10-2 Issues in Facilities Design Minimize investment in new equipment Maximize production throughput rate Utilize space most efficiently Provide for the safety and comfort of employees Maintain a flexible arrangement Minimize materials handling cost Facilitate the manufacturing process Facilitate the organizational structure
10-3 Patterns of Flow Straight line flow U flow L flow Serpentine flow Circular flow S flow (refer to Figure 10-1)
10-5 Activity Relationship Chart (Rel Chart) Each pair of operations is given a letter to indicate the desirability of locating the operations near each other. The letter codes are: –A: Absolutely necessary –E: Especially important –I: Important –O: Ordinary importance –U: Unimportant –X: Undesirable (refer to Figure 10-2 for an example.)
10-6 Activity Relationship Chart for Meat Me Fast-Food Restaurant
10-7 From-To Chart From-to charts are similar to the mileage charts on roadmaps. They can show: –Distances separating pairs of work centers –Numbers of materials handling trips between pairs of work centers –Materials handling costs between pairs of work centers (See Figure 10-3 for an example of a From-to distance chart.)
10-8 From-To Chart Showing Distances Between Six Department Centers (Measured in Feet)
10-9 Types of Layouts Fixed Position Layouts – suitable for large items such as airplanes. Product Layouts – work centers are organized around the operations needed to produce a product. Process Layouts – grouping similar machines that have similar functions. Group Technology Layouts – layouts based on the needs of part families. (Refer to the examples in the next four figures)
10-14 Computerized Layout Techniques CRAFT. An improvement technique that requires the user to specify an initial layout. Improves materials handling costs by considering pair-wise interchange of departments. COFAD. Similar to CRAFT, but also includes consideration of the type of materials handling system. ALDEP. Construction routine (does not require user to specify an initial layout). Uses REL chart information. CORELAP. Similar to ALDEP, but uses more careful selection criteria for initial choosing the initial department PLANET. Construction routine that utilizes user specified priority ratings.
10-15 Flexible Manufacturing Systems An FMS is a collection of numerically controlled machines connected by a computer controlled materials flow system. These systems typically are best for systems with moderately high output and moderately high need for flexibility. For low volume high variability systems, stand alone systems are better, and for high volume, low variability, fixed transfer lines are better. Refer to Figure 10-21 to see the environments where FMS systems are appropriate. Figure 10-22 shows a typical FMS system.
10-16 The Position of FMS in the Manufacturing Hierarchy
10-18 Advantages of the FMS Reduced work-in-process inventories Increased machine utilization Reduced manufacturing lead time Ability to handle different part configurations. Reduced labor costs
10-19 Disadvantages of the FMS The main problem is cost. Systems cost upwards of $10 million. They require upgrading of other related systems (such as the materials handling system) that can be equally expensive. There are few cases reported in the literature that show the investment in FMS had a reasonable payback period.
10-20 Facility Location Goal is to find the optimal location of one or more new facilities. Optimality depends on the objective used. In many systems, the objective is to minimize some measure of distance. Two common distance measures: Straight line distance (Euclidean distance). The distance between (a,b) and (x,y) is given by the formula: Rectilinear Distance (as might be measured following roads on city streets).
10-21 The Single Facility Rectilinear Distance Location Problem Goal: locate n facilities to minimize the weighted sum of rectilinear distances from the new facility to existing facilities. Solution: locate the new facility at the median location of the existing facilities. This is accomplished by taking the median location component by component of existing locations.
10-22 The Gravity Problem The objective is to minimize the weighted sum of the squared Euclidean distances of the new facility to the current facilities. It is an uncommon problem but has a simple solution. The optimal solution is that both the x and y coordinates of the new facility are the ratio of the weighted x and y coordinates of the existing facilities divided by the sum of the weights.
10-23 The Straight Line Distance Problem The objective is to minimize the weighted sum of the straight line distances of the new facility to the current facilities. No simple algebraic solution method exists. Finding the optimal solution requires an iterative solution procedure that may begin with the gravity solution.