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Cord Pull
D&T Online
Submitted by: Geoff Howard
ReceptionWhole Class ProjectResistant MaterialsEngineering
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Lesson Context
A CNC Lathe introductory project

Resources Needed
CNC Lathe, CAD/CAM software, squared paper;
Round bar stock of a range of light metals, close grained timber and plastics suitable for machining.

Project Brief
Most homes include several pull cords to switch on lights or close blinds for example. Design and make a toggle to go on the end of such pull cords in your home.

Design and Manufacture
Investigate uses of pull cords in your own home and list those used (e.g. for lights, blinds, fans, curtains)
Sketch out, using squared paper, the profiles of some ideas for new designs based on a solid of revolution.
Use CAD software designed for use with your CNC lathe to produce your design on screen.
Test your design using a machining simulation program.
Produce your final design in your chosen material.

Expected Outcomes
CNC machined Cord Pulls in a variety of materials

Image
A Cord Pull example

Additional Information
When the profile is drawn out on squared paper, the intersection between its centre line and the right hand face of the bar stick is point X=0, Z=0.
Draw up a table of X and Z for each point on your design if you wish to edit the G-Codes generated by the software. Remember that in the X axis we use values of diameter and the Z axis gives negative values as we proceed towards the lathe chuck.

MS Word file of pupil hand-out