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Precision Hardened Shafting for Linear Motion Applications

March 16, 2020

Lintech offers shafting for use in linear motion applications. The type of shafting offered is Hardened steel which is rated at about 60 on the Rockwell C scale. Hardened steel provides for the best duty life and performance under a load. The steel is also manufactured to dimensions with pretty tight tolerances – a few ten-thousandths of an inch to provide accuracy and consistent fit-up when used with a ball bushing. The most common shafting tolerance range is called Class L. Class L shafting is used with self-aligning bushings. Class S shafting is used with non self-aligning bushings. The tolerance range for the Class S shafting is about .0005” smaller than class L.

Shaft Size Classifications

Self-Aligning Bushing Non Self-Aligning Bushing

170 Series Flexibility

March 2, 2020

The 170 series linear motion tables are offered with a broad range of options and configurations. The 170 can be supplied with 2 different carriage lengths supported by up to 6 linear bearings. The 6-inch carriage can have 2 or 4 bearings underneath. The 12-inch carriage can have up to 6 bearings. This choice enables the same table cross section to have an 11,670-pound load rating. The longer carriage with more bearings also dramatically increases the moment load capability.

170 Series Carriage Options

Round Rail Linear Ball Bushing Bearings

February 17, 2020

Lintech manufactures various Inch size Linear Ball Bushing versions:

The closed LBC and the open LBO are super linear ball bushing, inch series self-aligning bearings. These ball bushing versions are suited for the Lintech SL series class L shafting. These products are utilized together to form a precision linear positioning system that can handle large load requirements. These products will also perform well in applications where there is slight misalignment between a pair of shafts. Sometimes, due to other limitations, it is very difficult to maintain a high degree of parallelism between shafts and ball bushings with SL shafting can help to prevent the linear system from binding. The closed LBCA and the open LBOA are all steel plain type linear bearings that work with Lintech SS series class S precision shafting to form a positioning system that can operate in a high temperature environment.

Metric Ball Bushing Configurations:

When considering metric ball bushings, there are two standards available. There are Asian as well as European standards which maintain slightly different tolerances. The closed LBCM and the open LBOM are Asian style self-aligning ball bushings that should be matched with Lintech’s SM metric precision shafting to form a positioning system where Asian metric standards are required. The closed LBCME and the open LBOME are European style super linear ball bushings that also should be matched with SM metric precision shafting to form a positioning system where European metric standards are required.

Ball Bushings

Linear Bearing Life Calculator

February 4, 2020

There are many factors which impact how long a bearing of any type is going to survive. Like many materials, however, after a number of times that it is stressed, it will fail. This is your starting point when trying to calculate a reasonable travel life. It is not an exact calculation but a “reasonable expectation”.

There are many ways in which linear bearings will be utilized. Often, a linear rail may have more than one bearing block to support a given load. Lintech provides the tools to calculate estimated life for all kinds of loading in catalogs and online. However, Lintech also offers an online calculator for “quickly” determining the expected life of a linear rail with 2 blocks on it.

Linear guide life calculator

Any life calculations available for bearings help to predict how long a particular arrangement will survive the steel “flexing”. However, then it is helpful to examine factors beyond the calculation which could reduce that predicted life. Factors such as contamination, environmental conditions, misalignment, vibration, electrical currents, improper lubrication, temperature extremes, etc. Having any of these factors present eliminates reasonably predicting life. So, it is best to examine the potential conditions of an application and to reduce or eliminate any factor which could negatively impact the bearing life.

Selecting The Type Of Linear Motion System To Fit Your Needs

January 16, 2020

When selecting a positioning table, each of the following items should be reviewed thoroughly by the user. Some items will not be of major importance for a specific application. However, by reviewing each and every item, a positioning table can be selected that will give the required performance over the life of the system.

The items below are covered in more detail on the pages referenced of the Lintech Positioning Systems Catalog.

