Cutting Costs

1. Select your material and grade carefully

Choosing your material is an essential factor when it comes to cost. 

The first thing to consider is which material to choose for your application; it’s a careful balance between the properties you require and cost. 
Aluminium is light weight, readily available, easy to machine and has a comparatively low cost. 

Plastics are light weight, have a high rate of material removal and are low cost. However, sometimes the low costs are negated by minimum order values, long lead times and often being more challenging to machine to tight tolerances.

Stainless steel is heavier than aluminium and plastic and is often used for applications where aluminium would not be up to the job – such as harsh environments. It does have its shortcomings though: it’s less readily available in thicker plate sizes, has lower rates of material removal, meaning longer run times than aluminium and plastic, and it’s generally more expensive. As there’s a financial implication of using stainless steel, you’ll only want to use it where the application requires it.

Once you’ve selected your material, the next consideration is the specific grade. Each grade will have differing properties and costs so getting familiar with them will help you select the grade that will be most suitable for your application and budget. There’s no point in selecting a high-performance aerospace grade aluminium if a cheaper alternative grade will do the job. An experienced machined parts supplier should be able to guide you on material selection. Our ‘Materials Resources’ page, also known as our materials encyclopaedia, is a great starting point.

3. Consider tolerances

It’s vital to think about the most appropriate tolerance for your machined part. By thinking about where tighter tolerances are necessary, and where more open tolerances can be applied, it’s possible to reduce run time on the machine and cut costs. 

For example, if you are machining a shaft that will be inserted into a tube , there will be a certain tolerance that will allow for the two components to function properly together when assembled. If the size difference between the two components is small, a tighter tolerance will be required. If close fitting isn’t required, a smaller shaft could be machined and a wider tolerance applied.

Another possibility would be leaving some faces ‘as stock’ – a particularly good option for components that are part of an assembly where some or all faces will be hidden. This would allow a smaller billet of material to be purchased and less machining time too.

5. Keep machined features as simple as possible

Taking machined features into consideration in the early design stage can be a gamechanger:

• Corner radii – specify as large an internal corner  radius as possible so a larger, standard cutter can be used
   
• Tapped holes – generally maximum strength from a tapped hole will come from a thread depth of 2.5 x Ø. Any longer won’t bring any additional strength, but it will add cost through custom tooling requirements
  
  
• Pockets and recesses – if your design features complex pockets to reduce component weight, it may be possible to adjust this to a simple circle or square which would be far simpler and therefore quicker to machine. With some planning, it may be possible to create a design with comparable strength and just slightly weightier than ideal. Of course, it may not always be acceptable to make this compromise, but where budget is tight and there is some design flexibility, small savings such as this can be very handy.  
   
• Upstands – the location of these or other features such as islands or bosses, should be considered with tooling in mind and ideally you don’t want them too close to the edge of the part. You could group these features together, or for an enclosure, consider tabbing them to the wall of the enclosure to save machining time and reduce cost.