It is possible to carry out the coding of the parts in a visual way, identifying in a general way the physical characteristics of the parts and then giving them an appropriate classification. General form factors are defined from twists, straight shapes, the relationship between the height, length, and width dimensions of the parts, among others. At the conclusion of this process, the parts being coded should be part of a representative subset of the entire universe of products the organization produces.

The identification of part families and allows their practical and efficient allocation to a cell-based manufacturing system. This method is the most widely used because it allows the use of digital tools for the systematic storage and retrieval of the information being coded.

For the most part, parts classification and coding systems can be classified as follows:

• Systems that are based on design features of the parts.
• Systems based on the manufacturing characteristics of the parts.
• Systems that mix both types of part characteristics.

The main classification and coding systems used in the industry will be reviewed below.

To learn more about barcodes, check out the following video:

Coding systems

Not all parts classification and coding systems are suitable and applicable to all manufacturing organizations, as each company may have a unique and different set of parts to produce. Therefore, each organization needs to design its own coding methodology according to its needs, which implies great effort and the dedication of a great amount of time by the engineers in charge of this task.

The automation of classification and coding processes has benefited from modern image recognition and computer vision techniques. The incorporation of machine learning and artificial intelligence into manufacturing processes has been the basis for the development of technological solutions capable of classifying and coding large sets of part families in just a few minutes.
Among the main reasons for using a part coding system are the following:

 

There are various codes that can be obtained from companies specializing in computer-aided manufacturing systems, but whether the coding system used is developed in-house or obtained commercially, it must have the ability to communicate with the rest of the systems used in the organization, such as CNC machines and CAPP systems.

Part coding systems are composed of numeric characters, alphabetic characters, or a mixture of both. A code is assigned to each part, which may be given in terms of its design or manufacturing characteristics only. However, certain more complete and complex systems assign codes in terms of both characteristics. Depending on the type of method used to encode the parts, codes ranging from approximately 12 characters to 30 characters are possible.

According to Groover (2018), the features that are typically included in parts classification and coding systems are as follows:

Part design features

• Main dimensions
• Basic external shape
• Basic internal shape
• Length/diameter ratio
• Type of material
• Part function
• Tolerance
• Surface finish

Part manufacturing features

• Main process
• Operating sequence
• Lot size
• Annual production
• Machine tools
• Cutting tools
• Main dimensions
• Basic external shape
• Length/diameter ratio
• Type of material
• Tolerance
• Surface finish

In practice, there are several ways to classify coding methods, one of the most used divides them into (figure 1).

Figure 1. Classification of coding methods

7.1 Hierarchical coding

This type of coding is also known as monocode. In this code the meaning of the characters depends on their predecessor. With each character that is added to the code, the information of the previous element is expanded, making it impossible to try to interpret a character individually. The codes generated by this system are relatively short and contain a large amount of information. The main disadvantage of coding this way is its difficulty to be applied in a computerized system (Kalpakjian, 2020).

Example of hierarchical coding

 

7.2 Coding by attributes

They are also known as chain codes or polycodes. In this method, each character represents a characteristic, meaning, each character of the code or its position has no relation to the other characters. This system can generate relatively long codes that clearly identify the specific characteristics of a part and are compatible with most computational solutions.

As each character in the code has an independent meaning, it is necessary to reserve an element to represent each characteristic being coded. As a requirement for this type of coding, it is necessary to have a table indicating the correspondence between the characters and the characteristics of the parts they represent.

Figure 2 shows an example of a table used in attribute coding.

Figure 2.  Example of polycode

 

Such a table can be a matrix of considerable size. One of its main differences with the hierarchical code type is that the order of the columns and rows of the table is interchangeable, but once the design is decided, it must remain fixed. Below, is a very simple table with a coding by attributes, the table is self-explanatory.

Character to be used	First character Outer shape	Second character Inner shape	Third character External machining	Fourth character Finish part
1	Revolution	Solid	Winch	In gross
2	Prismatic	Revolution	Cylindrical surface grinding machine	Medium finish
3	Mixed	Prismatic	Milling machine	Fine finish
4	N/A	N/A	Brush	Mirror finish
5	N/A	N/A	Flat surface grinding machine	Coating

 

Use the table above to answer the following questions.

