A large range of fabrication techniques is available to product designers when it comes to producing metal parts. Casting and machining are two of these most widely used options. How do they compare, though?
This article gives a general overview of these two indispensable metal manufacturing techniques and their common advantages. Once you’ve done this, you’ll know how casting and machining differ and which method is probably best for your purpose.
Understanding Machining
In the subtractive manufacturing process of machining, excess material is removed from a workpiece using various tools, including cutting tools, discs, and abrasive wheels. Moreover, unwanted materials are eliminated using this process to shape the product as desired. CNC machining operations are frequently performed on stock mills, such as flats, bars, and welded or cast parts.
Examples of machined products are drilling bits, plaques, flanges, car parts, nuts and bolts, and numerous other tools and parts used in various industries. Here are some of the common machining methods:
Milling
CNC milling involves removing material from the workpiece using revolving multi-point cutting tools. When using CNC milling, the workpiece is usually fed to the cutting tool in the same direction as the tool’s rotation by the CNC machine. In manual milling, however, the machine feeds the workpiece in the opposite direction as the cutting tool rotates.
Rotating multi-point cutting tools are used in milling to shape the workpiece. Milling tools such as end mills, helical mills, and chamfer mills can be vertically or horizontally oriented. The CNC milling process also uses CNC-enabled milling equipment, sometimes called mills or mill machines. These machines can be oriented either vertically or horizontally.
Turning
Turning is a machining process that creates a cylindrical shape by rotating the metal on a lathe while a cutting tool moves linearly along the diameter to remove metal. To make various shapes, the cutting tool can be angled differently. Turning can be done manually, with an automated lathe that doesn’t require constant operator supervision, or with a traditional lathe. The most popular kind of automation used nowadays is CNC or computer numerical control.
Lathes and CNC turning machines are the tools used in turning. Turret lathes, engine lathes, and particular-purpose lathes are among the available varieties of lathes.
Grinding
Grinding removes tiny amounts of material from cylindrical and flat surfaces. When feeding material into the grinding wheel, surface grinders reciprocate the work on a table. Typically, the wheel cuts between 0.00025 and 0.001 inches deep.
The workpiece is mounted on centers and rotated with a cylindrical grinder while an abrasive wheel’s periphery is applied. When producing small parts in large quantities, centerless grinding creates a surface where the ground surface only relates to itself.
Drilling
Drilling is a type of machining where the workpiece is drilled with cylindrical holes created by multi-point drill bits. To drill vertically aligned holes with diameters equal to the drill bit used for the operation, the machine feeds the rotating drill bit perpendicular to the plane of the workpiece’s surface. Nevertheless, specific machine configurations and work holding devices can also carry out angular drilling operations.
Drilling creates cylindrical holes in the workpiece by spinning drill bits. The design of the drill bit permits the waste metal, or chips, to separate from the workpiece.
Exploring Casting
Casting is a manufacturing technique that pours molten metal into a mold, allows it to solidify, and then cools it to room temperature to create the desired-shaped metal parts. Regardless of their size, it can create intricate and complex parts.
Casting is, therefore, appropriate for mass production since it can yield isotropic metal parts in large quantities. Additionally, various types of casting vary depending on the material and mold used to satisfy particular user requirements. Below are some of the standard casting processes:
Sand Casting
Sand casting is a versatile metal forming technique that creates intricate metal castings using non-reusable sand molds. It’s a crucial process for producing metal components in different capacities, from ounces to tonnes. This method is precious in numerous industries due to its exceptional ability to shape alloys with elevated melting temperatures, including titanium, nickel, and steel. Molding sand is a composite of inexpensive, recyclable materials with remarkable heat resistance.
Die Casting
It is also known as metal die casting. High pressure die casting is a precision-driven manufacturing process that involves melting a metal with a low melting point and injecting it into a long-lasting die-casting mold. These steel molds, made with cutting-edge techniques such as CNC machining, ensure high levels of accuracy, precision, and repeatability when producing metal components.
The process has a long history, dating back to the nineteenth century. It has evolved into two distinct procedures: hot chamber and cold chamber die casting. Each process can handle a wide range of materials due to their different melting points, such as aluminum in cold chamber casting and zinc, tin, lead, and magnesium alloys in hot chamber casting.
Squeeze Die Casting
Squeeze die casting solidifies molten metal between hydraulic press plates by applying high pressure, a technique that combines the casting and forging processes. It generates highly dense, nearly pore-free, net-shaped casting. Direct and indirect are the two main categories, and each has special benefits. Comparable to high-pressure die casting, indirect casting is pouring metal into a die and pressing it under pressure. Shorter production cycles, better metallic properties, and improved mechanical properties are the outcomes of the process.
