CNC Machining Guide

Cost reduction tips

Use these 3 design tips to cut the costs of your CNC machining project.

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CNC Machining Guide

Cost reduction tips

Learn more about what affects the costs in CNC machining. Use these three actionable design tips to cut the price in half and you keep your project on budget.

Cost reduction tips

Tips to keep your CNC project on budget

The cost of CNC machined parts depends on the following:

  1. Machining time & model complexity: The more complex the geometry of a part is, the longer it takes to machine and the more expensive it will be.
  2. Start-up costs: These are related to CAD file preparation and process planning. They are significant for smaller volumes but are fixed. There is an opportunity to reduce the unit price by taking advantage of economies of scale.
  3. Material cost & finishes: The cost of the bulk material and the ease with which that material can be machined greatly affect the overall cost.

As a rule of thumb:

To minimize the cost of CNC machined parts, stick to designs with simple geometries and standardized features.

In the next sections, we re-examine some of the design rules we visited previously with cost-reduction in mind. With these 3 design tips, you can drastically reduce the cost of your CNC machined parts.

Tip #1: Increase the size of all fillets or add undercuts to sharp edges

Cost reduction tip #1

To reduce machining times, add a fillet that is as large as possible to all internal (and external) vertical edges. This way a larger tool can be used, removing more material with each cut, and a circular toolpath can be followed, cutting each corner at a higher speed.

When a 90° internal edge is needed, reducing the radius will not do the job. In these cases, use an undercut instead (see above).

To minimize cost:

  • Add a radius that is slightly larger than 1/3 of the depth of the cavity.
  • Add a small fillet also to external edges.
  • Use undercuts when a 90° internal corner is required.

Pro tip: Use the same radius for all edges to save time on tool changes.

Tip #2: Minimize the number of machine orientations

Cost reduction tip #2

The part above requires at least two machine setups in a 3-axis CNC mill. After the features on one side are machined, the workpiece is rotated manually. This requires manual labor increasing costs.

Alternatively, a multi-axis CNC machines can be used. This also increases the machining costs though by about 60 to 100%.

To minimize cost:

  • Design parts that can be machined in one or two setups in a 3-axis CNC mill.
  • If this is not possible, consider splitting the part into multiple geometries that can be machined in one setup and assembled later.

Tip #3: Consider the cost of the material

Here is a table that summarizes the cost of the same part CNC machined in some of the most common materials. Each dollar sign indicates approximately a 25% price increase.

Cost Metals Cost Plastics
$ Aluminum 6061 $ POM (Delrin)
$$ Alloy steel 4140 $$ ABS
$$ Aluminum 7075 $$$ Nylon (PA 6)
$$$ Brass C360 $$$ Polycarbonate (PC)
$$$$ Stainless steel 304 $$$$ PEEK

It is obvious that selecting a material with physical properties that surpass the requirements of your application can quickly and unnecessarily increase the cost of your CNC machined parts.

To minimize cost:

  • Select the material with the lowest cost that has properties that fulfill your design requirements.
  • Use online instant quoting to get quick feedback on the price of each material.