How to reduce the cost of CNC machined parts?

What is CNC Machining?

CNC machining is a proven digital manufacturing process that produces high precision parts with excellent physical properties directly from CAD files.

The cost of machining with CNC machines can vary greatly depending on the application. Whether you are creating a prototype or preparing for mass production, it is important to check the overall budget for your project before placing an order.

The calculation of CNC machining costs appears to be very complex. We have to consider many factors, and the final cost assessment is more difficult compared to other manufacturing methods.

Therefore, we first analyze the factors that affect CNC machining. Then some feasible guidelines are proposed for these factors, which are proven to reduce the cost of CNC machined parts. By being aware of these factors early in the development cycle, you can minimize costs without having to pay a high price.

What are the factors that affect the cost of CNC machining?

The production time and cost of materials will determine the price of CNC machined parts. Before you find a CNC machining company, you can understand the factors that affect the cost of CNC machining. In order to provide cost effective service and high quality products, our engineers will inspect and review your design upon receipt of the project and then select the most machining solution.
1. Quantity
The number of CNC parts in an order affects the total cost. Generally, the higher the quality, the higher the machining cost, but each additional unit will be cheaper, which means that a large order will increase the overall cost, but lower the price per unit. For the same part, a part requires multiple operations and steps before it can be completed for production. If all the setups and tools are used to run only one prototype sample, all costs must be allocated to one part, whereas if a large batch of the same parts are run using the same operations and setups, the total cost can be allocated to all parts and maximize the price savings per part.
2. Materials

The material chosen will affect the cost of CNC machining in two ways: the cost of raw material and the cost of machining. The price of raw materials depends on their own value and rarity. Experienced procurement engineers will have a basic understanding of common machined materials such as metals (brass, aluminum, steel, copper, stainless steel) and plastics (PVC, ABS, PC, nylon, Delrin), the price of which varies with the type of material. Expensive materials may have better performance and be more durable for use. In addition, hard-to-process materials cost more to manufacture than other types of materials, and materials with poor machinability can also increase costs. For example, aluminum and ABS are easy to cut, while titanium and stainless steel are more difficult to machine. Engineers can choose the right material according to the production application, requirements and service life.

3. Equipment
CNC manufacturing machines and equipment, as well as tools or other products, also have a significant impact on the cost of CNC parts. Today, modern machines are not cheap, especially those with multiple functions, such as five-axis machining centers. Simpler machines cost less per unit of time. Capacity, model and size also constitute factors that reflect cost. For example, a regular CNC lathe will cost less to produce than a vertical CNC lathe, while a CNC machining center will cost more than a milling machine.
4. Geometry and design
Part geometry will affect CNC costs in many ways. The larger the part, the more material is required for the manufacturing process, which increases the cost. On the other hand, the more complex the part, the more difficult the machining process will be and the longer the production cycle time, which also increases the cost. Designs with easier-to-use features will be simpler and save a lot of time. Conversely, parts that have design tools that are difficult to complete or require multiple operations to complete will be slower to machine or even need to be scrapped.
5. Additional Processes
Some machined parts require additional handling, multiple secondary operations or surface finishing, all of which add to the cost, and if the final product requires some details and features to be added to the internal/external surfaces, the last product will definitely be more expensive.
6. Tolerance and precision
Precision tolerances and high accuracy always bring a higher price for CNC machining. Usually, parts do not need to have a unique tight tolerance unless it is necessary in a specific case, so the designer should submit drawings based on the production function. Tight tolerances are usually reserved for the interface of the part with other parts. In addition to this, the internal surface of the part is difficult to achieve tight tolerances and machining holes or cavities may produce burrs, which require additional time to remove. typical tolerances for Machinedsgn products are +/-0.02mm or as per customer requirements.
7. Labor Costs
Labor costs depend on many factors and vary from region to region and industry to industry, but for CNC manufacturing, Guangdong, China is the ideal location for manufacturing and developing CNC products and services.
In addition, machinist skills, frequency of operation, inspection standards, taxes, environment, regulations and other factors will have an impact on CNC costs.

How to reduce the cost of CNC machining?

