{"id":1837,"date":"2016-11-15T11:00:01","date_gmt":"2016-11-15T17:00:01","guid":{"rendered":"http:\/\/blog.misumiusa.com\/?p=1837"},"modified":"2016-12-20T11:36:57","modified_gmt":"2016-12-20T17:36:57","slug":"working-with-linear-bushings-pt-3-length-load-and-surface-treatment","status":"publish","type":"post","link":"https:\/\/blog.misumiusa.com\/working-with-linear-bushings-pt-3-length-load-and-surface-treatment\/","title":{"rendered":"Working with Linear Bushings Pt 3: Length, Load, and Surface Treatment"},"content":{"rendered":"

Simple linear movement could be achieved using simple parts but as designs evolved and demand increased so did mechanical parts.\u00a0 Diving into linear bushings specifically, there are a variety of types to accommodate for different loads. \u00a0Bushing length and load capacity relationships will be examined as well as bushing materials.<\/p>\n

There are four length types of Linear\u00a0Bushings<\/a>\u00a0[1] Single, [2] Double, [3] Long, and [4] Singles exclusively designed for dual use. The bushing length difference affects the following guiding performances.<\/p>\n

a\uff09Load Capacity
\nb\uff09Guiding Accuracy<\/p>\n

a) The Relationship between Bushing Length and Load Capacity<\/strong><\/p>\n

Longer bushings have more ball bearings<\/a> and the load on each ball bearing in contact will be smaller. This effect can be confirmed from the fact that the load ratings increase as the lengths of\u00a0single, double, and long bushings increase. Therefore, selecting a linear bushing with longer length improves the load capacity which then extends life and reliability. (Fig.1)<\/p>\n

\"fig-1-bushing-length-and-load\"<\/p>\n

b) The Relationship between Bushing Length and Guiding Accuracy<\/strong><\/p>\n

As the bushing length increases, the accuracy improvements can be expected as follows.<\/p>\n\n\n\n\n
<\/td>\nA)<\/td>\nAccuracy improvement by averaging effect of guide rail (shaft) errors (Averaging Effect: see * below) ([Fig.2])<\/td>\n<\/tr>\n
<\/td>\nB)<\/td>\nAccuracy improvement by reducing errors due to clearances ([Fig.3])<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n\n\n
<\/td>\n*Averaging Effect on Shafts: By increasing the bushing length and the number of ball bearings, error elements such as unevenness and swells on shaft surface are averaged, and the effects of the error elements are reduced to less than half.<\/p>\n

\"fig-2-averaging-effects\"<\/p>\n

\"fig-3-bushing-clearance\"<\/p>\n

Therefore, load capacity and guiding accuracy can be improved by increasing the length of linear bushings. For this reason, [4] Singles (exclusively designed for dual use) are used for higher accuracy applications in some cases. ([Fig.4])<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\"fig-4-dual-use\"<\/p>\n

Explanation of Rail (Shaft) Deflection Calculations ([Fig.5])<\/strong><\/p>\n

Deflection of shafts for linear motion mechanism composed of\u00a0linear bushings\u00a0and shafts are calculated as follows.<\/p>\n\n\n\n
\u03b4\uff1d\uff37\u30fba3<\/sup>\u30fbb3<\/sup>\/\uff13\u30fbE\u30fbI\u30fbL3<\/sup><\/p>\n

a\uff1aDistance from supported end to the load point.
\nb\uff1aDistance of supported end opposite of a to the load point.
\nL\uff1aShaft support span distance.
\nE\uff1aYoung’s Modulus
\nI\uff1aShaft Sectional Moment of Inertia
\nI\uff1d\u03c0\u30fbd4\/64\u22520.05d4
\nd\uff1aShaft Radius<\/p>\n

When a\uff1db\uff1dL\/2, \u03b4\uff1dW\u30fbL3\/0.96\u30fbE\u30fbd4. In order to reduce the shaft deflection, design with increased shaft diameter (affects by 4th power), or reduce the supporting span distance (affects by 3rd power).<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\"fig-5-shaft-deflection\"<\/p>\n

Characteristics and Application Examples of Materials and Surface Treatments<\/strong><\/p>\n

Construction materials and surface treatments of linear bushings are as follows.<\/p>\n\n\n\n
\n\n\n\n\n\n\n\n
Outer Cylinder Material<\/strong><\/td>\nSurface Treatment<\/strong><\/td>\nRetainer Material<\/strong><\/td>\nBall Bearing Material<\/strong><\/td>\nApplication Example<\/strong><\/td>\n<\/tr>\n
SUJ2(Bearing Steel)<\/td>\n–<\/td>\nResin\/SUS440C Equiv.<\/td>\nSUJ2<\/td>\nGeneral slides requiring wear resistance<\/td>\n<\/tr>\n
SUJ2(Bearing Steel)<\/td>\nLow Temp. Black Chrome<\/td>\nSame as Above<\/td>\nSUS440C Equiv.<\/td>\nGlare intolerant optical equipment
\nPrecision positioning for clean room use<\/td>\n<\/tr>\n
SUJ2(Bearing Steel)<\/td>\nElectroless Nickel Plating<\/td>\nSame as Above<\/td>\nSame as Above<\/td>\nSlides for clean room use with chemical resistance
\nSlides requiring wear resistance<\/td>\n<\/tr>\n
SUS440C Equiv.(Stainless Steel)<\/td>\n–<\/td>\nSame as Above<\/td>\nSame as Above<\/td>\nLow loading clean room use and food\/medical related equipment<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n

Characteristic Comparison of Surface Treatments<\/strong><\/p>\n\n\n\n
\n\n\n\n\n\n\n
Outer Cylinder Material<\/strong><\/td>\nSurface Treatment<\/strong><\/td>\nCharacteristics<\/strong><\/td>\n<\/tr>\n
SUJ2(Bearing Steel)<\/td>\n–<\/td>\n– SUJ2 is steel and will rust<\/td>\n<\/tr>\n
Same as Above<\/td>\nLow Temp. Black Chrome<\/td>\n– Low friction coefficient superior in wear resistance
\n– Formation of thin and uniform layer
\n– Black plating color does not reflect light, and has good heat absorption<\/td>\n<\/tr>\n
Same as Above<\/td>\nElectroless Nickel Plating<\/td>\n– Often used in clean rooms for good chemical resistance and corrosion resistance
\n– Hard plating layer retains glossy finish
\n– Plating layer is non-magnetic<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n

As you can see there are a variety of materials and surface treatments for bushings.<\/p>\n

Now that different linear guide mechanisms<\/a>, bushing comparisons, and guide performances have been examined, it is time to apply these principals to applications.\u00a0 In the next two series of blogs, we will review different types of linear applications that use linear bushings<\/a> in their designs.\u00a0 Stay tuned!<\/p>\n","protected":false},"excerpt":{"rendered":"

Simple linear movement could be achieved using simple parts but as designs evolved and demand increased so did mechanical parts.\u00a0 Diving into linear bushings specifically, there are a variety of types to accommodate for different loads. \u00a0Bushing length and load capacity relationships will be examined as well as bushing materials. There are four length types of Linear\u00a0Bushings\u00a0[1] Single, [2] Double, […]<\/p>\n","protected":false},"author":46,"featured_media":1847,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"footnotes":""},"categories":[6],"tags":[91,95,12,331],"class_list":["post-1837","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-featured","tag-linear-bushing","tag-linear-guide","tag-linear-motion-2","tag-load"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t