CNC machining is a good way to realize when you want to create prototypes or mass produce end-use products. But the processing cost is often the main reason why people stop. There are several things that affect the cost of CNC parts, including materials, design, surface treatment, quantity and turnaround time. Fortunately, experts with rich CNC machining experience can greatly help you reduce cutting costs and final product pricing.
This article will summarize the top 10 skills of our engineers. By following these proven skills, you can obtain parts optimized to minimize costs and still meet your design requirements.
What Will Affect The Cost Of CNC Machining Parts?
Before discussing how to reduce costs, let’s briefly outline the following six factors that affect the price of CNC parts
The longer it takes to process a part, the higher its cost. Machining time is usually the main cost driver of CNC machining parts.
The prices of different raw materials are often different. Even some materials with similar performance but not commonly used will be much more expensive.
Stricter tolerance requirements will lead to more difficult machining and increase the rejection rate, which will also lead to higher prices.
The CNC programming time required to produce 1 piece and 1000 pieces is the same, so if more quantities are required, the total cost will be shared equally, thus reducing the cost of individual products.
If surface treatment such as coating, smoothing, anodizing and black oxidation is required, several processing steps and a large amount of cost will be added.
The short delivery time means that the supplier needs to coordinate more workers to arrange your order first, and has to delay the processing of other orders. This is also a small factor in the additional cost, which is called urgent handling fee in the industry.
10 Cost Saving Design Tips
Now that you know where the cost of CNC machining comes from, let’s see how to minimize it.
1. Select The Most Suitable Material
When you design and process parts, selecting the right materials is the most important way to save costs. The most suitable material for you is not the most expensive one. You must find the most suitable material according to the use and function of the part.
There are many materials with almost the same performance, but the prices vary greatly. You can check whether these alternative materials can meet the functional use. For example, SKD61 can save 50% – 70% of the cost by replacing SKH51 with the commonly used mold thimble.
On the other hand, softer materials such as 6061 aluminum are easier to cut, which means that the processing time is shorter. Harder materials require more expensive processing tools and are more prone to damage and wear tools. To sum up, harder materials require longer processing time and tool wear rate, thus increasing the cost of processing parts.
2. Try Not To Use 90 ° Internal Angle
A sharp or 90 degree internal angle will take up more processing steps and time, and will increase additional costs. However, most of the internal corners do not need 90 degrees, and the fillet does not affect the use of functions.
If you adjust the design to include fillets, the machine can run continuously to create your part. CNC machining tools such as milling cutters and end mills will automatically leave circular internal corners. Small or narrow fillet radii require more tool paths and special small tools, which will increase processing time and require tool replacement. In contrast, a larger radius at the corner means that a larger tool can cut them effectively.
For optimal design, ensure that the L: D ratio (length to diameter) of the inner corner radius is 3:1 or less. In addition, keeping all the inner corners have the same radius can reduce the processing time.
3. Minimize Internal Cavity
Metal or plastic parts with deep cavity design are usually time-consuming and difficult to process. Creating a cavity requires the removal of a large amount of material, which can lead to material waste, and it is difficult to remove chips, or special processes (such as wire cutting EDM or sink EDM) may be required to reach the depth. These will cost you more money.
Try to limit the depth of the pocket in the design to 4 times the length, and the ideal design depth is 2 to 3 times its diameter.
4. Avoid Thin Wall Design
Machined parts with too thin walls will require more time to process because they are very fragile. And it is difficult to maintain accurate tolerances because they often vibrate or deform. Slow processing, special processing technology and high scrap rate make these thin-walled parts more expensive.
The processing of thick wall parts is more stable and the processing cost is lower. In order to keep the processing price low, please avoid thin-wall design. The wall thickness of metal parts should be greater than 0.8mm and the wall thickness of plastic parts should be greater than 1.5mm.
5. Use Standard Outlet Size
When the machined parts are designed with threaded holes, the hole depth and thread size will affect the total price. In general, increasing the thread length in the fixture will not make the part stronger, so you do not need to pass through a hole larger than 3 times the hole diameter and shorten it as much as possible. If the length of the thread is 3 times the diameter, it will increase the risk of fracture and require more processing time. Very small threads require manual tapping, which also makes the price higher.
6. Avoid Complicated Parts
Special tools, multi axis CNC machines or some customized fixtures are required to process oversized, micro sized or complex designed parts, all of which will increase the total cost.
In some cases, such as complex parts that need to operate on multiple faces, you can try to split the parts into two or more separate parts, and then weld or bolt them together after processing. You may find that the cost is reduced.
7. Avoid Surface Finishing, Such As Tin Coating, DLC Coating, etc.
The surface finishing of CNC machined parts is an additional process to obtain the required surface characteristics or properties for aesthetic, corrosion-resistant, wear-resistant or other purposes. However, these heat treatment, sandblasting, special coating, anodizing and other finishes will increase the total cost. Therefore, they should be carefully evaluated according to the purpose.
If you want to reduce the total cost, it is a good choice to choose the standard machined surface. The machined surface is a fast and affordable choice, which is usually used for non display applications such as mounting brackets. The surface finish is equivalent to 125 RA in (3.2 RA m).
8. Avoid Excessive Use Of Strict Tolerances
Deke has ultra precision processing equipment and production experience, and can meet the tolerance of ± 0.001mm. However, we still recommend that tight tolerances should not be used excessively for non special purpose parts. Because the smaller the tolerance, the more processes and time the factory needs, which means that the price will be much higher.
9. Batch Order
Although modern CNC lathes and milling machines can operate more efficiently than before, they still require engineers to program and set them up. As we all know, the quantity of parts you order has a great impact on the unit price. If you order 10000 parts or only 10 parts, the price will vary greatly. Because mass production of the same parts can maximize the production efficiency and cost-effectiveness of CNC machining.
10. Promote Work And Prepare Production Plan In Advance
Develop product blueprint, promote design work, and complete final product design before production. This will allow CNC processing suppliers sufficient time to purchase raw materials, formulate production plans and deliver products within the agreed time. According to the production experience of Dongguan gaolue for many years, the longer delivery time can reduce the overall cost by 4% – 6%.
These are the top 10 design tips to help you reduce the cost of processing parts. In short, keep it simple and follow the standards. Let these design techniques go deep into your mind and apply them to your actual products, which will certainly help you reduce many unnecessary costs