Table 3. Factor and Response Table for Steel Casting Cleaning Factor (X)
Part Specific Range
Blasting (X9-1) Cutting (X9-2) Scarfing (X9-3) Chipping (X9-4) Grinding (X9-5) Welding (X9-6) Rewelding (X9-7) Rechipping (X9-8)
ing, molding, coremaking, melting) and enabling processes (human resources, purchasing, quality) (Fig. 1). Labeling these activities helps create a hierarchal classification of the process and subprocess families, which can be used to develop a computer-based tool for inputting process knowledge data. In the hierarchy, the Process
kingdom (to borrow from biology classification terms) has three families: joining, finishing and shaping, which
Method of Measurement
Units
Continuous/ Discrete C/D
Clock/scale Man hrs/ton Continuous Clock/scale Man hrs/ton Continuous Clock/scale Man hrs/ton Continuous Clock/scale Man hrs/ton Continuous Clock/scale Man hrs/ton Continuous Clock/scale Man hrs/ton Continuous Clock/scale Man hrs/ton Continuous Clock/scale Man hrs/ton Continuous
ONLINE RESOURCE
Visit
www.moderncasting.com to download more charts and tables on process knowledge.
RESPONSES AND
RESPONSE CATEGORIES Major categories of responses include casting dimensions, casting defects, defects per million opportunities (DPMO) and quality costs. These categories can be expanded further into subcategories and then coded for tabulating purposes. Casting dimensions is coded as Y1, casting defects is Y2, DPMO is Y3 and quality costs is Y4. An example subcategory coding is below:
Code Name Y1-1 Casting dimensions Y2-1 Runout Y2-2 Inclusions Y2-3 Shrinkage Y2-4 Misrun Y2-5 Erosion Y2-6 Penetration Y2-7 Hot tear Y2-8 Type II sulfides Y2-9 Incorrect impacts Y2-10 Incorrect mechanicals Y2-11 Blowholes, pinholes
Y2-12 Cracks Y2-13 Broken molds Y2-14 Flash Y3-1 DPMO-Redlights Y3-2 DPMO-Missed deliveries Y3-3 DPMO-Quality issues Y3-4 DPMO-Retests Y3-5 DPMO-Re-heat treats Y4-1 Quality cost- internal failure
Y4-2 Quality cost- external failure
Fig. 1. This process hierarchy flow chart shows the breakdown of the levels of activities involved in casting.
May 2013 MODERN CASTING | 27
includes molding, deformation, and casting classes (Fig. 2). For an example, let’s look at green sand steel casting in the factor and response table in Table 1. Various fac- tors occurring in green sand molding are listed in the left column, with their related responses in the far right column. Similar tables for melting and cleaning are shown in Tables 2 and 3. Metalcast- ers can use these tables as basis to create their own table using the factors and responses they have identified in their facility. Te part specific range columns here are left blank because this range in which a response occurs must be deter- mined by you for your individual facility. Not all the data for every response shown is needed—only the data for those relevant to a part and the customer’s specifications. Collecting the data while
Response (Y)
Y4-1 (Internal failure cost) Y4-1 Y4-1 Y4-1 Y4-1 Y4-1 Y4-1 Y4-1
the casting is made will allow metalcast- ers to determine the value for the factors. Other ways to represent process
knowledge include process maps (box-arrow diagram), process flow charts, swimlane process maps, SIPOC diagrams, value stream maps, cause-and-effect diagrams, cause-and- effect matrixes (Table 4), FMEA, and P-matrix case studies.
Determining Your Range Te customer provides specifica-
tion limits for product characteristics. However, metalcasting facilities need to determine the specification limits for the process parameters. Te starting point for determining the specification limit is to determine the standard deviation value of the parameter. Tis can be determined by taking at least 30 consecutive values
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