Process planning : Machining processes and parameters used to convert a piece part from an engineering drawing. The act of preparing detailed work instructions to produce a part. Defines in detail the process that transforms raw material into the desired form Manufacturing process Transform an Idea into a Saleable product

Examples of process plan Rough planDetailed plan The detailed process plan contains: Route Processes Process parameters Machine and tool selections Fixtures

REQUIREMENTS IN MANUAL PROCESS PLANNING Ability to interpret an engineering drawing. Familiar with manufacturing processes and practice. Familiar with tooling and fixtures. Know what resources are available in the shop. Know how to use reference books, such as machinability data handbook. Able to do computations on machining time and cost. Familiar with the raw materials. Know the relative costs of processes, tooling, and raw materials.

Steps of manual process planning: 1.Global analysis of the part 2.Elementary selection of machining processes, tools and cutting parameters 3.Definition of associated surfaces and choice of jobs and machine tools 4.Selection of machine tools 5.Sequencing the operations according to precedence relationships 6.Selection of positioning surfaces and clamping points (workpiece holders and dimensional data references) 7.Transfer of dimensions and tolerances in design to those in manufacturing 8.Determination of machining condition, time and cost 9.Final preparation of the file

1.Global analysis of the part Geometric Shape Tolerance Surface finish Size Material type Quantity Value of the product Urgency

One-of-a-kind and Small batch Objectives: Lead-time, Cost Approaches: process selection, use existing facilities. Mass production Objective: Cost Approaches: process design, optimization, materials selection, facilities design

2.Elementary selection of machining processes, tools and cutting parameters Selection of possible machining operations for each feature Tool and machining parameter selection for each feature 3.Definition of associated surfaces and choice of jobs and machine tools Requirement of position and orientation between features Grouping of individual operations in order to respect geometric conditions Selection of machines and tools for each group

4.Selection of machine tools Number of tools necessary to carry out the jobs Size of the batch Accuracy of selected operations 5.Sequencing the operations according to precedence relationships Dimensions with a datum as anteriority

Geometric tolerances with data references Technological constraints in order to execute operations properly

Economic constraints which reduce production costs and wear or breakage 7.Transfer of dimensions and tolerances in design to those in manufacturing Dimensions directly produced Dimensions resulted from a chain of dimensions 6. Selection of positioning surfaces and clamping points (workpiece holders and dimensional data references)

8. Determination of machining condition, time and cost 9. Final preparation of the file

Shortcomings of manual process planning: Time distribution: 15% technical decision making 40% data and table look-out and calculation 45% text and documents preparation Manufacturing logic remains in the process planners mind Often incomplete and inconsistent results …

PROCESS PLANNING CLASSIFICATION MANUAL COMPUTER-AIDED VARIANT GT based Computer aids for editing Parameters selection GENERATIVE Some kind of decision logic Decision tree/table Artificial Intelligence Objective-Oriented Still experience based AUTOMATIC Design understanding Geometric reasoning capability

ADVANTAGES 1. It can reduce the skill required of a planner. 2. It can reduce the process planning time. 3. It can reduce both process planning and manufacturing cost. 4. It can create more consistent plans. 5. It can produce more accurate plans. 6. It can increase productivity.

VARIANT PROCESS PLANNING

ADVANTAGES OF THE VARIANT APPROACH 1. Once a standard plan has been written, a variety of components can be planned. 2. Comparatively simple programming and installation (compared with generative systems) is required to implement a planning system. 3. The system is understandable, and the planner has control of the final plan. 4. It is easy to learn, and easy to use.

PROBLEMS ASSOCIATED WITH THE VARIANT APPROACH 1. The components to be planned are limited to similar components previously planned. 2. Experienced process planners are still required to modify the standard plan for the specific component. 3. Details of the plan cannot be generated. 4. Variant planning cannot be used in an entirely automated manufacturing system, without additional process planning.

GENERATIVE APPROACH A system which automatically synthesizes a process plan for a new component. (i) part description (ii) manufacturing databases (iii) decision making logic and algorithms MAJOR COMPONENTS:

ADVANTAGES OF THE GENERATIVE APPROACH 1. Generate consistent process plans rapidly; 2. New components can be planned as easily as existing components; 3. It has potential for integrating with an automated manufacturing facility to provide detailed control information.

