Tag: metalworking fluids

Considerations for Coolant Selection

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Finding the optimal metalworking fluid is a difficult task because no fluid is “one-size-fits-all.” Each shop has its own unique set up of machines, operations, metals, etc. Operators have to consider many factors before selecting the optimal fluids or fluids for their shop. The optimal fluids should successfully perform the following core functions:

  • Lubricate the cutting edge
  • Disperse heat from the cutting edge and workpiece
  • Flush away chips from the cutting edge

Additionally, there are secondary functions a coolant can improve your operations. These include:

  • Corrosion protection
  • Extending tool life
  • Reducing energy consumption and machining forces
  • Improve surface finishing

To find a coolant that can perform these functions, you should take the following factors into consideration.

Machine Requirements

The types of machines in your shop will determine what type of fluid you will need. Older, swiss-type lathes can use neat oils. Whereas newer and more sophisticated CNC mills and lathes perform better with a water-soluble product. This is because higher speeds and higher pressures need more cooling than swiss-type lathes. The water does an excellent job cooling the cutting edge and workpiece. For neat oils, the cutting diameter plays a key role in determining the appropriate viscosity. The smaller the diameter, the lighter the viscosity should be to maintain and improve flow characteristics.

If your machine is operating at high speeds and/or high pressures, it is wise to consider a low-foam coolant or a specialized “high-pressure” coolant to use. Synthetic coolants are also an option as they tend to have lower foam rates than semi-synthetic and soluble oils. If your shop has a wide variety of machines and operations, you can consider using different fluids that are tailored to each operation. Over-consolidation can cause issues and may not be worth the savings. Fluids can be bought in smaller quantities and be used in limited cases to ensure performance and tolerances are met.

Shop Preferences

Machines do the heavy-lifting in metalworking, but there are still people behind each operation programming the CNC or working the lathe. Operators always get coolant spray on their skin and could be subjected to mist or spray. Finding a product that does not cause irritation nor spray/mist is paramount to keeping your operators safe and happy.

Shops have to consider the costs and labor involved in changing fluids as well as maintaining fluids. Cheaper fluids may save money, but will require more maintenance, monitoring, and change-outs. If your time is limited, investing in higher cost fluids will free up time to complete other machining tasks.

The ancillary equipment in the shop also can influence what type of fluid you need. If your sumps are equipped with oil skimmers, paying extra for a fluid with advanced tramp-oil-rejection characteristics may be unnecessary. Automatic mixers makes synthetic coolants a more attractive option since the concentration control required for synthetics is much more stringent than semi-synthetics and soluble oils. Understanding what is in your shop will help determine what fluid is appropriate for you.

Operations and Water Quality

As mentioned before, operations with higher speeds and pressures will call for a fluid with robust extreme-pressure (EP) additives to cut the toughest metals. In slower operations, a soluble or neat oil can be sufficient.

Your shop’s location will play a key role and fluid selection since the tap water is different in each town. If your shop has harder tap water, your machining might be negatively affected with higher chloride and sulfur content. Softer water is susceptible to more foaming. Avoid using softer water in higher pressure machining to limit foaming issues. It is recommended to charge up a sump with tap water and then use deionized (DI) water for topping off the sump and maintenance.

Shops can install a DI-Water line that can hook right up to an automatic mixer and improve coolant mixing. Distributors, like Twin Specialties, offer water testing services in the context of metalworking fluids. We can learn more about your water and make product and operational recommendations to improve coolant performance.

Workpiece Materials

Not all metals are the same. Some are soft, some are hard. Some metals are more reactive and require more care and specialized fluids. Magnesium requires certain additives or fluids that designed to machine magnesium. When machining carbide, it is best to use an amine-free coolant that does not react with the carbide and result in cobalt leaching. Harder metals like Inconel or titanium require coolants with EP additives and superior cooling to ensure heat is dispersed and friction is reduced. If you machine titanium or exotic metals in limited circumstances, it may be beneficial to keep a pail or a few gallons of a robust coolant in storage used specifically for those jobs and operations.

