Low Cost Automation Tutorial

#115 Clean Room Compatible LCA - 6: Slide Mechanisms for Clean Room LCA

Category : Clean room technology

May11, 2012

It is appropriate to consider that "There definitely will be particulate generation from locations where two sliding parts meet and slide together" from a standpoint of friction, wear, life of slide mechanisms. Therefore, the cleanliness technology for clean room LCA will be based on Item-2 of the "3 principles of cleanliness", < Do not generate contamination>.

There is a lubrication technology to reduce the issues of friction, wear, life and aging variations. This lubrication technology is also utilized for the clean room LCA equipment.

Cleanliness technology for slide mechanisms

The fundamental concept is to devise countermeasures for the following two main reasons of particulate generation from slide mechanisms.

a) Particulates generated by repeated sliding and wear of two objects
b) Splashes of oil/grease (see [Fig.1])

[Fig.1] Comparison of particulates by greases used on ball screws

From [Fig.1]

・	Since ball screws have rotating motion, they have great effects of splashing grease. In general, a lot of standard grease would be splashed for the first 20 hours, then the splashing would remain stable at high levels.
・	Low particulate grease would have small initial splash amounts and remain stable for long duration.
・	For both grease types, proper greasing maintenance is required. (see [Fig.2])

[Fig.2] Grease before and after the test

To reduce particulate generation of slide sections	Example of measures
Reduce sliding sections overall	Reduce usage of sliding/rotating/meshing mechanisms Example ・Sliding/rotating >> Non-contacting slides, etc. ・Meshing (gears, etc.) >> Reducing gears by servo mechanism usage ・Shorten transfer mechanism path
Reduce friction force	1.Reduce vertical loads >> Weight reduction designs by increased bearings to increase contact surfaces 2.Reduce acceleration and deceleration >> Reduce the effects of vertical load by reducing acceleration and deceleration
Suppress wear by lubrication	Clean lubrication usage and maintenance
Adoption of anti-wear parts	Adoption of bearings with ample specification margins. Use of ceramic balls, etc.
Suppress mechanical play and vibration	Suppress motion speeds and acceleration Optimized mechanism precision
Localized exhaust measures	Supported by mechanism structure Sealing of particulates by use of bellows

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