrial automation.

Air slides handle different load types through integrated guide systems that manage radial forces, moments, and combined loading while accommodating horizontal, vertical, and angled orientations with appropriate design modifications.

Horizontal Load Handling

Horizontal installations handle the full rated load capacity since gravity effects are minimized and guide systems operate under optimal conditions.

Side load capacity depends on guide design and spacing, with typical systems handling radial forces up to 50% of axial force rating without performance degradation.

Moment resistance enables handling of off-center loads and cantilevered mounting configurations that would cause binding in traditional cylinder systems.

Speed optimization achieves maximum performance in horizontal orientations since gravity doesn’t assist or oppose motion, allowing full utilization of pneumatic force.

Vertical Load Applications

Vertical installations require consideration of gravity effects on both extend and retract operations, with load weight either assisting or opposing pneumatic force.

Extend force calculations must account for load weight: F_net = F_pneumatic – F_gravity for upward motion, ensuring adequate force margin for reliable operation.

Retract force benefits from gravity assistance: F_net = F_pneumatic + F_gravity for downward motion, potentially allowing smaller cylinder sizes or higher speeds.

Safety considerations include fail-safe behavior during air pressure loss, with mechanical locks or counterbalances preventing uncontrolled descent of heavy loads.

Angled Mounting Configurations

Inclined installations combine horizontal and vertical load components, requiring vector analysis⁴ to determine effective forces and guide loading conditions.

Angle effects modify both axial and radial force components, with steeper angles increasing the gravity component and reducing effective horizontal force capacity.

Guide loading increases with mounting angle as gravity creates side loads on the guide system, potentially requiring larger or more robust guide designs.

Performance optimization may require pressure adjustment or cylinder sizing changes to maintain adequate force margins at the operating angle.

Dynamic Load Considerations

Acceleration forces add to static loads during motion, with F_total = F_static + F_acceleration where acceleration forces depend on mass and desired acceleration rates.

Deceleration loads can exceed static loads significantly, requiring cushioning systems or controlled deceleration to prevent shock loading and component damage.

Vibration effects from external sources or system dynamics can affect positioning accuracy and component life, requiring isolation or damping systems.

Impact loading from sudden load changes or external shocks requires robust design and proper safety factors to prevent damage and maintain reliability.

Load Distribution Effects

Concentrated loads create higher stress concentrations and may require load distribution plates or fixtures to spread forces over larger areas.

Distributed loads generally create more favorable loading conditions but may require longer carriages or multiple mounting points for proper support.

Off-center loading creates moments that must be handled by the guide system, with performance degradation occurring as loads move further from the centerline.

Multiple load points may require custom carriage designs or multiple air slides working in coordination to handle complex loading patterns.

What Control Functions Do Air Slides Provide?

Control functions enable air slides to integrate seamlessly into automated systems while providing the precision and reliability required for modern manufacturing.

Air slide control functions include position control through sensors and feedback systems, speed control via flow regulation, force control through pressure management, and safety functions for reliable operation.

Position Control Systems

Absolute positioning uses linear encoders or potentiometers to provide continuous position feedback with resolution down to micrometers for precision applications.

Incremental positioning employs magnetic sensors or optical encoders to track relative movement, enabling accurate positioning without absolute reference points.

End-of-stroke detection uses limit switches, proximity sensors, or pressure switches to signal completion of motion and trigger next sequence steps.

Intermediate positioning enables stopping at multiple points along the stroke using programmable sensors or servo control systems for complex motion profiles.

Speed Control Methods

Flow control valves regulate air flow rates into and out of cylinder chambers, with meter-in control affecting acceleration and meter-out control influencing deceleration.

Pressure control systems maintain consistent operating pressure to ensure repeatable speed performance despite supply pressure variations or load changes.

Electronic control uses proportional valves and servo systems to provide precise speed control with programmable acceleration and deceleration profiles.

Manual adjustment enables field optimization of speed settings through adjustable flow controls or pressure regulators for application-specific tuning.

Force Control Capabilities

Pressure regulation maintains consistent force output by controlling air pressure supplied to the cylinder, enabling force adjustment for different application requirements.

Force limiting prevents overload damage through pressure relief valves or electronic monitoring systems that detect excessive force conditions.

