MG - brand history:
No, MG is not a typo of the famous American manufacturer GM is actually a British sports car brand that was first launched in 1924. MG actually stands for Morris Garages, a subsidiary of Morris Motors, an old British automaker. Morris Garages was at first a Morris car dealer in Oxford, but very soon they began selling their own modified versions.
Initially, the cars produced at MG were Morris chassis with bodies made by Carbodies of Coventry. These models sold quite well, prompting the company to move to a more large plant to keep up with demand. In 1928, the company grew large enough to separate from the parent company, and then MG became MG Car Company Limited. In the same year, the first original MG car appeared, the 18/80 model, which was no longer based on the Morris chassis.
In 1935, William Morris sold Morris Motors, which was later taken over by the Nuffield Organization. This was the start of a company in racing. A further change of leadership occurred in 1952 when british motor Company (BMC) merged with MG. At this point, the history of the company became "foggy". In an attempt to cut costs, the MG plant was closed, causing unexpected unrest among workers and customers.
The MGB model was released in 1962. Modern and more comfortable than its predecessor, it was produced with some improvements until 1980. The GMC was produced between 1967 and 1969, but its large size and poor handling prevented it from becoming a customer favorite.
When BMC was taken over by the Rover Group in 1986, MG became the property of British Aerospace in 1988 and later, in 1994, the property of BMW. This continued until 2000, when the Germans sold it back to the British, along with Rover, who claimed victory. The company became MG Rover Group and established operations in Longbridge, Birmingham.
While MG was owned by the Rover Group, they sold rebranded Austin sedans such as the Metro, Maestro and Montego. In addition, the two-seat MG RV8 was released in 1992, as well as a range of new MGF models in 1995. It was the first mass-produced car since the 80s, when production was soon discontinued.
After BMW sold the MG, new models emerged such as the MG ZR, Rover 25 and MG ZS. By 2005, production of Rover and rebranded MG models had ceased, and there were rumors that the Chinese, specifically the Nanjing Automobile Group, were interested in buying the British marque. In July of that year, Nanjing had already bought the rights to the MG name.
The Longbridge plant continued to produce the TF models, while a new plant in China took care of the MG 7. In addition, a new facility in Ardmore, Oklahoma, took over the global production of the TF. New generation sports car, which was supposed to appear in 2008, was announced in 2006. The MG3, MG 5 and MG 7 models also received some updates.
Most machine tool operators find it difficult to imagine a machining process without the use of a cutting fluid (coolant). However, in some cases, there is a need for dry processing, which may be due to the lack of appropriate equipment preparation, or other conditions for the work. Analytical data from various sources indicate that the cost of providing workpiece cooling is 2-3 times higher than the cost of cutting tools. In addition, the world community is increasingly concerned about the protection of health and environment during production work. Disposal of used cutting fluid is a major concern for most businesses, and inhalation of its fumes can cause significant harm to human health. Due to the high costs of coolant disposal, European manufacturing enterprises more and more often use dry or semi-dry (with a minimum amount of coolant) machining technologies, in contrast to enterprises in the United States. However, countries such as Germany still have to reckon with the current economic and working conditions and use coolant. However, new regulations have already been proposed that limit the use of coolant in machining.Let's talk more about dry machining. Can materials be machined without coolant? In most cases you can, but this question requires more detailed consideration.
First, the cutting fluid performs a number of tasks:
- Cooling. That is why the liquid is called coolant.
- Grease. Tough materials such as aluminium, build up on the cutting edge, so it is necessary to reduce friction and, consequently, their heating.
- Chip cleaning. In many cases, this task is the most important. If chips hit the surface being machined, it will damage the surface and cause a much faster tool blunting. In the worst case, a cutter or cutter inserted into a slot or hole can become clogged with chips, causing them to overheat or even be damaged.
