Acrobat Project

Exploring One-Off Batch and Mass Production Techniques for

KS3

Rationale

One of the challenges of the increasing variety of technology available to students in KS3 is exploiting the benefits of new technologies, such as computer aided design and manufacture, without abandoning traditional hand-making skills. This project aims to address one-off, batch and mass production giving future designers an insight into modern techniques and future Ikea customers the ability to construct their flat-pack furniture.

Product

In this project the students will make an acrobat toy.

1st learning point: Levers

The action of the acrobat is generated using a pair of levers. A lever is a simple machine which gives us mechanical advantage, that is to allow us to do something quicker, more easily, or that we could not do in our own strength.

There are 3 different types of levers which give mechanical advantage.

The 3 different levers

First class lever:greatest advantage

Second class lever:medium advantage

Third class lever:least advantage

The 3 different methods of production:

One-off: a maker creates a single item in its entirety

Batch: a maker produces several identical items at once

Mass: great quantities of identical items are produced, sometimes continuously

Making the frame: jigFor batch production where several of the same item are made, instead of measuring and marking each individual piece, a device can be made to speed up the process. This is called a jig and can be seen in use making the acrobat frame:

Joining the frame

Clearance hole: these holes were seen being drilled with the aid of the jig; this hole allows the screw to pass easily through it.

Counter sink: this cone-shaped hole allows the screw head to sit flush with the surface of the wood.

Pilot hole: this hole is narrower than the thread of the screw to allow it to bite, but helps to guide the screw in a straight line and prevent the wood from splitting.

not flush flush

Hand-held drill technique

When using a hand-held drill it is important that the drill should:

1. Be introduced, maintained and removed at an angle of 90° to the wood.

2. Not be forced into the wood

3. Be supported with both hands if possible.

4. Be kept running during withdrawal.

Top tips for screwdrivers

When using a screwdriver it is helpful to use the following techniques:

1. Insert the screw into the pilot hole by hand and twist till thread bites.

2. Ensure screw, screwdriver and lower arm are all in a straight line.

3. Apply downward pressure while turning.

4. Once screw has started to bite, support screwdriver shaft with free hand.

Mass production• CAD: computer aided design Developing

designs by computer allows for alterations, modelling, and having a number of designers working on the same project without committing to production.

• CNC: computer numerically controlled This allows digital information from a computer to operate a manufacturing machine, e.g. a router or a laser cutter.

• CAM: computer aided manufacture

A computer instructs a machine how and what to cut/make; the advantage of this is that it is faster and more reliable than human control and adjustments can be made quickly by computer.

Designing the acrobat: Stage 1

Students should use 2D design to produce CAD templates for the body, arms and legs of their acrobats. These will then be cut out in batches using CAM. A common problem is ensuring that the parts fall within an acceptable size range. This is achieved by having a template box to check the size of parts against before submitting the parts as a complete file.

Stage 2

An important principle of generating CAD designs for milling machines is the use of a contour line that forms a cutting path for the tool around the image to be cut. This contour line must be set at a distance that is half the diameter of the cutting tool in order that the finished piece will be exactly the size that was drawn.

Stage 3Tessellating – it is important to arrange the images to be cut as close together as possible for the following reasons:

• Using as little material as possible reduces the impact on the environment and resources.

• Cutting as many images at once from a given sheet of material reduces machine setting-up time.

• Saving time and reducing material costs increases profitability.

Stage 4•To stop individual pieces coming loose when being cut and being damaged or damaging the CAM machine, small tabs are left connecting them to the main sheet.

• Students will need to cut around each piece to remove these tabs and free up the individual pieces.

•The pieces should then be smoothed prior to assembly.

Stage 5Drill holes in the arms, body and leg of the acrobat, which allow them to be joined and create pivot points so the acrobat will be able to swing.

The pivots are created by threading wire through the holes and using round-nose pliers to create a loop on either end to hold the wire in place.

Stage 6: final assembly

To connect the acrobat to the frame, string is ideal and to help thread this through the acrobat’s arms and frame it is helpful to tightly wrap a small piece of sellotape around the end of the string similar to the end of a shoelace.

It is important when attaching the acrobat that it is in an ‘upside down’ position so that when it falls to a position of rest a twist is generated in the strings.

Using the acrobatTo get the acrobat to swing, students should squeeze the bottom of the frame and then immediately relax. This will allow the levers to tension the twisted string and make the acrobat swing.

The acrobat can be encouraged to perform a handstand by squeezing and holding the frame.

Possible homework/extension work

• Research CAD/CAM and their applications.

• Create a presentation on one-off batch and mass production suggesting suitable products to be made using each technique.

• Draw and isometric sketch of their completed acrobat toy taking care to show accurately the layering of the parts of their acrobat.

• Create a leaflet to advertise their acrobat product which should include a company name, logo, pricing, special offers and, perhaps, a range of similar products.

Useful ResourcesClick these links

• Downloadable SMARTboard gallery illustration of levers

• 2D Design by Techsoft

• Denford CAM machine information