Science of the hottest high pressure coolant

2022-10-20
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Science of high-pressure coolant

high pressure coolant is a new and popular technology, and its use has increased by about 500% in the past 10 years. We have all heard or seen the obvious results that high-pressure coolant can produce. Unfortunately, this aircraft has a wingspan of 385 feet, and most manufacturers who buy high-voltage don't really know how to make the best use of it. There are even doubts about what kind of pressure is high pressure. When I say high pressure, it means at least 1000 pounds per square inch. This article will briefly introduce you to the rules of scientific use of high pressure

skill is not science

when I ask, "how does this process work", I almost always get a technical answer, such as "set it to 7, if not, try 7.5." Science is different; With it, you can know what will happen before you spend money. In this paper, metal cutting will be considered as a physical or chemical problem that must be analyzed in a standard scientific understanding

the rules of the universe are suitable for all of us, even in manufacturing. There are some strange ideas that the only way to continuously develop our business is to constantly try. Doing so will lead to personal theories that go beyond traditional scientific thinking. Although you may find an understanding of the new laws that govern the entire universe, this opportunity is one in millions. The problem with this line of thinking is that it is expensive and usually does not produce the best results

if you can't explain what happened in your first year of college, you don't really understand it. When we sent a probe to Mars and got shocking photos, the people who designed the device adopted the theory named after Newton, Bernoulli or Einstein. Standard scientific theories have proved formulas that can predict the results of physical interactions. Our business should also adopt these predictive scientific methods

how much coolant

how much coolant does your new CNC machine need? The general empirical answer is "use as much as you have", "use as much as you have randomly provided on the machine tool" or "it looks appropriate." The scientific answer (short type) is 0.5gpm/horsepower. Using the scientific understanding of generally accepted standards, we know that the energy per horsepower used for cutting is equal to 746 Watts by definition. If you use 10 horsepower, 7460 watts (10 × 746)。 So what happens to the energy you input into cutting? We all know that it becomes heat, and for this simple calculation, we can use a constant of 90%:

1 watt =3.41 BTU (British thermal unit, 252 calories)

7460 watts × 3.41 =25438 BTU at 90% conversion =22894 BTU

people who design radiators or household heating systems will calculate the amount of water required to absorb or take away 1 BTU of heat. There are many factors in the calculation: how hot the metal is, how cold the fluid is, the percentage of the fluid in contact with the metal, and the length of time. Without many such calculations, we can also make some assumptions about the following phenomena: the average process of properly guided coolant and the rule of empirical answers, using a 25% safety factor to obtain 0.5gpm/horsepower. Therefore, if you use 10 horsepower in cutting, you need 5gpm coolant to achieve high pressure effect

working principle

high pressure forms a local pressure increase, avoiding the formation of steam. The force of the liquid, the quality pointing to the cutting point and the acceleration result are combined to complete the machining task of the workpiece

force = (mass × Speed 2)/gravity

speed =14.7 (FT/s) × PSI

you will notice that stress is not part of this familiar equation. It is related to speed, but not in a one-to-one way. If you increase the pressure by 100%, the force can only be increased by 40%. If you increase the volume by 100%, the force can be increased by 100%

always increase the volume; Never raise pressure unless you have to. Why do we need to do this? Simple mechanical theory: please remember that all coolant must impact the gap between chip and tool. If your target area is small and you use high horsepower in cutting, you may have to fill this small area with more liquid. As the pressure increases, the same amount of coolant will be added through smaller and smaller pores. You must increase the pressure until all the coolant necessary to remove the generated heat enters the target area. (you can see the pore table on the site, which can tell you the amount of coolant passing through a certain pore for a given pressure.) The best strategy is to keep the pressure constant and change the amount of coolant based on the size of the drill bit or the horsepower used in cutting. Only increase the pressure when absolutely necessary

a separate unit can be used on new or existing machine tools

drilling problem

there is another situation in the drilling process: the really important pressure is the back pressure formed as the fluid comes out of the hole. The rule here is to use 10 GPM coolant per inch of bit diameter. A 0.500 inch diameter drill bit requires 5 GPM of coolant to achieve high pressure; A 0.250 inch drill requires 2.5 gpm

the most common problem is that the coolant hole is too small. The drill bit must be able to pass through enough coolant, otherwise its performance will be abnormal. Check the hole size according to the pore table or conduct funnel test: let the drill stand still, guide the coolant into the funnel for 30 seconds, and then measure the volume of coolant you collect