Potential Contamination

Contamination can occur frequently and in many forms. The main contaminants to watch for are: oxidation, tramp oil, and biologics. To combat oxidation, many fluids have anti-oxidant additives. It is key to monitor temperature as excessive heat will oxidize the oil. Antioxidants are limited in coolants; once all of the additive is consumed, the oil degrades quickly and will need be replaced sooner rather than later.

Tramp oils can change the oil’s viscosity, thus its flow characteristics. Having coolants with tramp-oil-rejecting compounds will help, but using oil skimmers is an excellent option to combat tramp oil. The skimmers remove the oil off the top of the sump and limits tramp oil being circulated through the machine. Oil filters are recommended to keep tramp oil from circulating through the system. Neat oil systems should use 5 micron filters and coolant systems should use 15 micron filters.

Outside biological contamination like bacteria can wreak havoc on your machine and cause clogs and ruin your fluid. Many fluids contain biocide additives to combat bacteria, but many factors allow it to grow uncontrolled. Be mindful to thoroughly clean your machine before recharging it. Any remnants of bacteria will multiply and ruin your fluid. Hot operating environments spur bacteria growth so it is recommended to implement as much climate-control in your shop as possible. Circulating the coolant will also make it tougher for bacteria to grow. Tank-side biocide additives like Grotan can supplement fluids and fight bacteria. Ensuring your coolant has proper concentration will ensure there is enough biocide to prevent bacteria growth.

Concentration

Monitoring concentration is key for maintaining your fluid. Some fluids, like synthetics, require tighter control and more monitoring. If you are limited by time, using a soluble or neat oil will reduce the time needed to monitor your fluid. Coolants typically run between 5 to 15% concentration. Using a refractometer to regularly track concentration is the best way to monitor and maintain coolants. Technical data sheets include refractometer charts and BRIX factor information to ensure the coolant is mixed optimally. If the line in the refractometer is blurry, that is a sign of contamination in the sump. Automatic mixers are ideal for charging sumps and eliminate human error or measuring biases that may occur when mixing coolant.

Takeaways

Selecting a metalworking fluid is a thorough and long process. Taking these considerations into account will set you up for long-term stability and success. Working with a metalworking fluid distributor and/or manufacturer is strongly recommended to help select to correct product. Twin Specialties offers a wide range of metalworking fluids and fluid maintenance resources to ensure you get the most out of your fluid.

How Long is Lubricant’s Shelf Life?

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When buying lubricants, you have to consider how long they will last. For high-volume users, this is not as much of an issue compared to smaller-volume users. High-volume users’ regularly consumer and reorder lubricants and typically have systems in place to monitor usage and spending. Small-volume users might be spread a drum or two of a lubricant through the course of a year. When consumption is spread out, you have to start to consider shelf-life into your purchasing decisions and operational processes.

Where can I find Shelf-Life Information?

Table made by George Wills and Dr. A.R. Landsdown

Information on a lubricant’s shelf life can be found on a technical or safety data sheet. If it is no t clearly defined, manufacturers and distributors can provide guidance on shelf life for its products. However, this information might be based on storage only or based on typical operations. George Wills and Dr. A.R. Landsdown provide a brief list of lubricants and their shelf-lives for products that have shorter shelf-lives.

Some technical data sheets (TDS) can show how long a lubricant can last in use before losing oxidation stability. This is measured in operating hours. Most oxidation tests will show a lubricant can last 5000+, 8000+, 10000+, etc. hours. However, like all scientific tests, this is done in a controlled environment (usually set by ISO or ASTM standards and specifications). We know that not every operating environment is like an ASTM or ISO test.

What Determines a Lubricant’s Shelf Life?

A lubricant’s shelf life depends on a variety of factors; some of which depend on the lubricant itself and some depend on usage. Greases have much shorter shelf life due to the presence of thickeners than oil-based lubricants. Highly-refined and synthetic oils have longer shelf lives due to better molecular stability. This is much more straight-forward and lubricant suppliers can inform you which lubricants last longer than others.

Using a lubricant is different for each operation. Some operations happen at low temperatures, others occur at high temperatures. The Arrhenius rate is a chemistry term that demonstrates how chemical reactions increase by changing temperature. For lubricants, as temperature increases by 10°C (18°F), the oxidation rate will double. The more oxidation that occurs, the faster a lubricant will break down and reduce the shelf life and effective use life.