Variable force control uses proportional pressure valves to provide programmable force levels during different phases of operation or for different products.

Force feedback systems monitor actual applied forces and adjust pressure accordingly to maintain desired force levels despite load variations.

Safety Control Functions

Emergency stop systems immediately exhaust air pressure and stop motion when safety circuits are activated, providing rapid response to hazardous conditions.

Overtravel protection prevents damage from excessive motion through mechanical stops, cushioning systems, or electronic limits that halt operation.

Pressure monitoring detects system faults such as air leaks, blockages, or component failures that could affect performance or safety.

Interlock systems coordinate air slide operation with other machine functions to ensure safe sequencing and prevent conflicts between system components.

Integration Capabilities

PLC interface enables integration with programmable logic controllers through standard communication protocols and I/O connections for system coordination.

Network connectivity allows remote monitoring and control through industrial networks such as Ethernet/IP⁵, Profibus, or DeviceNet for centralized management.

HMI integration provides operator interface capabilities for manual control, parameter adjustment, and system monitoring through touchscreen displays.

Data logging captures performance data for analysis, troubleshooting, and predictive maintenance programs that optimize system reliability.

How Do Air Slides Function in Different Industrial Applications?

Air slide functionality adapts to specific industry requirements through design modifications and application-specific features that optimize performance.

Air slides function across industries by providing contamination-free motion for food processing, precise positioning for electronics assembly, high-speed operation for packaging, and reliable performance for material handling applications.

Food Processing Applications

Hygienic design features include smooth surfaces, minimal crevices, and materials that resist bacterial growth while facilitating cleaning and sanitization procedures.

Washdown capability enables thorough cleaning with high-pressure water and cleaning chemicals without damaging internal components or affecting performance.

FDA compliance ensures materials and construction meet food safety requirements for direct and indirect food contact applications.

Temperature resistance handles hot washdown procedures and cooking environments with specialized seals and materials rated for elevated temperatures.

Pharmaceutical Manufacturing

Clean room compatibility prevents particle generation and contamination through sealed construction and appropriate material selection for sterile environments.

Validation support includes documentation packages, material certificates, and testing data required for FDA and regulatory compliance programs.

Chemical resistance protects against cleaning solvents, sterilizing agents, and process chemicals that could damage standard pneumatic components.

Precision control enables accurate dosing, filling, and packaging operations that maintain product quality and consistency in pharmaceutical production.

Electronics Assembly

Static control prevents electrostatic discharge damage to sensitive electronic components through proper grounding and anti-static materials.

Precision positioning enables accurate placement of components with tolerances measured in hundredths of millimeters for modern electronic assembly.

Clean operation prevents contamination of electronic components and assemblies that could cause quality problems or field failures.

Gentle handling provides controlled acceleration and deceleration to prevent damage to delicate components during assembly operations.

Packaging Industry Functions

High-speed operation enables rapid cycle times up to 300 cycles per minute for high-volume packaging lines that maximize productivity.

Product handling versatility accommodates various package sizes, shapes, and weights through adjustable mounting and control systems.

Precise timing coordinates with other packaging equipment to maintain synchronization and prevent product damage or line stoppages.

Compact design fits into tight spaces between other packaging equipment while providing full functionality and easy maintenance access.

Material Handling Operations

Load capacity handles heavy components and assemblies with forces up to several thousand Newtons depending on air slide size and configuration.

Durability withstands continuous operation in industrial environments with appropriate protection against contamination and mechanical damage.

Positioning accuracy enables precise placement of materials for assembly operations, quality inspection, or automated storage systems.

Integration capability coordinates with conveyor systems, robots, and other material handling equipment for seamless operation.

Automotive Manufacturing

Reliability ensures consistent operation in high-volume production environments where downtime costs thousands of dollars per minute.

Force control provides appropriate clamping and positioning forces for various automotive components without causing damage.

Environmental resistance handles the harsh conditions of automotive plants including coolants, oils, and metal working fluids.

Precision assembly enables accurate placement of components for quality assembly operations that meet automotive industry standards.

What Safety Functions Do Air Slides Provide?

Safety functions protect personnel, equipment, and products while ensuring reliable operation in industrial environments with various hazard potentials.