After understanding the factors that affect the cost of machining, you should develop ways to reduce prices based on these aspects.
To help reduce costs, you can change machining times, start-up costs, material costs, etc. Some product requirements are beyond your ability to change, but taking steps to ensure your design is optimized can significantly reduce CNC machining costs. Here are a few of our suggestions for reducing CNC machining costs.
1. Rounded corner design
Sharp 90 degree corners require the machine to stop, rotate the part, and then continue the machining process. As you might imagine, these extra steps take up machining time and often cost you extra. Making changes to the design of the inside corner of the part can have an impact on the reduction of CNC machining costs.
If you adjust your design to include rounded corners and the machine can run continuously to create your part, you may be able to reduce your bottom line. Go one step further and make sure the radius of the inside corners is at least 1/3 of the cavity depth. a larger radius at the corners means that a larger tool can cut them efficiently, rather than a smaller tool having to cross the corners with a smaller radius multiple times.
2. Add the radius to the internal vertical edge
All CNC milling machines are cylindrical and will create a radius when cutting cavity edges.
Use a smaller diameter tool to reduce the radius of the corner. This means that multiple passes need to be made at a lower speed, and smaller tools cannot remove material as quickly as larger tools can in a single pass, which increases milling time and therefore project costs.
To reduce costs, experts recommend that the corner radius should be slightly larger than the radius of the tool that will be used to machine the recess. This reduces the load on the tool and further reduces manufacturing costs.
3. Limit cavity depth
Machining deep cavities will greatly affect the cost of CNC parts because of the large amount of material that needs to be removed, which is very time consuming.
The cutting length of CNC tools is limited: usually, they will work best when the cutting depth reaches 2-3 times the cavity diameter, designing a deeper cavity because of the need for special tools or multi-axis CNC systems which leads to increased costs.
4. Increase thin wall thickness
Increase the thickness of thin walls to reduce machining time. Thicker solid parts will be more stable unless weight is a major factor.
Thin parts tend to vibrate. When machining thin-walled parts, it is difficult to machine accurately because multiple operations at lower depths of cut are required to avoid distortion or cracking.
The design wall thickness of metal parts should be greater than 0.8mm (the thicker the better). For plastic parts, a minimum wall thickness of 1.5 mm or more should be maintained. Thin walls are often encountered when holes or threads are very close to the edge of the part. When placing holes in your design, be sure to also follow the above guidelines.
5. Limit thread length
Limit the maximum thread length to three times the hole diameter. For threads in blind holes, it is best to add at least 1/2 the diameter at the bottom of the hole.
Specifying longer threads than needed may increase the cost of the CNC part due to the special tooling that may be required.
6. Designing holes to standard sizes
Use standard drill sizes when designing holes. CNC holes can be machined quickly and accurately with standard drill bits. For non-standard sizes, the holes must be machined with an end mill, which increases the cost.
It is recommended to limit the depth of all holes to 4 times the diameter. If you make deeper holes (10 times the diameter), this will increase the cost due to the difficulty of machining.
7. Specify tolerances only when necessary
Defining tight tolerances will increase the cost of CNC because it not only increases the machining time, but also requires manual inspection. If specific tolerances are not specified on the technical drawing, standard tolerances (±0.125 mm or higher) will be used to machine the part, which is sufficient for most non-critical features.
The decimal points of size are important. They specify the accuracy level and instrumentation of the measurement. For example, two decimal points indicate that a machinist can use a vernier caliper for measurements, while three decimal points indicate that a micrometer or equivalent CMM tool must be used. To reduce costs, avoid adding extra decimal points to the dimensions.
8. Keep the number of machine setups to a minimum
It is recommended to design parts that can be machined in as few machine settings as possible, preferably in only one setting.
Rotating or repositioning parts can increase manufacturing costs, as this usually needs to be done manually. In addition, for complex geometries, custom fixtures may be required, which further adds to the cost. Particularly complex geometries may require a multi-axis CNC, which further raises the price.
Consider splitting the part into several geometries that can be CNC machined in a single setup and then bolted or welded together. This also applies to deep groove parts.
9. Remove text
Adding text to the surface of a CNC machined part can significantly increase the cost because of the additional time consuming machining steps required. If text is necessary, prefer to engrave on relief text, which requires more material removal.
10. Avoid (multiple) surface finishes
Surface finish improves the appearance of CNC machined parts and increases their resistance to harsh environments, but it also increases costs.
Requiring multiple different surface finishes on the same part can further increase the price, so try to choose the surface finish after machining and only require multiple surface finishes when absolutely necessary.
11. Choose the right material to reduce costs
The choice of materials for machining parts with workpiece types has two effects on cost: the cost of raw materials and the cost of material machinability. Some materials are more expensive than others as raw materials, while others are more difficult to manufacture than others. The lower the machinability of a material, the more expensive it will be.
If the material used is potentially hazardous, additional safety precautions are required, which increases the cost of production. The following section focuses on the cost of material machinability.
Machinability refers to how easy it is to cut the material. The higher the machinability, the faster the material is CNC machined and the lower the cost.
