1.4 MULTI-DOMAIN PLANNING

In both examples so far the process domain has been limited to machining. It is very unusual to find a part that is manufactured using one type of an industrial process, such as machining only. Therefore another important test of the planner was planning for a product with mixed operation types and parts. The part selected is shown below. The product is a paper clip in the form of a ‘clothes pin’. The clip has two halves and a connecting spring. On one of the sides there is an advertising logo embossed on. The same side also has a hole drilled into it so that the clip may be mounted on a wall. In total there are a number of possible technologies that may be applied to the part. First, the spring is quite straight forward, and only involves the forming of some wire. In the second case, either of the clip halves could be made by injection molding (this was used in the actual production of the sample product used). But, in other cases, it is possible to machine the entire part from a piece of polypropylene. The decision can be based on the quantities of parts to be produced. For example, to machine two halves of a clip for a prototype might only cost a few hundred dollars, as opposed to $50,000 to $100,000 for molds for injection molding (the figure are based on my personal experience). A graphical representation of the clip is shown below.

 

Figure 1.2 A Test Part - A Large Plastic Clothes Pin

 

// This file contains a test part for the BCAPP system. The part is a

// large Plastic Clothes peg which is intended for use as an paper

// holder. It is also has an embossed logo on the side.

// -------------------- Main Geometry Definition ---------------------

//

 

main Big_Clothes_Pin {

EQUATION: ( : Spring;attach_spring Logo_Side;position_logo_side

Clip_half )

}

// ------------------ Assembly and positioning information ----------

Package {

quantity = 20

}

attach_spring {

translate_y = -0.4

translate_z = -0.275

}

position_logo_side {

translate_z = 0.55

rotate_y = 180

}

// -------------------- Defintion of Logo Side of Clip --------------

Logo_Side {

EQUATION: ( : ( & Clip_half ( ~ Screw_hole );position_screw_hole

);add_logo )

}

Screw_hole {

EQUATION: ( + HOLE CHAMFER )

}

HOLE {

form = CYLINDER

radius = 0.06

height = 0.6

}

CHAMFER {

form = CONE

radius = 0.125

height = 0.25

translate_z = -0.18

}

position_screw_hole {

translate_y = 0.85

}

add_logo {

operation = emboss

// description = ‘ add CBS logo ‘

}

// ---------- This is the box to put the pins into -------------------

Box {

description = #10_standard_box

EQUATION: ( & OUTSIDE ( ~ INSIDE ) )

}

Figure 1.3 Big Clothes Peg Product Description File

OUTSIDE {

form = BLOCK

width = 15.2

depth = 6.1

height = 1.3

translate_z = -0.1001

}

INSIDE {

form = BLOCK

width = 15

depth = 5.9

height = 1.1

}

// ---------- This is the clip spring (This is a tough definition) ---

Spring {

form = SPRING

ends = L

inside_radius = 0.12

outside_radius = 0.2

length = 1.50

turns = 14.5

rotate_y = 90

}

// ------------ The geometry for one half of the clip is defined here

Clip_half {

EQUATION: ( & ( ~ B ) ( ~ C ) ( & A E ) ( ~ D ) )

material = polypropylene

color = hong_kong_red

}

A {

form = BLOCK

width = 1.4

depth = 5.9

height = 0.55

material = polypropylene

}

B {

form = CYLINDER

radius = 0.28

height = 1.45

translate_x = 0.275

translate_y = 1.95

rotate_y = 90

}

C {

form = CYLINDER

radius = 0.1

height = 1.45

translate_x = -0.275

translate_y = 1.2

rotate_y = 90

}