Parting of Moulded Parts

Adapted from: http://www.solidworks.com/swexpress/april/200204_techtip_02.cfm

What is the different between this two chairs?

“Solid”stool by Patrick JouinChair One by Konstantin Grcic for Magis

Design optimised for moulding

Design optimised for layered-manufacturing

模mó模本、模范、模仿、模型、模压、模拟、模糊、模棱、模式、模特儿mú模板、模具、模样、模子

Design for Manufacturing

Zero draftimpossible to de-mould

Draft addedeasy to de-mould

form compromised

Change direction of pull or no. of parts

easy to de-mould but more complicated

Discussion

What is the general rule for product parting design?

Design the form as a blob

Try to find out a de-mouldable

direction of pull

Define direction of pull and part-

line

Resulting part-line too costly or risky

to make!

Divide problematic form to more parts

Number of parts exceed budget!

Add draft by modify the form

Form looks bad!Modify the form

Parting Follows Form

Myto by konstantin grcic

Form Follows Parting

Example - Art Lebedev Reflectius

Example – Electrolux Trilobite

Citroen C-Cactus concept

Product Design Considerations

There is always a trade-off between aesthetics, design considerations, and mouldability

Designer can only assure authenticity by taking drafting and parting decision in his own hand

Current main-stream CAD application can only perform automatic draft operation on straight-up side walls

For curved or double-curvature side walls draft feature must be place in the model early on