Copper is a very good conductive material, especially brass C360 is the most machinable metal, easy to grind and can be machined at high speed and may have the mechanical, chemical or electrical properties required for the application. But copper is much more expensive than aluminum. While aluminum is about 60% as conductive as copper, the weight and cost savings may prompt you to reconsider aluminum.
Steel is 10 times less machinable than aluminum and takes at least twice as long to process. Note that different grades of steel have different machining properties. For example, 304 stainless steel (the most common stainless steel alloy) has a 45% compatibility index, while 303 stainless steel (an alloy with a very similar chemical composition) has a machinability index of 78% and is therefore easier to machine. Stainless steel 17-4ph is difficult to cut. If high strength and corrosion resistance are not important, you can change to 316L or 304.
If hardness is an issue, 4140 may be your first choice, but 1018 is very low cost and takes an admirable surface hardening.
The processability of a plastic depends largely on its stiffness and thermal properties. Some plastics have excellent wear, corrosion or chemical resistance, others perform well under heat or flame, while others have excellent strength, impact or electrical properties.
POM (Delrin) is the easiest plastic to machine, followed by ABS. polyetheretherketone and nylon are other common engineering plastics that are difficult to machine. In general, the softer the material, the greater the risk of dimensional stability and drawing during milling.
For machining parts, many excellent materials can be machined, each with its own unique properties, applications and costs. Prices vary widely from stock material to stock material, but are usually based on general availability, making it necessary to select the most appropriate material for the situation.
12. Labor Costs
The machinist involved in making the part must be paid for his work. He takes the time to set up the machine for custom CNC operations and ensures that all operations are performed in a manner that produces good results. If the part is harder, more complex, and requires a higher level of expertise and trained mechanics, then production costs go up. These additional skills and experience come at a cost because they are primarily gained from on-the-job experience, not formal education. The more labor-intensive it is to produce a part, the more expensive it is.
The post-processing, finishing or assembly of the part also requires some additional labor work, which also adds to the labor cost. Therefore, outsourcing some precision parts to China is a good option because China has a high manufacturing capacity and labor costs are not particularly high.
13. Machine Costs
Modern machining and manufacturing equipment is different and very expensive. Can parts be done with multi-axis machines or do they require multiple machines. And how many different machines and operations are required. The size and capabilities of the equipment needed will add to the factors that affect the total cost.
You can rent several different types of CNC machines for this project. Which one you choose may affect the cost of your job. For 3-axis machines, including CNC mills and CNC lathes, multi-axis machines are relatively expensive to run.
When we get a project, our engineers will first check the production process, then choose the most economical production method, and finally we will get the production time. Since different production process will have different production time, sometimes the price of the workpiece will be high.
However, don’t worry, because our engineers are very professional and the prices we quote are accurate. Our price is not necessarily the cheapest, but it must be the best for the same quality.
14. Increase the number of parts purchased
Finally, there is the quantity of parts. The greater the number of parts, the lower the cost per additional unit. This means that large orders increase the final cost of the part, but lower the cost per unit. If you are making multiple identical parts, you can reuse the same CAM programming and fixtures, or you can cut multiple parts from the same inventory at once. The number of parts you order has a big impact on the unit price. So-called economies of scale can be a powerful tool because you know how to reduce CNC machining costs. Increasing the quantity from one to 50 reduces the unit price by more than 50%.
YAANG specializes in producing custom CNC precision parts with no minimum order quantity. Specializing in various models, small lots and prototype orders. We can give you a quick quote and delivery.
Consider ordering larger quantities for your next order.
15. Keep it simple
The overarching theme in these tips for reducing CNC machining costs is simplicity. When you design a complex part, it may require special tooling or fixtures, several machine setups or the help of special materials that will cost you more money.

How to control costs at the inquiry stage?

When you submit your next order for quotation, ask yourself the following questions to help you reduce your CNC machining costs:

• Have I optimized my part using machinability design guidelines? Learn how to optimize your CNC machinable part design if you don’t already know.
• Do I need all the features of my part for it to be fully functional?
• Can the part be broken into multiple, simpler parts for machining and then assembled?
• Can I change this material to something that is easier to machine and still meets my requirements?

After you have applied each of our tips for reducing CNC machining costs to your design, you can be sure that you have optimized your part for CNC machining. When you get to that point, you can find a CNC machining company that can make your parts come to life and at a low cost.
Yaang is the CNC machining partner you can trust. Our high quality comes from an attention to detail that is second to none. We identify materials, produce parts and ship them from one location. Our customers know they can trust us because we stand behind every product we make and are willing to do everything we can to ensure you are satisfied with your CNC machined parts.

Once you have optimized your design to reduce CNC machining costs and are ready to quote, please call us at +8618267732328 or submit your request online.

Source: China machining solutions provider – Yaang Pipe Industry (www.machinedsgn.com)