Air slide safety functions include fail-safe operation during power loss, overload protection through coupling slip, emergency stop capability, and integrated safety monitoring systems that prevent accidents and equipment damage.

Fail-Safe Operation

Power loss behavior ensures predictable system response when air pressure or electrical power is interrupted, preventing uncontrolled motion or load drops.

Spring return options provide controlled retraction when air pressure is lost, returning the system to a safe position without external power.

Mechanical locks can hold position during power outages, preventing load movement that could create safety hazards or damage equipment.

Gravity compensation systems balance heavy loads to prevent rapid descent during power failure, providing controlled motion even without air pressure.

Overload Protection

Magnetic coupling slip prevents damage when applied forces exceed design limits, automatically disengaging to protect internal components from overload.

Pressure relief valves limit maximum system pressure to prevent component damage and ensure safe operation within design parameters.

Force monitoring systems detect excessive loads and automatically reduce pressure or stop operation to prevent equipment damage or safety hazards.

Mechanical stops prevent overtravel that could damage the air slide or connected equipment, providing positive position limits.

Emergency Stop Functions

Rapid exhaust valves quickly vent air pressure when emergency stop circuits are activated, providing immediate cessation of motion.

Safety interlocks prevent operation when guards are open or safety devices are not properly engaged, ensuring personnel protection.

Dual-channel safety systems provide redundant monitoring of safety functions to meet higher safety integrity levels required by safety standards.

Manual reset requirements ensure deliberate action is required to restart operation after an emergency stop event, preventing inadvertent restart.

Contamination Safety

Sealed construction prevents process contamination that could create safety hazards in food, pharmaceutical, or chemical applications.

Leak detection systems monitor for air leaks that could indicate seal failure and potential contamination risks in critical applications.

Material compatibility ensures that air slide components don’t introduce hazardous substances into the process or work environment.

Cleaning validation provides documentation that air slides can be properly cleaned and sanitized for safe operation in hygienic applications.

Personnel Protection

Guarding integration coordinates with machine guards and safety systems to prevent personnel access during operation.

Soft start functions provide gradual acceleration to prevent sudden motion that could startle operators or cause injury.

Visual indicators show system status and motion to alert personnel of operating conditions and potential hazards.

Noise control reduces air exhaust noise to acceptable levels for worker safety and comfort in industrial environments.

Equipment Protection

Cushioning systems reduce shock loads during direction changes or end-of-stroke impacts that could damage connected equipment.

Vibration isolation prevents transmission of vibration to sensitive equipment or structures that could affect performance or cause damage.

Thermal protection prevents overheating of components during continuous operation or in high-temperature environments.

Diagnostic monitoring detects developing problems before they cause failures that could damage equipment or create safety hazards.

How Do Air Slides Function Compared to Other Linear Actuators?

Functional comparison with alternative technologies helps determine when air slides provide optimal performance for specific applications.

Air slides function with superior space efficiency and contamination resistance compared to rod cylinders, offer faster operation than electric actuators, and provide cleaner operation than hydraulic systems while maintaining moderate force capabilities.

Comparison with Rod Cylinders

Space efficiency provides 50% reduction in installation space since air slides eliminate the need for rod extension clearance that doubles traditional cylinder space requirements.

Contamination resistance prevents accumulation of debris on exposed rods that causes seal wear and system failure in dusty or dirty environments.

Side load handling capability eliminates the need for external guides that add cost and complexity to traditional cylinder installations.

Stroke length capability extends beyond traditional cylinder limits since internal pistons cannot buckle like exposed rods in long-stroke applications.

Electric Actuator Comparison

Speed advantage enables air slides to achieve higher velocities due to low moving mass and rapid air expansion compared to electric motor acceleration limitations.

Cost effectiveness provides lower initial cost for simple positioning applications where electric actuator precision may not be required.

Environmental tolerance handles harsh conditions better than electric actuators that may be damaged by moisture, dust, or chemical exposure.

Safety benefits include inherent fail-safe behavior and non-flammable working medium compared to electric systems with fire and shock hazards.

Hydraulic System Comparison

Cleanliness advantage eliminates oil leaks and contamination risks that make hydraulic systems unsuitable for food, pharmaceutical, and clean room applications.