Lubrication and build-up on the cutting edge
Let's talk about lubrication. I paid the least attention to this topic, but this does not mean that lubrication is not important in processing. First of all, lubrication contributes to more effective work cutting tool with less heat. When the front edge of the cutter slides over the workpiece, it heats up due to friction. In addition, the chips also rub against the cutter, generating additional heat. Lubrication reduces friction and therefore heat. Thus, one of the functions of lubrication is to improve cooling efficiency by reducing heat generation. The main function of the lubricant is to prevent build-up on the cutting edge. Anyone who has seen how aluminum sticks to a cutter immediately understands the importance of this issue. Built-up edges can cause damage to the tool very quickly and thus delay work.Fortunately, the presence or absence of build-ups mainly depends on the type of material being processed. Most often, build-up occurs when machining aluminum and steel with a low content of carbon or other alloying elements. In this case, you need to use very sharp cutters with large rake angles (positive rake angle is your friend!). Also, spraying a small amount of coolant helps to cope with this problem, and the efficiency of this method is not inferior to the traditional method. Most importantly, do not forget to take these measures before the formation of adhesions between the chips and the surface being machined.
Chip cleaning
The next problem with dry machining is chip removal. Compressed air can be used for this purpose. However, this cleaning method may not be fully effective in some operations, such as drilling. Deep boring and drilling are two of the most problematic dry machining operations in terms of chip removal. To solve the problem, you can use process air supplied to the tool, but spraying a small amount of coolant is a better solution. Liquid coolant is better at this task, because it has a higher density, better transfers chips and cools the machined surface. But the correct application of spraying allows you to extend the life of the tool compared to the traditional method described above. It should be noted that natural chip removal is more effective on horizontal milling and turning machines than on vertical ones, especially in dry or semi-dry machining, due to the presence of gravity.Cooling
Let's talk about cooling. Temperature is the most important factor affecting the life of a cutting tool. A slight heat softens the material, which has a positive effect on the processing. At the same time, strong heating softens the cutting tool and leads to its premature wear. The permissible temperature depends on the material and coating of the cutting tool. In particular, carbide withstands significantly higher temperatures than high speed steel. Some coatings, such as TiAlN (titanium aluminum nitride), require high operating temperatures, so these tools are used dry. There are many examples where cutting out coolant while maintaining technology results in longer tool life. Carbide tools are susceptible to the formation of microcracks in the event of sudden temperature changes during uneven heating and cooling. Sandvik recommends in its educational course not to use coolant, at least in large quantities, in order to prevent the formation of microcracks. It should also be noted that high heat adversely affects the accuracy of processing, since as a result of heating, the size of the workpiece changes.How can workpieces be cooled without coolant? First, let's look at the most common cooling methods. There are two types of coolants - water-based coolants and coolants based on oil. Coolants are most effective for cooling water based. How much? Comparative data are shown in the following table:
| coolant | Specific heat |
Steel A (hardened) Decrease in temperature, % |
Steel B (annealed) Decrease in temperature, % |
| Air | 0.25 | ||
| Oil with additives (low viscosity) | 0.489 | 3.9 | 4.7 |
| Oil with additives (high viscosity) | 0.556 | 6 | 6 |
| Aqueous moisturizer solution | 0.872 | 14.8 | 8.4 |
| Water-soda solution, 4% | 0.923 | - | 13 |
| Water | 1.00 | 19 | 15 |
First, the data presented in the table indicate that the efficiency of various types of coolants directly depends on their specific heat capacity. Secondly, it should be noted that air is the worst refrigerant - its characteristics are 4 times inferior to those of water. Also interesting is the fact that oil coolants are almost 2 times inferior to water in terms of cooling properties. Given this fact, as well as safety issues, it is not surprising that many enterprises use water-based coolants - they are the best coolants. However, water-based coolants only work effectively up to a certain cutting speed, and the higher the speed becomes, the worse they cool the material and tool. One of the reasons for this phenomenon is that at a high cutting speed, the coolant does not have time to penetrate into all the recesses and cracks in the material. As a result, the cooling becomes less and less qualitative, resulting in a decrease in the cooling efficiency of the carbide tool at a cutting speed exceeding a certain value.
