April 2012 Archives

#114 Clean Room Compatible LCA - 5: Materials for Clean Room LCA - 2

By システム管理者 on April 20, 2012 12:00 AM | No Comments | No TrackBacks

Materials selection for clean room LCA follows the "3 principles of cleanliness". Especially, following two countermeasures are of the importance.

* Do not generate contamination.
* Do not allow contamination to accumulate.

Next table explains the relationship of "3 principles of cleanliness" and LCA mechanical system materials.

[Table 1] Relationship of "3 principles of cleanliness" and LCA mechanical system materials

3 principles of cleanliness

LCA mechanical system materials

Explanation

Do not bring in contamination
↓

Countermeasures during equipment load in

*	Not closely related to structural materials
*	Suppression of bring in contamination during load in is important

a）	Cleaning before the equipment is loaded into clean rooms (use water cleaning, etc.)
b）	Equalize equipment and clean room temperatures to avoid water condensation.

Do not generate contamination
↓

Do not generate rusts, abrasion dusts, gases

a）	Corrosion resistant metals, Surface treated materials
b）	Obtain corrosion resistance by surface treatments
c）	Use of electro-passivated products
d）	Do not use general construction materials such as wood, paper, concrete, etc.

e）	Use low evaporative greases
f）	Use wear resistant materials

a）	Prevent rusts by uses of stainless steel, aluminum, and surface treated materials.
b）	Plating (nickel, Reydent, etc.), surface coatings
c）	Select low out-gassing components for vacuum chamber and etc.
d）	Generates particulates in exposed states. Aging variations exist
e）	Use low evaporative greases for sliding components
f）	Select materials and bearings of low particulate nature

Do not allow contamination to accumulate
↓

Do not let statically charged

Do not let air flow congested

a）	Electrically conductive materials
b）	Electrically conductive surface treatments
b）	Punch perforated SUS sheet steel

a）	Use electrically conductive materials to avoid static charging, and ensure grounding.
b）	Use anti-static surface treatments for plastics
c）	Use sheet metals that do not congest air flow

#113 Clean Room Compatible LCA - 4: Layout Arrangements for Clean Room LCA

By システム管理者 on April 13, 2012 12:00 AM | No Comments | No TrackBacks

Layout of LCA (Low Cost Automation) mechanisms for clean room usage are to be designed with emphasis on the following two knowledge's.

1. Consider the relationship of LCA and localized cleanliness formats (see Vol. 244).

2. Apply "3 principles of cleanliness" (see Vol. 114) to the areas where contaminations are to be avoided.

Here, LCA mechanism layout formats for clean room usage regarding the item 2. above explained.

LCA mechanism layout formats and "3 principles of cleanliness"

(1) Do not bring in contamination.

Moving LCA mechanism will generate particulate. The key point is not to bring in any contamination into the process core (work area).
Contamination is introduced by air flow and gravity (free-fall). Devise mechanism layouts to avoid the effects.

■Example
a）	Drive mechanisms will generate particulates and lubrication scattering. These contaminants are relatively heavy and will fall by gravity. In order to obtain clean process cores, position the drive mechanisms below the process cores. (In case of Walking beam mechanisms and etc. (see [Fig.1])
b）	In case of Pressurized turbulence type of simplified clean designs, provide exhausts near the contamination generating mechanisms ([Photo 1]), or cover the entire mechanism and provide a localized exhaust ([Fig.2]).

[Fig.1] Example of locating the mechanism below the work are (Walking beam transfer mechanism)

[Fig.2] Example of localized exhausting

(2) Do not generate contamination

・This item is closer related to material selection than layout design.

(3) Do not the contamination accumulate.

Make fixture structure and layout less prone to contacting and accumulating contaminants.
■Example
a) Fixtures that hold workpieces inverted or vertically.
b) Do not create any congested air flow on workpiece surfaces.
In order to obtain better cleaning effects, concentrate all the contamination generating mechanisms down flow.

[Fig.3] Layout improving examples of not creating air flow congestions on workpiece surfaces

#112 Clean Room Compatible LCA - 3: Cleanliness Localization Technology

By システム管理者 on April 6, 2012 12:00 AM | No Comments | No TrackBacks

In order to attain cost effective clean environments, creating clean spaces only where needed. Cleanliness localization technology fits this concept. Here, cleanliness localization by LCA concepts, unlike the micro environment (SMIF and etc.) explained in Vol. 242 Clean room compatible LCA - 2: Standard structure of clean rooms, will be explained.

(1) Cleanliness localization technology

Cleanliness localization technology is a concept of designing and creating simplified clean environments appropriate only for the subjects. There are following 3 representative types.

[Table 1] Types of cleanliness localization

Cleanliness localization type

Characteristic

App. example

Pressurized turbulence type ([Fig1 - a])

・	Clean technology for cases where the work is performed from the front side of the bench
・	Filter unit is placed above or in front

・	Inspection work bench inside of a clean room
・	Work bench for precision parts assembly

Simplified clean booth ([Fig.1 - b])

・	For cases where stable cleanliness is desired by manually handling then automating.
・	Human-less operation can achieve stable cleanliness

・	Product pre-shipping inspection and packaging
・	Localized automated equipment booth
・	For engineering evaluation

Simplified clean spot type
([Fig.1 - c])

・	When independent equipment only is desired to be clean
・	Not affected by surrounding environment

・	Clean booth for specialized machines
・	Clean booths with temp./humidity controls

[Fig.1] Types of Cleanliness localization

(2) Vital points on simplified clean booth design and construction for cleanliness localization

Basics for simplified clean booth design are the same as Cleanliness 3 principles. The vital points for the designs are as follows in the table. Since the subject is invisible minute contamination flow, the objective is to obtain the best condition by adjusting the flow of clean air, rather than aiming for a perfect condition with a first shot.

[Table 2] Vitals of simplified clean booth design and construction

Vitals of simplified clean booth design

Improvement examples

Do not create any congestion of air from HEPA filter unit

・	Provide slopes on corners inside the booth to create clean air flow

Direct clean air flow where needed

・	Create direct flows with anti-static treated sheets (non PVC sheets: HPEDT) ([Fig.3])

Locate exhausts where clean air is easily expelled out

・	Locate them on the booth bottom according to the clean air flow

Avoid using materials inside of the booth that can collect contamination

・	Use shade-less lamps on ceiling
・	Use non-rusting punched material for the bench
・	Plastics are to be anti-static treated

Use booth construction materials that can be grounded to avoid static attraction of contaminants

・	Plastics are to be anti-static treated
・	Surface treated aluminum frame surfaces are non-conductive, so use conductive bolts to tie them to the base material to make conductive.

[Fig.2] Vitals on simplified clean booth design and construction
<Do not create clean air congestion>

[Fig.3] Vitals on simplified clean booth design and construction
< Direct clean air flow where needed>

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