Maintenance simplicity reduces service requirements since air slides don’t require fluid changes, filter replacement, or leak repair that hydraulic systems need.

Environmental safety prevents oil spills and disposal issues associated with hydraulic fluid leaks and system maintenance.

Fire safety eliminates flammable hydraulic fluids that create fire hazards in welding, machining, and high-temperature applications.

Performance Trade-offs

Force limitations restrict air slides to moderate force applications since pneumatic pressure limits prevent the high forces available from hydraulic systems.

Precision constraints limit positioning accuracy compared to electric servo systems due to air compressibility and temperature effects.

Energy efficiency remains lower than electric systems due to compression losses and heat generation in pneumatic systems.

Operating costs may be higher than electric systems due to compressed air generation and consumption in continuous duty applications.

Application Selection Criteria

Optimal applications include moderate force requirements, high-speed operation, contamination-sensitive environments, and space-constrained installations.

Poor applications include high-precision positioning, continuous duty cycles, very high forces, and energy-sensitive operations where efficiency is critical.

Hybrid solutions sometimes combine air slides with other technologies to optimize overall system performance and cost effectiveness.

Economic analysis should consider initial cost, operating expenses, maintenance requirements, and productivity benefits over the system lifecycle.

What Maintenance Functions Are Required for Air Slides?

Maintenance functions ensure reliable operation and maximize service life while minimizing downtime and operating costs.

Air slide maintenance functions include preventive inspection schedules, air treatment system service, guide lubrication, seal replacement procedures, and performance monitoring to maintain optimal operation and prevent failures.

Preventive Maintenance Schedule

Daily inspections include visual checks for air leaks, unusual noises, erratic motion, or visible damage that could indicate developing problems.

Weekly maintenance involves air filter inspection and replacement, pressure regulator adjustment, and basic performance verification to ensure consistent operation.

Monthly service includes guide lubrication, sensor cleaning, mounting bolt torque checks, and detailed performance testing to identify degrading components.

Annual overhaul encompasses complete disassembly, internal inspection, seal replacement, and comprehensive testing to restore like-new performance.

Air Treatment Maintenance

Filter replacement maintains clean, dry air supply that prevents contamination damage and extends component life significantly.

Dryer service ensures proper moisture removal to prevent corrosion and freezing problems that can cause system failure.

Drain system maintenance removes accumulated condensate that could cause erratic operation and component damage.

Pressure system checks verify regulator operation and system pressure stability for consistent performance.

Guide System Service

Lubrication schedules maintain proper lubrication levels without over-lubrication that can attract contamination and cause problems.

Contamination removal prevents buildup of debris that increases friction and accelerates wear of guide components.

Wear inspection identifies developing problems before they cause failure and affect system performance or accuracy.

Alignment verification ensures proper guide operation and prevents binding or excessive wear from misalignment.

Seal Replacement Procedures

Inspection criteria identify when seals need replacement based on leakage rates, performance degradation, or visual condition assessment.

Replacement procedures require proper tooling, seal selection, and installation techniques to ensure reliable operation and prevent premature failure.

Testing protocols verify proper operation after seal replacement and ensure the repair was successful before returning to service.

Documentation maintains service records for warranty compliance and predictive maintenance program development.

Performance Monitoring

Force output testing detects coupling degradation or internal wear that affects system capability and reliability.

Speed measurement identifies flow restrictions or pressure problems that reduce system performance and productivity.

Position accuracy verification ensures sensor operation and system alignment meet application requirements.

Air consumption monitoring identifies efficiency problems and leakage that increase operating costs and indicate developing problems.

Troubleshooting Functions

Diagnostic procedures systematically identify root causes of performance problems to enable effective repairs and prevent recurrence.

Component testing isolates problems to specific system elements, avoiding unnecessary replacement of functional components.

Performance comparison against baseline measurements identifies degradation trends and enables predictive maintenance scheduling.

Documentation systems track problem patterns and maintenance effectiveness to optimize service procedures and intervals.

Conclusion

Air slide functions encompass linear motion generation, contamination protection, space optimization, and precise control, making them essential for modern automation applications requiring reliability, cleanliness, and efficiency.

FAQs About Air Slide Functions