Heat-resistant coatings such as TiAlN that do not require cooling can be used, but it is possible to do without them. For example, you can use compressed air for cooling, but you must remember that large volumes of it will be required to achieve efficiency comparable to water cooling. In cases where cooling is required, it is much more efficient to use humidified air containing atomized liquid. Spraying also provides lubrication, which can be useful for materials such as aluminium. In addition, at high cutting speeds, humidified air penetrates into all cavities in the material better than water with water cooling.
Another method of cooling is the use of chilled air. There are many ways to cool the air, and it naturally cools as it exits the nozzle, but a more efficient solution is to use a device called a vortex tube. The above data on various types of coolants, as well as detailed information on research related to the use of air and vortex tubes for cooling, can be found in scientific work Brian Boswell "The use of air cooling and its effectiveness in the dry processing of materials."
This work can be very useful if you want to understand the details. Boswell is considering equipping some lathe chucks with air channels, but concludes that most effective option is the use of vortex tubes. If you are going to use only air, it must be directed to the right places to ensure effective cooling. Boswell found that adjusting the vortex tube was much easier because the nozzle could be further away from the material being processed. At the same time, this device is able to cool the material as efficiently as a traditional water cooling system.
Parameters of dry machining of materials
Let's assume that you don't have accessories like a vortex tube, but you use dry or humidified compressed air for lubrication and chip removal. How does this affect the machining conditions (feed and cutting speed) compared to conventional wet machining?- Consider separately such a parameter as feed per tooth. The adjustable value, depending on the type of cooling, is the cutting speed. In this case, the feed rate for a given feed per tooth will decrease slightly.
- If a certain cutting speed threshold is exceeded, the adjustment depending on the type of cooling does not work. In most cases, the cooling system will be turned off altogether. Let's call this threshold value the critical cutting speed. This speed will be slightly slower, but it can definitely be accepted as the recommended speed for TiAlN-coated tools. TiN (titanium nitride) coated tools will still run more efficiently at these speeds with cooling, so the critical cutting speed is somewhere between the speeds recommended for TiN and TiAlN coated tools. Obviously, the critical speed will depend on the type of material being processed, so there is no universal value for all cases.
- For cutting speeds below critical, a special correction factor is applied. Like the critical speed, the coefficient depends on the material being processed and takes values from 60% to 85%. In other words, for some materials a factor of 60% of the recommended speed is used (tool manufacturers' recommendations are based on the wet machining method), while for other materials the factor can be as high as 85%. The coefficient depends on the thermal conductivity of the material (heat-resistant alloys are quite difficult to process, since they conduct heat poorly, and a large amount of build-up is formed during cutting), the lubricating properties of the coolant, etc.
This is the last question regarding dry machining. Often, the quality of the dry finish is lower than with wet machining. There are many factors that affect quality, but in most cases it all comes down to a decrease in cutting speed. To maintain the quality of processing, it is important to compensate for the decrease in speed by using a tool with a larger radius (for example, a milling cutter). A secondary factor is lubrication, which reduces wear and ensures smooth cutting. In this case, humidified air will help you.
Results
So what are the conclusions?It is clear that machining with the use of a cutting fluid is superior in parameters to dry or semi-dry machining, if you do not take into account the cost of coolant and have the appropriate equipment available. However, the effects are not as pronounced as it might seem. Humidified air can be used when machining viscous materials, and vortex tubes and other air cooling devices are no less effective than the traditional wet method. In this case, you will at least have a stream of compressed air to clean the workpiece from chips. It should be understood that dry machining leads to a change in cutting speed by 20-25%. Feed per tooth depends on the implementation of water cooling. Proper coolant nozzle orientation can increase feed per tooth by up to 5%, and delivering high pressure coolant through the spindle allows for even greater productivity gains.
In some cases, the refusal to use coolant is quite a challenge:
- Heat resistant alloys and titanium should be machined with wet cutting, except when using tools where dry machining is recommended. The above materials have insufficient thermal conductivity to be used solely for air cooling.
