1.4.1 Wasting

Wasting Processes

Wasting processes shape the object or component by the removal of material.

It is a subtractive process which, in some circumstances can be very wasteful. Some materials such as metals and polymers may be able to be recycled but the waste from wood cannot always be used to make products.

These are the processes available but not all are suitable for the full range of materials, for example chiseling is not suitable for plastics.

They are presented here in order of the typical amount of waste produced but this is only a guideline. For instance, drilling a very large hole could remove more waste than turning a small piece of wood.

Lathes (used for wood, metal, polymers, styrofoam)

This can either be a wood lathe (wood) or a centre lathe (which can use metal and polymers) but both involve the rotation of the material to be worked; hence the name turning.

A cutting tool then moves left to right and towards the centre to shape the material. The machine may also be a CNC controlled version which allows for greater speed and accuracy.

How a CNC lathe works

Chiseling and carving (Wood)

Only suitable for use with wood although you can use a cold chisel on metal for cutting through sheet metal. Flat chisels can be used to remove wood for making joints. Gouging chisels can be used for carving out wood to make decorative items.

Sanctuary of Truth - Pattaya

Milling (Metal and Plastic)

Milling is the machining process of using rotary cutters to remove material. Traditionally a milling machine would have cutters that could be moved in three axis and operated manually but with the advent of CNC machining the same procedure is computer controlled allowing for more complex shapes to be produced.

How Apple use CNC milling to make the Macbook unibody

Die cutting, creasing and folding (paper and board)

Products such as fold flat cardboard packaging are often produced from a flat sheet of corrugated cardboard which are supplied to manufacturers in a flat pack form. Such products are printed on one side and then cut and creased with a die or cutting tool.

Routering (Wood and Plastic)

Routering is very similar to milling in its use of rotary cutters to remove material but it is for softer materials such as wood, foam and some metals. It can be CNC operated or in hand-held form as a plunge router which can perform a variety of tasks from putting a profile on an edge to cutting our shapes from panels. It can also be mounted into a table allowing the user to feed material into the cutter rather than moving the router itself.

Planing (Wood)

Planing involves shaving away at the wood with a sharp blade which is mounted into the body of the plane. A variety of different planes are available and the process dates back thousands of years.

Cutting Wood

Here are a few examples of hand saws used primarily for wood.

Can you name them and what they are used for?

Cutting Metal

Here are the two main types of saw used primarily for metal although they can also be used on plastics. Electric saws can also have a metal blade fitted in order to cut soft and thin metals. Can you name them?

There are a few examples of electric saws. Some are hand-held while other are bench mounted. Can you name them?

Drilling (Wood, Metal and Plastic)

Holes in materials are generally made by using a drill and a drill bit. There are two main types of drill and again, can be hand powered or electrically powered. Can you name them?

Drill Bits (tools)

Different materials call for different types of drill bits and different speeds; metal should be slow and wood fast with plastic somewhere in between.

Filing

Files are used to apply a final shape to a product or to remove imperfections. There are several types of file ranging from rasps which remove a lot of wood quickly but leave a rough surface through to tiny needle files used for finishing jewelry.

Rasp file (rough)

Needles Files (small)

Abrasives

Abrasives are products that are used to affect the surface finish of a materials. On wood you would used glass/sandpaper to remove the rough surface and leave the wood smooth. Hence the term ‘sanding it down’. The lower the ‘grit’ number, the more coarse and abrasive the paper will be.

Wood, particularly after having a varnish or lacquer applied, can be given a final smooth finish by using wire wool.

Abrasives

On metal you would use emery cloth and/or silicon carbide (wet and dry) paper as glass paper is not durable enough and can scratch the surface. Metals can be given a smooth finish by using wire wool.

You can finish high quality metal items to a smooth and shiny surface by using metal polish such as Brasso.

Sanding Belt

Wet and Dry

Brasso

Abrasives

Many polymers used, such as Acrylic, are self finishing so do not need abrasives other than for cut edges.
For polymers you can use most abrasives but wet and dry works the best for a smooth finish. The cut edges of polymers can also be given a smooth finish by using wire wool.
You can also use metal polish on polymers such as Acrylic for a very smooth final finish.
Remember that you cut and file to shape then ‘sand’ to finish.
In other words, abrasives affect the surface finish and feel of the material rather than shaping it so never waste time trying to ‘sand’ something into shape unless it is a very soft material such as styrofoam.
“File to shape, sand to finish”

Summary

Wasting is a subtractive process. Any process that removes material to shape the object is a wasting technique.
Because of the nature of wood, it is commonly shaped through wasting techniques.
Metal and plastic can exist in a molten state so they are often formed or cast into the shape necessary. Wasting techniques are not used quite as much with those materials.
Wasting techniques are often the least environmentally friendly due to the amount of waste material but it can often be recycled or reused.
A range of tools and processes can be used to shape an object by removing materials
A range of abrasives are used to affect the surface finish of materials.

Revision notes

If you remove material it is a wasting technique (forming)

If you change shape by force/heat it is deforming (forming/redistribution)

If you change shape by changing state, it is reforming (redistribution)

If you join pieces together it is considered fabrication (also additive)