Factors Influencing the Choice
These are some of the factors that can influence the choice of machining techniques:
Production Volume
Production volume is a critical factor that helps manufacturers decide whether to use machining or casting techniques. Machining will be preferred, for low to medium production volumes, where flexibility and faster setup times are a significant consideration. The process of machining produces small quantities or prototypes with a high level of efficiency.
Casting, however, excels in big-batch production contexts. With the production of molds finished, the casting process is able to be conducted in a highly automated way, making it possible to produce a large number of parts whose individual processing is minimal. For companies that seek to make a large number of duplicated parts regularly, casting is the most suitable choice for production due to its high volume production capacity.
Material Properties
The properties of the final product’s materials also play an essential part in deciding the best manufacturing method between machining and casting. The range of materials for machining is diverse; it allows you to use metals, plastics, and composites. This helps overcome casting issues for materials that are hard to cast, such as high-strength alloys with complex internal structures.
Melting and pouring items into the mold suits the melted materials, including various metals and some plastic. Through casting, it is possible to create intricate shapes and minute details. This can be an advantage when designing objects that require specific material parameters.
Complexity of Design
Design variability is a major determining factor when choosing between manufacturing and casting as the final part. Machining can manufacture components with very complicated geometries or delicate details. Its high accuracy enables it to achieve tight tolerances and smooth surface finishes, such that it is suitable for applications involving precise design and details.
Casting is more suitable for intricate shapes or inner cavities, while wheeled mold and two-part molding techniques are ideal for simpler forms. It allows the manufacturer to generate detailed drawings with the help of the process, as there is no need to have additional assembly or machining operations. The casting process may be more efficient for pieces with a more intricate design or complicated geometry than the manufacturing procedure.
Dimensional Accuracy and Surface Finish
Precision and surface finishing are key parameters always required in most manufacturing processes. Machining is characterized by excellent parameters such as dimensional accuracy and surface quality. Its close-tolerance cutting tools, as well as the smooth processed surfaces, not only satisfy the needs of many demanding industries but also outperform these industries’ standards.
Casting, being able to attain dimensional and surface qualities to a great extent of standard, may sometimes have inaccuracy a little and the finish could be better than machining. On the other hand, the recent introduction of advanced casting techniques, namely investment casting or pressure sand casting, ensures that casting liberates the need for accurate dimensions and a smooth surface finish for specific applications.
Cost Considerations
The cost components, determinants in manufacturing decisions, are as essential as the manufacturing itself. The manufacturing process is more costly on a per-part basis, generally, obviously, when targeting mass production. The process requires labor and time, which leads to high costs due to the operations needed for each part on its own. On the other hand, machining gives an edge in flexibility and a shorter time required to make preparations, which can, to some extent, cover the costs in the event of small volumes.
Molding is more economically viable usually for big production runs, which provide lower cost per part in terms of the material and manpower. While establishing the mold has a higher initial cost, casting can help achieve cost-effective metering in creating many parts consistently. Hence, it is necessary to pay great attention to the capacity of volumes and costs of the process when the production method is chosen.
Advantages of Machining
There are several advantages of machining techniques:
Precision and Accuracy
Machining leads to the sequence of the process unmatched in the manufacturing process. Employs multiple precision techniques such as Milling, turning, and grinding machines, producing ultra-precise tolerances and surface finishes. This precision at this level is essential to industries such as aerospace, automotive, and medical devices, as even a slight deviation from the mark can be hazardous in most cases.
With the characteristic of producing parts with intricate shapes, machining can produce parts with multiple features that can meet the most complicated needs, which is done consistently and precisely.
Versatility in Materials
The ability to machine from a variety of materials is one of the main attractions of this technology. There are metals like aluminum, steel, and titanium, as well as plastics, composites, and exotic alloys. That machining process has been developed to suit the specific requirements of those different materials.
This adaptability is a crucial factor contributing to the diversity of manufacturing areas. It allows manufacturers to replenish different components for various industries, ranging from construction and infrastructure to electronics and engineering.
Customization Possibilities
With machining comes excellent variety with unlimited customization possibilities to exact the desired parts that are crafted specifically with the particular application in mind. Whether developing new models, including the unique manufacture of separate elements, or producing small portions with specific features, machining gives us the flexibility to respond individually.
