CNC machining is a highly versatile manufacturing technique that delivers precision and consistency across various applications. However, costs can rise quickly if not managed properly. For engineers, designers, and business owners, knowing how to calculate and control CNC machining expenses is vital for remaining competitive. CNCJY.COM has been dedicated to providing customers with cost-effective CNC machining solutions for many years. Today, we will discuss how to calculate CNC machining costs for your project and share practical strategies to reduce expenses while maintaining quality.
1. How Much Does CNC Machining Cost?
CNC machining costs can escalate quickly, making it a significant concern for engineers and manufacturers. Several key factors determine the cost of CNC machined parts. Some of these are fixed requirements, such as part size or material, while others can be adjusted to save time and money during production. Below is a breakdown of the primary cost contributors:
- Part Size
Larger parts require more material, robust workholding, and longer machining times, all of which increase costs. - Material Selection
Certain materials are more expensive or harder to machine. For example, tougher metals require slower machining speeds, resulting in higher costs. Select materials that balance cost, machinability, and performance. - Machine Type and Operations
Different CNC machines (e.g., CNC mill, lathe, waterjet) have varying operating costs. Choosing the right machine for the task can greatly impact pricing. - Part Design and Tolerances
Complex designs with intricate features and tight tolerances increase machining and inspection time. Simplifying designs and relaxing tolerances where possible can help lower costs.
For example, machining two prototype parts from aluminum might cost $650, but scaling production to 100 units can bring the cost per part down to $40.
2. How to Calculate CNC Machining Costs
The cost of CNC machining can be calculated using the following formula:
Total Cost = Material Cost + Machine Time Cost + Labor Cost + Setup Cost + Finishing Costs
Key Factors in CNC Cost Calculation
- Material Selection – Materials like aluminum are more cost-effective due to their machinability. Harder materials, such as titanium or stainless steel, increase machining time and tool wear, leading to higher costs.
- Machine Time – Machine time is determined by the complexity of the part and the machining operations required (e.g., milling, drilling, turning). Advanced setups using multi-axis machines are faster but can have higher hourly rates.
- Setup Costs – Setup involves preparing the machine, programming toolpaths, and creating custom fixtures or soft jaws. These costs are fixed and can be distributed across a higher quantity of parts for cost savings.
- Tolerances and Surface Finishes – Tighter tolerances (e.g., ±0.001”) require additional machining time, inspection, and tool changes. Special surface finishes like anodizing or polishing increase costs.
- Production Volume – Economies of scale play a significant role. Larger batch sizes reduce the cost per part.
- Tool Wear and Maintenance – Tool wear increases costs over time, especially when machining harder materials. Proper tool selection and maintenance can help manage this expense.
Example: Calculate CNC Machining Cost Step by Step
To better understand how CNC machining costs are calculated, let’s walk through a practical example. We’ll break down the cost components step by step based on a hypothetical part.
