How to Calculate the Rejection Rate and Rework Rate in Aluminum Casting Production?

Ⅰ. The rejection rate of aluminum castings

1. Definition

This percentage is obtained by dividing the waste material cost by the total cost of production or by dividing the total quantity of waste materials by the total number of aluminum castings produced.

2. Purpose

It is used as a result of measurement to determine whether a process is standardized to produce and assemble parts.

3. Formula

Rejection rate (%)= (waste material cost ÷ total cost of production) × 100% or (total quantity of waste materials ÷ total number of aluminum castings produced) × 100%.

4. Term

Waste material amount: the value of the materials used in the waste.

5. Total production costs

The sum of labor, materials and factory burdens (water, electricity, etc.).

6. Application information

The waste calculation is derived directly from the financial system of our company. If the company's financial system is not able to separate the value of waste materials from labor and expenses, the solution should be coordinated with relevant departments as soon as possible.

Ⅱ. The rework rate of aluminum castings

1. Definition

It refers to the proportion of time spent in rework activities, which is determined by dividing the rework hours by the productive labor hours or dividing the total quantity of reworked (repaired) products by the total production quantity.

2. Purpose

It is used as a result measurement to highlight the operational workstations that need improvement in the first quality.

3. Formula

Rework rate (%) = (rework hours ÷ productive labor hours) × 100% or (total quantity of reworked (repaired) products ÷ total production quantity) × 100%.

4. Terms

(1) Rework hours

The time it takes to reprocess, sort, and repair parts that will become wastes. This time can be spent on articles being processed, finished products, and purchased components or materials by aluminum casting manufacturers. Rework time includes such activities as repair, repacking, resorting, and additional inspection. Rework time includes internal or external activities. It shall include direct time plus the direct time component of overtime hours.

(2) Production labor hours

Total working hours of direct production workers (including direct hours plus the direct hours in overtime hours).

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