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When you want to create a prototype or mass manufacture end-use products, CNC machining is a good way to achieve. But the machining cost is often the main reason why people stop. There are several things that will affect the CNC machined parts cost, including materials, design, finishes, quantity, and turnaround time. Luckily, an expert who has rich CNC machining experience can greatly help you to reduce the cutting cost and product final pricing.
This article will summarize the top 10 tips from our engineers, by following these proven tips, you can get the parts that are optimized to minimize costs and still comply with your design requirements.
Before looking at how to reduce costs, let DEK briefly outline below 6 factors that will affect CNC parts’ prices
Now you are clear where the cost of CNC machining comes from, let’s see how to minimize it.
When you design a machined part, choose the right material is the most important method for saving cost. It’s not the most expensive material that is best for you. You have to find the most suitable material according to the purpose and function of the parts.
There are many materials with almost the same performance, but the price is a huge difference, you can check whether these alternative materials can meet the functional use. For example, in common use mold ejector pin, use SKD61 material instead of SKH51 can save 50%-70% cost.
In order to give you a general idea of the range of costs that may be required to select materials, I conducted a quick search of the prices of different materials to find 6″x 6″ x 1″ plates. While ordinary plastics like ABS will cost you about $15, peek of the same size, known for its robustness and dimensional stability, costs as much as $225. Similarly, for metals, a 6061 aluminum plate costs about $24, a 304 stainless steel plate costs $139, and a precision ground 316 stainless steel plate costs as much as $285 each!
On the other hand, the softer materials such as aluminum 6061, cut more easily, which means less machining time. The harder materials require more expensive machining tools, and are more likely to break and wear tools. To sum up, harder material will take long processing time and tool wear rate then will increase the cost of machined parts.
Sharp or 90-degree internal corners will take up more machining processes and time, and will increase extra the cost. However, most parts of the internal angle do not need 90 degrees, with rounded corners that do not affect the use of functions.
If you adjust your design to include rounded corners, the machine can run continuously to create your part. CNC machining tools like milling cutters and end mills automatically leave rounded internal corners. A small or narrow internal corner radius needs more passes and special small tools, which will increase machining time and require change tools. In comparison, the larger radius at the corners means larger tools can cut them efficiently.
For optimum design, make sure the radius of your internal corners has an L:D ratio (length to diameter) of 3:1 or less. In addition, keep all internal corners have the same radii can reduce machining time.
Metal or plastic parts with deep internal cavities (deep pockets) design are often time-consuming and hard to machining. To create the cavities need to remove a lot of material, which can result in wasted material, and difficulty removing chips, or may require a special process such as Wire Cut EDM or Sink EDM to reach the depth. These will cost you more money.
Try to limit the depth of pockets in your design to 4 times the length, ideal design is the depth up to 2 to 3 times their diameter.
The machined parts with overly thin walls will take more time to machine because they are very fragile. And because they often vibrate or deform, it is difficult to maintain accurate tolerances. Slow processing, special processing technology, and high scrap rate make these thin-walled parts more expensive.
Thick wall parts are more stable and cost less to machining, to keep the machining price low, please avoid the thin wall design, the metal parts’ wall should thicker than 0.8mm and the plastic parts’ wall should thicker than 1.5mm.
When a machined part design with tapped holes, the hole depth and tap size will affect the total price. Typically, increasing the length of thread in a hold doesn’t make the part any stronger, so you don’t need to thread a hole more than 3 times the hole’s diameter and keep it shorter if possible. If the length of thread going 3 times than diameter will increase the risk of breaking and take more machining time. Very small threads will require hand tapping, also make the price higher.
So, use standard tap sizes can reduce risk and cut down the cost. For example, use 4-40 size of the tap is more common and cost-effective than 3-38 size. In addition, design the threaded holes bigger than 2-56″ if possible. That will save your money.
To machining the very large size, micro size, or complex design parts will request special tools, multi-axis CNC machines, or need some customized jigs, all of these will add to the total cost.
In some cases, the complex parts such as those needing operations on multiple faces, you can try to split the part into 2 or more separate parts, and then welded or bolted together after machining, you’re likely to find a cost reduction.
Surface finishing of CNC machined parts is additional processing to achieve a desired surface characteristic or property for cosmetic, corrosion resistance, wear resistance, or other purposes. But these heat treatment, bead blast, specialized coating, anodizing, and so on finishes will add to the total cost. So they should be carefully evaluated according to the purpose.
If you want to cut down total cost, it is a good choice to choose the standard as-machined finish, the as-machined finish is a quick affordable choice often used for non-show applications such as mounting brackets. The surface finish is comparable to 125 RA µin (3.2 RA µm).
DEK has ultra-precision processing equipment and production experience, which can meet the tolerance as tight as ±0.001mm. However, we still suggest that close tolerances should not be used excessively for non-special use parts. Because of the tighter tolerance, the more process and time the factory will take, which means that the price will be much higher.
Not every part needs tight tolerances, in addition to some precision mold components, medical parts, and aerospace accessories, other parts we suggest follow the common standards such as ISO 2768 standard, which is reasonable for the CNC machined parts design.
Although modern CNC turning and milling machines can run efficiently than before, but they still need engineers to program and setup. As everybody knows, the number of parts you order has a significant impact on the unit price, ordering 10,000pcs of parts or just 10pcs, the price is hugely different. Because mass production the same parts can maximize the CNC machining production efficiencies and cost-efficiency.
If you need 50K pieces of the same parts, after testing the samples. it will be much cheaper to order 50K at one time than 5000 parts for 10 times.
Make a product blueprint, promote the design work, and complete the final product design before beginning production. This will allow the CNC machining supplier to have enough time to purchase raw materials, make the production plans and deliver products within the agreed time. According to DEK’s production experience for many years, longer lead time can reduce the overall cost by 4%-6%.
Above are the top 10 design tips for helping you to reduce the cost of machined parts, to summarise, Keep it simple and follow the standard. Let these design tips go deep into your mind and apply them to your actual products, which will surely help you reduce lots of unnecessary costs.
If you have more profound tips, welcome to share them with me. If you are looking for a professional and cost-efficient CNC Machining supplier, don’t hesitate to contact our sales team today!
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