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What Does Soft Machining Mean?
Soft machining is a form of machining that employs low cutting forces to remove excess material from soft and ductile raw materials. This machining process is effective for prototyping parts and handling brittle materials because it operates under lower pressure, temperature conditions, and force.
Unlike hard machining, it minimizes thermal damage and has less tool wear, making it a perfect choice for cutting soft and ductile materials like soft metals, composites, plastics, and elastomers. Machinists don’t have to put soft materials through heat treatments since they can be easily machined.
Benefits of Soft Machining
Soft machining offers extensive advantages, including:
Cost Effectiveness
Soft machining is highly cost-effective for prototyping and low volume production since it doesn’t require expensive tooling and setup. It enables seamless testing of new designs before mass production, reducing the risks of costly errors. The materials used in soft machining are typically more affordable than hard CNC machining and ideal for low-budget projects.
High Dimensional Accuracy and Superior Surface Finish
Manufacturers utilize soft machining for applications requiring fine tolerances due to its high precision and surface quality. For instance, soft machining of biocompatible plastics provides smooth edges on surgical tools and implants. The lower material removal rate of the soft machining processes ensures precision, smooth surfaces, and minimal tool wear.
Complex and Delicate Geometries
This process offers higher flexibility in handling intricate designs and can accurately produce geometries, particularly in materials that are too soft for conventional methods. Soft machining provides excellent results in machining delicate, flexible, or thin-walled components that are likely to deform under high cutting forces. Soft machining has proven resources in different industries, especially electronics. It allows the creation of micro-features on PCBs without compromising the substrate.
Versatility in Material Processing
In soft machining, machinists can work on various materials using the same setup, including composites, soft metals, plastics, and elastomers. For instance, manufacturers in the aerospace sector machine lightweight composites like glass-reinforced composites and carbon fiber-reinforced plastics with the same setup for plastic or metals.
Low Energy Consumption
Soft machining entails energy-efficient processes compared to traditional hard machining. It requires less power since it requires lower cutting forces and pressure. Its lower carbon footprint makes it a widely embraced approach for industries prioritizing sustainability.
Standard Methods Used in Soft CNC Machining
Soft machining encompasses various high-precision techniques with distinct nuances and benefits. Here, we will discuss the standard methods machinists employ in soft machining.
Milling
Milling is a versatile and low-speed cutting method for handling intricate designs in soft machining. It involves using a cutter with multiple cutting edges to remove excessive material from the workpiece. Milling is commonly used in the soft machining of parts with desired shapes and tight tolerances. It is a critical step in the rapid prototyping of parts in the automobile, medical, and aviation industries with strict tight tolerance demand.
The cost-effectiveness of this approach renders it as an essential process for handling low or full-scale production. It allows the creation of complex 3D parts and achieve highly polished surface finish. Machinists rely heavily on milling to create large-scale parts and handle designs or parts that are challenging to produce with conventional techniques. The CNC milling process is compatible with all types of materials, including metals, plastics, polymers, alloys, etc., and can repeatedly create identical parts with tight tolerance.
Drilling
This process of making holes with utmost accuracy and control in the workpiece uses drill presses that can be applied to a milling machine. Drill bits used in drilling holes in a workpiece are designed so that formed chips fall away from the workpiece, ensuring the cutting zone is debris-free.
Maintaining a perpendicular position during prototyping helps minimize drifts and misalignment. Performing a center drill before drilling ensures hole accuracy. Moreover, multi-axis capabilities and head rotation allow for precise angled drilling in soft machining.
Turning
Turning refers to the use of relatively low force to shape a workpiece into the desired form by rotating it continuously as it engages a stationary cutting tool in a linear direction. This precision machining process forms a cylindrical shape using lathe machines.
Although machinists can turn prototypes manually or automatically, manual turning can be demanding since it requires continuous supervision. In contrast, automatic turning is more efficient for mass and low-volume production since it requires little human input or intervention. Machinists program parameters such as cutting forces and speed from a computer when using CNC machining methods like CNC turning.
CNC turning enables consistent and efficient creation of workpieces tight tolerances and high accuracy in high-volume production. Machinists employ single-point cutting tool in soft machining, engaging the blank from different angles to achieve the desired shape.
Grinding
This process relies on abrasion to remove excessive material from raw materials, creating the final shape of the workpiece. It provides ultra-fine finishes and tight tolerances in soft machining operations. In soft machining, machinists use a rotating abrasive wheel to grind the material’s surface, ensuring tight tolerance. This moving abrasive wheel works as a minuscule cutting tool when it comes in contact with the workpiece surface. It shears off all small chip particles from the workpiece.
Common Materials Used in Soft Machining
Manufacturers often use soft machining for ductile materials with relatively low hardness, including:
Non-Ferrous Metals
The absence of iron content in non-ferrous metals makes them a compatible material for soft machining. Examples of nonferrous metals include copper, aluminum, zinc, magnesium, and lead. They are usually easy to cut, turn, grind, and drill. These metals provide fine finishes and are incredibly cost-effective. Non-ferrous metals exhibit excellent thermal and electrical conductivity, making them ideal for machining prototype parts.
These lightweight metals reduce the overall weight of parts in the prototyping and product development processes. Furthermore, finishing machined nonferrous metals with processes like anodizing provides better results.
