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Facility Design – An Introduction

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1 Facility Design – An Introduction
R. Lindeke, Ph. D. IE 3265 Sp. 2006

2 Facility Layouts: A Decision that Encompasses:
Placement of ‘Departments’ Placement of Workstations/Machines Placement of Stockholding points within Factory or Warehouse Development of Controlled Traffic Patterns to generate smooth workflow throughout

3 Decision Makers: What is the desired flexibility and required output?
What is the forecast product demand and its growth? What are the processing requirements? Number of operators Level of flow between work stations and between work areas How can the design balance requirements on Workstation loading Facility Space Available

4 Signs of a Successful Layout
Directed Flow Patterns: Straight line or other smooth patterns of movement Backtracking kept to a minimum Predictable Processing Time Little WIP in Facility Open Floors: allow communication and easy tracking of work & employees Bottleneck operations under control Work Stations close together

5 Signs of a Successful Layout, cont:
Orderly Handling & Storage of Raw Materials and Finished products No extra handling or unnecessary handling of materials Can easily adapt to changing conditions Considers demand growth or decline Considers product change over Considers technological change

6 Workstation Layouts Within a cell:
IMPROVED LAYOUTS: Standard Layouts End to End Front to Front I/O Back to Back (poor) Circular or U Flow

7 Considering Circular or U-Flow:
Advantages: One operator can tend several machines Common I/O station simplifies material transfer to/from cell to the rest of the facility Automation can be tried for several machines Disadvantages: Limited Queuing space or WIP storage within cell Requires excellent balance and high quality to keep flow active between workstations in the cell

8 Flow Patterns within Process Departments (Job Shops)
Aisle Aisle Aisle A. Parallel Flow B. Perpendicular Flow Aisle C. Diagonal Flow Aisle

9 Some Job Shop Ideas: Flow is in-out of the department not between machines Traffic patterns must support movement from and to aisles Diagonal designs often save floor space in 1 way aisle shops

10 Overall – Flow is a Function of Aisles
As a designer, aisle placement is of primary interest and often marks successful or failed designs! Aisle Size is a function of Load Size! Set Aside is controlled by Largest Load Area (Rules of Thumb) Load Area Aisle Set Aside < 6 ft2 5 -10% of calc. size 6 – 12 ft2 % of calc. size 12 – 18 ft2 % of calc. size > 18 ft2 % of calc. size

11 Aisle Consideration, cont.
Aisle width is controlled by the traffic that flows on it Type of Traffic Min. Aisle Width Large Wheeled Indoor/outdoor Tractors 12’* Large Forktrucks 11’ Small Forktrucks 9’ Narrow Aisle trucks/AGV’s 6’ Manual Platform Trucks 5’ Personnel 3’ Personnel w/doors 1 side Personnel w/doors both sides 8’ *For each direction of flow NOTE: Consider turning radiuses at intersections!

12 General Aisle Issues: Good Aisle Designs …
Avoid curves/jogs/non 90 intersections Avoid outside wall paths (these are used for utilities so machine/workstations should back to walls if possible Are straight and lead to door ways Allow Flow to be controlled by entrances and exits (as it should)

13 Facility Designs Seeks:
To maximize directed (forward) flow Materials move directly from sources to destination without jogging around and by paths that don’t intersect other flows* Minimize total flow (volume) of all products Distances minimized, too Minimize cost of flow – expensive flows should be short while lighter or less critical flows can be longer *No Backtracks!

14 An Example: Flow Straight Thru: A-B-C-D is 250’
25’ 50’ 75’ B C Flow Straight Thru: A-B-C-D is 250’ Flow w/Backtracking: A-B-C-A-D is 550’ Backtracking is an Economic decision! Cost of Added Equipment (replication of A) VS. Cost of added flow movement and traffic patterns (aisle set aside) for each product that flows along backtrack

15 The Technical Jobs of Facilities Design:
Determination of Space requirements: Workstation space for: Equipment Footprint + machine travel + access (load/maintenance) + shop services (air/electrical/water, etc) Materials – consider unit load size + tooling/scrap etc Personnel – ingress & egress 30 – 42” for passage between stationary or operating machines

16 The Technical Jobs of Facilities Design:
Determination of Space requirements (cont.): Departmental (Cell) Requirements: (WSreqr + G.Service + M.Handlingreqr) G. Service areas offices, records, data, inspection/QC, etc. Material Handling inside traffic set asides to move product, tools, raw materials, etc

17 The Technical Jobs of Facilities Design:
Determination of Space requirements (cont.): Specifics for Work Centers: Use a Worksheet (see handout) Lists various resources and their requirements considering services, physical loading (special needs?) List and sum all areas required Add in Aisle Allowance See handout (one for each work center or assembly line)

18 The Technical Jobs of Facilities Design:
The second job is to effectively provide for minimum flow and cost of flow Here the designer performs studies of the space requirements and desired travel patterns Using Qualitative Tools: SLP (systematic layout planning) based on activity relationship charts to suggest appropriate layouts Software to optimize the relationships Using Quantitative tools: Mileage Charts: area to area distance matrices From -To Charts: Move/Volume/Cost Matrices Appropriate software to compute and optimize the arrangements

19 Typical Activity Relationship Chart:
These charts are often called an AEIOUX chart – the letters used to explain relationships that are learned during our facility studies:

20 Completing the Activities Relationship Chart:
After listing all departments on chart, Conduct Surveys to assess relationships with each department’s staff Interpret results of surveys as closeness needs – itemize and record closeness requirements to support assessed relationship Establish the relationships: A – absolutely necessary E – Especially Important I – Important O – “ordinary” closeness okay U – Unimportant X – Undesirable Allow all concerned parties to review proposed chart for accuracy of closeness settings

