Effective prototype machining requires the use of easily machinable materials. Plastics, metals, and composite materials are compatibly used in the process. However, plastic (polyvinyl chloride), aluminum, and acetyl are preferably used due to their low fabricating and machining costs compared to metals such as steel. The choice of these materials is important in ensuring the accuracy and high geometric tolerances of CNC prototypes. As outlined here, materials help achieve the weight, machinability, strength, and flexibility in prototype machining.
Plastics Make Lightweight CNC Prototypes
Plastics are preferably used for machining prototypes whose performance and functioning depend on light weight and excellent corrosion resistance. These materials have low density and low reactivity with water and air components. Due to their good mechanical interconnectivity, plastics can also be bonded easily among themselves and with other materials. The ease of plastic prototype machining is reflected in research finding that the material can be machined into a prototype within 30 minutes, supporting a quick turnaround from design to prototype.
This property is critical when targeting low machining and prototyping costs. In return, they can be molded into different geometrical conformations. While plastics may have a rough surface due to machining, they possess a high feature transfer fidelity due to low mold shrinkage. Poor heat conductivity of plastics ensures that temperature increases in the machining equipment do not translate to the prototype affecting tolerance and surface quality.
On the other hand, plastics have a high corrosion coefficient, making them less suited for CNC prototyping of easily worn parts. Similarly, for transparent plastics, heat from machining may cause polymer rearrangements in its structure affecting the optical and autofluorescence properties of the material.
However, alternatives can be explored. Delrin is easily machinable plastic and is preferably used instead of aluminum in prototyping. While aluminum and steel may require a coating to reduce corrosion, Delrin has higher corrosion resistance. Delrin-machined prototypes can be tested in diverse environments because the material is additionally strong, has high friction coefficient, and is resistant to fuel effects.
The material can be used in machining, testing, and developing prototypes of bushings, wear pads, fluid parts, gears, and pulleys. On the other hand, the material has low mechanical interconnectivity and cannot be bonded with itself or other prototype machining materials.
Metals are Strong and Stable
Surface integrity concerns in prototype machining are best addressed when working with metals. Both aluminum and steel offer high CNC prototype strength and stability. Metals exist as sheets/plates and bars making them more stable during CNC prototype machining. On the other, they possess high tensile strength, unlike ceramic or glass. CNC machining is preferably used in metal prototype machining because the technique best helps achieve the desired geometry and tolerance.
Both materials are suitable for high-temperature prototypes with smooth surfaces and aesthetic appearances. CNC machining ensures minimal disruption at the surface of the material. Aluminium is suited for lightweight machining prototypes, with moderate strength and corrosion resistance. Steel, on the other hand, is useful for prototyping stronger and heavier machine parts. Additionally, steel is less costly than plastics and composite materials, thus lowering the prototyping costs.
However, steel can be hard to machine and is corroded easily compared to aluminum. Stainless steel is preferably used in prototype machining compared to mild steel. While both are costly to machine, stainless steel edges mild steel with good corrosion resistance and easy welding attributes, which are essential for the geometrical and aesthetic appearance of the material.
Other commonly used metals in CNC prototype machining include brass, titanium, and copper. Copper has low surface integrity, but is suitable for making corrosion-resistant and high electrical conductivity prototypes. Titanium is used in high-value prototypes and offers excellent performance in high-stress machining parts.
Composites are Effective for Multi-Functional Parts in Prototypes
Composites may be composed of ceramic, metals, polymer, or carbon. Mechanical interconnectivity within CNC prototypes may necessitate the use of composites instead of single or several materials to achieve functional objectives. Interface composites allow induced bonding within the prototype through chemical, mechanical, or thermal means. Porous media composites allow the infiltration of a secondary material into the CNC prototype, while blended feeds allow a ratio-based combination of materials in a prototype to support functional variation.
The essence of composites in prototype machining varies with type and role. Composites may be used to enhance the mechanical properties of the prototype, especially when the primary material has functional flaws under strenuous conditions. Other reasons may be potential functional degradation or discoloration. Secondly, composites may aid in complementing functionality, whether thermal, electrical, optical, or chemical. Composites may be required to achieve optimal functionality of prototypes and enhance performance. Weight-saving applications of composites are well established in prototype machining. This is achieved through redirecting prototype loads and concentration of stress in selected areas. On the other hand, overhanging geometric combinations in a prototype structure can be reduced and replaced with lighter composite materials.
Overall, effective prototype machining benefits from the varying properties of materials used. Plastic and aluminum are preferably used due to their low weight and high corrosion resistance attributes, while steel offers strength and geometrical accuracy.
Composites, on the other hand, are used to adjust prototype qualities during and after machining. Material selection for prototype machining requires careful consideration of their properties alongside the functional and performance properties of the prototype. These determine the time and costs associated with the process and the general outcomes of the final machine part.