Title: Types of Quality Inspections
Course: PW-Course-Import-Test > Section: Module 1: Introduction to Quality Control

Module 1

The basic principles of quality and the inspection process remain the same but an inspector’s job functions may slightly differ. Quality inspectors can work in different locations in a company and their work may differ slightly according to where they are.

Quality inspection is is a critical appraisal involving examination, measurement, testing, gauging, and comparison of materials or items. An inspection determines if the material or item is in proper quantity and condition, and if it conforms to the applicable or specified requirements. In this section we will familiarize you with the different types of inspections depending on where in the manufacturing process they occur.

Inspections are generally divided into three categories:

1. Incoming or receiving inspection
2. In-process inspection
3. Final inspection

Now, let's learn about these three inspection categories in detail.

1. Incoming or Receiving Inspection

Incoming or receiving inspection starts earliest and inspects raw materials and components before production begins. Many companies will choose to perform some level of inspection at this stage. Early inspection here helps to identify quality issues at a component level earlier rather than later down the road during production.

At times if a company has gained enough confidence in a supplier they may not inspect any of the components or parts they send but just review the Certificate of Conformance or Certificate of Analysis sent by the supplier with the part. Once this review is complete and the certificate confirms that the material meets the required specifications, the material is marked as accepted. This material now can be further used for manufacturing purposes.

Say a medical device company is manufacturing catheters that have a handle as shown in the picture above. As you can see this handle has various pieces (components) that are assembled together. These various components are received from the supplier, inspected by receiving inspection and then sent to the assembly process (manufacturing) if they meet the specifications.

If components do not meet specifications they are rejected and a non conformance is initiated. You will learn all about this in subsequent modules.

2. In-process Inspection

Quality inspection is is a critical appraisal involving examination, measurement, testing, gauging, and comparison of materials or items. An inspection determines if the material or item is in proper quantity and condition, and if it conforms to the applicable or specified requirements.

In-process inspection takes place when the various components are assembled together during the manufacturing process. In-process inspection can take at various stages in the manufacturing process. The frequency of the in-process inspection is determined by several factors like complexity of manufacturing and criticality of the part to patients, to name a few.
In-process inspection, like receiving inspection, is on a sampling basis. Practically, it is not possible to inspect all the products that are manufactured. This would slow down the manufacturing process and prove to be costly.

Like in the case of receiving inspection, if the manufactured product does not meet specifications, it is rejected and a non conformance is initiated.

3. Final Inspection

Final inspection is most commonly carried out towards the end of the manufacturing process when the product is ready to be placed in its packaging to ship to customers. Some of this final inspection can happen on the packaged product to ensure that it has been packaged correctly. This is the last inspection that the product sees before it is shipped to the customer.

This inspection, if done correctly, prevents any nonconforming (bad) product from being shipped to the customer. Final inspection can be done on 100% of the product, but most frequently, it is done on a sampling basis.

Inspections can also be divided according to the method used to perform the inspection. There are four methods of inspection/testing:

1. Visual inspection
2. Dimensional inspection
3. Verification inspection
4. Mechanical testing

These four methods of inspection are detailed below:

1. Visual Inspection

Regardless of technological advancements in inspection techniques the primary and most important inspection / test technique is visual inspection. Time has proved that visual inspection is the most effective technique of all. Visual Inspection is a very effective inspection method, and it should be the primary method included in any effective Quality Control Program. Visual inspection can be performed by an unaided eye or a magnifying device such as a microscope.

Examples of visual inspection include verification of color, shape of the part, defects on a part, and particulates on a part, to name a few.

2. Dimensional Inspection

Dimensional inspection is performed when the size of a component or device is critical and needs to be monitored. This the the second most common inspection method. Depending on the dimension to be measured there are several tools that can be used to perform the measurement. Common tools used for dimensional inspection are rulers, calipers, drop gauges, pin gauges and micrometers. As like any other inspection, training of the quality inspector in the use of the various tools is essential.

Examples of dimensional inspections include measuring the length of a part, diameter of a circular feature on a part to name a few.

3. Verification Inspection

Verification inspection involves review of any supporting documentation that is available with the component or finished device that is being inspected. This can include a review of Certificate of Conformance or Analysis sent by the supplier with the parts. Verifying the quantity of components sent by a supplier or the number of parts manufactured by counting also falls into this type of inspection.

Examples of verification inspection is review of Certificate of Conformance or Analysis sent by the supplier with the parts.

4. Mechanical Testing

Mechanical testing is performed to determine various mechanical properties of materials such as strength, hardness, ductility, toughness, brittleness, etc. There are several types of tests to determine various mechanical and physical properties of material. The most common type of mechanical testing performed in the medical device industry is tensile testing. Tensile testing is destructive testing and is always performed on a sampling basis. In the medical device industry tensile testing is performed on a finished device that has been bonded. The tensile testing will indicate the strength of the bond, which may be a critical factor for the performance of the device.

5. Attribute and Variable Inspections

Attribute inspections generate pass or fail data after the inspection. Examples of such inspections are verifying if the parts are blue in color or verifying if there are 100 parts in a bag. The response the quality inspector will provide for these inspections is either pass or fail. So say that is the parts are not blue in color the quality inspector will ‘fail’ that inspection.

Variable inspection generates continuous data after the inspection. Examples of such inspections are measuring the length of a part. Unlike ‘pass’ or ‘fail’ results, when you measure a length you are going to have numerical data and which will vary from part to part that is measured.

Sampling Inspection and 100% Inspection

Sampling inspection involves inspecting a relatively small number of items from a batch or lot and then using the results of this sample to either accept or reject the entire lot. The accept/reject criteria is the number of defective items found in the sample.

Sampling inspection relies on statistical probability and it is possible that a good batch will be wrongly rejected, or a bad batch will be wrongly accepted. This can have significant economic consequences and so it is typical to use a published sampling plan, such as ANSI/ASQ Z1.4-2003.

On the other hand, 100% inspection involves inspection of all the items in a batch. This type of inspection is mostly avoided since it is time consuming and expensive. Also 100% inspection is not always 100% effective, as you will soon learn performing the exercise on the next page.