July 2011 Archives

There are following four types of Transfers that effect locations of objects as: In-feed, Transport, Loading, and Storage. Each is explained in relation to LCA. (Storage is omitted)

(1) Classification of transfer functions

A flow of material to assembled products is simplified as the following.

The previous LCA discussion (Vol.83) on non-circular gears and link mechanisms as an example, selecting of standardized component specification selection is explained.

The selection of standard components vary depending on the environments where the LCA are applied. The table below shows the examples for general manufacturing applications.

(1) Selection criteria based on LCA usage environments

(2) Explanation on standard component selections by LCA functionality

The figure below is an example of motion control LCA. The table below explains the standard component selection.

(3) Other constraints

1. Overall size determined based on special constraints.
2. Not to overlook safety aspects such as cover and etc.

LNFB		HCDG		LFZB		CMSG
LHSS		SFJ		SHA

There are "material flow" and "information flow" when considering the "Flows" regarding Production. The following section explains the "Material Flow: Transfer" and associated LCA.

(1) What is Transfer?

Materials, parts, and semi-finished products being moved with locational changes applied is the state of "Transfer". Dedicated units are called Material Handling machines. For one-person assembly cell unit production schemes, manual moving of materials corresponds to this and supportive LCA is also required.

(2) What is Transfer?

Importance of the LCA in Transfer are listed below.

1. Necessary for almost all production lines.

No single production line completes everything from start to finish in one process.

2. One transfer mechanism needed for every product variety.

Subjects to be transferred will vary in shape, weight, and properties (solids, powder, fluids)

3. Significant effects on the entire layout.

The entire line layout is almost determined by how the transfer mechanisms are arranged.
On the other hand, inappropriate transfer scheme will cause the following issues.
* Losses in investments * Losses in space * Losses in flexibility * Increase in failure rate

(3) Things that designers should consider.

In factory automation schemes, machining operations tend to be handled by machining centers where multiple machining processes are performed with one process station in order to save transfer equipment layout space as well as reducing transfer time.
However, giving the multi-process capabilities to the machines also increases complexity, propriety, and cost, so system optimization by applying transfer units based on LCA concepts.
The transfer LCA for cellular manufacturing schemes need to be designed with human engineering viewpoints.

Matter to be considered by the designers for both cases.

(2) Stepping Motors and Ball Screw Drive

-Ball screws provide good transmission efficiency and utilization of motor efficiency since [1] they directly convert motor's rotary motion into linear motion, and [2] the screw pitch works as a deceleration mechanism.

-[Fig.4] is a drive mechanism with ball bushings and a ball screw drive on the Y-axis, typically used where reduced cycle times and increased positioning accuracy are needed.

(3) Air Cylinder Drive

-[Fig.5] is an air cylinder driven guide bearing of a clamp mechanism, and [Photo 2] is a magnetically coupled air cylinder mechanism. They both use linear bushings (arrow leader).

-Since the air cylinders cannot be velocity controlled during acceleration and deceleration, shock absorbers are used to reduce the shocks when stopping ([Photo 2]).

(4) Vertical Guide Example

-For vertical guiding applications, use of flanged linear bushings can achieve compact and simple mechanism without dedicated retaining mechanisms provided. ( require a vertical base plate for guide rails)