The wonderful uses of cutting fluid and machine tool guide oil in CNC

We understand that cutting fluids possess important properties such as cooling, lubrication, rust prevention, cleaning, etc. These properties are achieved by various additives that have different functions. Some additives provide lubrication, some prevent rust, while others have bactericidal and inhibitory effects. Certain additives are useful in eliminating foam, which is necessary to prevent your machine tool from taking a bubble bath daily. There are other additives as well, but I won’t introduce them here individually.

 

Unfortunately, although the above additives are very important, many of them are in the oil phase and need better tempers. Some are incompatible with each other, and some are insoluble in water. The newly purchased cutting fluid is a concentrated liquid and must be mixed with water before use.

 

We want to introduce some additives that are essential for emulsion-type concentrates to emulsify with water into a stable cutting fluid. Without these additives, the cutting fluid’s properties will be reduced to clouds. These additives are called “emulsifiers”. Their function is to make ingredients that are insoluble in water or each other “miscible,” much like milk. This results in an even and stable distribution of various additives in the cutting fluid, forming a cutting fluid that can be arbitrarily diluted as per requirement.

 

Now let’s talk about machine tool guide rail oil. The guide rail oil must have good lubrication performance, anti-rust performance, and anti-wear performance (i.e., the ability of the lubricating oil film to withstand heavy loads without getting squeezed dry and crushed). Another important factor is the anti-emulsification performance. We know that cutting fluids contain emulsifiers to emulsify various ingredients, but the guide rail oil should have anti-emulsification properties to prevent emulsification.

 

We will discuss two issues today: emulsification and anti-emulsification. When cutting fluid and guide rail oil come into contact, the emulsifier in the cutting fluid mixes with the active ingredients in the guide rail oil, leading to the guide rail being left unprotected, unlubricated and prone to rusting. To prevent this, it is important to take appropriate action. It is worth noting that the emulsifier in the cutting fluid not only affects the guide rail oil but also other oils on the machine tool, such as hydraulic oil and even the painted surface. The use of emulsifiers can cause wear, rust, loss of precision, and even damage to many machine tools.

 

 

 

If your machine tool guide rail working environment is airtight, you may skip reading the following content. However, in most cases, only about 1% of machine tools can fully seal guide rails. Therefore, it is essential to carefully read and share the following information with relevant friends who will thank you for it.

 

Choosing the right guide oil is crucial for modern machine shops. The accuracy of machining and the service life of metalworking fluid depend on the quality of guide oil. This, in turning machining, directly affects the production efficiency of machine tools. The ideal guide oil should have superior friction control and maintain excellent separability from water-soluble cutting fluids commonly used in metal processing. In case the selected guide oil and cutting fluid cannot be entirely separated, the guide oil will emulsify, or the performance of the cutting fluid will deteriorate. These are two primary reasons for guide rail corrosion and poor guide lubrication in modern machine tools.

 

For machining, when guide oil meets cutting fluid, there is only one mission: to keep them “away“!

 

When selecting guide oil and cutting fluid, it is important to evaluate and test their separability. Proper assessment and measurement of their separability can help avoid losses during the mechanical processing process and ensure accurate equipment operation. To assist with this, the editor has provided six simple and practical methods, including one technique for detection, two for inspection, and three for maintenance. These methods can help easily solve the separation problem between guide oil and cutting fluid. One of the techniques involves identifying symptoms caused by poor separation performance.

 

If the rail oil is emulsified and fails, your machine tool may have the following problems:

 

·The lubrication effect is reduced, and the friction is increased

 

· May result in higher energy consumption

 

·The material surface or coating material in contact with the guide rail is worn

 

·Machines and parts are subject to corrosion

 

Or your cutting fluid is contaminated by guide oil, and some problems may occur, such as:

 

·The concentration of cutting fluid changes and performance becomes difficult to control

 

·The lubrication effect becomes worse, the tool wear is serious, and the machined surface quality becomes worse.

 

·The risk of bacteria multiplying and causing odors increases

 

·Reduce the PH value of the cutting fluid, which may cause corrosion

 

·There is too much foam in the cutting fluid

 

Two-step test: Quickly identify the separability of guide oil and cutting fluid

 

Disposing of cutting fluids contaminated with lubricants can be quite costly. Hence, it is wiser to prevent the issue rather than dealing with it after the symptoms surface. Machining companies can easily test the separability of specific rail oils and cutting fluids using two standard tests.

 

TOYODA anti-emulsification test

 

The TOYODA test is conducted to replicate the situation where guide rail oil contaminates cutting fluid. In this test, 90 ml of cutting fluid and 10 ml of rail oil are mixed in a container and stirred vertically for 15 seconds. The liquid in the container is then observed for 16 hours, and the contents of the liquid at the top, middle, and bottom of the container are measured. The solvents are then separated into three categories: rail oil (top), the mixture of the two fluids (middle), and cutting fluid (bottom), each measured in milliliters.

