The Costs of CNC Machining(remove chrome from metal Mirabelle)

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Computer numerical control (CNC) machining is a manufacturing process that uses computer-controlled machines to shape materials like metal, plastic, wood, foam, and composite into custom parts and products. CNC machining is highly valued for its accuracy, repeatability, and ability to produce complex parts from a wide range of materials. However, like any manufacturing technology, there are costs associated with CNC machining that must be taken into account. In this article, we’ll take a closer look at the various factors that influence the costs of CNC machining.
Machine Purchase or Lease
The first major cost consideration for CNC machining is the actual CNC machine itself. CNC machines suitable for manufacturing can range from small table-top models costing a few thousand dollars, up to large 5-axis models that can cost hundreds of thousands of dollars or more. Very basic 3-axis milling machines may start around $10,000, while more full-featured CNC machining centers often range from $75,000 to $500,000+.
For companies that will be doing their own in-house machining, the machine must either be purchased outright or leased over time. Leasing can help spread out upfront costs, though companies won’t build long-term equity in the CNC equipment. When purchasing machines, it’s important to consider not just the base price, but also any additional costs for delivery and installation, training, and ongoing machine maintenance and repair.
Tooling and Accessories
In addition to the CNC machine itself, there are costs associated with tooling, workholding, and other accessories needed to actually machine parts. This includes end mills, drills, inserts, vises, fixtures, collets, and more. While basic tooling can be economical, specialized tooling for complex parts can be quite expensive. For example, a precision-ground carbide end mill for machining hardened steel can cost over $100.
The type of tooling required is determined by the material being machined, part tolerances, surface finishes, and features being produced. Complex parts often require multiple specialty tools and extensive tool libraries. Companies doing short production runs may prefer disposable carbide tooling, while higher volume production may warrant more expensive indexable tooling for longer life. Either way, factoring tooling costs is an important part of estimating CNC machining expenses.
Raw Material Costs
The costs of the raw material stocks being machined must also be taken into account. Common CNC machining materials like aluminum, steel, brass, and plastics have relatively low material costs. But for exotic alloys like titanium or Inconel, material costs per pound can be quite high in comparison.
Part sizes and required material usage is also a factor, as large blocky parts will require more raw stock than small delicate components. For prototype work, material costs may be insignificant. But for larger production volumes, raw material can be a substantial portion of overall costs. Carefully optimizing parts for minimum material waste is key.
Programming Time
Creating CNC machining programs takes considerable time and expertise. While basic 3-axis milling operations may be programmed directly at the machine control, more complex CNC machining typically requires CAM (computer-aided manufacturing) software for programming. Depending on part complexity and quantities, programming alone can represent a significant cost.
For specialty engineering firms, programming time is billed at hourly rates comparable to skilled machinists. For very high volumes, the time invested in optimal programming has significant benefits in reducing overall machining time and associated shop costs. Programming expenses can pay for themselves over time through enhanced efficiencies. But for lower quantities, programming is a fixed cost that simply must be absorbed.
Production Run Time
The actual production time required to machine parts on the CNC equipment is another major cost driver. Hourly machine shop rates ultimately depend on the time needed to produce the required parts. Simple low-quantity jobs may only incur an hour of production time versus complex parts in the tens or hundreds of hours.
Shop rates vary based on local labor costs and markets, but typical rates range from $50-$150 per hour. Production time is influenced by many factors - number of operations, cycle times, part complexity, batch sizes, and shop loading. As with programming, longer production runs allow the fixed time costs to be distributed over more parts.
Post-Processing Costs
After initial CNC machining, additional secondary processing steps are often required to achieve the finished part. Typical post-processing may include heat treating, plating, anodizing, powder coating, painting, passivation, cleaning, surface treatments, welding, assembly, and more. Performing these operations in-house adds to production costs or they may be outsourced to specialty shops at additional expense.
Post processing costs can vary tremendously. Simple solvent cleaning may only add a few dollars per part. Conversely, exotic finishes like physical vapor deposition (PVD) can cost hundreds of dollars and be a major portion of the overall part cost. Just like other process steps, longer production volumes allow post-processing costs to be spread over more parts and reduce per-part expenses.
Overhead Expenses
In addition to the direct production costs described above, CNC machining shops and other manufacturers also incur general overhead costs including:
- Building lease and utilities
- Equipment maintenance and repair
- Shop supplies - cutting fluids, lubricants, compressed air, etc
- Insurance costs
- Staff payroll and benefits
- Property taxes and licenses
- Marketing and sales expenses
These overhead costs contribute to hourly shop rates and must be covered in order to remain a viable business. As volumes increase, the fixed costs can be divided over more parts to reduce per-unit impact. But every manufactured part must carry some share of general overhead in addition to direct production costs.
Optimizing CNC Machining Costs
To help reduce CNC machining costs, here are some best practices to consider:
- Consolidate operations and machine sequentially when possible
- Standardize on tooling inserts and holders when feasible
- Use CAM programming and simulation to optimize programs
- Take advantage of entire machine envelope to maximize material usage
- Optimize part nesting to minimize raw material requirements
- Use stock feeders to automate material delivery when practical
- Employ higher performance tooling for reduced cycle times
- Consider multi-function machine tools to eliminate secondary processes
- Leverage production volumes to spread fixed costs over more parts
- Consider outsourcing non-core competencies to reduce overhead
The total costs for a given CNC machined part are always a sum of the specific manufacturing requirements and constraints. Evaluating each element and making informed choices is key to cost-effective CNC machining. With attention to manufacturing engineering principles, CNC machining can often deliver high-value precision parts at very competitive costs. CNC Milling CNC Machining