For product designers and engineers, receiving a CNC machining quote can sometimes feel like opening a “black box.” You send out two files that look similar: one comes back quoted at $45, and the other at $180.

Why the discrepancy?

At Boona Prototypes, we believe in transparency. CNC machining is a subtractive manufacturing process where Time = Money. Understanding the variables that drive that time up (or down) allows you to “hack” the cost calculator, optimizing your designs for budget without sacrificing quality.

Whether you are prototyping a single bracket or scaling to low-volume production, here is the definitive guide to calculating and controlling your CNC costs.

The The Core Formula: How We Calculate Price

Before diving into specific savings, you must understand the basic pricing model used by machine shops worldwide.

Total Cost=Material Cost+(Machining Time×Hourly Rate)+Setup & NRE

1. Material Cost: The raw block of plastic or metal.

2. Machining Time: How long the machine runs. This is influenced by volume removal rates and complexity.

3. Setup & NRE (Non-Recurring Engineering): CAM programming, fixture design, and machine preparation.

Industry Benchmark: Machine Hourly Rates

Note: These are estimated industry averages for calculation purposes.

Key Takeaway: If your part can be made on a 3-Axis machine, do not design it requiring 5-Axis movement unless absolutely necessary. The hourly rate alone can double your cost.

Variable 1: Material Selection and Machinability

Material cost is twofold: the price of the raw block and the Machinability Rating.

Machinability refers to how fast a tool can cut through the material. Aluminum 6061 is the industry standard. Harder materials like Titanium require slower cutting speeds (feeds and speeds) to prevent tool breakage, which increases machine time significantly.

Material Cost & Machinability Comparison

Budget Tip: Unless your part requires the specific heat resistance or chemical properties of Stainless Steel, stick to Aluminum 6061 or Delrin for prototyping.

Variable 2: Geometry and Complexity

Complexity is the enemy of affordability. In CNC machining, complexity usually manifests in three ways that drive up the “Setup” and “Run Time” portion of the equation.

1. Deep Pockets: End mills deflect/vibrate when they stick out too far. To machine a deep cavity, we must reduce cutting speed.

   • Rule of Thumb: Keep cavity depth to less than 4x the tool diameter. Anything deeper requires specialized tooling.

2. Internal Radii (Corners): CNC tools are round. They cannot cut a perfectly sharp 90-degree internal corner. The smaller the radius you require, the smaller the tool we must use. Smaller tools remove material slower.

   • Parameter: If possible, use a corner radius > 1/3 of the cavity depth.

3. Number of Setups: If a part needs to be machined on all 6 sides, a human operator must manually flip the part and re-calibrate the machine 6 times.

   • Cost Impact: Each flip adds roughly 15–30 minutes of labor/setup time.

Variable 3: Tolerances and Precision

“Standard” tolerances exist for a reason. At Boona Prototypes, our standard tolerance (ISO 2768-m) is sufficient for most functional parts. When you specify tighter tolerances (e.g., $\pm 0.005mm$), the cost rises exponentially.

The Cost of Precision

$\pm 0.125mm$

$\pm 0.050mm$

$\pm 0.010mm$

Why the increase? Tight tolerances require slower finishing passes and mandatory manual inspection or CMM verification to ensure the part passes Quality Control (QC).

Variable 4: Quantity (The Power of Amortization)

This is the most powerful lever you have. CNC machining has high “front-loaded” costs (CAM programming and machine setup).

If the setup cost is $200:

• Ordering 1 part: Setup cost per part is $200.

• Ordering 100 parts: Setup cost per part is $2.

Case Study: Price Break Estimates

Example based on a simple Aluminum 6061 bracket.

Boona Advantage: Unlike many competitors, we have No Minimum Order Quantity (No MOQ). We are happy to make that single $180 prototype, but we will always advise you on the volume breaks so you can get the best value.

How to “Hack” the Calculator: 3 DFM Tips

To instantly lower your quote from Boona Prototypes, check your CAD design against these three Design for Manufacturing (DFM) rules:

1. Standardize Tapped Holes: Stick to standard metric sizes (M3, M4, M5). Custom thread sizes require custom taps, which we may have to order specifically for your project.

2. Avoid Thin Walls: Walls thinner than 0.8mm (metals) or 1.5mm (plastics) are prone to warping. Machining them requires very slow speeds to prevent vibration, increasing run time.

3. Limit Thread Depth: A threaded hole does not need to be threaded all the way to the bottom. A thread depth of 2x to 3x the diameter provides maximum holding strength. Going deeper adds risk of tap breakage without adding strength.

Conclusion: Get an Accurate Quote Today

Budgeting for a CNC project doesn’t have to be a guess. By selecting the right material, accepting standard tolerances where possible, and understanding the volume price breaks, you can significantly reduce your manufacturing costs.

At Boona Prototypes, we combine speed with precision. We offer:

• ISO 13485 & IATF 16949 Certified quality.

• 3-Day Turnaround for rapid prototyping.

• Free DFM Analysis with every quote to help you spot cost-drivers before we start cutting.

FAQs

What is the most cost-effective material for CNC machining?

For metals, Aluminum 6061 is generally the most economical choice due to its low raw material cost and excellent machinability (it cuts fast, reducing machine time). For plastics, Delrin (POM) or ABS are usually the most budget-friendly options. Avoid Titanium or Stainless Steel unless your application specifically requires their thermal or chemical properties, as they are significantly harder to machine.

Why is my CNC quote higher than a 3D printing quote for the same part?

CNC machining is a subtractive process that requires significant Setup (NRE) time—programming the CAM, setting up fixtures, and selecting tools. 3D printing (Additive Manufacturing) has virtually zero setup time. However, CNC becomes cost-competitive or even cheaper than 3D printing as quantities increase (e.g., 10+ units) or when specific material strength is required.

Does Boona Prototypes have a Minimum Order Quantity (MOQ)?

No. We have no MOQ. We are happy to machine a single prototype for you. However, keep in mind that the “Setup Cost” is charged whether you order 1 part or 100 parts. Ordering 10 units often drastically reduces the price per unit compared to ordering just one.

How do tight tolerances affect the final price?

Tight tolerances (e.g., $\pm 0.01mm$) increase costs because they require slower machining speeds, specialized finishing tools, and mandatory quality control inspections (such as CMM). To save money, only apply tight tolerances to critical features (like bearing fits) and leave the rest of the design to standard tolerances (ISO 2768-m).

What file formats do I need to upload for a quote?

For the most accurate quote, please provide a 3D CAD model (formats: .STEP, .STP, .IGES, or .X_T). If your part requires specific tolerances, threads, or surface finishes, please also include a 2D PDF drawing calling out those details.

Why is 5-Axis machining more expensive than 3-Axis?

5-Axis machines are more complex and have a higher hourly operating cost. Additionally, programming a 5-axis path requires advanced CAM skills. We recommend using 3-axis machining for simple parts to keep costs down, reserving 5-axis only for complex geometries or parts with curved surfaces (like impellers or turbines).

Can I reduce costs by supplying my own material?

generally, no. Machine shops buy material in bulk at wholesale prices. If you supply your own material, the logistics and handling often negate any savings. Furthermore, if the material you supply has hard spots or impurities that break our tools, it can complicate the project. It is usually cheaper and faster to let us source the certified material for you.

How quickly can Boona deliver CNC machined parts?

For standard rapid prototyping orders, we can often go from CAD to finished part in as little as 3 days. Complex orders, hard metals, or parts requiring surface treatments (like anodizing) will typically take 7–10 days.