Custom CNC machining is not a new concept in the industrial and manufacturing world. It comes with vast applications, including punching, plasma cutting, forming, laser cutting, welding, and many more. But what does custom CNC machining mean and how does it work? This guide provides a comprehensive view of this engineering methodology.
To begin with, CNC is an acronym for the term “Computer Numerical Control.” It is a subtractive manufacturing process that specializes in creating custom-designed components from a workpiece, using a set of commands, coupled with computer-controlled machining equipment. The custom machining process involves chipping off layers of the solid part to be produced, with each movement inching the workpiece closer to the final machined product.
What is Custom CNC Machining?
Custom CNC machining encapsulates the use of several materials in several industrial applications. They include plastics, metals, foam, glass, wood, and composites. CNC designers and machinists use these materials in large CNC machining, aerospace component machining, and other manufacturing processes. Custom CNC machining is incomplete without CNC machines. These are computerized pieces of equipment that automate the machining of engineered parts. Using these tools, the subtractive manufacturing process provides a methodology which differs from liquid injection moulding and 3D printing, both of which implement formative manufacturing and additive manufacturing processes, respectively.
What makes CNC machining different from other methodologies, like 3D printing? It uses a subtractive manufacturing process, through which the machining tool removes parts from the workpiece to create the final machined component. On the other hand, 3D printing methodology uses an additive manufacturing process, through which the printing machine assembles layers of material to create the finished product. What makes the custom CNC process unique is that it is easy to produce engineered components with high precision and accuracy. In the same vein, it is cost-effective, making it a sought-after methodology in the manufacturing industry. However, one main drawback is its limitation when handling complex designs.
Step by Step Procedure of Custom CNC Machining
Custom CNC machining has evolved tremendously in the engineering world. In earlier times, CNC machine shop used punched tape cards. Fast forward to today, CNC manufacturers use computer-controlled equipment to perform various CNC machining operations on a workpiece, including cutting, sawing, broaching, lapping, honing, and drilling. Regardless of the intricacies performed using this methodology, the underlying processes remain the same, in the following order:
- The design engineer creates the computer-aided design (CAD) model using related software.
- The design is fed into the system, which converts it to a set of CNC programs.
- The CNC machine takes this set of computer instructions.
- The CNC machine designs the final component from the workpiece using these programs.
Types of Custom CNC Machining Operations
It is worth noting that CNC machining is applicable in several industries, including aerospace, automotive, construction, agriculture. As such, the finished components include the following:
- Surgical tools
- Automobile frames
- Hydraulic components
- Aeroplane engines
Custom CNC machining involves removing layers of materials from a workpiece using any of the processes:
- Thermal, and
Embedded in these processes are milling, drilling, and turning operations. Starting with the first machining process (milling), CNC multipoint cutting equipment cuts out layers of materials from the workpiece fed by the CNC machine. Both movements occur in the same direction. On the other hand, the drilling process involves drilling cylindrical holes in the workpiece. Another factor worth pointing out is that the CNC machine feeds the drilling tool perpendicularly to the solid part’s surface. As such, the holes drilled vertically align have diameters that are the same as that of the drill bit. But that is not all to the drilling process. CNC shops can employ unique CNC machines to perform angular drilling operations. Some of these procedures include:
Undertaking Custom CNC Project Based on Size Considerations
Some custom CNC machining projects are simple and less time-consuming, while others are intricate and daunting to undertake. The level of machining challenges encountered boils down to one unique factor – size. Machining large or heavy parts poses several difficulties to most CNC shops. The “size” factor hinges on two elements:
- Large components
- Heavy components
Machining large components require special CNC machining tools to position and process the workpiece. Additionally, the successful machining of the solid material (metal, plastic, et cetera) doesn’t focus on the equipment alone. Experienced operators are required to carry out the process with precision and accuracy. Setting up the machine is complex and may occupy more workspace than anticipated. In the process, several factors may influence the finished components’ high-fidelity. CNC shops that take on these projects may have to install cooling systems to reduce heat production in the manufacturing plant. Besides, it also involves a significant degree of stress.