Machinery Lubrication compiled a chart from its experts to show what can increase or decrease a lubricants shelf life.

Table Courtesy of Noria Corporation and Machinery Lubrication

 

How can you Reduce Oxidation?

Oxidation occurs when the lubricant comes into contact with air. Certain lubricants are more susceptible to faster oxidation and degradation due to the composition of the lubricant. However, these are known and can be accounted for, whereas human factors are a much greater influence on degradation and chemical stability.

Storage is key to maintain longer shelf-life and higher lubricant performance. Some things that can improve shelf-life include:

  • Storing lubricants in proper ambient temperatures. Cooler temperatures around 68°F are ideal.
  • Storing lubricants in dryer environments. Ambient humidity and moisture increase oxidation and lubricant breakdown.
  • Storing lubricants indoors. Outdoor storage can expose lubricants to more extreme and volatile conditions.
  • Storing lubricants in proper containers. Poor-quality steel containers can expose the oil to iron and fuel oxidation. Plastic or plastic-lined drums are ideal for storage.
  • Reduce agitation of the lubricant. The move the lubricant is agitated or moved, the more surface area of oil is exposed to air and can oxidize.
  • Evaluate usage and purchase lubricants accordingly. This smooths out spending, but also reduces the likelihood of using older products.
  • Practice First-In-First-Out (FIFO) when using lubricants. This prevents lubricants from sitting and aging.
  • Label lubricants, containers, and machines. Knowing when a lubricant was made or put into use allows individuals to be more mindful of when to change lubricants.

How do I Get Informed?

Unfortunately, there is no industry consensus on shelf-life. Following the tips above will extend and maintain shelf-life. Speaking with manufacturers, distributors, and engineers is the best option in getting product-specific shelf-life information. Manufacturers will know exactly what goes into their products and can provide shelf-life information and best practices for storage.

Twin Specialties can provide information about Best Practices for Lubricant Storage and Managing Metalworking Fluids. We work with manufacturers to provide transparency and information about lubricant shelf-life and usage. Contact Twin Specialties for information about lubricants, best practices, and shelf-life.

7 Steps for a Successful CNC Restart

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After an extended production shutdown, it is imperative to get restarted quickly and efficiently. Maintaining your coolant can be the difference between success and failure. It is key to clean, refill (if necessary), and run according to the manufacturer’s recommendation.

These steps will depend on whether you emptied the sump before the shutdown. If you have emptied the coolant, ensure that the machine is cleaned out; Astro-Clean A can be used to clean the machine and remove and residual coolant and contamination in tough to reach places.

If your coolant remains in the sump after the shutdown, follow these steps for a successful restart:

  1. Inspect the coolant sump/tank for any problems.
    • Remove any tramp oil by using skimmers.
    • Remove any swarf or solids with filters or skimming nets.
    • If there are significant solids, the tank and machine should be cleaned out before proceeding.
  2. Do not add any coolant unless there is not enough to circulate through the machine. If you need to add coolant, add coolant at or above the target concentration.
  3. Circulate coolant through ALL pumps for 60 minutes to ensure all nozzles are flushed out.
  4. Check the concentration from the nozzle using a refractometer (either manual or digital).
  5. Top off the sump to 95% capacity to the target concentration + 2%.
  6. Check the pH and odor. Test the pH from the nozzle.
    • If it is too low (8-9 pH), add 3% volume of coolant and circulate for 30 minutes. Repeat until pH is acceptable.
    • If pH is below 8, the coolant is spent and must be replaced. Use Astro-Clean A to clean out machine.
  7. Add fresh coolant to bring tank/sump volume to 100%.

Bonus Tip: To keep coolant fresher during shutdowns, run skimmers and fish-tank fans to prevent tramp oil contamination and coolant breakdown. Circulating the sump coolant may reduce odor.

Following these steps will ensure a successful restart. Equally important is continuous monitoring of the sump/tank. One individual should check concentration daily and pH weekly. If something is off, act accordingly and quickly. Keep records in a coolant log for each machine to ensure continued success.