- Materials that build up on the cutting edge (some stainless alloys and aluminium) require the use of coolant or at least humidified air to provide lubrication.
- Without coolant, it is very difficult to remove chips from deep holes. This problem can be solved by supplying humidified air under pressure.
- If your spindle is not the fastest in the world, you will most likely have to reduce the cutting speed due to its insufficient RPM. This is especially true when machining aluminum (or other soft materials such as brass), as well as when using small carbide cutters. However, in this case, the rejection of traditional liquid cooling is not critical.
- It is often possible to increase the feed rate by reducing the chip thickness.
The aluminum drawing process involves metal pressure treatment, during which a workpiece with a diameter of 7-19 mm is pulled through a hole of a smaller diameter. Production involves the use of cutting fluids (coolants) of a certain type.
For wire rod with a cross section of 7.2 mm to 1.8 mm, the processing takes place on multiple equipment without slipping. In this case, aluminum is used, which has a high density.
With thinner drawing (0.59-0.47 mm), aluminum is processed on sliding machines. The speed of the workpiece passing through the equipment is 18 m/sec. In this case, a wire drawing lubricant is used in the form of an emulsion.
The choice of lubricants also depends on the type of processing equipment. If a technician applies coolant by spraying during operation, the pump volume must be taken into account. Recently, low-viscosity materials have been more frequently used for aluminum forming.
Since aluminum forming produces a high concentration of attrition particles, drawing lubricants must have a low viscosity. This will extend the life of the coolant and increase the economics of the process.
Moreover, an increase in viscosity is observed with an increase in the fineness of processing. Rougher aluminum drawing processes require thicker oils, while liquid lubricants are used for finer operations.
Aluminum drawing, the coolant for which has a set of required characteristics, should be created on the basis of mineral oils or synthetic substances. This will maximize the protection of the surfaces of mechanisms and processed materials from wear and corrosion.
The drawing of aluminum wire with annealing puts forward increased requirements for lubricants in terms of its temperature characteristics. In carrying out such a process, deposits should not remain on the surface of the material.
World renowned manufacturer of cutting fluids High Quality is the German brand Zeller Gmelin. This company has developed a range of products to help optimize the aluminum drawing process.
Sale of cutting fluids directly from the manufacturer
The highest quality coolants for this type of metalworking are available under the name Multidraw AL, Multidraw ALM, Multidraw ALF, Multidraw ALG. Each product meets certain conditions for the drawing process.
The company LLC "" has the right to sell these coolants in Russia. All products have the appropriate quality certificates and have passed a number of laboratory tests. The manufacturer's reputation is impeccable. This guarantees the quality of lubricants, which are sold at the best prices.
We offer our clients a full range of services. You can buy the optimal type of lubricants by contacting our competent specialists. After listening to your conditions of metal forming, our experienced staff will select the required type of product. This will minimize production costs and increase the competitiveness of finished products.
Realization is carried out wholesale and retail. Delivery is carried out in the shortest possible time to almost every city in our country. The presence of products in our own warehouse allows you to send the order very quickly. There is a possibility of self-delivery of products from a warehouse in Podolsk.
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To this end, Quaker Chemical Corp. conducted a series of tests on the face machining of aluminum blanks to evaluate the effects of various coolants on cutting power and tool wear. When machining with a new cutting tool, the coolant had no effect on the machining forces generated at the same cutting speed. However, the more the tool machined the workpiece, the greater the difference in power needed to effectively machine with different coolants.
These results show the following
The effect of metallic fluid on cutting power is minimal with newer cutting tools. Thus, the difference between the effect of two different coolants on cutting power may not be noticeable until the cutting edges of the tool begin to wear.
The increase in power when milling aluminum is a direct result of wear. cutting edge. The rate of this wear is directly affected by both the cutting speed and the fluid used in metal processing.
