Linear motion systems are exposed
to a variety of extreme industrial environments. The careful specification and
selection of the components of the motion system, as well as the careful
engineering revisions, can mitigate the risk in adverse industrial conditions.
An important step in the design
of a mechanical linear motion system is to understand the environmental
conditions under which the system will operate. Key design considerations
include temperature, dust and dirt levels, chemical exposures, cleaning
processes, vibrations and shock loads, and other relevant environmental factors
that may arise from radiation and motion systems. Document these key elements
before choosing a material. Capture real data and study defect codes from
previous products so you can work on facts, not opinions.
Based on the data collected, we
select the appropriate materials, coatings and lubricants to use the supply
chain application experience to select the appropriate linear motion
components. Then, develop a robust test verification plan, which includes
durability and environmental tests, to ensure that the selected materials
provide the expected service life and serviceability. Also consider using the
High Accelerated Life Tests (HALT), where the team gradually provides
environmental stress at a much higher level than you can see in the service.
HALT is usually done at the development stage to eliminate design problems and
marginal components.
Component selection based on environmental considerations.
Next generation web-based
selection and sizing tools simplify the task of selecting the appropriate
component material to take into account the environmental aspects of the linear
motion system design. Enter the key application parameters that the tool enters
into the calculation, such as the load / linear life of the bearing, the load /
life of the ball screw and the critical speed of the ball screw.
Also enter the environmental conditions that are important to select the right
material, the coverage strategy and the lubrication scheme. For example, you
can choose:
· Water / chemical spray / fog
· Shock / Compression Applications / Vibration
· High dust
· High pressure / temperature wash
· Water / chemical splashes,
· Clean room
This application recommends
linear sliding characteristics such as chrome plating, stainless steel parts or
plain polymer bearings to address environmental conditions.
Component function:-
Ball guides or bearing rails,
shafts or aluminum surfaces support the bearings and are generally available in
standard steel, stainless steel, Armoloy or chrome plated. Linear bearings
provide the load and moment load capabilities of the system. Examples are
bearings of round-ball linear ball bearings, profile rails, wheel guides or
polymer guides. Mainly available as standard, corrosion resistant
("CR") linear bearings or plain polymer bearings. Hardware options
for screws, bolts and nuts that hold linear units are generally available in
standard or stainless steel. The sealing or protection cover of the linear
device offers the option of no cover, bellows, cover or seal (ideal sealing).
Finally, standard or cleanroom grease options are available for lubrication
within the linear unit.
Linear ball bearings, profile
rails, wheel guides or polymer guides are also available as corrosion resistant
linear bearings ("CR") or plain polymer bearings. Suitable for clean
room, high temperature or cleaning, chemical spraying and fogging or chemical
cleaning applications.
1. Environment-specific solution: cleaning:- This environment is
characterized by the factory settings of the machine. You can expect some
particles in the air and humidity. But employees will generally operate in this
environment without the form of protective equipment (masks, respirators,
topical dust or chemical hoods).
The solution:-
· Ball Guide: Standard
· Linear Bearing: Standard
· Hardware: Standard
· Cover: No cover
· Lubrication: Standard grease
Reason for this set of solutions: - There is little concern about
particles or corrosion, so that standard aluminum and steel parts can be used
in these environments.
2 .Moderately heavy dust particle counts: - This environment is
characterized by sufficient airborne particles that require the operator to
wear respiratory protection. Paper mills and factories equipped with large
industrial mills are examples of dusty environments.
The solution:-
- · Ball Guide: Standard
- · Linear Bearing: Standard
- · Hardware: Standard
- · Cover: Closed (ideal), cover or bellows can be accepted
- · Lubrication: Standard
The reason for this set of solutions: - Since there is no concern
about corrosion, standard steel components can be used. On the contrary, it is
important to avoid the entry of particles into bearings, ball guides and
drive mechanisms (which can be screws or belts). For large particles, you can
use bellows covers or aluminum covers. For fine particles, the linear motion
system must have a solid sealing system that protects the internal parts
mentioned above. These stamps have two options. The first is a magnetic stripe
seal consisting of a stainless steel magnetic stripe that extends from one end
of the channel to the other in a structural support system. The band is fixed
to the end cap and is held tight by the spring load. As it passes through the
carriage cavity and the strip passes through the system, it goes up to the
magnet just in front and behind the car. The second potential sealing
technology, the plastic cover band, uses a compatible rubber strip that works
with the extrusion of the base, such as a top freezer bag. The combination of
tongue and groove profile prevents particles, preventing them.
The sealing or protection cover of
the linear device does not include any cover, bellows, cover or seal (ideal
seals). Standard or cleanroom grease options are available for lubrication
within the linear unit.