Plastics
Soft machining of plastics is a core aspect of CNC machining due to their versatility and can undergo soft machining with specific properties. Plastics are compatible with soft machining because of their lightweight nature and ease of processing. However, they are known for their poor thermal conductivity. Hence, machining experts recommend removing generated heat and chips from the cutting area during plastic machining.
Although plastic prototype parts are often cast or drawn, product developers and engineers usually employ soft machining processes like grinding, drilling, milling, and turning to shape plastics into the desired form. However, using sharp cutting tools with smooth surfaces to machine plastics is essential. It allows the tool to deliver quick cuts on the plastic and move away without complications, resulting in a smooth machined surface. Typical plastics processed through soft machining include:
- Elastomers: rubbers, latex
- Fibers: CF, GF, AFU
- Thermosets: silicon rubber, epoxy and formaldehyde resins, and polyurethane.
- Thermoplastic: polypropylene, polyethylene, PVC, PVDF, PTFE, polyamides, polyesters
Composites
Composites are advanced machining materials with hard and layered structures. They offer exceptional mechanical properties, including higher fracture toughness, low weight, and resistance to wear and corrosion. Some composites like Kevlar, glass fiber, and carbon fiber composites exhibit high ultimate tensile strength (UTS) that exceeds that of metals.
Composites often require special tools and methods to shape them into specific dimensions due to their high impact resistance and strength properties. Soft machining composite materials help shape parts with high accuracy and tolerance while maintaining the integrity of the material. Examples include glass-reinforced composites, carbon fiber-reinforced plastics, and fiberglass.
Industry Applications of Soft Machining
Soft machining is ideal for making complex parts that require high accuracy and tight tolerance in varying fields, such as:
Aerospace
Soft machining in the aerospace industry provides precision and performance for demanding environments. It enables the manufacturing cabin components, fuselage parts, and wing ribs. Soft CNC machining also aids the creation of actuators, engine housing, motion control sensors, filter bodies, and landing gear parts and discs.
Consumer Goods
Manufacturers of consumer products such as jewelry, musical instruments, and furniture rely heavily on soft machining to achieve aesthetics and functionality for CNC-machined parts. Soft machining is suitable for creating consumer electronics, furniture, pianos, carving, and engraving.
Electronics
The electronics sector benefits enormously from the perks of soft machining. It is ideal for machining the casing of different electronic components using CNC routers and CNC machining processes. Soft machining also facilitates the production of CNC-machined electronic components like jigs, PCBs, and semiconductor devices such as gad distribution channels, wafer plates, solder flex stencils, and wafer carriers.
Medical
Manufacturers of CNC medical parts and instruments apply soft machining because of its flexibility, high accuracy, and tight tolerance. It aids in the rapid prototyping of parts and medical instruments and the production of orthopedic implants for knee and hip replacement. More particularly, the application of soft machining in the medical field enables the manufacturing of surgical instruments and endoscopic tools and is suitable for creating parts for diagnostic equipment.
Challenges of Soft Machining
Product engineers and manufacturers across industries encounter various challenges when soft machining different products. We’ll explore some of these challenges and helpful considerations to ensure success in this section:
Tool Selection and Optimization
Soft tooling is often less durable compared to hard machining. Rapid wear and deformation occur due to high pressure and temperature conditions. As a result, this can reduce the tool life and call for frequent tool changes, increasing production costs. Therefore, experts recommend optimizing tool geometries, using lubricants, and choosing the right tool coating to prevent the material from sticking to the tool in soft machining.
Heat Dissipation and Thermal Expansion Problem
Soft materials exhibit low thermal conductivity, resulting in localized heat buildup during machining. Due to unwanted thermal expansion, localized heat buildup can cause dimensional inaccuracies in machined parts. For instance, excessive heat can cause material softening or melting in acrylic machining, impacting surface quality.
Therefore, ensure that cutting parameters like depth of cut, speed, and feed rate relative to the material properties are optimized to avoid overheating and deformation. Also, AT Machining experts recommend using coolants and lubricants to reduce heat buildup and ensure a superior surface finish.
Risk of Material Deformation and Burr Formation
Deformations such as warping and bending sometimes affect the accuracy of soft materials during soft machining. Machining defects such as burrs can form, requiring secondary finishing operations. More so, machinists often utilize specialized tooling when machining soft polymers to avoid excessive material distortion.
Unsuitability for Hard or Tough Materials
Soft machining has limited applicability, especially when machining very hard materials like superalloys, hardened steel, tungsten, or ceramics. Machinists rely on specialized or hard tooling and hard machining techniques to cut hard metals. For example, aerospace components manufacturers often employ hard machining for titanium parts while aluminum undergoes soft machining.
Conclusion
Soft machining is ideal for prototyping since it aids design validation and product testing before mass production. It is commonly used in industries prioritizing precision, subtle processing conditions, and minimal material waste. Soft machining processes are ideal for handling different delicate precision-machined parts in medical, aerospace, and electronics industries since they ensure precise material removal with minimal mechanical stress.
AT-Machining is a top CNC machining services provider with cutting-edge technology and expert knowledge in different machining processes. We take pride in technical revisions, material selection, and design modifications for efficient implementation, as well as cost-effective production at faster turnaround times. Our highly skilled and certified personnel can manage all aspects of your projects, from prototyping to production, with the utmost attention to detail. Contact us today to speak to our team of professionals about improving your production line and processes!
