ME 530 – Designing for ProductionME 530 Designing for Production

Chp 5 - Manufacturing Processes in Design

D A T l B dMechanical Engineering Dr. A. Tolga BozdanaAssistant Professor

Mechanical EngineeringUniversity of Gaziantep

Classification of Manufacturing Processes

The common methods of material processing are as follows:

1 Solidification (casting) processes: molten metal plastic or glass casting1. Solidification (casting) processes: molten metal, plastic or glass casting

2. Deformation processes: forging, rolling, extrusion, etc.

3. Material removal or cutting (machining) processes: turning, milling, drilling, etc.

4 P l i i j ti ldi th f i t4. Polymer processing: injection molding, thermoforming, etc.

5. Powder processing: sintering, compaction, and so on.

6. Joining processes: welding, soldering, riveting, bolting, etc.

7. Heat and surface treatment processes: carburizing, nitriding, electroplating, etc.

8. Advanced processes: EDM, ECM, waterjet, laser machining/ablation, etc.8. Advanced processes: EDM, ECM, waterjet, laser machining/ablation, etc.

9. Assembly processes: subassembly of finished products.

1

Some TerminologyFinal products made by the industries can be divided into two major classes:

Consumer goods: products purchased directly by consumers (e.g. TV, car, tires etc.)

Capital goods: purchased by other companies to produce goods and supply services(e.g. aircraft, machine tools, construction equipment etc.)

Production variety: refers toProduction rate: refers to the number of Production variety: refers todifferent product designs/typesthat are produced in the plant.

Production rate: refers to the number ofproducts produced per unit time (ñ), e.g.part/hour.

Production quantity: refers to the number

p p

q yof products produced annually (n):

low production: n < 102low production: n < 10

medium production: 102 < n < 104

high production: 104 < n

2

high production: 104 < n

Break-Even Analysis This analysis is conducted to determine “break-even point” for a product where its production

cost (i.e. total cost) is equal to its revenue (i.e. money earned by sales).

T t l t f d t i l fi d d i bl t Total cost of a product involves fixed and variable costs:

– Fixed Costs: costs that are not directly related to level of production (e.g. .rents and rates, research & development marketing machinery administration etc )research & development, marketing, machinery, administration, etc.)

– Variable Costs: vary directly with level of production (e.g. raw materials, labour, tooling, etc.)

PROFITosts

V i bl

PROFIT

Break‐Even Pointal

es & Co

Variable Costs

Sa

Fixed Costs

LOSS

3

Costs

Production Quantity

Factors in Process Selection1. Cost of manufacture

The most important factor in the selection of nC

nCCC LC

M ~

manufacturing process and material.

Consider the life cycle cost of a productCM : material cost per unit

CC : capital cost of machinery and toolingallowing for maintenance and disposal.

The unit cost of a part (C) depends upon

p y g

CL : labour cost per unit time

n : production quantityp ( ) p pthe material, tooling and labour costs. ñ : production rate

2. Quantity of parts (Production Volume)

It refers to the minimum number of parts to justify the use of manufacturing process It refers to the minimum number of parts to justify the use of manufacturing process.

The concept of economical lot size: the break-even volume (i.e. the optimumproduction quantity for a product at desired level of production with profits).

The concept of flexibility in manufacturing: related with the production variety

4

(e.g. a process can be adapted to produce different products and/or variations ofthe same product).

Factors in Process Selection3. Complexity

The complexity of a part refers to its shape, size and type/number of features on it.

Most mechanical parts have 3D shape although sheet-metal parts are simply 2D.

Parts can also be symmetrical or nonsymmetrical.y y

Many processes will not allow the manufacture of parts with undercuts.

Thus candidate processes are defined based on the complexity of part geometry Thus, candidate processes are defined based on the complexity of part geometry.

4 Materials4. Materials

Functional requirements (properties of materials) play an important role.

Melting point, level of deformation, strength and ductility are usually the chief factors.

For instance, the melting point of material determines applicable casting processes.

Also, some materials may be too brittle for shaping by deformation processes while others may be too reactive to have good weldability.

5 The next slide shows Prima selection matrix for material and process selection.

Prima Selection Matrix

6Courtesy of: Process Selection: From Design to Manufacture, K.J. Swift & J.D. Booker, 2003

Factors in Process Selection

5. Required quality of the part

The quality of the part is defined by three aspects:

1. Freedom from internal defects (voids, porosity, micro cracks, segregation) andexternal or surface defects (surface cracks, extreme roughness, discoloration).

2. Improved surface finish (i.e. lower surface roughness) of a part determines itsappearance, affects the assembly with other parts, and increases its resistance tocorrosion, fatigue and wear.

3. Good dimensional accuracy and meeting tolerances in order to justify the use ofy g j yselected material and process for the manufacture of part for achieving requiredfunctionality without incurring extra costs.

Concluding Remarks:g

The achievement of good quality in above aspects is influenced by producibility ofindividual parts as well as the assembly of parts together.

7

p y p g

For this purpose, the design methodologies (DFM / DFA) should be incorporated.

DFM and DFA GuidelinesDesign for Manufacturing (DFM)

1. Minimise total number of parts (without making other parts too heavy or complex)

2. Standardise the components (to reduce costs and to enhance quality)

3. Use common parts across product lines (use same materials, parts and subassemblies)

4 D i ltif ti l t ( t t t l b d i )4. Design multifunctional parts (e.g. a part may serve as a structural member and a spring)

5. Design parts for the ease of fabrication (affects material selection)

6 A id t ti ht t l (t d t ith t d t i ti th f ti lit )6. Avoid too tight tolerances (to reduce costs without deteriorating the functionality)

7. Avoid or minimise the secondary operations (unless required for special/aesthetic purpose)

8 Utilise the special characteristics of processes (care about built in causes or side effects)8. Utilise the special characteristics of processes (care about built-in causes or side effects)

Design for Assembly (DFA)

1. Minimise the total number of parts (part not need to be assembled is not required in design)

2. Minimise the assembly surfaces (fewer surfaces need to be prepared for assembly)

3. Avoid separate fasteners (snap fits must be preferred wherever possible instead of screws)

4. Minimise assembly direction (design parts to be assembled from one direction)

5. Maximise compliance in assembly (adjust assembly forces required for non-identical parts)

6. Minimise handling in assembly (design parts so that assembly positions are easy to achieve)

DFM – Casting Guidelines

9

DFM – Casting Guidelines

Prevent shrinkage cavity.

10

DFM – Sheet Forming Guidelines

11

DFM – Sheet Forming Guidelines

12

DFM – Injection Moulding Guidelines

13

DFM – Machining Guidelines

14

DFM – Machining Guidelines

15

DFA – General Guidelines

16

DFA – Handling Guidelines

17

DFA – Joining Guidelines

18

DFA – Insertion Guidelines

19

DFA – System Guidelines

20