Inspection in Production Management – Concept, Objectives and Stages

Production control is introduced not merely to ensure that the goods will be produced on time, but is also meant to see that the goods produced are of the right quality. This is done through inspection of the products manufactured. Since the purpose of inspection is to compare the products with the standards of quality set earlier, it too, can be regarded as an effective agency of production control. One way of inspection is to examine the quality of finished products at the end of the process of production. But this may involve too much of wastage in the form of rejected products.

To minimize the rejection of defective products, inspection may be conducted at every stage of production. Inspection can occur at three points: before production, during production, and after production. The logic of checking conformance before production is to make sure that inputs are acceptable. The logic of checking conformance during production is to make sure that the conversion of inputs into outputs is proceeding in an acceptable manner. The logic of checking conformance of output is to make a final verification of conformance before passing goods on to customers. Inspection before and after production often involves  acceptance sampling  procedures; monitoring during the production process is referred to as  process control.

Similarly, materials, machines and tools may be inspected against certain established standards to find out their performance and accuracy. Inspections may be made either in respect of samples selected at random or of each particular product (i.e. cent percent inspection). The inspectors may inspect materials, semi-finished and finished products either at the work bench or in special laboratories on testing rooms.

Objectives of Inspection

• The major objective of inspection is the prevention of defects.
• Detect defects as they occur in processing.
• Detect trends in the process which might lead to defects.
• Remove defective parts from production to stop further handling and processing costs.
• Remove defective parts to prevent poor performance of finished product.
• Inform all levels of management on the performance of manufacturing departments or units.
• Provide records for evaluation of individual machine or worker performance.

Stages or Levels of Inspection

There are several stages or levels at which inspection may be performed. These may be referred to in broad categories as: (i) Receiving inspection, (ii) Pre-production inspection, (iii) Production inspection and (iv) Product tests.

1. Receiving inspection is the process of examining purchased goods or materials as they are received into the plant. Its primary purpose is to establish whether or not these goods and materials are acceptable (i.e., of good quality). It should be an inspection of quantity as well as quality. Receiving inspection is also known as inwards goods inspection.
2. Pre-production inspection refers to inspection of materials prior to their actual processing or fabrication. This includes first-piece inspection or first-off inspection, inspection of equipment and tooling and pilot batch or pilot-plant operation. The primary purpose of pre-production inspection is to check on the ability of a machine or process to produce parts to specifications. First-piece inspection refers to the practice in which an operator of a machine/process brings the first part he/she produces on a new setup to an inspector to verify its correctness before he/she proceeds with the rest of the work order. This inspection assures that the tools and equipment have been properly set.
3. Production inspection includes inspection after every operation is completed and the quality characteristics are checked in comparison with quality standards set in the design. Usually 100 percent inspection is done to ensure that no defective item gets into the next stage of production after a certain operation is carried out. Two common forms of production inspection are: (a) Patrol or floor inspection and (b) Centralized inspection.
   1. In Patrol or floor inspection system, the inspection is performed at the place of production. It suggests the checking of materials in process at the machine or in the production time by patrolling inspectors. These inspectors move from machine to machine and from one to the other work centers. Inspectors have to be highly skilled. This method of inspection minimize the material handling, does not disrupt the line layout of machinery and quickly locate the defect and readily offers field and correction.
   2. In Centralized inspection, inspection is carried in a central place with all testing equipment; sensitive equipment is housed in air-conditioned area. Samples are brought to the inspection floor for checking. Centralized inspection may locate in one or more places in the manufacturing industry.
4. Product tests – In addition to inspection of dimensions, appearance and quality characteristics, some inspections are called functional tests of individual parts and components or subunits. These include tests of physical and chemical properties, tests for performance, endurance and efficiency of operation and the like. Functional tests are conducted on finished parts or sub-units or products. This is usually referred to as product test.

Inspection vs Quality Control

Inspection shall be differentiated from quality control. Inspection involves checking to see if a product meets or does not meet a stated standards. The result of the inspection process is acceptance or rejection of production. quality control, as distinguished from inspection, is directed towards future production rather than the past production. also, inspection methods only enable one ‘to be wise after the event’. Quality control serves to make one ‘get wise before the event’. Truly speaking, quality control is a basic function, while inspection is one technique of executing it. “Quality control sets   burglar alarm which prevents law from being broken. Inspection, on the other hand, is simply the police dragnet that catches the burglar after the law has been broken. Quality control enlarges the production pile, inspection only enlarges the scrap pile”.