Tuesday, August 6, 2024

Assembly Design - Process Planning & Industrial Engineering Perspective

Lesson 65 of Industrial Engineering ONLINE Course.








Chapter of 2. Assembly Planning and Design - Halevi's Book


1 Introduction
Definitions

2.Why Assembly Planning
21 Assembly planning benefits
22 Design dilemma
23 Assembly dilemma

3. What is Assembly Oriented Planning 
3.1 Definition
3.2 Assembly techniques
3.2.2 Automatic assembly
3.2.3 Robotic assembly
324 Comparing of robots-human and automation

4 Design Constraints for Assembly
4.1.1 Reducing number of components
4.1.2 Parts variation
4.1.4 Placing the component into a product
4.2 Fastening
4.2.1 Joining with no separate fasteners required
4.2.3 Joining requiring more than One Separate Fastener

5 Component Design for Placement
5.1 Component which is nearly identical on both sides
5.2 Headed Fasteners
5.3 Components design for placement


Process planning provides instructions step by step to transform raw material into the form specified and defined by the engineering drawing of the part. Then it also provides instructions to assemble the parts into sub-assemblies and final assembly.

Why Assembly Planning?

1. To understand cost impact or estimate assembly cost and make efforts to reduce it.
2. To increase output of an existing product.
3. To understand quality impact and increase it.
4. To decide the assembly system to use in relation to batch quantity.
5. To plan flexible labor roles so that absenteeism does not disrupt production.

Assembly-oriented design means defining a product in its structure, geometry and material in such a way that an optimum can be achieved for selected assembly process which runs in a specific assembly system, for certain specified target criteria.

Gideon Halevi gives an example of using a shaft and tightening it with a nut on a mating component. In the first design there is a shoulder on the shaft. In the next alternative the shoulder on the shaft is removed, but an additional washer is added. In the third alternative, more wear resistant material is used for the shaft and shoulder is removed.


The three main assembly systems are:

1. Manual assembly
2. Automated assembly
3. Robotic assembly

1. Manual Assembly

Man can observe keenly, has inherent decision making ability based on the context and can provide motion in multiple ways. Because of his versatility, he can use simple tools to do assembly. He can identify defective parts before assembly and minimize poor quality. Manual assembly is economical in low volume - high product variety production systems.

2. Automatic Assembly

In high volume production of a single product, automated assembly that gives the lowest cost and highest productivity per unit time is possible. In automated assembly, the simplest design that is normally followed is to have a separate work station for each individual assembly operation. The assembly process is carried out on the initial part held in an assembly carrier. As the assembly carrier moves from station to station additional parts get added. The transfer mechanism of the carrier from station to station can be continuous or intermittent. The stations can be placed on a rotary table or they can be arranged in a straight line order. The carrier motion is categorized as rotary or in-line (straight line).

Assembly  Automation and Product Design, Boothroyd, 1991
https://books.google.co.in/books?id=XFtgaNFzMHQC    

3. Robotic Assembly

Using robots in assembly is one of the largest application areas for robots. Robots are appropriate for automating assembly of products in smaller volumes. If volume is large dedicate automation is economical. Where a variety exists in a product family, the programmable robot will work better.

The speed of robot assembly can be lower compared to dedicated automation. The automated assembly can deliver between fifteen to six parts per minute. Robotic assembly will produce between one and four parts per minutes.

To increase use of robots in assembly further, improvement in methods to deliver oriented parts is required and robots are to be available at lower prices. 

A computer simulation package will help in examining feasibility of robot assembly process.

4. Hybrid Automation - Manual Assembly Systems

When there is more customization and variety in products, it is seen that in early stages of assembly uniformity is more and later stages there is customization. So some initial assembly stations can be automated and later stages can be put under manual assembly.

Design Constraints for Assembly

Components

Reducing number of components
Parts variation
Placing the component into a product

Fastening
Joining with no separate fasteners required
Joining requiring more than One Separate Fastener


Reducing number of components

For each products reduce number of components so that assembly operations can be minimized.

Parts variation

In each product, variants are produced to increase market for the product by satisfying the desires of variety of market niches instead of only one standard product for the entire target market. In this case of product variants, effort has to be there to minimize unique products. The assembly of unique parts is placed at the end of assembly line.

Kinematics

Robots are single arm machines. Therefore, Halevi recommened that assembly operations are to be designed for single hand operation in case of robot assembly. Industrial engineers will remember that as part of principles of motion economy, it is recommended both hands should be used simultaneously, and both must do similar work instead of one hand being used for holding.