Example Scenario
Part Description:
A simple aluminum bracket with the following specs:
- Material: Aluminum 6061
- Dimensions: 100 mm x 50 mm x 10 mm
- Features:
- 4 drilled holes (10 mm diameter)
- 1 pocket (50 mm x 25 mm x 5 mm depth)
- Quantity: 10 parts
- Tolerance: ±0.1 mm
- Finish: Clear anodizing
Step 1: Material Cost
- Material chosen: Aluminum 6061
- Material price: $5 per kg
- Raw blank dimensions: 105 mm x 55 mm x 12 mm (to allow for machining and finishing tolerances)
- Density of Aluminum 6061: 2.7 g/cm³
Material volume of blank:
105 mm x 55 mm x 12 mm = 69,300 mm³ = 69.3 cm³
Material weight per part:
69.3 cm³ × 2.7 g/cm³ = 187.11 g (0.187 kg)
Material cost per part:
0.187 kg × $5/kg = $0.94
Material cost for 10 parts:
$0.94 × 10 = $9.40
Step 2: Machine Time Cost
- Machine type: 3-axis CNC milling machine
- Machine hourly rate: $75/hour
- Machining time per part:
- Pocket milling: 10 minutes (0.167 hours)
- Drilling 4 holes: 5 minutes (0.083 hours)
- Total machining time per part: 0.25 hours
Machine time cost per part:
0.25 hours × $75/hour = $18.75
Machine time cost for 10 parts:
$18.75 × 10 = $187.50
Step 3: Labor and Setup Cost
- Setup time: 1 hour to program the CNC machine, prepare tools, and set up fixtures
- Hourly labor rate: $50/hour
- Setup cost:
1 hour × $50/hour = $50
Labor cost for 10 parts (distributed):
$50 ÷ 10 = $5 per part
Step 4: Finishing Cost
- Finish: Clear anodizing
- Cost of anodizing: $2 per part
Finishing cost for 10 parts:
$2 × 10 = $20
Step 5: Total Cost Calculation
Now, let’s sum up all the costs:
| Cost Component | Per Part | For 10 Parts |
|---|---|---|
| Material Cost | $0.94 | $9.40 |
| Machine Time Cost | $18.75 | $187.50 |
| Setup/Labor Cost | $5.00 | $50.00 |
| Finishing Cost (Anodizing) | $2.00 | $20.00 |
| Total Cost | $26.69 | $266.90 |
Step 6: Cost Per Part Analysis
For this example, producing 10 aluminum brackets costs $266.90 in total, which breaks down to $26.69 per part. If the batch size were increased, the setup cost would be distributed across more parts, significantly lowering the cost per unit.
3. How To Reduce CNC Machining Cost Effectively but Keep Quality?
Now you know what factors affect the cost of CNC machining and how to calculation. So making informed design and production decisions based on the factors that can help you save costs. As a professional CNC machining service provider, CNCJY has summarized the following top 10 tips to reduce CNC machining cost but keep high quality from years of practical experience. We believe there is always a solution that can meet your actual needs and help you save costs at the same time!
1. Simplify Part Designs
Complex part designs tend to require more machining time and specialized tools. Features such as deep pockets, non-standard geometries, or intricate aesthetic details can increase costs without adding to the part’s functionality. Removing unnecessary or overly complicated features is an effective way to reduce machining time and tool wear. Additionally, splitting a complex part into multiple simpler components that can be assembled later – through welding, bending, or bolting – can reduce the number of machining operations required.
Top 5 Cost-Saving Design Tips for CNC Machining
Here are five additional design tips to help reduce costs while maintaining quality:
Avoid Sharp Internal Corners
Sharp internal corners are a common design mistake. CNC tools are round, making sharp corners impossible without secondary processes. Add a radius to internal corners—ideally 30% larger than the cutting tool’s radius. Larger radii reduce cutting time and tool wear. For tight fits, consider relief cuts (e.g., dog-bone features) to ensure proper assembly.
Avoid Deep Pockets
Deep internal pockets or cavities increase machining risks such as deflection, tool breakage, and chip evacuation issues. Follow a width-to-depth ratio of 1:6 or shallower. For drilled features, a width-to-depth ratio of 1:10 is acceptable. Additionally, allow relief at the bottom of drilled holes to accommodate the drill tip.
Be Mindful of Thread Depth
Threads and tapped holes are common but often designed deeper than necessary. Excessive thread depth increases machining time and risk. A rule of thumb is to make the thread depth twice the hole diameter (e.g., 6 mm depth for a 3 mm thread). For blind holes, leave an unthreaded length at the bottom to improve chip evacuation.
Watch Out for Thin Walls
Thin walls are weaker, harder to machine, and prone to defects like chatter or breakthroughs. Maintain a minimum wall thickness of 0.8 mm for metals and 1.5 mm for plastics. Double the thickness for cantilevered or deep thin walls to reduce machining risks.
Simplify Part Marking
Engraving is a cost-effective way to include part markings during machining. Use sans-serif fonts with a minimum size of 20 points for easy readability. Avoid raised or embossed markings, as they require additional machining steps and increase costs. If additional finishes, such as anodizing, are required, consider laser marking for a low-cost, high-contrast result.