3. Water / chemical splash: - This environment represents a
condition in which the product may be exposed to intermittent splashing of
liquids. For example, large print applications where ink deposits change
periodically and sometimes / without realizing it, spill. In this environment,
the fluid contact with the linear guide may be the result of improper handling
of the product or components, but is generally not included in the general
application process.
The solution:
· Ball Guide: Chrome
· Linear Bearing: Corrosion resistance.
· Hardware: Stainless steel
· Cover: Can be included (or more) or bellows
· Lubrication: Standard
Reason for this set of solutions: For such applications, ball
guides and linear bearings must be resistant to corrosion. For round rail bearing technology, this means chrome or 440C
stainless steel shafts. Linear bearings must have chrome bearing plates and
stainless steel balls. The softer stainless steel ball bearings and shafts
generally result in a 30% load reduction, which should be considered as part of
the design. For profile rail bearings, a thin and dense chrome coating such as
Duralloy is recommended. Plain bearings, also known as prism guides, are an
alternative to rolling element bearings. Prism guides are engineering polymers
that are highly resistant to chemical corrosion. For sealing, depending on the
severity of the chemical splash, the bellows may be sufficient, but a
completely sealed device is ideal.
4. Chemical spray / mist for water: - This condition is a more
severe step than the environment described above. Here the spray or fog is part
of the process and the linear guides
are directly exposed to this element. It can be characterized by a condensing
environment similar to that found in refrigeration applications. The cooling
water, which tarnishes the mechanical parts during processing, is also part of
this class. In this environmental scenario, the bearings and guides will come
into contact with the fluid if mechanical protection is not provided.
The solution:
· Ball Guide: Chrome
· Linear Bearing: Corrosion resistance.
· Hardware: Stainless steel
· Cover: Closed
· Lubrication: Standard
The reason for this set of solutions: - For these applications, a
completely sealed device is essential. Since chemical spraying is hard, it is
better to avoid rolling element bearing
technology and use prism guide bearings as mentioned above. For the same
reason, ball screw drive systems should be avoided whenever possible in these
environments. In contrast, polyurethane belt drive systems are more suitable
for handling corrosive chemical environments.
Ball guides or bearing rails and
shafts are often available in standard steel, stainless steel, Armoloy or
chrome plated. This linear bearing component provides the load and moment load
capabilities of the system. Suitable for applications such as standard machine
shops, impact press applications with medium to heavy dust particle counts and
vibrations.
5. High pressure / wash temperature: - This environment generally
represents food processing applications. Here the equipment can be washed very
often under pressure. The slide not only comes into contact with the fluid, but
also acquires considerable force during the cleaning process.
The solution:-
· Ball Guide: Chrome
· Linear Bearing: corrosion resistance.
· Hardware: stainless steel
· Cover: no cover
· Lubrication: standard or potentially food or high temperature grease.
Reason for this set of solutions: - The cleaning environment will oxidize
the standard steel parts. Chromed and corrosion resistant ball bearings and
guides should be used with stainless steel hardware. Prism guides can also be
used, but due to polymeric materials that are not as temperature sensitive as
rolling elements of metallic materials, they should be avoided in high
temperature applications. The linear unit must be open (without sealing) and
have a cleaning liquid or outlet to remove the cleaning liquid. For high
temperature applications, special high temperature greases can be used. For
such high temperatures, it is necessary to remove all seals and other plastic
elements from the system.
6. Cleanroom: - Although some families of linear units can be
configured for Class 100 cleanroom environments, they are generally referred to
as ISO Class 3 cleanroom environments (sometimes Class 1000).
The solution:-
· Ball Guide: Chrome
· Linear Bearing: Anti-corrosion and seal / windshield wiper removal
· Hardware: Stainless steel
· Cover: No cover
· Lubrication: Clean room grease
The reason for this set of solutions: - For cleanroom environments,
linear slider movement should minimize particles. A metal coating is required
to prevent the appearance of rust. In addition, it is necessary to eliminate
the sliding elements of the linear system. This means that there are no seals /
cleaners on the bearing guides or covers on the linear devices. It is necessary
to use special grade grease for clean room.
7 .Impact / Press App /Vibration: - These application is often
characterized by several different processes. The agitators and vibration
tables associated with the classification equipment fall into this category.
Due to the initial impact dynamics, the application of the press higher than
the normal load on the car or seat is also taken into account in this kind of
application.
The solution:-
· Ball Guide: Standard
· Linear Bearings: Polymer plain bearings
· Hardware: Standard
· Cover: Optional
· Lubrication: Standard
Reason for this set of solutions:- Polymer style bushings,
also known as the prism guides mentioned above, can handle higher impact
loading applications than rolling elements. Under these conditions, the rolling
elements may split in half due to point-to-point contact with the bearing
surface or they may become trapped in the tracks of the rolling element of the
bearing. However, prism guides allow the same load distribution along a flat
surface, which makes them ideal for vibration. The use of prism guides can be
combined with the cover, depending on the number of particles, if necessary.
