Have you ever wondered how a machine shop goes about quoting a particular part? While it can seem random to the uninitiated, the cost of custom CNC machining is anything but arbitrary. Though every shop is different, there are a number of basic elements that factor into a machining quote, and understanding these principles can help save you time and money when designing and ordering your parts. Below, we’ve outlined some of the most common areas that effect part price in a CNC machining quote
Common Elements In A CNC Machining Quote
Material
This is a very important factor that machinists consider when doing the CNC machining cost calculation. As CNC machining is a subtractive process, it tends to use more material than what will be on the final product. Machinists buy these materials in blocks, and they calculate the prices per block.
The choice of material to be used for the machine components influences cost in two ways: raw material cost and material machinability cost. Some materials are more expensive as a raw material than others while others are more difficult to fabricate than others. The lower the material machinability, the more expensive it is. In the event that the material to be used is potentially hazardous then additional safety precautions are required hence the cost of production goes up. The choice of material used significantly impacts on the overall price of the machine.
Manufacturing equipment required
Modern machining and manufacturing equipment vary and are extremely expensive. It is important to know whether a part can be completed using one multi-axis machine or will require multiple machines. As well as how many different machines and operations will be needed. The size and capability of the equipment needed will add to the factors that will influence of the overall cost incurred.
Quantity of parts
The number of parts ordered for a machine influences the overall cost. This is because large orders are expensive, however the higher the number of parts the lower the cost of each additional unit. This means large orders increase the final cost of the part but reduce the cost per unit. The turnaround time for the parts is also important in determining cost as a part to be shipped in a number of weeks will be more affordable than that to be shipped in two to three days.
Cost of Labour
Once CNC machining is set up, it requires almost no human intervention. Irrespective of the situation, a programmer, machinist, and engineer is required. For programming, a programmer helps to converts a CAD file into a CAM file while some AutoCAD technology can help to automatically program the toolpath. This has greatly reduced the reliance on humans for such steps.
A machinist will help to set up the machines for production in processes like cutting the billet, loading, and many more. In this case, the cost depends on quantity and complexity. Another factor here is quality control and post-processing and it varies from industries to another. All these factors play a major role in determining the cost of CNC machining.
Part tolerances
This refers to how close the physical part needs to be to the design submitted. It is usually measured in hundredths or thousandths of an inch. Unnecessarily tight tolerances on a part increase the overall cost due to its complexity and demand. Tight tolerances should be reserved for where the part interfaces with others. Our typical tolerance accuracy ranges from +/-0.01mm to 0.1mm, depending on customer’s requirement.
Part Finish
Part surface finishes provide a smoother outer surface, wear resistance, and remove roughness or tool marks. Creating various finishes can be achieved with bead blasting or anodizing, although can add to the final cost of the manufactured part. An experienced machine shop will help you determine the optimal surface finish for parts based on part function.
Miscellaneous
The list of miscellaneous costs associated with part pricing is long and varied. Items that could fall under this category include cleaning/deburring, part marking, assembly, packaging, secondary processes and more.