CAD/CAM Integration: Process Control

Week-2

2/11/2012 1

Process planning

• Process planning is the link between the “Design” and the “Making” of a product

• If we are to use computer aided software then the process planning also has to be automated (computerized)

• Process planning is defined as the function in a production facility that determines which processes and design parameters to be used in the making of the product

2/11/2012 2

2/11/2012 3

Process planning output

• A plan that describes the sequence of selected manufacturing process or assembly operations

• Also called operations sheet, route sheet, operation planning summary

• It includes tool design and selection, jigs and fixtures design and selection

• Factors influencing process planning – Part geometry – Accuracy and surface finish – Production quantity – Machines and facilities Availability

2/11/2012 4

Manual Approach

• A skilled person studies the design sheet and develop the instructions required to make the part

• For small machine shops with skilled people this can be enough to proceed with production

• If the production line is automated the process plan would contain the details of each operation

• The process planner has to be an expert with machine operations, tooling, material, standard practice and cost

2/11/2012 5

Steps of process planning (1)

• Study over all shape of the part – Identify basic structure of the part – Potential difficulties in its production – Is part too long or thin…

• Determine the best raw material shape – By determining the outer envelope of the part – Reduce waste by choosing best stock material – Stock is ¼ inch larger than finished part dimensions

• Identify datum surfaces and determine setups – Determine minimum number of setups required to

machine

2/11/2012 6

Steps of process planning (2)

• Identify part features – Shapes comprising the part’s features or subfeatures

determine the shapes of the TOOLS, movement of MACHINE, and tool PATH of cutting

– Group part features based on required setups – Order the sequence of operation – Select tool for each operation – Select and design fixtures for each setup – Make final check on the plan – Generate detailed plans for producing individual features

• Choosing feeds and speed, estimating costs and time

– prepare the final process plan document

2/11/2012 7

Variant approach

• Advanced manual planning

• The manual process plan is stored in database

• Database are available for certain family of parts (group)

• Each part is assigned a code based on its features and saved in a certain group

• A new part has to be given a code that describes the part using the group technology concept

• Save time and make consistent plans

2/11/2012 9

Machining features and subfeatures

Features Sub-Features

2/11/2012 10

Example: process control

• Rotational part

• Use lathe machine

• Find the datum surfaces

• How many setups needed for surfaces and threading

2/11/2012 11

Solution

Setup 1 • Chucking (fixing) the workpiece • Turn S3 to 100 mm diam • Face S1 • Core drill S2 • Counter bore S4, S5 Setup 2 • Turn S6 to 50mm diameter • Undercut the neck • Thread S6 • Face S7 Setup 3 • Fix the workpiece from S1 and S2 • Mark six holes, S8 • Center drill and drill six holes

2/11/2012 12