Bearing Designs – Linear (ball, cross roller, round rail, square rail, and air) bearings, along with rotary bearings.(See pages A-10 to A-12)

Drive Mechanisms (acme screws, ball screws, belt, and worm gears). See pages (A-13 to A-15)

How to Select a Positioning Table which includes safety factors and travel life. (See page A-16)

Load Capacities of all the critical elements of a positioning table need to be thoroughly reviewed in order to select the proper table for a given application. This includes capacities for bearings, drive mechanisms, and table structures. (See pages A-17 to A-27)

Maximum Speed of a positioning table sometimes depends on the bearing components and sometimes depends on the drive mechanism. (See page A-28)

Acceleration & Thrust Forces are parameters that can put extra stresses on positioning table components in certain situations. (See page A-29)

Accuracy & Repeatability are two of the most misunderstood parameters when selecting a positioning table. By determining what it is you really need, will help you select a cost effective positioning system. (See pages A-30 to A-33)

Table Physical Size (See page A-34)

Lubrication (See page A-35)

Mounting Considerations (See page A-36)

Motor Couplings (See page A-37)

EOT (end of travel) & Home Switches (See page A-38)

Encoders (See page A-39)

Power-off Brakes (See page A-40)

Multi-Axis Systems (See page A-41)

Environments (See page A-42)

Testing (See page A-43)

Custom Systems (See page A-44)

Application Guide (See page A-45)

Motor Sizing (See pages A-46 to A-49)

Lintech Positioning Systems

Linear Motion Systems – Drive Mechanism Load Capacities

January 2, 2020

Linear positioning table drive mechanisms will have static and dynamic load capacity ratings for the acme screw, ball screw, and belt drive assembly. These values are used to help select a correct drive mechanism for a given load/life table application. For most acme screw driven positioning table applications, the screw (and not the linear bearing) is the major factor in determining the life of the table. This is due to the high friction of the nut assembly. For most ball screw driven positioning table applications, the linear bearing system (and not the screw) is the major factor in determining the life of the table. This is due to the high efficiency and high load capacity of the nut. For most belt driven positioning table applications, the linear bearing system (and not the belt) is the major factor in determining the life of the table. This is due in large part to the fact that belt driven tables usually travel lots of inches at high speeds. The use of adequate safety factors is a key element in the selection process of the drive mechanism for a given application. Selecting a system with no safety margin can lead to problems relating to performance and long-term life.

The actual (axial) load a drive mechanism “sees” needs to be determined first. Then the effects of that load on the drive mechanism can be reviewed. For both screw & belt driven positioning tables, the actual load the drive mechanism experiences will vary as the table moves. During acceleration and deceleration intervals of a positioning table, the force exerted upon the drive mechanism changes as the acceleration or deceleration rate varies. In most cases, the extra force acting upon the drive mechanism during the acceleration interval is offset by a reduced force during the deceleration interval. Therefore, using just the forces acting upon the drive mechanism during constant velocity can be used. The applied (axial) load “as seen by the screw nut or belt” depends upon the table orientation. See the equations below.

Drive Capacities

Static Loads can exert an extreme force upon the drive assembly in a non-moving state. For acme screw driven tables, if the static load rating of a particular screw is exceeded, the nut assembly can permanently be deformed, or crack outright. For ball screw driven tables, if the static load rating of a particular screw is exceeded, a localized permanent depression in the screw shaft and ball nut could cause the system to not operate smoothly or fail prematurely. For belt driven tables, if the static load rating (maximum belt tensile force) of a particular belt is exceeded, the belt will permanently stretch, or tear. To ensure proper life, external forces should never come close to the static rating. Repeated forces at or near the maximum rating can fatigue the elements causing premature failure. Some static forces will be known and can be accounted for (i.e. drilling, insertion, stamping, engraving, etc.). Other unexpected forces that are difficult to determine could come from vibrations, impacts, or inertial forces. To ensure proper life, external forces should never come close to the static rating. Repeated forces at or near the maximum rating can fatigue the elements causing premature failure. Thus, a safety factor should be considered to account for these forces. Also, by using a safety factor, extra unforeseen loads that arise within an application sometime in the future, would not affect the positioning table chosen.

Hand Wheel Lock on TRCA Carriages & Pillow Blocks

December 16, 2019

This option adds an aluminum clamping block to the end of a pillow block, which then provides for a manual lock of the bearing to the shaft. The threaded hand wheel shaft presses into a bronze insert which makes contact to provide a “pressure lock” to the shaft. The threaded steel screw will not back drive and does not make physical contact with the steel shaft (no steel to steel contact). The lock will be installed as shown below when ordered with a SLBC, SLBO, DLBC, DLBO, or TRCA series. Multiple locks can be installed onto a TRCA assembly.

P_TRCA

TRCA Lock

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