This page contains more detailed information on how Styrotech CNC calculates pricing, and is based on the points summarised on the previous page.

To recap, when it comes to calculating pricing for CNC machining and cutting jobs, it can be quite difficult to set and publish a range of definitive prices without creating a complex formula.

The key determinants of pricing a CNC job are usually:
- The size of the object to be machined,
- The complexity of the shape (i.e. how many ‘binary surfaces’ it contains),
- The raw material to be used,
- The quality of finish that’s required.

Clearly there are differences in the capabilities of each machine. For example, when preparing quotations we’ll consider if the job demands 3 or 5-axis cutting, what the dimensional parameters are and the processing speed of each machine, which will determine how long it will take to actually ‘cut’ – a larger object will take longer to cut than a smaller one. Each of these factors combine to determine which machine is able to complete a project, and how long it will take to finish, which in turn helps determine the cost of a job, and when it can be slotted into the production schedule. In conjunction with this, we’ll look carefully at the size and shape of the object in question. The most critical aspect is confirming how complex the shape is, and how many ‘binary surfaces’ are on it. 

For example, take two given objects of the same size:

The first is a simple object (for example a keel bulb, rudder or centerboard core, as shown above left), which due to its shape has few ‘binary surfaces’ in it (which the CNC machine interprets as the shape it needs to cut). Basically, the fewer binary surfaces on an object, the less time it will take to cut, and hence it’ll cost less (but this of course is affected by its size - larger objects, no matter how simple the shape, will take longer to cut).  The second object is about the same size, but is a more complex shape featuring considerably more binary surfaces (as per the image above right) so because of this, the object will take longer to cut, and thus be more expensive.

The material to be used will affect the machining time and hence the price. Styrotech CNC is currently able to machine polystyrene, all sorts of woods, plastics, EVA and urethane foams. Each one of these materials requires a different machining strategy. Take for example a 2D sheet cutting job. If the material to be cut is 3mm thick, it will only take one pass to cut each geometry (a geometry refers to the time that the CNC machines cutting tool is ‘in’ the job, cutting, before needing to be relocated to the next geometry. The image above right demonstrate a simple, 2D Geometry). If the 3mm material is replaced with a 9mm sheet, then it will mean that it will take longer to cut, as each geometry requires 3 x passes of the router tool to complete (for example), thus meaning that it takes 3 times as long to complete the job, and is thus more expensive.

The desired finish quality of the job has a significant impact on the time it will take to machine, and hence the price. For example, a high standard of finish will require a small ‘step over’ (the ‘step over’ is the distance between each pass of the CNC machines’ tool). For example, a high standard of finish will require a ‘step over’ of 0.01mm (this finish will require very little work to complete to a very high standard). If the required quality of finish was lowered, and a ‘step over’ of 0.05mm was used, then the time needed to machine it will approximately halved, the job will cost less, but the quality of finish will be lower.

For these reasons it's impractical to state that machining costs 'this' amount. Every job is different, and every quote is based on different information - essentially each quote is customised.

To find out more, or to have your project quoted, please contact us providing as much information as possible including a CAD file or, if this is not available, then dimensions and drawings of what the object looks like. 


At FormScan3d we are frequently scanning items that require CNC machining to deliver a projects real customer value.

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Peter Bull - FormScan 3D

Auckland

All prices are shown in New Zealand Dollars and inclusive of GST unless otherwise stated.