Automatic process planning: Concerns all the aspects of manual process planning Automated sequence planning: Geometric constraints Technological constraints With the aim of minimizing: time machine change tool change setup change etc.

One approach: Automated machining sequence planning for milling 2.5D prismatic parts Use of feature based design Minimized tool changes Considering a single setup designing machinable components.FBD system

FEATURES IN DESIGN AND MANUFACTURING A high level geometry which includes a set of connected geometries. Its meaning is dependent upon the application domain. Design Feature vs Manufacturing Feature

DESIGN FEATURES For creating a shape For providing a function Slot feature

DATA ASSOCIATED WITH DESIGN FEATURES Mechanical Engineering Part Design Feature Type Dimension Location Tolerance Surface finish Function

MANUFACTURING FEATURES For process selection For fixturing Drilling Round hole Turning Rotational feature End milling Plane surface, Hole, profile, slot pocket Ball end millFree form surface BoringCylindrical shell ReamingCylindrical shell...

DATA ASSOCIATED WITH MANUFACTURING FEATURES Feature type Dimension Location Tolerance Surface finish Relations with other features Approach directions FEATURE RECOGNITION Extract and decompose features from a geometric model.

Pre-defined features in a feature libraryDesign Feature tree: Parent child relationship Child: at least one of its imaginary faces is coincident with a real face of the parent feature. Each parent feature must be produced before its child features. The number of necessary tool changes should be minimal. Key points in developing the algorithm

1.operation tree produced from the feature tree Components of the algorithm Nonfunctional islands are eliminated in the feature tree Feature operation tree Dimensional relationships 2.Operation matrix based on the operation tree Any row with -1 element could not be performed

3.index of priority (IOP) Sum of all elements in each row in the operation matrix The higher operation IOP, the earlier it is performed Process planning model: Internal representation system

Case study

Corresponding features Feature set

Feature tree

cutting tools and machining parameters determination by the system( from the feature tree )

Operation tree

Operation matrix from the operation tree Operation 1:1 is deleted

Second operation matrix Tool change precedes IOP

Last operation matrix

Process planning model

Optimum operation sequencing and tool selection One approach 1.Precedence constrains generating package (PCG) 2.Operation sequencing and tool selection package (OSTS) 1.PCG Geometrical and technological constraints for precedence detection Depth of machining

X and Y axes constraints Technological constraints such as for a hole Output:

2. OSTS Based on operation matrix IOP' (sequencing) Unless otherwise (minimum tools used): PR1: tool with higher frequency PR2: tool mostly used in last operations PR3: tool mostly used in all operations PR4: random selection Priorities: T* (minimum tool changes) IOP (sequencing)

Tolerance charting A technique for design specification enhancement through machining Information given in a tolerance chart: Raw stock dimensions and tolerances Machining sequence specification (datum, dimension, tolerance) Each operation’s stock removal and its tolerances Resulting dimensions and tolerances from determined sequences

DIMENSIONS 1.Condition dimension Dimension in the drawing and to be respected 2.Machining dimension (WD, MD, TD) Working Dimension (moving of the tool) Machine dimension (distance between to heads) Tool dimension (diameter, step,...)

RoughSemi finishfinish milling turning0.5Ø and length0.2Ø and length0.05Ø and length drilling broaching grinding boring Economic tolerances

rough0.5 Semi finish0.2 Finishing with tool0.1 Grinding0.05 Super finish0 Minimum stock removal Minimum Raw Dimension (RD)

TOL CD > OR =  TOL WD  WD = CD - Find the condition dimension ( all the final drawing dimension and all the minimum stock removal) - Find the chain corresponding to each condition dimension ( one chain per condition dimension) - Calculate the tolerances of the machining dimensions. -Calculate the machining dimensions (rough, semi finish and finish) and the raw dimensions. Methodology General rules:

Example: Final drawing Convert to bilateral tolerances

Calculation of WDs:

Calculation of WDs’ tolerances Thanks for the attention Good luck