CNC machining is an integral part of many industries – with its help, you can produce the tools and details you need with unparalleled precision. Companies are often looking for ways to cut budgets – and cutting CNC machining costs is no exception. To reduce the price of CNC processes and the cost of machining services, one should first understand how they work and know the factors that affect the price. CNC machining has long been widely used in many industries. Given the wide range of possibilities that CNC machines offer, it is a fact that complexities, problems, and unnecessary costs can and often do arise during machining. How to improve CNC machining and reduce production costs? Does it take longer to machine parts while using the machine economically? We write about it below!
What factors affect the price of CNC machining cost?
To eliminate a particular portion of the cost, preparing a structurally, technically, and economically appropriate design of the finished product and planning and defining the machining process itself carefully is necessary.
Machining time, which significantly affects its price, depends mainly on the complexity of the geometry of the workpiece.
Initial costs, including CAD design development and process planning, account for a large portion of the value of a small-volume product, but for large or batch quantities, these costs are fixed, so batch sizes can be reduced, raising the price per unit of product.
Prices for materials and finishing are factors that affect the total value of the product. In addition, the proportion of the number of finishes on the product’s surface will also have an impact. In some cases, companies using a cheaper production method will reduce the end result of the final production model. How to understand the cost of production?
How to calculate the cost of CNC machining?
The cost of CNC machining will depend on several factors, including the time it takes to complete a project and specific machines, such as three- and five-axis machines. Companies in the CNC industry often set their hourly rates for different types of devices. For example, a five-axis machine usually costs around 400 to 500 zlotys per hour, while a three-axis machine usually costs less. It’s worth remembering that these are just the operating costs of a CNC machine (any CNC milling machine generates costs). They can serve as reference points, although it will also be necessary to consider the work’s value. In addition, the price is also affected by several other factors, which will be presented in the following sections of the article. Since costs can vary, contacting a potential CNC shop/company is best before deciding on an order to see how it will affect your budget.
What affects the cost of CNC parts?
Before lowering the cost of CNC machining, you should first understand the factors that affect the cost of CNC parts – machining time, startup costs, material costs, and more. Here is some basic information on each factor that can be used to reduce production costs ultimately:
- Machining time: this is often the main cost factor in CNC machining. Typically, the longer the process takes, the higher the price.
- Initial costs: these are usually fixed. They are intended to cover CAD file preparation and product planning. In small batches, startup costs can be high.
- Material value: the price of the chosen bulk material and the ease of processing the raw material are crucial factors in CNC machining costs.
- Other manufacturing costs: Some CNC machined parts have special requirements – such as tight tolerances or thin walls. They usually require specific tools, additional machining steps, and lower cutting speeds. All of these factors affect processing times and ultimately increase costs.
- Material surface finish: adding a finish to a part can improve its appearance and make it more resistant to harsh conditions. While this can be beneficial, it increases processing costs.
Cost of CNC machine tools
When hiring a company to complete a project, we can choose from many types of CNC machines. Some of them cost more, which can affect the price we end up paying for their use. For example, 3-axis machines that are more standard can cost between 100 and £200 per hour. Others, such as multi-axis machines, are more complicated to operate, so that they will be priced higher – usually from 300 to 500 zloty per hour. The price of a used machine can vary depending on many factors, including the company’s prices and how much it has to pay the operator. It’s best to talk to representatives to get an idea of machine prices before starting a project.
How to reduce CNC machining costs – practical tips
To help cut costs, changes can be made to CNC machining time, startup costs, material costs, and more. Some product requirements can’t be changed, but taking steps to optimize your design can significantly reduce the needed budget. Here are some of our tips for reducing CNC machining costs.
Rounded inside corners
A sharp 90-degree angle requires stopping the machine, turning the part, and continuing the process. As you can imagine, these extra steps consume processing time and often incur additional costs. Redesigning the inside corners of a piece can reduce the price of CNC machining. If you adjust the design to include rounded corners, the machine can run continuously, creating the part you need while reducing the value of the texture. Taking it a step further, it’s a good idea to ensure the inside corner’s radius is at least 1/3 the depth of the groove. A larger radius in the corners means that a larger cutter can cut them effectively – you won’t need a small cutter that has to cut corners with smaller radii repeatedly.
How to reduce the cost of CNC – Avoid deep pockets
Deep pockets can negatively affect the cost of CNC machining because getting them means removing a lot of material. Removing material is time-consuming and may require special tools to achieve the desired depth. It is worth trying to limit the depth of the pockets in your design to four times the length. CNC tools have limitations regarding grooving – ideally, the depth should be two to three times the diameter. You can cut four times the diameter, but it will cost more.