Machining custom heavy parts come with its downsides as well. First, the CNC shop would have to procure specialized CNC machining equipment to handle and process the workpiece. There is a need to hire professional CNC machining operators. Such parts may be too heavy for the workspace and stress the machining tools.
Sourcing Free Custom CNC Models for Machining Projects
Designing a custom CNC model for a project can be challenging, as the designer has to factor in several factors to ensure the production of high-fidelity components. Hence, it is not a walk in the park for most CNC clients. However, it is mandatory to design a model from scratch to machine a workpiece. Free CNC project files exist on the following platforms: vetrics.com, openbuilds.com, CNC Facebook groups, and Pinterest. Some projects to embark on include:
- Encrypted personal storage vaults
- Personal protective equipment (PPE)
- CNC furniture
- Marine steam engine
- CNC engraving
- Accessories, including earrings, brooches, rings, bracelets, tie clips, belt heads, necklaces, cufflinks, bow ties, to mention a few.
Cost of Undertaking Custom CNC Projects
CNC machining comprises two parts – multi-axis CNC machining and 3 axis CNC machining. The former entails indexed CNC 3+2 axes, continuous 5 axis CNC machining, and mill-turning. On the other hand, the latter entails CNC turning and CNC milling. When implementing any of these operations in custom CNC machining, the manufacturer has to consider costs, which are broken into three parts: machine costs, material costs, and labour costs.
Custom CNC Machine Costs
It is worth noting that the cost of CNC machines takes two-third of the total cost of the custom CNC project. The rate comes with its unit of measurement – cost per hour. To arrive at this calculation, divide the CNC equipment purchase cost by the sum of the machine’s operating hours. Generally, this is pegged at eight years. Each year comprises 5,000 work hours. There are various types of CNC machines, which implies that the cost differs from one to another.
For CNC turning machines, expect the cost to be around $35/hour. Whereas, for 3-axis CNC milling equipment, its cost is pegged at $40/hour. It excludes the operator’s cost, which can be around $35/hour. Multi-axis CNC tools have costs, ranging from $75 to $120 per hour, or even more. Owning and operating CNC machines cost way less or are on par with that of industrial 3D equipment.
Custom CNC Material Costs
When totalling the cost of custom CNC production, the manufacturer has to consider material costs. As discussed before, there are several materials used in CNC machining, including metals and plastics. For materials with dimensions of 6” x 6” x 1”, here is a breakdown of the expected costs:
Aluminum 6061, Aluminum 7075, and stainless steel 304 cost $25, $80, and $90, respectively. Plastic materials, like ABS, POM (Delrin), and Nylon 6, are $17, $27, and $30, respectively. There might be material wastage when machining components, seeing that CNC machining is a subtractive manufacturing process.
Custom CNC Labour Costs
The only element of labour comes into play when setting up the process, including the CNC machines and CNC programs. However, these are one-off costs, unlike 3D printing, which entails surface polishing, cleaning, and support removal. Custom CNC has remained consistent over the years. While being constant, the designing, tooling, and other machining processes have evolved to enhance the product’s aesthetics, precision, and accuracy. The noticeable change in the CNC industry encapsulates the manufacturing supply chain networks. Online manufacturing networks is a game-changer in automating the quoting process.
It is easy to precisely calculate the production cost of a CNC component using its design specifications, material type, and other factors – thanks to artificial neural networks and machine learning. As such, the pricing process is instant and affordable, reducing the cost of CNC manufacturing.
Bottomline of Custom CNC Machining
CNC machining has taken over the engineering industry, as its application is prevalent in aerospace, consumer electronics, automotive, medical, defence, and oil and gas. Its operations include punching, flame or plasma cutting, welding, forming, and shearing. This methodology comes with several manufacturing possibilities. These include tooling, production, prototyping, and hybrid manufacturing. It comes with several merits, like adaptability, minimal waste, agile technology, reduced labour cost, optimal productivity, accuracy and consistency.
CNC machining provides manufacturers and clients with consistent product quality. This process exceeds that of manual machining as it is possible to exactly repeat it. As such, manufacturing several parts accurately becomes easy, increasing production speed and efficiency.
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