the next most common problem is that the coolant hole is in the back corner of the drill tip. This is the most common for small diamonds. The clearance is usually only 5 degrees, so there is no space for coolant to come out of the hole. In use, the bottom of the hole blocks the hole. In order to achieve the corresponding function, at least 50% of the holes must be in the secondary extrusion. Some bit manufacturers still do not understand this simple relationship between hole size and positioning. You have to make sure - there is a clear difference between 100 holes and 10000 holes. If you don't have a large enough coolant system to maintain all the pressure, the suppliers who don't get the appropriate information will suggest welding the holes specially issued with the aluminum based new material industry support policy at the end of the closed drill bit. The size of the holes drilled is small, so the pressure gauge on the coolant system will show the full pressure. Never do this; This is conceptually wrong

generally, the drilling rule and the horsepower rule will give you the same answer. If there is a conflict between them, a larger volume should be used

coolant concentration is one of the elements rarely understood in most processes. What concentration should be used? Is 5% appropriate? Or 6%? Tribology is a study of lubrication. We are all familiar with one of its main concepts: the larger the surface area of contact, the higher the need for lubrication. Plane bearings require higher lubrication than rolling bearings, and rolling bearings require higher lubrication than ball bearings

cutting tools follow the same rule: the larger the tool surface in contact with the workpiece, the higher the lubrication required, so the higher the coolant concentration. The contact area of single point turning tool is the smallest, and the concentration of 5% can be used. The whole tip and edge of the drill bit are in contact with the workpiece, and a concentration of at least 8% is always required. Reamers have more surface contact, so 10% may be required. The tool that requires the highest lubrication is a tap. Its 60 degree cutting edge makes it the tool with the highest surface contact among all commonly used tools

control wear

you don't need to spend weeks dealing with machining tasks with short tool life or poor surface roughness. You may remember a processing task that runs poorly until you increase the coolant concentration and solve all the problems. How much money, time and reliability have been lost? Look at the tool surface in contact with the workpiece, and you can determine the appropriate coolant concentration before encountering problems. For example, increasing the coolant concentration from 5% to 8% can usually increase the life of the drill head with the help of this biocompatible polymer material by 1000% or more. Have you ever found, however, that those expensive German reamers that take 14 weeks to arrive are often scrapped in one shift

why does the tool life become so high after using high-pressure coolant? You always hear that the machine tool begins to wear and tear from the moment you turn it on. This is true. The way we can describe this phenomenon is to use a wear line (see the figure above). Larger initial wear is called running in, and then we get a long-term stable and predictable wear period, and then the wear will generally accelerate to close to scrap. This is what you see on the precision machining blade without any splitting problem, as well as the axle bearing or anti fracture base on the car. Almost all mechanical equipment follow this wear mode to varying degrees

damage is different. Chips entering the chip tool gap can cause damage. This is a random event. We all know that any group of random events, if plotted, will provide us with a normal distribution. These are two shapes that differ greatly (in response to tool failures with very different modes). The properly applied force of high-pressure coolant will wash the chips away from the cutting area, so that they will never contact the tool or workpiece and cause damage. If you look at the process and say, "I usually process 30 or 40 parts per blade, but sometimes the tool breaks when processing two parts, but sometimes it can process 60 parts." Then you described a correct distribution phenomenon. The tool life data can be plotted and the blade situation can be understood without actually seeing them, because wear and damage are fundamentally different failure modes from the bracket fixed on the driving frame. High pressure coolant will wear the tool rather than damage it

why

high pressure coolant can solve heat problems, chip problems and poor lubrication problems. How much benefit can you get from using it? Problems related to heat, chips or lubrication are functionally eliminated. The bigger the problem, the more benefits you get. For example, chip damage is almost always a problem when drilling with low-pressure coolant. The tool and chip meet in a narrow way in the drilling hole. As the chip comes out of the hole, they are cut twice at the cutting point and squeezed between the edge and the side of the hole. This will lead to poor hole roughness and shortened tool life. If the drill has a coolant hole of the correct size and you have enough coolant of the right concentration, amazing results will be produced. I have held seminars all over the world. Every time, I ask everyone participating in the seminar to estimate how long it takes to drill a hole with a diameter of 0.125 inch ± 0.001 and a depth of 1.300 inch in steel 1018. The average result of each group is almost 45-60 seconds per hole. With high-pressure coolant, such holes can be processed in 1.2 seconds, and the tool life is at least 4000 holes. Rare materials such as heat

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