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
Operational Costs And Shop Minimums
Right off the bat, it is important to understand the concept of shop minimums. These are essentially the price of entry into any custom machining arena, regardless of part size, shape, quantity, etc. and will be the starting price to do any type of fabrication or CNC work. Put plainly, there is a base cost associated with turning on, calibrating and operating a piece of equipment, and this must be factored into all quotes in order for a shop to remain viable and keep the lights on.
Each shop is different, but minimums are commonly applied to setups, programming, material usage and more. If a part price seems excessive, it is often due to a shop’s minimum charges relative to part quantity. Feel free to discuss ideal production quantity with your manufacturer.
Common Elements In A CNC Machining Quote
Material
This one is pretty self-explanatory and accounts for the cost of the raw material required to machine a given part. Plate, bar, tube, etc. all come in standard sizes which can be used to determine the best material yield and dictate the most affordable production quantity. Material prices generally go down as purchase quantity increases. Material prices will go up when ordering non-standard sizing, or expedited turnarounds.
Setup
Setup costs refer to the time it takes an operator to load and calibrate tooling, install fixtures and work-holding and establish machine/part zeroes and offsets. For simple parts, the setup is not overly complicated and shop minimums would apply. For complex components that require multiple setups and a variety of tooling/fixtures, the time required can increase significantly. Setup costs account for a large amount of a part’s price and will be most impacted by order quantity. People mistakenly think that ordering lower quantities will keep their part price down, but in many cases the opposite is true.
Programming
In order to machine a part, a programmer must first generate code to tell the CNC which operations to perform. This can be done by hand or with the help of CAD/CAM software. Depending on the complexity of the part, the programming process can take minutes or hours. This time is factored into a machining quote, and will fluctuate based on order quantity.
Machining Time
Machining time accounts for the number of minutes it takes to machine a part. This is a fixed cost that will not vary as order quantity increases/decreases. A shop will take the number of minutes multiplied by their machining rates to determine the cost of run time in a CNC quote.
Tooling
Every shop will keep a wide variety of tooling on hand, but certain parts require more specialized options to achieve a specified geometry. When applicable, the cost of this tooling will be factored into a part price to account for the expense incurred to a shop.
NRE (Non Recurring Engineering)
This is a broad term used to define “one-time” costs associated with part production. NRE costs are usually quoted separately as they are non-recurring and do not affect individual part price in the long term.
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 (heat treating, surface finishing, etc.) and more. In a nutshell, if a shop is paying an employee or outside vendor to perform additional work associated with a particular part, their time will be accounted for and will be reflected in the quoted price.