Through the applications of CNC technology (computer numerical control) and the inclusion of advanced software, machinists can now quickly program complex shapes and patterns, accommodating minor iterations and design changes without much effort.
Minimal Material Waste
On the other hand, the machining process is distinctive because it causes a small proportion of material wastage compared to different manufacturing methods. By the subtractive method, metal parts are created by removing the redundant material from solid blocks
Consequently, the utilization of raw materials is maximized with a decrease in the adverse environmental effects of production. In addition, recycling the chips and portioned dregs minimizes waste levels, thus elevating machining to be an industrial choice in the world of sustainable practices.
Benefits of Casting
The casting process has several benefits for your rapid prototyping and all other needs. Some of them are:
Mass Production Capabilities
Casting specialized in mass-scale production so that it could produce many parts with high efficiency in a comparable moment. With an EMI, you can mass-produce highly automated parts, giving you high throughput and low per-part production costs compared to machining. Such is casting popular among industries with a high rate of standardized part production, automotive, construction, and household counterparts.
Complex Geometry Feasibility
Another essential feature of casting is its perfectness at producing parts with a highly complicated design, which sometimes could not be done through machining or other manufacturing methods. Casting benefits component manufacturing by creating a problematic form for a single operation without borrowing the extra machining operations.
It allows engineers to get creative with their designs and go beyond the state-of-the-art technology boundaries in this way for complexity.
Cost-Effectiveness for High Volumes
Since casting is a cost-sensitive process for high-volume production runs with lower material and labor costs per part, it is one of the favorable methods to mass-produce products. Once we have the initial mold, we can save a lot on the volume production of further parts because the processing of the mold is complicated and expensive.
Still, the subsequent parts of the mold are produced at a lower price than the machining. Such scalability of casting contributes to the fact that this particular manufacturing method is the most desirable in industries characterized by the high importance of economies of scale, such as in producing consumer goods, industrial parts, and construction materials.
Variety of Material Options
Casting provides building materials with hundreds of different options to fit the application needs in any field. Whether it is an alloy of aluminum, steel, iron, or any other group of specialty materials, casting provides room for all types of materials containing every kind of performance characteristic and property. Along with this variety, manufacturers can opt for the materials that meet the most applicable criteria, whether strength, durability, corrosion resistance, or other necessary attributes.
Design Considerations for Each Process
Before selecting either of the processes, some design considerations will determine the most suitable one for your needs:
Design for Machining
The design for machining necessitates looking into the suitable materials, optimizing the part geometry for the major machining processes, and minimizing the need for secondary operations. The designer should prioritize features that are easy to machine and can be reached quickly with no or least effort. However, the designer has to ensure that the material stock is adequate for machining allowances.
Design for Casting
Casting Design involves precisely considering parameters such as block shape, draft angles, and material stream characteristics. Designers must look into creative molds that allow the materials to run efficiently and significantly decrease the chance of imperfections, i.e., porosity, shrinkage, or deformation. Considering draft angles and filets into places where the part will be molded can facilitate effortless removal and lower the probability of casting defects.
It is also advisable to consider the location of borders and heights to secure uniform filling and solidification of the cast. Through casting design optimization, manufacturers can produce a highly functional part with minimum defects and cost for production.
Conclusion
Machining and casting offer distinct advantages and considerations in the realm of manufacturing. Machining provides unparalleled precision, versatility in materials, customization possibilities, and minimal material waste, making it well-suited for applications requiring high-quality, complex parts in low to medium production volumes. On the other hand, casting excels in mass production capabilities, feasibility for complex geometries, cost-effectiveness for high volumes, and a wide variety of material options, making it an ideal choice for industries with high demand for standardized components. Contact Zintilon to learn about which techniques is best for you.
However, if you know the most suitable for your project, Zintilon has you covered. Get a quote today!
FAQs
Which Process Is Better for Producing Prototypes?
Machining is often preferred for prototypes due to its flexibility and ability to create parts from various materials quickly. Machining allows for rapid iteration and refinement of designs, making it ideal for prototyping applications where design changes are frequent.
What Are Some Common Materials Used in Casting?
Common materials used in casting include metals such as aluminum, steel, iron, and copper alloys, as well as various types of plastics and composites. The choice of material depends on factors such as strength requirements, corrosion resistance, and cost considerations.
How Can You Reduce Costs When Machining Parts?
To reduce machining costs, consider optimizing part designs to minimize material waste and machining time, selecting cost-effective materials, and maximizing efficiency in machining processes. Additionally, batch processing and automation can help lower labor costs and improve productivity.