 

As can be seen, the example is made with a few characteristics, to perform a good attribute coding, in practice, the coding table should include as much information as possible about the parts to be coded.

7.3 Hybrid coding

Also known as coding of decision trees, these systems mix hierarchical and attribute coding. Hierarchical coding is used where possible and attribute coding is used for the rest of the characters required; in this way, these coding systems obtain all the basic information about the part being coded. It is the most widely used method for the classification and coding of parts for the formation of families since it allows representing as much information as possible about the characteristics of the parts to be coded.

The generated codes are between 6 and 30 characters long, but if only the design features are coded, they will most likely be no longer than 12 characters. If they include design and manufacturing features, more characters will be used; a suitable coding of this type will be between 20 and 30 elements.

There are several systems for parts classification and coding, among the most popular we can mention: Opitz, Multiclass and KK-3; all of them are hybrid coding systems, being really useful in parts design and machining applications. Figure 3 shows an example of the Opitz system representation.

Figure 3. Example of the Opitz system

METAL WORKING. (2022). GROUP TECHNOLOGY: OPERATIONAL EXCELLENCE IN THE INDUSTRY 4.0 ERA.
Retrieved from https://metalworkingmag.com/technical-articles/14704-group-technology-operational-excellence-in-the-industry-4-0-era
For educational purposes only.

 

In the following, the hybrid coding method will be exemplified from the tables used above. The hierarchical classification will be applied for the first digit (the part can only be classified as revolution or prismatic); the second character will be classified using the table by attributes and will represent the internal shape, the third character will also be classified using the table by attributes and will represent the type of machine to be used in the external machining, and the fourth character will be coded in a hierarchical manner and will refer to the presence or absence of holes in the part.

We will code a part with the following characteristics:

 

Selection of the coding system

The selection of a parts coding system for a manufacturing organization is made based on the objectives to be achieved and the complexity of the organization's parts manufacturing catalog. If the objective is to code simple parts from a relatively small manufacturing catalog, the hierarchical classification method can be used, which, as studied above, stores large amounts of information in a few code characters.

If the parts catalog and the variety of finished products are numerous, the most optimal system is attribute coding, with which it is possible to collect with the part code a large amount of information. 

Finally, if the parts catalog is large, the variety of products is wide, it is required to represent as much information as possible from the part and to have the facility to obtain a system in a commercial way that can be widely integrated. Then, the suggested coding method is the hybrid system.

Properly designed classification and coding systems of parts bring the following benefits:

1. Easy creation of part families.
2. Enable rapid recovery of the design characteristics of a part.
3. They avoid the creation of duplicate designs due to the recovery of information on previous parts, thus avoiding the need to redesign them.
4. Promote standard designs.
5. Improved parts cost, material estimates and processing times.
6. CNC machine programming is facilitated, given that for new parts it is possible to use part of the programs previously made.
7. It rationalizes the design and construction of supports or tools as they are reusable between parts of the same family.
8. They facilitate the introduction of computer-aided process planning (CAPP) by helping to identify certain parts of process plans previously implemented on similar parts.

The development of parts classification and coding systems has been a fundamental part of the evolution of group technology. Classification and coding systems are the basis of the family-of-parts concepts and are therefore the foundation on which group technology is based.

Coding systems have evolved from visual inspection of parts and their grouping by elementary characteristics to modern interactive or automatic computer-assisted systems, which allow more complex associations to be made.

The capacity of group technology increases with the selection of the classification and coding system that best suits the needs of the organization, therefore, knowing its fundamentals and the correct way to implement it is an indispensable requirement for any professional involved in modern manufacturing processes.

In the following topic, you will study the advantages and disadvantages of implementing group technology in the areas of design, manufacturing, and management of a manufacturing organization.

Make sure that you:

• Build hierarchical coding of technology groups.
• Create coding by attributes of technology groups.
• Make hybrid coding of technology groups.

