Removal of Chips and Oils from Machined Parts

Swarf is a term used to describe metallic and abrasive particles removed by a cutting or grinding tool. The swarf produced from machined parts resembles sawdust from woodworking in this context. Many manufacturing processes produce swarf, including drilling, grinding, slotting, knurling, reaming, sawing, broaching and tapping. The three main metal machining processes are drilling, milling and turning. Drilling is the most common machining process; it is estimated that three-quarters of the metal removed in operations results from drilling. It is typically performed with a twist drill and spiral swarf exits through the flutes in the drill. Milling machines use rotating, moving cutters to drill holes, create slots, cut gears and bore holes. This process allows material to be removed from metals on both flat and irregular surfaces of a wide variety of shapes and sizes. Turning involves cutting with fixed tools applied to a rotating metal workpiece on a lathe. However, swarf is dangerous in many ways and requires more rigorous cleaning procedures to ensure environmental safety. Because it does not decompose easily and typically has sharp edges, it can cause cuts and lacerations if not handled properly. Gloves and protective eyewear should always be worn during such operations. Small metal particles and strips can penetrate under the skin as dust, or objects flying from machines can strike any part of the body. The extremely sharp edges of larger swarf can also cause serious cuts and even loss of limbs. Additionally, swarf may contain reactive metals that are highly flammable and are typically coated with oils used as coolants during machining operations. Workshops and workstations must ensure they have the necessary fire prevention measures in place and are equipped with extinguishers designed for metal fires. Contact with metalworking fluids during machining operations can cause irritation to skin, eyes, nose, lungs and throat; respiratory diseases, skin diseases and even cancer have been associated with exposure to metalworking fluid. This is because the vapors they produce can easily penetrate the human body through various routes. The severity of the illness will depend on the type of fluid used, the type of infection and the duration of exposure. Of the four metalworking fluids, straight oils are the most flammable because they can easily accumulate heat and therefore can produce vapors that may lead to hazardous and dirty working conditions. This creates fire and explosion hazards. Swarf can be quite flammable due to its high surface area; this is especially true for metal swarf containing iron, titanium, calcium and magnesium. Additionally, swarf stored in boxes or piles, especially if coated with metalworking fluids, can be prone to spontaneous combustion. Since most swarf has razor-sharp edges, it often flies several meters during machining procedures and can cause injuries. Needle-like swarf can cause puncture wounds that may be minor or serious depending on size. Swarf can also cause serious damage to machines. Cleaning swarf and oils from machined parts is a critical step in the production process to ensure that the finished product meets quality standards and functional requirements. It should be remembered that the choice of cleaning method depends on factors such as the type of machined parts, the composition of swarf and oils, relevant materials, required cleanliness standards and environmental considerations. Safety regulations must always be followed, appropriate personal protective equipment (PPE) must be used, and the environmental impacts of the selected cleaning method must be considered. Detailed information on frequently used methods and points to note for effectively cleaning swarf and oils from machined parts is provided below:

1. Mechanical Cleaning:

Brushing: Stiff brushes, nylon bristle brushes or wire brushes are used to physically remove swarf and oils from part surfaces. This is particularly useful for removing larger swarf. Air Blowing: Pressurized air can be used to remove swarf and oils from crevices and hard-to-reach areas.

2. Chemical Cleaning

Solvent Cleaning: Solvents such as isopropyl alcohol, acetone or specialized degreasers can be used to dissolve and remove oils from machined parts. This method is effective for cleaning complex and intricate parts. Alkaline Cleaning: Alkaline solutions can break down oils and greases. Immersion in an alkaline cleaning bath followed by rinsing can help remove both swarf and oils. Emulsion Cleaning: In some cases, water-based emulsion cleaners can be used to clean both swarf and oils. These emulsions may be more environmentally friendly than solvent-based solutions.

3. Ultrasonic Cleaning:

Ultrasonic cleaning involves immersing parts in a tank filled with a cleaning solution and exposing them to high-frequency sound waves. The vibrations help dislodge and remove swarf and oils from part surfaces and cracks.

4. Steam Cleaning:

Steam cleaning uses high-pressure steam to dislodge and remove swarf and oils. It is effective on parts with complex geometries and hard-to-reach areas.

5. Detergent Cleaning:

Specialized detergents can be used with water to create an effective cleaning solution. Detergent solutions can break down oils and help remove swarf.

6. Aqueous Cleaning Systems:

These are automated cleaning systems that use water-based solutions to remove swarf and oils. They may include various stages such as washing, rinsing and drying.

7. Vacuum Systems:

Vacuum systems can be used to remove loose swarf and oils from part surfaces. These systems can be combined with brushes or air jets to increase cleaning effectiveness.

8. Manual Cleaning:

In some cases, particularly on delicate parts not suitable for aggressive cleaning methods, manual cleaning using cloths, rags and brushes may be necessary.  

Swarf and Sustainability

Swarf generation in the manufacturing industry is a common byproduct of metal machining operations. Traditionally, swarf is considered waste and is typically discarded as scrap. However, with growing environmental awareness and a shift toward sustainability, swarf recycling has become increasingly important. Recycling swarf rather than disposing of it (landfill or incineration) has environmental advantages. Metal swarf is generally recyclable and is the preferred disposal method due to environmental concerns regarding potential contamination with cutting fluid or waste oil. The ideal way to remove these fluids is to use a centrifuge that will separate the fluids from the metal and allow both to be recovered and prepared for further processing. Among the advantages of swarf recycling are keeping cutting fluid out of the waste stream and reducing the amount of ore mining and metal refining required to meet demand for metal stocks. Production from recycled scrap metal stocks uses at least 4 times less energy per unit of production to obtain an aluminum ingot from extracted ore, and this includes the environmental impact of mining.   Sources: https://www.cohenusa.com/blog/what-is-swarf-recycling-your-machiningscrap-for-cash/ https://en.wikipedia.org/wiki/Metal_swarf https://www.aboutmechanics.com/what-is-swarf.htm https://www.airbench.com/latest/what-you-need-to-know-about-coolantsand-swarf/ https://www.kemet.co.uk/blog/cleaning/removing-swarf-and-oils-frommachined-parts   Prepared by: Murat Soygür