 

If the test result recorded is 90/0/10 (90 mL of cutting fluid, 0 mL of mixture, and 10 mL of guide oil), it indicates that the oil and cutting fluid are completely separated. On the other hand, if the result is 98/2/0 (98 mL of cutting fluid, 2 mL of mixture, and 0 mL of guide oil), this means that an emulsification reaction has taken place, and the cutting fluid and guide oil are not well separated.

 

SKC cutting fluid separability test

 

This experiment aims to replicate the scenario of water-soluble cutting fluid contaminating guide oil. The process involves mixing the guide oil with various conventional cutting fluids in a ratio of 80:20, where 8 ml of guide oil is mixed with 2 ml of cutting fluid. The mixture is then stirred at 1500 rpm for a minute. After that, the state of the mixture is visually inspected after one hour, one day, and seven days. The condition of the mixture is rated on a scale of 1-6 based on the following criteria:

1=completely separated

2=Partially separated

3=oil+intermediate mixture

4=Oil + intermediate mixture (+ cutting fluid)

5=Intermediate mixture + cutting fluid

6=All intermediate mixtures

 

Research has proven that using cutting fluid and guideway lubricating oil from the same supplier can improve their separation. For instance, when mixing Mobil Vectra™ digital series guide rail and slide lubricant and Mobilcut™ series water-soluble cutting fluid in an oil/cutting fluid ratio of 80/20 and 10/90 respectively, two tests revealed the following: Mobil Vectra™ Digital Series can easily separate from the cutting fluid, while Mobil Cut™ cutting fluid leaves a layer of lubricating oil on top, which is quite easy to remove, and only a small amount of mixture is produced.(data from ExxonMobil Research and Engineering Company).

Pictured: Mobil Vectra™ Digital Series guide and slide lubricants clearly have better cutting fluid separation properties, producing only a very small amount of mixture. [(Top picture) 80/20 oil/cutting fluid ratio; (Bottom picture) 10/90 oil/cutting fluid ratio]

 

Three tips for maintenance: the key to ensuring efficient operation of the production workshop

 

It’s important to note that determining the optimal separation of guide oil and cutting fluid is not a one-time task. Several uncontrollable factors can influence the performance of the guide oil and cutting fluid during the equipment’s operation. Thus, it’s crucial to conduct regular maintenance and upkeep work to ensure the efficient operation of the workshop.

 

Maintenance is essential not only for guide oil but also for other machine tool lubricants like hydraulic oil and gear oil. Regular maintenance helps in preventing pollution caused by the cutting fluid coming into contact with different types of machine tool oil and prevents the growth of anaerobic bacteria in the cutting fluid. This helps in maintaining the cutting fluid’s performance, extending its service life, and reducing the generation of odor.

 

Cutting fluid performance monitoring: To ensure optimal performance of your cutting fluid, it is important to regularly monitor its concentration. You can do this by using a refractometer. Normally, a distinct thin line will appear on the refractometer indicating the concentration levels. However, if the cutting fluid contains more emulsified rail oil, the fine lines on the refractometer will become blurred, indicating a relatively high content of floating oil. Alternatively, you can measure the concentration of the cutting fluid through titration and compare it with the concentration of fresh cutting fluid. This will help determine the degree of emulsification of the floating oil.

 

Removing floating oil: Modern machine tools are often fitted with automatic floating oil separators, which can also be added to the equipment as a separate component. For larger systems, filters and centrifuges are usually utilized to eliminate floating oil and other impurities. Additionally, the oil slick can be manually cleared using industrial vacuum cleaners and other tools.

 

 

If the guide oil and cutting fluid are not properly maintained, what negative impact will it have on CNC machined parts?

Improper maintenance of guide oil and cutting fluid can have several negative impacts on CNC machined parts:

 

Tool wear can be a common issue when the cutting tools do not have proper lubrication from guide oil. This can result in increased wear and tear, which ultimately leads to premature failure.

 

Another problem that can arise is the deterioration of the quality of the machined surface. With adequate lubrication, the surface finish may become smooth, and dimensional inaccuracies can occur.

 

Inadequate cooling can cause heat damage, which can be detrimental to both the tool and the workpiece. Cutting fluids helps dissipate the heat, making it important to ensure that adequate cooling is provided.

 

Proper management of cutting fluids is crucial for efficient chip removal during machining. Inadequate fluid management can result in chip buildup, which can negatively affect the machining process and lead to tool breakage. Additionally, the absence of appropriate fluids can expose precision turned parts to rust and corrosion, particularly if the fluids have lost their anti-corrosive properties. Therefore, it is important to ensure that the cutting fluids are managed effectively to prevent these issues from occurring.