The relationships between these variables are linear (cutting speed, cutting edge wear and cutting power all increase together). Armed with this knowledge, fabricators can potentially predict the condition of the cutting edge at any point in the milling process, as well as the power needed at other, untested cutting speeds.
Entering the lab
Testing focused mainly on two types of coolants: microemulsions and macroemulsions, each of which was diluted at a concentration of 5% in water. The main difference between the two is the size of the suspended oil droplets. In a macroemulsion, particles with a diameter of more than 0.4 microns, which give an opaque white look Coolant The microemulsion has a smaller particle diameter and has a translucent appearance.
The experiment was performed on a Bridgeport GX-710 three-axis CNC machine. The blank was a block of 203.2 by 228.6 mm by 38.1 mm 319-T6 aluminum alloy, cast, containing copper (Cu), magnesium (Mg), zinc (Zn), and silicon (Si). Machining was carried out with a face mill with a diameter of 18 mm with eight inserts with a 15-degree rake angle and radial radii of 1.2 mm. It machined with an axial depth of 2mm and a radial depth of 50.8mm. Each composition of the coolant was supplied to the cutting zone for 28 transitions during milling with two different speeds cutting, 6,096 rpm (1460 m/min) and 8128 rpm (1.946 m/min), for material removal 1,321.6 cm3. Feed rates at both speeds were 0.5 mm per revolution (0.0625 mm per insert per revolution).
Speed, wear and power
The power measurements for this study during processing were obtained using an instrumental control system and adaptive control. The test results are shown in the charts in this article. As expected, more high speeds cutting led to a higher processing speed. However, as described above, the differences in cutting power between the two fluids were minimal with the new cutters.
At the start of the process, workpiece material properties and cutting edge geometry are the dominant factors influencing cutting power. Differences between the working characteristics of the metal medium appeared only after the geometry of the cutting edge changed during wear. The choice of metalworking fluid directly affected the rate at which this wear occurred and, accordingly, the required cutting power at any given point in the milling operation.
Assuming a certain a basic level of performance for the two fluids being compared, testing should be performed until the inserts begin to wear to determine which fluid allows higher cutting speeds to be maintained for a longer period of time.
The constructed graphs made it possible to say that the rate of increase in power can be used to predict the state of the insert at any given point in the milling operation. Likewise, power measurements made at multiple cutting speeds can be used to obtain the required power at other, unverified cutting speeds.
Proof
While the x-axis in Figure 1 consists of the raw material removal volume data, Figure 2 uses the natural logarithm of this variable. Plotting the volume of material removed in this way results in a slope that is accurate speed, with which the power increases with subsequent processing. This measurable measure is needed to predict tool wear and cutting performance at different cutting speeds. However, these data only show that cutting power and material removal increase together. Confirmation of insert wear is especially important because driving force Increasing power requires additional testing (in particular, to correlate the line slopes in Figure 2 directly with insert wear that occurs during machining).
These tests added two additional coolants: one more macroemulsion and one more microemulsion. Each of the four fluids was applied at a cutting speed of 1.946 m/min. until 660 cm3 of material has been removed. This provided sufficient time for abrasion and, in some cases, metallic adhesion to occur. We then measured the wear of the flanges for four fluids in relation to the parameter that relates the cutting power to the volume of the metal slot (in particular, the slope of the power compared to the natural volume of metal removed). As shown in Figure 3, this confirmed the linear relationship between insert wear and increased cutting power during machining.
Other Findings
While test results cannot necessarily be extrapolated beyond aluminum milling, research shows that microemulsion works better if the goal is to machine at the highest possible speed. This is because a denser microemulsion with smaller diameter oil droplets tends to remove heat more efficiently than a macroemulsion and its relatively large droplets. However, transactions related to more slow speeds cutting, can contribute to the macroemulsion and its relatively greater lubricity.
Whatever the detail The best way finding the right coolant is to try different formulations in action. Understanding the relationship between cutting speed, tool wear, and cutting power, and how cutting fluids can affect these factors, is critical to making the right choice.