The easiest assembly action is to place a component down vertically onto a firm base. Hence at an assembly station, the base is first securely positioned and oriented. The assembly is carried out in a sandwich like operation. The assembly sequence needs to be planned for minimizing time.

Placing the component into a product

A horizontal and vertical datum are to be provided as a reference point based on a major component of the product which acts as a building nest for assembly. It is preferable not to move the assembly to a new jig as a new datum becomes necessary then. It is important consider ease of visual inspection/calibration/adjustment, and testing.

Facilitating Orientation

Orientation is easy and does not require lot thinking two cases.

1. Completely symmetrical components like ball bearing, cylinder, cube etc.
2. Completely asymmetrical components - There are special features in some portion of the component that make orientation a habit.

Design for Assembly
Slides - Presentation by Dr. Richard Farr - (Detailed Presentation)
https://www.slideshare.net/lizrf1/design-for-assembly-dfa
 Fastening Methods

Alternative methods

Joining with no separate fasteners required - using pressure
Joining requiring One Separate Fastener per joint
Joining requiring more than One Separate Fastener per joint (bolt, washer, nut)
Joining by heat (welding and heat sealing for plastics)

Component Design for Placement

 Component which is nearly identical on both sides
Headed Fasteners
Components design for placement

Component which is nearly identical on both sides

The correct side can be indicated by color coding.

Headed Fasteners

Screw, rivet, bolt etc.

To facilitate feeding down a tube, a head diameter to overall length of fastener ratio 1:1.25 is recommended

Components design for placement

Generous lead-in chamfers or radii have to be provided on mating components.

Shafts entering holes should be designed to be self-centering through design of shaft end shape.

Standardized fasteners are to be used instead of variation so that wrong parts do not jam feeders in case of errors.


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https://www.youtube.com/watch?v=Ac0SqxD-lDo

Channel for more related videos: https://www.youtube.com/channel/UCDv5DyUgl5YZFhNBFWTa7Uw

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Production Process Planning - Foundation for Production  and Production Industrial Engineering.


2023

https://www.cambridge.org/core/journals/ai-edam/article/abs/optimal-robotic-assembly-sequence-planning-with-tool-integrated-assembly-interference-matrix/4E39EA767B86CF6838657558284C4770

2022

https://medium.com/mlearning-ai/ai-solves-80-part-assembly-in-minutes-b63c3d5edcb9



DLMS: Ten Years of AI for Vehicle Assembly Process Planning

Nestor Rychtyckyj
Ford Motor Company
Manufacturing Quality and Business Systems, Vehicle Operations General Office
From: IAAI-1999 Proceedings.
https://www.aaai.org/Papers/IAAI/1999/IAAI99-116.pdf

Artificial intelligence techniques for assembly process planning
Cheung, Yen Ping (1991) Artificial intelligence techniques for assembly process planning. PhD thesis, University of Warwick.


Application and Implementation of the Structured Assembly Process Planning in A Auto Enterprise Based on TS16949
Jiakun Sun, Ying Wang, Fupeng Yin and Huihui Qiu.
MATEC Web of Conferences 51, 01013 (2016)
https://www.matec-conferences.org/articles/matecconf/abs/2016/14/matecconf_ic4m2016_01013/matecconf_ic4m2016_01013.html

Assembly Automation
Process Planning Is Critical to Success of Assembly Automation Projects
March 1, 2001
John Sprovieri

Advanced process planning in lean product and process development
https://ieeexplore.ieee.org/document/6297682

ASSEMBLY SEQUENCE PLANNING WITH THE PRINCIPLES OF DESIGN FOR ASSEMBLY
DS 80-4 Proceedings of the 20th International Conference on Engineering Design (ICED 15) Vol 4: Design for X, Design to X, Milan, Italy, 27-30.07.15
https://www.designsociety.org/publication/37787/ASSEMBLY+SEQUENCE+PLANNING+WITH+THE+PRINCIPLES+OF+DESIGN+FOR+ASSEMBLY


Search Google for "Assembly process planning" - Interesting results

Related Article

Design for Machining - Industrial Engineering and Productivity Aspects


Design for Manufacture and Assembly will be discussed in detail in product industrial engineering module.


Updated 6.8.2024, 6.8.2023,  4 August 2021,  19 July 2021
Pub 24 December 2020


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