CNC mills are powerful tools for crafting custom parts. The process can become expensive, especially when working with stainless steel. But you can save your project expenses by making only some small changes.
Cutting CNC mill stainless steel costs can make a significant difference to your bottom line. With the right approach, such as optimizing tool selection, using efficient setups, and other things, you can reduce your expenses without sacrificing quality or precision. Strategic planning and using the right material grades can also contribute to substantial savings.
Read on to discover practical tips that can help you save money while maximizing the effectiveness of your CNC milling service. We’ve also broken down the cost factors of milling stainless steel.
What is CNC Mill Stainless Steel?
CNC milling stainless steel is a precision machining process used to create parts from stainless steel alloys. Stainless steel itself is a blend of iron and chromium, with other elements like carbon added to enhance specific qualities. Chromium, in particular, gives stainless steel its resistance to rust and wear, making it an ideal material for tough applications.
A milling machine uses a rotating CNC mills cutting tool to remove material from a stationary piece of stainless steel. The process is controlled by a computer, which guides the tool with incredible precision. This allows for the creation of complex, custom parts with smooth finishes and exact specifications. The movement of the workpiece on the milling table ensures that the tool can cut on multiple planes, giving the operator flexibility in shaping the steel as needed.
CNC milling is a common choice for machining stainless steel because of its accuracy and ability to handle intricate designs. However, it’s important to select the right tools and settings to avoid damaging the steel or wearing out the cutting tools too quickly.
Cost Break Down of CNC Mill Stainless Steel Cost
There are various factors involved in calculating the cost of CNC milling stainless steel. Let’s break them down, so you can manage the expenses effectively.
Raw Material Cost
The price of stainless steel is one of the first costs to consider. The type and quantity of the metal you need will affect the overall cost. For instance, a 6″ x 6″ x 1″ sheet of Stainless Steel 304 might cost around $90, while Stainless Steel 303 could be as much as $150.
Larger or more complex parts require more material, which naturally drives up the cost. Balancing material choice and part requirements can help you avoid overspending on raw materials.
Machine Type
The type of CNC machine used also plays a big role in the cost. A 3 axis CNC machine is generally more affordable and works well for simpler parts. However, if your part has more intricate geometry, a 5 axis CNC machine is the better choice despite the higher cost.
While a 5 axis CNC reduces manual labor and can finish parts faster, it’s more expensive to run. In some cases, outsourcing to a CNC milling service shop can save you money.
Cutting Tolerances
The precision required for a part also affects CNC mill stainless steel costs. Parts that need tight tolerances (high accuracy) take more time to machine and often require specialized tools and inspection equipment.
As the tolerance tightens, the complexity increases, leading to higher machining and inspection costs. Achieving a high level of accuracy can also result in more frequent errors, increasing the overall cost of production.
Milling Time
Time is a critical cost factor in CNC milling. The longer it takes to machine a part, the higher the cost. Milling time depends on factors like machine speed, material hardness, and part complexity. For example, more complicated geometries or longer parts will take more time to mill.
Also, any manual processes such as assembly, finishing, or post-machining activities can add to the total production time and cost.
Part Geometry
The design of your part is another factor in pricing. Simple shapes are cheaper to machine than complex ones. Features such as thin walls, deep cavities, intricate lettering, and sharp internal corners require more machining effort, precision, and time. More resources are needed to produce these complex parts, raising the overall cost.
Production Cycles
Optimizing production cycles can help reduce costs. The cycle time for machining is influenced by factors like feed rates, tool paths, and the number of passes required. Using advanced CAM software, improving machine performance, and selecting the right cutting tools can streamline the process, making it more cost-efficient.
Labor Costs
Labor costs are an unavoidable part of the CNC milling process. These costs include wages for engineers and machinists who are involved in programming, setting up machines, running operations, and inspecting parts.
Programming is often the most expensive part of labor, as it requires specialized knowledge to convert CAD files to CAM files. Setup, quality assurance, and post-machining processes also contribute to labor costs. This cost can vary from one country to another and from shop to shop.
How to Reduce CNC Mill Stainless Steel Without Compromise Quality
Reducing CNC mill stainless steel costs while maintaining high-quality results can be challenging, but with the right approach, it’s possible. Here are several strategies to achieve this balance:
1. Use the Right Tooling
Choosing the correct tooling is one of the most effective ways to maintain the quality of stainless steel milled parts while lowering costs. High-speed steel (HSS) is a more affordable option but is typically slower and less durable compared to carbide tools.
Carbide tools, made from Tungsten or Titanium Carbide, are faster and can handle higher cutting speeds, making them ideal for mass production. They also provide a better finish, ensuring high-quality output. However, the trade-off is the higher initial cost of carbide tools.
To further reduce costs, keep your tools sharp. Dull tools not only wear out faster but can also cause tool breakage or damage the workpiece, leading to increased expenses. Regular tool maintenance and replacing worn tools can save you money in the long run by improving both tool life and machining precision.
2. Use Lubricants
Lubrication plays a vital role in controlling machining costs. When milling stainless steel, high friction causes excessive tool wear, which can significantly raise costs. Lubricants help reduce friction, extending tool life and reducing the likelihood of damage.
