Project Overview  Structural part Introduction  Laser cutting & forming  Model Making  Designing & Developing  Manufacturing  Building & Analysing

LESSON 02

LESSON 2 STARTER Key words: CAD, Library, heat processes, acrylic, MDF, profile, forming. Learning objective: Learn how to create laser cut sets of parts, form thermoplastic component parts using heat and equipment, and understand how to build a complex structural design using plastic parts. Laser cutting is a wasting or subtractive process, in that it cuts and removes material to create parts and products. How has the designer planned for the intelligent manufacture of the VEX acrylic parts here? What do you think they were trying to do? Observing the cutting process (see optional video), how could the process be more efficient? How could businesses use CAD drawings effectively and in a cost effective way? (What rules might they follow?)

Laser Cut Part Forming & Building Designing for laser cutting This screen shot is from the software running the laser cutter (in this case the CTR Laser). The designer has looked to: - waste as little space as possible - waste as little material as possible - leave little unusable waste - ensure certain parts cut before others (coloured linework) - bunched the linework nearest to the source of the laser on the machine (top left) How do each of these make efficient cutting? How could this file be cut more efficiently?

Laser Cut Part Forming & Building Designing for laser cutting Power vs Speed Software running laser cutters provide certain options. In this instance, the order of cutting, the speed of cutting and the power of the laser can be set. What would happen if the black line work cut before the red line work? What would happen if we increased the speed? What would happen if we decreased the power?

Laser Cut Part Forming & Building Forming plastics Thermo plastics such as acrylic can be heated to a softening temperature, then bent and shaped before the temperature cools to a point where the rigid quality of the material returns. In applying heat, we are changing the properties of the material, in favour of the maker. Step 1: line up the parts on the strip heater and soften. Step 2: Check to see if they are soft Step 3: Form against a good right angle (here a new bench hook) Task: make notes (either write or sketch) of the process of forming acrylic parts.

Laser Cut Part Forming & Building Task: Using the guidance below, make some formed acrylic parts for a clawbot Simple formings such as the ends of the chassis rail are easy to form, but longer lengths need some thought… Using accurate squared blocks of wood can help to force cooling plastic to stay in place as it hardens as shown here. Using a set of steel rulers can help support acrylic parts over the heating wire without risk of them touching the wire. Reminder Task: keep making notes on technique.

Laser Cut Part Forming & Building Check for accuracy Your parts need some level of consistency in their size and shape. As laser cut parts before forming, they are matching. In forming, you must try to maintain this quality… If two parts do not match, you could reheat one of them, which will revert to its original shape due to the “memory” of plastics. If, as in this case, parts are consistently curving during forming, you have two choices: 1. make a jig that prevents or restricts this negative aesthetic and forming 2. Accept the level of inaccuracy (a lack of tolerance) only if it is consistent across all similar pars. Task: sketch a possible jig design to form the claw parts (left) and/or the chassis rails (right)

Compare the components Look at the acrylic parts in direct comparison to the metal (steel) parts for VEX. Task: List as many ways in which they are a. different b. the same Also compare parts that you have formed the same way each time. How have you achieved: a. matching forming b. differences Laser Cut Part Forming & Building

Build the frame Task: Using the existing VEX bearings, pop rivets, screws and nuts, build yourself the frame of the VEX Clawbot. Start by laying the components into the arrangement Then build the frame using the fixings and tools provided Laser Cut Part Forming & Building

3D printing as well? If you are also 3D printing VEX parts, or have done the 3D print unit already, now is the time to combine both manufactured part sets. Considerations to make: 1. Use screws instead of pop rivets for connections 2. Or use nail varnish to bond the connections 3. Explore the tolerance of parts to one another 4. Tight parts to the acrylic frame tightly 5. Using locking screws for the claw Laser Cut Part Forming & Building

LESSON 2 PLENARY As a class, let us consider the following questions? A. If we had used a thermoset plastic for the parts today, instead of thermos plastic, what would have been the result? B. How was intolerance in the parts avoided in the laser cut parts? C. How was intolerance a result of the forming techniques used with the laser cut parts? D. How do jigs, formers and templates potentially support the forming of plastic parts more accurately?

Summary Today you have:  Learnt the related issues that apply to laser cut parts that are subsequently formed  Learnt about thermoplastics, their properties, and how to form them using equipment  Built a structure using accurately cut and formed components Learning objective: Learn how to create laser cut sets of parts, form thermoplastic component parts using heat and equipment, and understand how to build a complex structural design using plastic parts.