21 Using Activity Relationship Chart to build Designs:
Using Pure SLP ideas we develop a “Meatball” diagram and move departments around to shorten A & E lines while increasing length of X lines

22 Using Activity Relationship Chart to build Designs

23 Using Activity Relationship Chart to build Designs
An alternative approach begins with looking at each department as equal sized rectangles listing letter relationship with all departments in the Facility Receiving: A -; X-; E-B; I-D; O-C,E; U- F,G Milling: A -; X-; E-A,D; I-E,F; O-; U- C,G Press: A -; X-; E-; I-; O-A,F; U- B,D,E,G Sc. Machine: A -; X-; E-B; I-A,E; O-; U-C,F,G Plating: A -E; X-; E-G; I-B; O-C; U- A,D Shipping: A -; X-; E-F; I-E; O-; U- A, B, C,D Assembly: A -F; X-; E-; I-B,D,G; O-A; U- C

24 Using Activity Relationship Chart to build Designs
Select template with highest number of A relationships; tied templates selected subject to hierarchy: most E’s, Most I’s, fewest X’s Here select Plating department (F) Next template chosen should have A relationship w/ 1st chosen – any ties broken as above Here Assembly, department E Next template chosen should have the highest joint relationship with first two chosen Here is Shipping – G This continues until all departments are chosen

25 In doing the Design: By This Order:
Place F in Center. Then follow in order keeping Ideas (AEIOUX) of arrangements: F E By This Order: G A B C D B D E F G A C

26 A Final Step: now we consider actual departmental areas:
Code Function Area Ft2 # Units (2000 per) A Receiving 12,000 6 B Milling 8,000 4 C Press 6,000 3 D Sc. Machines E Assembly F Plating G Shipping

27 Leads to the following Proposed Layout:
When equal sizes are replaced with scaled sizes we develop these layouts: Obviously, many variants would be possible (no X’s and few A and E’s) We determine appropriate layout only after quantitative analysis is applied to the proposed arrangements

28 Addressing the Quantitative Approaches:
Mileage Charts: showing Distances between Departments Distances measures “Euclidian-wise” using computed straight lines between department centroids Distances measure “Recti-linear” were department to department distances are computed by moving horizontally and vertically along expected aisle routes

29 Mileage Chart Format A B C D E XXX 100 200 300 400 100(?) BackTracks:

30 From-To Charts Charts, based on Routings, that show each relevant part’s movement through the proposed facility Format is similar to Mileage chart but are rarely symmetrical or fully populated More expensive travel can be handled with increased Volumes or have other special handling costs attached

31 Examining Quantitative Design
We begin with a Qualitatively designed facility (one that meets perceived activity relationships) To keep it simple, lets look at a Flow–thru facility: Consider that each of the departments (A to E) are 100 units square A B C D E General Flow Direction

32 Representative Products are selected for study:
These might be “group seeds” or “large volume” products or in other ways represent how the product will move thru the facility Lets explore 3: (Pr 1, Pr 2 and Pr 3) Product Prod. Quantity Routing Pr1 30 A-C-B-D-E Pr2 12 A-B-D-E Pr3 7 A-C-D-B-E

33 Mileage Chart: A B C D E XXX 100 200 300 400

34 From To Chart (based on Routing)
XXX Pr2 12 Pr Pr 3 2*7 = = 44 Pr Pr2 12 = 42 Pr 3 2*7 = 14 Pr 1 30 Pr 3 is heavier and costlier to move – we double volume to make it equivalent to Pr 1 & Pr 2

35 From To Issues The filled cells below the diagonal represent moves against the general directed flow of the original facility design ( they – may (should) – cost more than moves above the line for the same distances) Cells Close to the diagonal are short distance moves while cells remote from the diagonal are long distance moves The number of moves (not filled cells!) must equal the total of each move in the routing sheets for the products

36 Costing Transport in the Layout:
For comparison: all forward moves cost $1/unit vol/unit distance All Backtrack move cost $1.25/unit vol/unit distance Costs A B C D E xxx 1 1.25

37 Layout Total Transport Cost
Form: M*F*C “cell products” Sum each cell of resultant matrix  it is the facility transportation cost (for comparison)

38 General Flow Direction
Can we do Better? Lets Swap Departments B & C This will change our Mileage and Cost Matrices as well as arrangements in From/To Matrix A C B D E General Flow Direction

39 New Mileage Chart: A C B D E XXX 100 200 300 400

40 New From-To Chart A C B D E XXX Pr 1 30 + Pr 3 2*7 = 30 +14 = 44
Pr 1 30 Pr 3 2*7 = 14 Pr Pr2 12 = 42

41 New Cost Matrix: Costs A C B D E xxx 1 1.25

42 New Transportation Costs:

43 Examining these results:
Swapping 2 departments lead to a reduction in cost of: $9900 or about 28% of the original cost Can we improve further? Not with this fundamental design Can we redesign the general footprint? Then we can keep looking!

44 New Fundamental Design:
And applying a Euclidean Concept of distances! Distance from A to B is: ( ).5 = 142 units Distance A to E is: ( ).5 = 224 units Typically, with Euclidean distances, were would not consider transport cost differences in either direction – this facility shape doesn’t favor general directions of flow! A C D B E

45 Mileage Chart (now) A C B D E XXX 100 142 200 224

46 Transportation Cost Picture:
A further savings of $1000 – as manager we decide if the new configuration design is worth the savings gained!


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