What Does CNC Machining Cost?


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What Does CNC Machining Cost? - Wednesday, June 8, 2016

When you employ the services of a custom machine shop, there are a many things that can influence the quote you receive for any given project.

Shop owners must be acutely aware of all the things that affect the cost of contract machining and manufacturing so they can provide accurate quotes to customers without losing their shirt.

So what are some of these factors?

Materials

As with any kind of manufacturing, the materials you’re working with influence the cost of machining. Some materials are much more difficult to machine than others, and some are just more costly as a raw material, many are both.



Some materials must be machined much slower than others, even with modern advancements in tooling and machine technology. Some materials can more rapidly wear out the expensive consumable cutting tools used and can vary from one tool making hundreds, even thousands of parts, to one part consuming multiple tools. And if you are asking the shop to work with potentially hazardous materials that require additional safety precautions, the overall cost may increase substantially. So the choice of materials for your components can be a huge cost influencer even before the part is designed.

Part Geometry

The dimensions and overall geometry of the part is, of course, an important factor in price quoting for machining jobs. Obviously, the larger the part is physically, the more material that will be required to manufacture it. The more detailed and complex the geometric design, the more it will cost to create. Parts that require very tight tolerances, long tooling reaches, better surface finishes, or difficult to form geometries all will cost more to make than simpler parts. It is surprisingly easy to design a part that cannot be manufactured at all, or is unnecessarily extremely expensive to manufacture. It is always wise to consult a knowledgeable manufacturer during the design phase of the part. This knowledge can help you design a part that is both functional, and efficient to manufacture.

Manufacturing Equipment Required

The machines required to create a part can greatly influence the cost. Can a part be completed using one multi-axis machine or will multiple machines be necessary? How many different machines and operations will be required? What size machines will be required? Modern machining and manufacturing equipment is extremely expensive and varies substantially with each machine type, brand, quality, size, and capability. Each of these factors must be accounted for in the accurate cost determination of a part or product.

Additional Treatments and Finishes

Many machined products require additional treatments, such as heat treatments, specialty machining operations, surface finishing, and specialized coatings. All of these requirements will increase costs of the base product and should be evaluated for necessity and value.

Machinist Skill

More complicated machining jobs require the expertise of more highly trained and skilled machinists. The skill and experience of a talented machinist doesn’t come without costs — and for good reason. Regardless of any formal training program, nothing can take the place of on-the-job experience and on-the-job training. But many modern machinists have both a related formal education and on-the-job training. And even with a lifetime of machining experience, the industry changes and evolves so quickly, that a machinist must be a lifetime learner in order to maintain his/her skillset on the leading edge. Competitive Louisiana machine shops offer ongoing training and cross-training opportunities and most growing shops offer a wide range of experience in their employee base. A simple component, running on a basic CNC machine, can often be run effectively by low experienced, and thus lower paid trainees. As the complexity and difficulty of a component increases, so also must the experience and competence of the machinist running it, so as you can see, the cost would increase accordingly. The more competent CNC machine shops will account for these differences in their quoting and cost accounting measures.

Run Quantities & Frequencies

One of the most significant cost influencers that is often misunderstood, is run quantity. Many parts require multiple operations and steps to completion, sometimes very many. Each of these operations must be setup and tooled up for. From a basic hand-finishing operation where you have to get the needed tools and supplies together to perform, to a very complex machining operation that has many tools to be loaded, dialed in, and adjusted to yield the required tolerances. Setups can vary from minutes to days or even weeks to complete for individual operations. If all of the needed setups are required to only run a prototype sample – all of that associated cost must be allocated to that one sample and thus can be very expensive. If those same setups are performed to run ten thousand pieces, those same setup costs can be allocated over the ten thousand pieces and thus reduce the price per piece cost tremendously. The frequencies of these runs can also come into play. If a client requires 50 pieces delivered every week all year long, many custom machine shops will either run 200 pieces at a time or even the entire year’s quantity requirement all at once, and thus similarly allocate the setup costs across the higher run quantities. As a result, offering the machine shop assurances of repeat work and accurate demand estimates, can often be used to reduce the cost of the components.

Inspection Criteria

If a part is "mission critical” where a failure could result in loss of life or threat of injury, or legal, political, or social liability risks are high, the level of required inspections can sometimes exceed even the costs of machining the part. (Consider a heart valve or aircraft component). Even with modern techniques and technology, tolerance and material defect risks exist in any manufacturing operation. Therefore when a defective part absolutely cannot be tolerated, multiple and redundant layers of inspection can be performed to ensure that no defective parts make it through the processes undetected. The techniques, labor, and equipment often required for these inspections, can be very expensive and add considerable cost to the product. Conversely, if the potential for failure and associated consequences are negligible (consider a fishing reel component), the layers and levels of inspection scrutiny can be substantially reduced, thus considerably lowering the inspection-related costs of a component. So consideration should always be given and clear criteria designated to the appropriate level of inspection when considering the cost of a machined component.

Taxes, Environmental, & Regulatory

Other costs may not be so obvious, but are important to remember nonetheless. Machining components require the use of many different materials, lubricants, coolants, chemicals, and safety concerns. Any special requirements due to the nature or material of construction of a component can drastically affect the costs. 

Parts made from materials such as magnesium or beryllium can require special handling and safety equipment. Most parts and modern machines require the use of synthetic or oil-based coolants for efficient machining. Local and federal regulations dictating the proper disposal and handling of these items all affect the overall cost of running specific components. Income, property, inventory, and sales taxes along with local, regional, and federal fees and regulations affecting practically every sector of business operations vary substantially from one area to another and can each significantly influence cost differences.

Design

Are your CAD drawings accurate, detailed, and complete? You may need the assistance of an experienced engineer or machinist to perfect your design plans in order to ensure that your finished product comes out the way you anticipate. A tolerance analysis is easily overlooked and can also cause assembly or function problems randomly down the road. This design consultation phase can add some initial cost to the project but can save a lot in the long run. It is better to ensure that your drawings and CAD models communicate exactly what you are looking for before the manufacturing begins, than to have it manufactured twice to get what you want. Missing dimensions or specifications can stop the flow of manufacturing and lead to excessive loss of efficiency while this information is sought out. 

Competent machine shops should quickly recognize and point out missing or vague information on a drawing during the quoting phase. This information should be provided or worked out with the shop to ensure there are no false starts or surprises, all potentially costly.


Conclusion

In summary, the following are major influencers of machined component costs:

  • Material Selection
  • Part geometry
  • Manufacturing Equipment
  • Run Quantities and frequencies
  • Treatments and finishes
  • Machinist’s skill level
  • Inspection requirements/Error acceptance tolerance/Liability risks
  • Taxes, Environmental, & Regulatory

Other influencers exist, such as payment terms, client/shop relationships, overall skill, experience, and competency if the machine shop organization, industry specific influencers, price fluctuations of materials, and local skilled labor markets, just to name a few more. 

Machining touches virtually every part of our modern society, although often not recognizable to many. The keyboard used to type this was molded in a machined plastic injection mold. The paper we use to print it on was formed in a machine that was built from machined parts. 

Generally, almost everything we use in our day-to-day existence is no more than a generation or two from a machined component. So understanding the cost influencers on machined components and using them effectively can ultimately reduce the cost of everything we use.

 

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