Wastage and Addition Techniques


Wastage and Addition Techniques, figure 1

Brazing, soldering and welding all use molten metal to join metal together. Soldering uses solder melted at a relatively low temperature to join metal. It’s particularly used for electrical circuits and plumbing joints. Brazing heats joints to a higher temperature and uses brass to flood the joints. The strongest of all of the addition joints is welding which uses an electrical current to melt welding rod to flow together and cool between joints. Polymer can also be welded with plastic rod.

Lamination sandwiches layers together to strengthen or protect, plastic laminated paper, foam board, goretex fabric and plywood are all examples of lamination.

3D printing adds material in layers suirted through a nozzle to print the CAD drawing sent to it. 3D printing mainly prints plastic but metal, resin and food printing is all being developed.

Batik is a decorative textile technique where hot wax is painted onto cotton fabric with a brush or Tjanting tool, this creates a resist where dye cannot soak in. The areas around the wax are dyed and when dry the wax is ironed and melted off.

Sewing is an addition that can be done by hand or on a sewing machine, it can be used to join fabric or add decoration on the fabric. Pleats, gathers, darts, tucks, elastic shirring, godets and under stitching can be added to improve shape and drape to clothing.

Interfacing and boning can be bonded or sewn into fabrics to create shape, rigidity and structure.

Bonding any material together takes adhesive glue to stick it. Different glues are developed for different jobs, PVA for wood and paper, epoxy resin for most materials and liquid solvent cement for polymers.

Printing adds ink to decorate paper and board. Lithography is where an oil based ink and water are transferred onto an aluminium plate which has the image areas treated with a chemical which repels water and attracts the ink. Flexography uses a flexible printing roller to coat surfaces. Screen printing squeezes ink through a frame which has a mesh image on it. Digital printing uses cyan, magenta, yellow and black (CMYK) to create all the colours necessary, inkjets and laser printers enable you to send an image directly from your computer to print.


Tools, equipment and processes:

There are a range of tools, equipment and processes that can be used to shape, fabricate, construct and assemble high quality products and prototypes.

Wastage and Addition Techniques, figure 1

Die cutting is the cutting of a shape by pressing a die cut shape through the material. Dies are a sharp metal blade fixed into a block in the shape of the cut, rounded metal edges can also be in the block to create creases. Can be used on paper, thin wood and polymer sheets.

Perforation is a line of cuts through thin material which create an easily folded and ripped line such as cheque books and raffle tickets. A perforating blade can roll over the material or press down like a die cutter.

Abrading is the grinding and polishing of a material to change its shape.

Lathes turn a long length of material with specialist shaped tools. Turning spins the material round whilst layers are shaved off. Turning is used for items like furniture and stair spindles.

Milling is a similar technique mainly used for metal work, a thin layer of metal is removed each turn at a carefully measured depth and speed. It can produce a really accurate finish.

Sawing is the oldest and most basic wastage technique, saws are used to cut away material. Different saws are available for different materials, which have a variety of shaped blades depending on what you’re cutting. Tenon, jigsaw, scroll and coping are all different types of saws. A mortice can cut slots into wood for a tenon to fit in to make a mortice and tenon joint.

Drilling uses a circular bit to create holes in materials, hand or electric drills can create holes through all materials. Drill bits come in a variety of standard sizes to fit other standard components. The tip of a drill is shaped differently to suit different materials such as wood and stone. A wider hole can be countersunk in first to allow screws or bolts to be flat (flush) to the surface of the material. Work would need to be held in place safely whilst drilling or cutting with a vice or clamp. Holes drilled into metal can have a thread tapped through them to allow a screw or bolt to be held.

Shearing is a method of cutting sheet material, particularly metal or flexible polymers. Shears use the same method as scissors but stronger to cut through tougher materials.

Overlockers can be used to join or edge fabrics using 2,3 or 4 threads to sew together whilst a blade trims the edges.