2. Optimize Tolerances and Surface Finishes
Tight tolerances and high-quality surface finishes can significantly increase CNC machining costs. Machining parts to tighter tolerances demands additional time for programming, cutting, and inspection, which drives up costs. Similarly, achieving a specific surface finish often requires slower machining passes and extra inspection steps. To reduce costs, only request tight tolerances or special finishes when absolutely necessary for the part’s functionality. Standard tolerances (+/- 0.125 mm) and finishes are usually sufficient for most applications.
3. Add Internal Radii to Sharp Corners
Sharp internal corners are difficult to machine because CNC cutting tools are round and cannot naturally produce sharp edges. Machining sharp corners often requires secondary processes, which add time and cost. To address this, add internal radii to corners, preferably at least 30% larger than the tool’s radius. Larger radii not only make machining faster and easier but also extend the lifespan of cutting tools by reducing wear.
4. Limit the Depth of Cavities
Machining deep cavities is time-intensive and may require specialized tools or multi-axis CNC systems. Removing large amounts of material from deep cavities increases machining time and can lead to tool deflection or breakage. To minimize costs, keep cavity depths to a maximum of four times the tool diameter. This ensures that standard tools can be used efficiently, reducing the need for slower machining techniques or custom tooling.
5. Use Standard Hole Sizes and Features
Using non-standard hole sizes or features is costly because it requires custom tooling or special machining operations. Instead, design holes with standard diameters that match commonly available drill bits. Standard-sized holes can be drilled quickly and accurately, reducing machining time. Additionally, limit the depth of holes to no more than four times their diameter, as deeper holes require longer machining times and special tools.
6. Increase Wall Thickness
Thin walls are challenging to machine because they are more prone to vibrations, deformation, and fractures during cutting. Machining thin walls accurately requires slower cutting speeds and additional care, increasing production time and costs. To avoid these issues, maintain a minimum wall thickness of 0.8 mm for metal parts and 1.5 mm for plastic parts. Thicker walls are more stable, easier to machine, and reduce the risk of defects.
7. Minimize Thread Lengths
Threads that are longer than necessary increase machining time and require specialized tools, especially for deep threads. For most applications, thread lengths up to three times the hole diameter are sufficient for strength and functionality. For blind holes, leaving an unthreaded section at the bottom of the hole (about half the hole diameter) makes chip evacuation easier and reduces tool wear, further minimizing costs.
8. Avoid Multiple Surface Finishes
Each additional surface finish applied to a part increases costs due to the extra machining steps involved. While surface finishes can enhance a part’s appearance or resistance to environmental factors, they should only be specified when absolutely necessary. For example, requesting multiple finishes on different areas of the same part can increase costs significantly, as it requires additional setup and handling.
9. Choose Materials Wisely
The choice of material has a direct impact on CNC machining costs. Materials with higher machinability, such as aluminum 6061 or POM (Delrin), are easier and faster to cut, reducing production time and tool wear. On the other hand, harder materials like stainless steel or PEEK require slower cutting speeds and specialized tools, resulting in higher costs. Additionally, consider the bulk cost of the material and its suitability for your design to strike a balance between performance and affordability.
10. Take Advantage of Economies of Scale
The unit cost of CNC machined parts decreases significantly as production volumes increase. This is because initial startup costs, such as CAD preparation and machine setup, are spread over a larger number of parts in high-volume production. Even a small increase in order quantity can result in noticeable cost savings. For larger runs, the cost per unit can drop exponentially, making bulk production a cost-effective option.
Cost control in CNC machining requires a holistic approach that considers design, materials, tooling, and supplier collaboration. By focusing on these aspects, you can not only reduce costs but also enhance the quality and reliability of your products. Whether you’re prototyping a new design or scaling up production, these strategies will help you achieve your goals more effectively.
At CNCJY, we specialize in delivering cost-efficient, high-quality CNC machining services tailored to your needs. From material selection to final inspection, we partner with you at every step to ensure optimal results. Let’s discuss how we can bring your designs to life while keeping costs under control. Contact us today!