Contact Twin Specialties about our coolant guide for information about success coolant management. Twin Specialties has over 65 years of experience with metalworking fluids and is your go-to source for metalworking fluids, cleaners, and rust preventatives/inhibitors.

5 Factors for Drawing Fluid Selection

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In drawing processes, there two main types of lubrication. Firstly, there is fluid or hydrodynamic lubrication, which is the separation of metal surfaces with a continuous film of lubricant that prevents contact of those metal surfaces. Secondly, there is boundary lubrication, which is separating metal surfaces by a film only a few molecules thick.

The drawing process generates extreme pressures and the lubricant needs to perform to ensure proper separation of metal surfaces.

Factors for Drawing Fluid Selection

There are many factors that will affect lubricant selection. We will examine these factors and how they may affect lubricant selection and use. Considering these factors will ensure proper separation and excellent performance.

Type of Metal

Not all metals are alike. The first classification for metals is whether it is ferrous, non-ferrous, or an alloy. The hardness of metal will also be a key factor. Harder metals will require higher pressures, thus higher operating temperatures. A harder metal will need a lubricant that provides excellent cooling to prevent poor finishes or melting. Resistance to rust and corrosion varies metal to metal. Porous metals, such as cast iron, are porous and can rust quickly during annealing. Applications with those kinds of metals may require a lubricant that has rust/corrosion preventative additives.

Severity of Operations

The severity of the operation will be key to determining what kind of lubricant you need. Operations with extreme pressures may require lubricants with extreme-pressure and anti-wear additives to maintain proper lubrication. Operating speeds play a key role in determining the viscosity needed. Higher speeds will require lower viscosities so that the lubricant will adequately circulate. As temperatures rise, viscosity can degrade quickly. When the lubricant becomes too “thin” or “runny”, proper separation may be lost. Some lubricants will include viscosity index (VI) improvers to help maintain proper fluid thickness as temperatures rise.

Tooling

The tooling used in drawing may affect the lubricant selection. Some of the tools used in drawing include:

  1. Dies for cold drawing
  2. Rolls for forming strips and shapes
  3. Cutting tools
  4. Extrusion dies
  5. Heading dies
  6. Plugs
  7. Mandrels

The material of the tools also matters. In high temperatures, tool life may diminish and a lubricant that extends tool life improves performance and reduce costs. Tooling can be made of the following materials:

  1. Steel
  2. Carbide
  3. Diamond (synthetic or natural)

Subsequent Processes and Applications

Once a workpiece has completed the metal working process, most likely it still has to go through more manufacturing processes. Some of these include: annealing, cleaning, painting, and assembly into the final product. Cleaning the workpiece is import for final assembly as you want to avoid rust and corrosion. Drawing fluids that are emulsifiable are easier to clean and are preferred by some manufacturers. The cleaning process used also matters. Whether you use a dip tank, spray washer, or vapor degreaser, selecting a fluid that can wash away while also reducing rust and corrosion will be dependent on the cleaning process. Many fluid manufacturers, such as Twin Specialties, supply cleaners that are developed with their drawing fluids in mind.

Economic Considerations

With limited budgets, manufacturers must be pragmatic in selecting a fluid. Opting for a less expensive product may have hidden costs that are not realized at time of purchase. Lower quality fluids may reduce tool life and the fluid itself may need to be changed more frequently. These costs can add up and may not be realized until the job is completed. If your budget allows for it, opting for a synthetic fluid may prove to be a smart choice. Even though lubricants do not make up most of the budget, selecting the right lubricant can create tremendous cost savings on other parts of the income statement.

Takeaways

Each manufacturer has unique conditions and budgets; thus, no lubricant can be a one-size-fits-all product. Analyzing your metal workpieces, operations, tooling, cleaning and assembly processes, and budget will provide clarity. That clarity can aid lubricant selection and allow you to focus more on your manufacturing.

Working with manufacturers and distributors to determine the proper lubricant is the best strategy to maximize efficiency and boost the bottom line. Twin Specialties can analyze your processes and budget considerations to find the optimal lubricant.