Limit the use of tight tolerances
When a part is designed with tight tolerances, it increases cost because it increases machining time and requires manual inspection. Unfortunately, achieving tight tolerances on the inside surface is difficult because machining holes and other grooves can cause edge burrs. These defects require an additional step beyond manual inspection – deburring. Deburring is a very time-consuming process that also increases the cost of CNC machining. If the design does not specify a tolerance, the standard tolerance of ± 0.001 or higher is used. It applies to many parts, so tight tolerances should be reconsidered and specified only when necessary. If we have advanced design knowledge, we can further reduce the cost of CNC machining, as they often have tighter tolerances. One final note on tolerances – the numbers representing dimensions are critical because they indicate the level of precision required for the part. In CNC machining, this level of accuracy translates into the tools that will be used for machining. The more decimal places, the more complex the tool and the higher the cost. Remember to remove all unnecessary decimal fractions from your design regarding tolerances.
Expand thin walls
Dealing with thin walls takes time because they are fragile. This is because they are repeatedly machined with a shallow embedment depth to avoid errors or cracks. A common cause of thin walls is locating holes and threads near the edges of parts. It is best to place them strategically. A thick border is more stable, and the cost of processing is lower. It is worthwhile to design metal parts with a wall thickness of more than 0.8 mm and plastic parts with a wall thickness of more than 1.5 mm, as long as weight is not an issue.
How to reduce the cost of CNC – Limit the length of threads
Threads that are 1.5 times longer than the diameter of the hole will not strengthen the connection, and lines that are longer than necessary may incur additional costs because special tools may be required to make them. Save costs by designing components with a maximum length of three times the hole diameter. Remember that threads in blind holes should have an additional half of the diameter at the end of the hole without the thread.
Optimizing the threaded hole
Two cost factors for threaded holes are thread depth and thread size. As we mentioned, increasing the thread length beyond this point will not make the part stronger. „Falling in” to a depth greater than three times the hole diameter increases the risk of thread breakage and additional time – both of which increase the final price. Very tiny threads also increase cost because they require manual threading, which increases time and risk. Instead, limiting the depth to three times the bore diameter and sticking to standard thread sizes in the design can help reduce CNC machining costs. It’s also worth trying to keep threaded holes larger than 2-56 inches.
Use a standard drill size
If you plan correctly and make sure the holes in the part are a standard size, CNC machines can use drill bits to create holes quickly and efficiently. However, non-standard sizes often require the use of cutters, which can negatively impact costs. Hole depth also plays an important role – although holes up to 10 times in diameter can be created, they are difficult to machine and more expensive. To minimize the cost of CNC machining, having holes up to 10mm in diameter, let’s design in 0.1mm increments. For holes more significant than 10mm in diameter, use 0.5mm increments. If designing in inches, refer to the fractal size of the bit and use a fractional part of an inch. Regardless of the size of the hole, let’s make sure that the length of the hole does not exceed four times the diameter.
Avoid multiple restorations
Finishing CNC machined parts helps protect them from harsh conditions and often improves their appearance. Unfortunately, it also increases costs. Going a step further and requiring multiple finishes on a part will cost more. If you want to save money, consider choosing an all-over finish. It’s a good idea to ask for multiple completions only when necessary.
Divide complex parts
If you have complex parts – such as complex geometries, rotation, or repositioning – machining the part may require custom fixturing, manual turning, or a multi-axis CNC system. All of these involve costs. Suppose we can’t reduce the complexity of the part. In that case, we can still find a way to reduce the cost of CNC machining by dividing the piece into two or more individually machined parts that can be assembled into the needed whole. Cost reductions can be achieved by dividing the part into two or more geometries that can be machined in a single setup.
Avoid small parts with large proportions
All parts with extreme proportions are often difficult to machine. For example, small parts with high elongations are difficult to machine because they tend to vibrate. As with many other aspects of the process, it increases costs if it is difficult to machine.
To reduce costs, design all components with less than four aspect ratios and consider attaching them to the wall or adding bracing to increase rigidity.
Order in bulk
The number of parts ordered has a significant impact on the unit price. So-called economies of scale can be a powerful tool when thinking about how to reduce costs. Increasing the quantity from 1 to 50 can reduce the unit price by more than 50%. How to reduce the cost of CNC machining? There is no single effective way to do this. Specific methods require the use of one type of material to do the manufacturing of final products as ordered. Industrial developments are helpful (especially in using a model for a specific order).