• Groover, M. (2018). Automation Production System and Computer Integrated Manufacturing (5th ed.). United States: Pearson.
• Kalpakjian, S., and Schmid, S. (2020). Manufacturing Engineering and Technology (8th ed.). United States: Pearson Education.

Videos

To learn more about manufacturing systems, watch the following video:

• LJP - Mechanical. (2021, December 02). Manufacturing System - Parts Classification and Coding [Video file]. Retrieved from https://www.youtube.com/watch?v=_Nt4OU2dkkk

To learn more about group technology, watch the following video:

• Tarun Kumar Aseri. (2020, April 20). Group Technology (Part Classification and Part Coding) [Video file]. Retrieved from https://www.youtube.com/watch?v=eZnd_7z7UI4

Readings

To learn more about part ECLASS Standard, we recommend reading:

• Dudek, K. (2018). Announcing ECLASS Standard for Teamcenter Data Classification. Retrieved from https://blogs.sw.siemens.com/teamcenter/announcing-eclss-standard-for-teamcenter-data-classification/

To learn more about AI classification, we recommend reading:

• Doyle, K. (2021). You're in Luck – AI Classification and PLM Helps You Work Smarter! Retrieved from https://blogs.sw.siemens.com/teamcenter/youre-in-luck-ai-classification-and-plm-helps-you-work-smarter/?spr_cid=120_690

To learn more about automatic identification systems, we recommend reading:

• Pontius, N. (2022). 50 Top Automatic Identification Systems and Technology Tools for Data Capture. Retrieved from https://www.camcode.com/blog/top-automatic-identification-systems-and-technology-tools/

Description

Based on a set of parts, the student will define the hierarchical coding and develop an analysis of the design attributes that define them.

Objective

To identify the advantages of group technology from the implementation of a parts coding and classification system.

Requirements

Read topic 18.2 Parts classification and coding from the textbook.

• Groover, M. (2018). Automation Production System and Computer Integrated Manufacturing (5th ed.). United States: Pearson.

Instructions

Individually

1. From the components shown in the figure below, consider all the parts to be classified in terms of a characteristic.

Banerjie, I. (2012). Types of Screws.
Retrieved from  https://indiandiy.blogspot.com/2012/03/types-of-screws.html?m=1
For educational purposes only.

 

2. Then, perform hierarchical coding using at least five hierarchical levels.
3. Next, develop a list of at least five design attributes that you would use for part coding.
4. Moreover, create a parts catalog using the attribute coding system.
5. Finally, prepare a report on the development of the activity, and include in your conclusion the answer to the following question:
   1. Which coding system would you recommend implementing for a company intending to manufacture, in large quantities, only the parts shown in the figure? Why?

Evaluation criteria

1. Classify the parts and perform coding with five hierarchical levels.
2. Define five design attributes for each part shown and make the catalog with the indicated coding system.
3. Prepare the report incorporating your personal conclusions about the activity and the answers to the questions posed.

Description

The student will apply the knowledge acquired about coding systems to classify a set of parts, using the most appropriate method for each situation. In addition, he/she will answer a questionnaire with review questions.

Instructions

Individually

1. Answer questions 18.6 and 18.7 of the review question in chapter 18. Cellular Manufacturing of the textbook, click here.
   
   Groover, M. (2018). Automation Production System and Computer Integrated Manufacturing (5th ed.). United States: Pearson.

2. From the components shown in the following figure:
   1. Make a hierarchical code using at least four levels.
   2. Develop a code by attributes that includes at least four characters.

OLOGYMART. (n.d.). Flexible Shaft Coupling OD18mmx25mm CNC Stepper Motor Coupler Connector 6.35 To 8mm.
Retrieved from https://ologymart.com/products/flexible-shaft-coupling-od18mmx25mm-cnc-stepper-motor-coupler-connector-6-35-to-8mm?variant=22076026126417
For educational purposes only.

 

3. Conduct research on Mexican websites that deal in golf cart parts and components. Locate a part and identify the type of classification the original manufacturer used to classify it. Justify your answer.