In recent years, the shortage of human resources has become chronic in many industries, but it has become a major problem even at manufacturing sites.

One of the effects of the shortage of human resources in the manufacturing industry is that visual inspections cannot be performed properly. Conventionally, visual inspections have been performed visually by experienced and skilled workers. However, because successors have not yet been nurtured, the number of human resources who can accurately perform visual inspections is steadily decreasing year by year.

In order to maintain quality even in such a situation, it is important to utilize the limit sample that is the criterion for judging good products and defective products. This time, after touching on the outline of the limit sample, we will tell you how to create it and the operation points.

What is Limit Sample?

A free sample is a product sample for checking when it is difficult to judge whether a product is “good” or “defective”. By using a free sample, you will be able to objectively judge the color gloss, gloss, surface scratches and roughness of the product.

Why Do You Need Sample Limit?

The main purpose for which a limit sample is required is to prevent the personalization of visual inspection. When the inspection is performed by human eyes rather than a machine, if there is no limit sample, the accuracy will vary depending on the person being inspected.

In addition, even if a certain person inspects, depending on the physical condition of the day, the judgment criteria for good and defective products may be blurred. Stable product quality cannot be achieved if the judgment criteria are different every time an inspection is performed. By using limit samples, you can suppress the variability.

Another purpose for which limit samples are required is to have a common understanding between the manufacturing company and the business partner. Even if only the manufacturing company has a limit sample, the business partner company cannot judge whether all the deliveries are good or not. Therefore, by having a limit sample, both companies will be able to check the quality of the product.

Differences from Standard Samples

If you use a limit sample, you can objectively judge whether it is a good product or a defective product, but what is often misunderstood here is the difference from the standard sample. If you are going to judge whether a manufactured product is good or defective, you may think that it would be good to have a sample that is manufactured accurately according to the drawing, a so-called standard sample.

The limit sample shows the boundary between good and defective products. If you use only standard samples as a standard, everything except those that are manufactured accurately according to the drawings will be defective. However, in reality, if it functions normally as a product, it may be judged to be a good product even if there is a slight error with the figures in the drawing. In order to ensure that products that function normally even if they do not follow the standard samples are not wasted, there are limit samples to know the last minute line.

By the way, in case it is difficult to judge even if you use a limit sample, it is also necessary to prepare another “Visual Inspection Standard”.

What Kind of Limit Sample Do You Need?

Among the samples used in visual inspection, there are also defective samples in addition to limit samples used to know the line of good products at the last minute, standard samples made accurately according to the drawings.

A defective sample is a sample to determine the conditions of a defective product. For example, if the height of the one produced according to the drawing is 5 cm and the limit sample is 4 .8cm, prepare a sample of 4.7 cm or less.

You may think that anything that does not meet the limit sample criteria should be considered defective. However, when inspecting visually, it is easy to detect large changes, but there is a problem that it is difficult to notice detailed changes. Therefore, a defective sample is to prepare a sample that assumes the detailed changes that are often common in advance, and to make it easier to find detailed changes by comparing with them.

How To Create Limit Sample?

When creating a limit sample, you generally have two choices: create an actual object or use a photograph. In both cases, there are many cases where the detailed parts are different from the product actually mass-produced when using the prototype stage as a sample, so it is created based on the good product and the defective product that came out at the mass production prototype stage.

In the case of the actual product, it is advantageous that detailed parts such as scratches and texture are easy to understand, but there is also a disadvantage that it takes time and effort to store and manage depending on the thing. In the case of photographs, the time and effort of storage and management is reduced, but if the shooting is not successful, it can not be used as a limit sample.

In addition, when creating a limit sample, it is necessary to obtain approval after confirming with the business partner. If you use a sample that has not been approved as a limit sample, you need to be careful because there is a risk that it will develop into trouble that is different from what the business partner assumed later.

  1. Operation Point of Limit Sample

The limit swatch does not work properly just by creating it. Specifically, it is necessary to carry out appropriate operations through steps such as “appropriate labeling,” “management using a ledger,” “appropriate storage,” “regular review,” and “update.” Let’s take a closer look at each step here.

  • Appropriately Label the Swatch

In the previous section, I explained that every time you create a limit sample, you must get approval from your business partner. Therefore, the first thing to do is to label it as a proof of approval. This allows people in the field to immediately know which one should be used as a limit sample for visual inspection. The main information on the label is the following 6 points.

  1. Specification title – Describe the specification number and specification name that clarify the conditions and contents that the product must meet.
  2. Product name – List the name of the product that is the basis of the free sample.
  3. Bad mode – Describes the bad mode that clearly indicates what kind of state is bad.
  4. Approval date – After confirming the created limit sample with the business partner, enter the date of approval.
  5. Management No. – Enter the number for managing the limit sample in your company.
  6. Date of expiry – Described when the supplier specifies the validity period of the limit sample.

The above information is described, and the person in charge of the company and the business partner affixed it as a label on both the limit sample and the defective sample.

  • Manage Using the Management Ledger

Approved limit samples are labeled and managed using a management ledger. In the management ledger, in addition to “management No.”, “product name”, “expiration date”, etc. written on the label, “storage location” is written.

This reduces the risk of not being able to find a limit sample when performing visual inspection, and enables smooth inspection. In addition, mistakes such as continuing to use limit samples that have expired are less likely to occur, and the risk of putting out useless defective products is reduced.

  • Keep Limit Samples Properly

Especially when managing limit samples of physical objects, you must also pay attention to the storage method. Of course, it is important to ensure that it is stored in the location listed in the management ledger, but even more indispensable is the management of the environment of the storage location.

If you store it in a place where the temperature difference is large depending on the time of day, or in a place where the sun is strongly exposed during the day, the risk of the limit sample deteriorating increases. If visual inspection is performed using a deteriorated limit sample, care must be taken because there is a risk that defective products may be regarded as good products.

In order to avoid such risks, in addition to securing a storage place that is as unlikely to deteriorate as possible, it is important to have a limit sample that will serve as a master for both your company and business partners, and to store it in a different place. As a result, it is possible to periodically check whether the limit sample at the manufacturing site has deteriorated, and it is also possible to have it compared with the master of the business partner, and it is always possible to make a judgment based on a certain standard.

  • Review Limit Samples on Regular Basis

Regular reviews are essential for proper operation of the limit swatches, but they have two purposes. One is to make sure that the limit sample is used. The other is to apply the changes to the specifications and the product itself to the sample.

Let’s take a closer look at each.

Check if limit samples are being used

This is a review to ensure that the limit samples created are not used in the field because they are difficult to understand, or that the way the photographs are taken is bad and does not function as a limit sample. Even though it has been approved by business partners, it is meaningless if it is not used in the field. After clarifying why it is not being used, we will make improvements so that it can be used in inspections.

Apply changes to the specifications or the product itself

Even though the specifications of the product have changed, if you use a limit sample that matches the specifications before the change, you will not be able to accurately judge whether it is a good product or a defective product. No matter how detailed the specification changes, we will always review the limit sample and use it after making corrections and improvements.

Update Limit Swatches on Regular Basis

In addition to regular review, limit samples must also be updated periodically. This is because, in addition to not functioning as a limit sample or changing specifications, it may deteriorate due to aging. Depending on the type of product, you should usually update at least once a year.

There are two types of limit sample updates: These are “new update” performed when a new limit sample is created, and “continuous renewal” performed when setting a new expiration date for a limit sample with an expiration date. When both are updated, let’s not forget to record the update date and time in the management ledger. In addition, limit samples that do not renew when they expire are always discarded and recorded in the management ledger.