Option C: CAD/CAM

C 2 – C A M S Y S T E M S

Additive manufacturing techniques.

 The manufacture of 3D parts by depositing molten material in a series of layers.

Subtractive manufacturing techniques (wasting).

 The manufacture of 3D parts by removing (cutting) unwanted material from a block.

Compare subtractive and additive manufacturing techniques.

 Subtractive manufacturing techniques remove material (waste) to manufacture parts.  Additive products have minimal wastage and the end product is built from a number of parts or a continuous extrusion of material.

Describe a Laser Cutter.

 A device that is able to laser cut and engrave 2D shapes.

Describe Rapid Prototyping (RP).

 A device that is able to produce a complete product including internal details.

Describe a Plotter Cutter.

 A device that is used to cut 2D shapes from card and vinyl.

Explain how CNC routers, milling machines, laser cutters and plotter cutter machines can be used to manufacture a variety of outcomes (subtractive).

 Consider a range of products that have been made using subtractive CNC equipment, for example, signs, vacuum form moulds, flat-pack furniture.

Explain how RP (rapid prototyping) machines can be used to manufacture a variety of outcomes (additive).

 Consider how rapid prototyping has been used to reduce development time and how one-off products are made for different situations.

Explain a situation in which it would be advantageous to use subtractive or additive manufacturing when making a product.

 Use product examples to illustrate the advantages of both processes.

Explain how a variety of tools can be used to make a complex outcome.

 Multi-tool CNC machines are used where the outcome requires more than one cutting process.

 For example, a CNC lathe is able to drill, ream, cut and part off.

Discuss the advantages and disadvantages of using large or small-diameter tools when machining.

 Large-diameter tools cut a larger area, thus reducing the amount of time needed to complete a task.  However, large-diameter tools leave large radiuses in internal corners.  Small-diameter tools have to use a higher spindle speed, and feed rate is normally slower, but they are able to perform more intricate jobs.

Define Machine Tool Step Variable.    This applies to 3D profiling. It is the amount of tool that passes over work already cut and determines the quality of the finished surface. It is expressed as a percentage—the higher the quality, the higher the percentage.

Outline how the machine tool step over variables can determine the output quality of a product.

 When using a ball nose cutter for 3D profiling, the tool step over should be reduced to give a better quality finish.

Raster, spiral and pocket cutting to manufacture.

   Raster cutting is where the tool path cuts in straight

X,Y paths.

Spiral cutting is where the tool path is circular, which is especially useful for round and curved objects. Pocket cutting is where the tool path is determined by individual Z coordinates across the product.

Discuss how machining paths alter the quality of a product and amount of time required in order to produce it (consider raster, spiral and pocket machining).

 Use post-processing software to simulate the amount of time needed to cut a product using raster, spiral and pocket machining techniques.

Limitations of using three-axis machining when making a 3D product.

 Consider undercuts and a flat base.

G code.

 Coordination-based code that also includes feed speed and stop/start

Outline how a 3D CAD drawing is converted into a CNC file using G codes.

  3D CAD drawings are converted to G code using post-processor software such as GeoCam.

Drawings are exported as an STL file, which triangulates the design, allowing the software to determine the path of X,Y,Z coordinates.

Feed Speed.  The feed speed is the rate at which the cutting tool moves in X, Y and Z paths

How feed speeds change depending on material and size of tool.

   Metals are cut at a slower feed rate than that of wood due to the hardness of the material. A larger diameter tool will waste more material, thus causing its feed speed to be reduced. Spindle speed is also altered to suit material and tool diameter.

How limitations of tooling can affect the manner in which an object can be designed and manufactured.

  The limitations of tool length and diameter affect the final design and manufacture of a product.

Internal corners will all have radius and deep pockets will not be able to be cut by small diameter tools.