Machined parts can be made in lots of ways but are typically produced on CNC machines. The shape of the part and its complexity will determine what type of machine will produce it. The most common type of machine is a 3 or 4 axis CNC milling machine that can produce parts in virtually any material. Machined parts are often produced when it is more economical to do so than using another process. Volume is usually a key consideration as the production of machined parts often suits lower volumes or prototype runs.
Some parts can be machined by hand. A piece of wood cut using a saw is essentially a hand machined item. Items cut and formed this way are usually produced in very low volumes where the size makes them impractical to machine in any other way. A CNC machine effectively cuts a part using a rotating tool, but does so very accurately.
Like any production process, machined parts have their limitations. Machining an item from a solid block doesn't usually change the properties of the material which can have advantages and disadvantages. Lubricants are usually used to prolong the life of cutting tools and prevent overheating. When using a lubricant, the material is restricted to one that is non-porous. Items machined in wood can be done so using different cutting tools and speeds without the need for any lubricant. The cutting tools slice through layers of the wood efficiently, reducing friction and heat build-up, thus eliminating the need for a lubricant.
The form of a machined part is limited to the type of cutting tool used. In most commercial applications, the smallest cutting tool available is around 1mm in diameter although smaller cutting tools are possible, if less popular. Cavities that are small and deep are more difficult to machine because access is restricted, and the cutting tool can't always reach them effectively. Therefore, it is important to address this in the design of the product.
A lot of rapid prototyping machine shops can manufacture parts within hours, but they tend to have very limited cutting tool profiles which can often restrict the features created on a part. We have worked extensively with many machine shops to understand the best profiles to use, minimising any delay when parts need to be machined quickly.
Some components have to be machined as they cannot be made using any other process. Examples of such parts are critical aircraft and engine components and those used in medical devices. Other manufacturing processes can introduce weak points in materials, especially items like mouldings and castings where invisible hairline fractures could eventually cause catastrophic failure.
One issue with machining a part is material waste. Because you're cutting away a solid block of material, there is a high percentage of wasted material. In most cases, this material can be recycled but even so, it introduces an additional process which effectively increases the carbon footprint. Ensuring the correct sized stock material is used can dramatically reduce the amount of wasted material.
A small selection of parts we designed for machining
CNC machining is a very precise process and for the bulk of items machined this way, the dimensional tolerances are fairly standard. It is easy to expect a machined part to have a tolerance of +/-0.1mm on a feature that is say 50mm long. Where greater precision is required, the machining process requires greater stability and control. It is possible to achieve much higher tolerances on certain features. If precision is critical, there are special CNC machines that have the ability to do this.
Often, when production begins to ramp up, machining certain items becomes uneconomical, and other processes are better suited. We are experienced in modifying designs for production volume increases to ensure your product is as profitable as possible. Often, components machined in an aluminium can be die-cast where the volumes are high. The transition often requires some design modifications, but the cost-saving is significant. The same applies to parts that are machined in most plastics. Often these can be re-designed for injection moulding.
Features like threaded holes and inserts can easily be added to a machined component. A lot of CNC machines have built-in tools to create these features without the need for secondary operations.
We have extensive experience in designing parts for machining. Whether they require are turned components or flat, we can design your parts in detail to ensure your product is as cost-effective as it can be. Get in touch with us today.
A machined part showing detailed features - component of a PET system machined in acetal co-polymer
If your project requires sheet metal design, we can help you with a solution. Get in touch with us today to find out more about our sheet metal fabrication design service.