Pewter -Made Part

For my pewter made part I decided to make a christmas tree decoration.

1. I firstly drew a rectangle of the size of my MDF block, 70mm by 120mm.

2. I then drew my chosen design within the area, making sure to keep a resonable distance around the sides of the design. I drew the design as I wanted it to appear and then split the small and large tree to two seperate blocks.

3. Because when the design is drilled out on the milling machine, a contour line needs to be added on the inside of the shape. The distance of the line depends on the size of the drill, in this case 2mm. This meant a 1mm contour line was essential so the shape was drilled accurately.

4. I then deleted the outside line and block filled the two trees in black. A block triangle is added as a funnel for pouring the pewter into the mould. Three lines are drawn between the triangle and tree for the metal to flow.

5. The two sides of MDF are milled on the CNC milling machine, one at a time.

6. After both sides have succesfully been milled out, a 'sprue' needs to be filed out, to ease the pouring of molten pewter into the mould.  

7. Clamp the two mould together with a spring clamp to ensure they are held together throughout the pouring. Place the clamped mould between heat blocks.

8. The pewter needs to be heated in a ladle until molten, and carefully pour into the mould until full. 

9. Leave until cool and solid. With the heat protection gloves still on, remove pewter part from the mould and run under the cold tap.  

10. Cleaning up: place pewter-part back into one side of the mould, to protect fingers from touching the board, and sand. Decrease the grain of the sanding board throughout the sanding to increase the finished quality. Repeat on both sides.

Overall I was pleased with my part, except for the two deep dints on the back from an unsmooth mould. I was unable to sand these out due to their deepness.

The Use of CNC Engraving/Milling Machines

In relation to ability, I think this was quite a simple method of designing and making a mould. Once the perimeter for the design is set 2D design is a simple piece of software to create a simple design for. It is a widely used piece of equipment in schools and is therefore a good addition to metalwork projects. It is a quick method as once the design is created the milling machine is doing all the work in a fraction of the time it would take to cut out the mould manually, and alot more accurately!

The one disadvantage of this process is that the mould will only last for two casts at most so if a project requied a multiple amount, other solutions may be more appropriate.

Metal Forming Techniques in Schools

Metal forming in schools appears to becoming less popular, with one of the main reasons being saftey issues. Although it would be a good project to use with CAD, and the creation of the moulds would be a suitable and resonably time consuming task,the pouring of the pewter would need to be extensively supervised and to be carried out in groups of no more than 4. It would also not be suitable for the younger end of KS3 and possibly more suitable for year 9's and into KS4 if they wish to use it within GCSE projects.