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CNC Precision Machining: Everything You Need To Know
Have you ever wondered how machinists make those heavy aluminum tools and engine parts? They definitely did not make them with hands or cast them in a furnace. They make these parts from a process called CNC precision machining.
For those who are new to the manufacturing world, CNC precision machining is a manufacturing process that enlists the use of computer programs to create any product to exact specifications. Therefore, this article will define the process, the different pieces of equipment used, its applications, the different programming, and the processing involved.
What is CNC Precision Machining?
If the question “What is precise machining?” still lingers in your mind, here’s the answer. Just as the name implies, CNC precision machining involves shaping raw material into a finished product by cutting out excesses as designated by a Computer-Aided Design (CAD) or Computer-Aided Manufacturing (CAM) blueprint. What’s more, machinists use this process in different manufacturing processes and on different materials.
Before making any product by precision CNC machining, using CAD or CAM programs to make the product’s blueprint is necessary. That is to say, these programs make highly detailed 3D outlines that a precise machining process must follow to replicate the product successfully.
From toys to medical devices, automobiles, or space shuttles, any product that has parts needs precision machining. Using Computer Numerical Control (CNC) equipment, the process utilizes actions like cutting, milling, turning, and electrical discharge machining to achieve the final product.
Although the process requires the overwatch of a skilled machinist, a machine does most of the work automatically. The Computer-Aided Design (CAD) software creates the design, and the Computer-Aided Manufacturing (CAM) software then translates it into manufacturing instructions for the machine. A final post-processor software codes the instruction into information the machine can understand. The machinists then load the instruction into the CNC equipment to start the manufacturing process.
Injection molding is a manufacturing process for producing parts by injecting molten material into a mold, or mold. Injection molding can be performed with a host of materials mainly including metals (for which the process is called die-casting), glasses, elastomers, confections, and most commonly thermoplastic and thermosetting polymers. Material for the part is fed into a heated barrel, mixed (using a helical screw), and injected into a mold cavity, where it cools and hardens to the configuration of the cavity. After a product is designed, usually by an industrial designer or an engineer, molds are made by a mold-maker (or toolmaker) from metal, usually either steel or aluminum, and precision-machined to form the features of the desired part.
Injection molding uses a special-purpose machine that has three parts: the injection unit, the mold, and the clamp. Parts to be injection-molded must be very carefully designed to facilitate the molding process; the material used for the part, the desired shape and features of the part, the material of the mold, and the properties of the molding machine must all be taken into account. The versatility of injection molding is facilitated by this breadth of design considerations and possibilities.
Injection molding machine molds can be fastened in either a horizontal or vertical position. Most machines are horizontally oriented, but vertical machines are used in some niche applications such as insert molding, allowing the machine to take advantage of gravity. Some vertical machines also do not require the mold to be fastened. There are many ways to fasten the tools to the platens, The most common are manual clamps (both halves are bolted to the platens); however, hydraulic clamps (chocks are used to hold the tool in place) and magnetic clamps are also used. The magnetic and hydraulic clamps are used where fast tool changes are required.
What is Aluminum Die Casting?
Aluminum die casting ;alloys are lightweight and posses high dimensional stability for complex part geometries and thin walls. Aluminum withstands good corrosion resistance and mechanical properties as well as high thermal and electrical conductivity, making it a good alloy for die casting. Low-density aluminum metals are essential to the die casting industry. The Aluminum Die Casting process retains a durable strength at very high temperatures, requiring the use of cold chamber machines. The molten metal is still contained in an open holding pot which is placed into a furnace, where it is melted to the necessary temperature. The open holding pot is kept separate from the die casting machine and the molten metal is ladled from the pot for each casting because these high temperatures would damage the normal pumping system. The pressure requirements for cold chamber castings are typically higher than those of hot chamber die castings.
WHAT ARE THE ADVANTAGES OF ALUMINUM DIE CASTING?
There are many reasons aluminum is the most commonly cast non-ferrous metal in the world. As a lightweight metal, the most popular reason for utilizing aluminum die casting is that it creates very lightweight parts without sacrificing strength. Aluminum die-cast parts also have more surface finishing options and can withstand higher operating temperatures than other non-ferrous materials. Aluminum die-cast parts are corrosion resistant, highly conductive, and have good stiffness and strength-to-weight ratio. The aluminum die casting process is based on rapid production that allows a high volume of die casting parts to be produced very quickly and more cost-effectively than alternative casting processes. Aluminum die casting has become the favored option for buyers worldwide. ;
Investment Casting (Lost Wax Casting)
Investment casting ;produces precise components while minimizing material waste, energy, and subsequent machining. It can also ensure the production of very intricate parts. This makes the investment casting process quite useful to design engineers. ;
Advantages Of the Investment Casting Process
Although most investment castings are small, the investment process can produce castings weighing more than 1,000 pounds. This capability is limited to a relatively small number of investment casters and requires special expertise in handling. Most cast parts fall in the ounces to a 20-pound range.
Versatile And Intricate Shapes:
Investment casting provides consistent and repetitive close tolerances along with intricate passages and contours. Many of these configurations are impossible to produce. For example, where machine tools cannot reach. Achieving net-shape or near-net-shape cast components can dramatically reduce post-cast processing costs.
Investment casting is a good alternative to weldments or fabricating. Many components can be combined into a single casting. The more that are combined, the better the manufacturing efficiency. Converting multi-piece components to a single investment casting typically delivers more dimensional accuracy and reduced part complexity.
Accurate And Smooth Surfaces:
The ceramic shell used is built around smooth patterns produced by injecting wax into a polished aluminum die. A 125 micro finish is standard, and even finer finishes are not uncommon. ;
Aluminium Gravity Die Casting
At Harrison, castings are able to produce quality aluminum gravity castings ;for a range of industries, including High Horsepower Diesel Engines, Defence, Gas Turbines, Machine Tools, Compressors, Pumps, Valves, Medical Equipment, Light Construction Equipment, Articulated Trucks, Photo Imaging and Printing.
What is Aluminium Gravity Casting?
Aluminum Gravity Casting is a permanent mold casting process, where the molten metal is poured from a vessel or ladle into the mold. The mold cavity fills with no force other than gravity, filling can be controlled by tilting the die. Undercuts and cavities can be incorporated into the component form with the use of sand cores. This process gives a better surface finish than sand casting as well as better mechanical properties, both due to rapid solidification.
Additionally, this process has a higher casting rate than aluminum sand casting, however, the metal molds are a higher cost than sand. Advantages of this process include the possibility of low gas porosity, and fine grain sizes can be achieved.
Compared to sand casting, this process requires less finishing and fettling and gravity die casting tends to produce a higher quality product. The Gravity casting production method is generally less cost-effective in the manufacture of tooling compared with sand casting.