Also, lubricants lower the temperature during the machining process, helping prevent work hardening and overheating, which can compromise the material and increase machining difficulty. The right lubricants also help flush away metal chips and debris, keeping tools and the workpiece clean. This reduces the risk of contamination and ensures smoother, more efficient machining, which lowers the production expenses.
3. Remove Thin Walls from Part Design
Thin walls, especially those less than 0.020 inches (0.5mm), are prone to flexing, warping, or breaking during machining. CNC machine shops typically charge higher rates for manufacturing thin-walled parts due to the increased difficulty and higher risk of failure.
To reduce costs, design parts with thicker walls where possible, keeping them above 0.794mm (1/32”) in thickness. If your design absolutely requires thin walls, consider alternative manufacturing methods like sheet metal fabrication, which can handle thin sections more effectively and at a lower cost.
4. Optimize the Inside Corner Radius
Corners in your design that are too sharp can increase machining time and costs. CNC tools naturally leave a rounded edge at inside corners. The wider the radius, the fewer passes the tool needs to make, which speeds up production.
Narrower corners, however, require smaller tools and more passes at slower speeds, which not only increases machining time but also raises the risk of tool deflection or breakage. For the most cost-efficient design, aim for an inside corner radius with a length-to-diameter ratio (L:D) of 3:1 or less. Keeping the internal radii consistent throughout the part will also eliminate the need for tool changes, further reducing complexity and cycle time.
5. Avoid Deep Pockets
While CNC mills can machine deep pockets, doing so can be very costly. The depth of cavities is limited by the length of the milling tool, and as the cavity gets deeper, the risk of tool deflection or fracture increases. Deeper cavities also make it harder to clear metal chips, which can slow down the process.
To keep costs down, limit the depth of cavities to no more than twice the tool’s diameter. If deeper pockets are absolutely necessary, minimize the depth and keep the tool length in mind when designing the part. Parts with cavities up to 4 times their depth are generally cost-effective, but anything beyond this starts to increase manufacturing time and tool costs.
6. Limit the Use of Tight Tolerances
Tight tolerances on parts, like specific radii, hole diameters, or chamfers, can significantly increase manufacturing costs. While tight tolerances are necessary for mission-critical surfaces, applying them across all features is costly and inefficient. The reason is simple: tighter tolerances slow down the machining process, as each part must be inspected carefully using tools like CMM (Coordinate Measuring Machines) or micrometers.
You can reduce the CNC mill stainless steel costs by limiting the use of tight tolerances to only those features that truly matter for the part’s function. For less critical dimensions, standard tolerances (like ±0.005″) are usually sufficient.
7. Split up Complex Parts
In some cases, what seems like a single complex part may be more cost-effective if split into simpler pieces. For example, parts with deep pockets or multiple faces often require lengthy machining processes that are time-consuming and costly.
By breaking the part into smaller components, each one can be machined separately, which may reduce setup time, machining time, and fixturing costs. These individual parts can then be welded or bolted together later. This approach not only simplifies the machining process but can also lead to better material efficiency, which helps keep overall costs down.
8. Avoid Multiple Finishes
Surface finishes are one of the main contributors to CNC machining costs. Requiring multiple finishes, like anodizing, chem film, or a combination of smooth and bead-blasted areas, can quickly add up. Each different finish requires separate processing steps, which means more time, labor, and resources.
A better approach will be to request a uniform finish throughout the part or leave it unfinished if appearance isn’t critical. If multiple finishes are necessary, ensure they serve a clear functional purpose to justify the additional cost.
9. Remove All Text and Lettering
Engraving text or logos onto parts requires additional machining steps, which increases costs. While it may be necessary for some designs, adding text can slow down production and require more time to finish. Instead of engraving or embossing text on the part, consider alternative methods like silk screening or painting the text after the part is machined. These surface finishing techniques are typically more cost-effective than machining text directly into the metal.
If text is absolutely required, opt for engraved lettering over embossed, and use simple fonts like Arial or Verdana in a size of at least 20 points. This reduces the time and complexity of the engraving process.
10. Order Larger Quantities
Ordering larger quantities of parts can reduce the per unit cost of CNC milling stainless steel. CNC machines require programming, setup, and calibration for each batch, which can add to the initial cost. However, once the setup is complete, producing multiple parts becomes more efficient and cost-effective.
Bulk orders allow manufacturers to spread the setup costs across more units, lowering the overall cost per part. And bulk orders tend to increase production efficiency, as the machine is running for longer periods and can perform multiple operations without interruptions. The sweet spot for cost-efficiency in CNC milling is typically between 100 and 10,000 parts.
Conclusion
Reducing CNC mill stainless steel costs doesn’t have to mean sacrificing quality. The factors we’ve discussed will help you cut costs while still achieving high-precision results. Careful planning, tool selection, and optimizing your design can lead to substantial savings. So, the next time you’re working on a CNC milling project, be sure to incorporate these strategies to stay within your budget.
At Zintilon, we specialize in custom CNC milling parts. Our expertise and advanced technology ensure top-quality results at competitive prices. Contact us and save on manufacturing costs.
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