2018-06-07 by Jun Tai
Do you know why the roughness is 0.8, 1.6, 3.2, 6.3, 12.5?
Do you know why the cylinder bore is 63, 80, 100, 125?
Do you know why the cylinder pressure is 6.3, 16, 25, 31.5?
Do you know why the thread size is 6, 8, 10, 12, 14, 16?
Do you know the innumerable tables in the mechanical design manual, and how do the parameter tables on all product samples come from?
French engineer Renault saw a lot of wire ropes on the hot air balloon. He thought of a way to get 10 times 5 times, get a number of 1.6, and then multiply and multiply, and get 5 priority numbers as follows:
1.0, 1.6, 2.5, 4.0, 6.3
This is a series of equal ratios, the number of which is 1.6 times the number of the first few, then there are only 5 kinds of wire ropes below 10, and only 5 kinds of wire ropes of 10 to 100, namely 10, 16, 25, 40. 63.
However, this method is too sparse, Mr. Lei will continue to work hard, will open 10 times 10 times, the R10 priority number is as follows:
1.0, 1.25, 1.6, 2.0, 2.5, 3.15, 4.0, 5.0, 6.3, 8.0
The common ratio is 1.25, so there are only 10 kinds of wire ropes within 10, and only 10 types of 10 to 100, which is more reasonable. At this time, some people must say that this series, the previous figures seem to be similar, such as 1.0 and 1.25, there is no difference, usually I am rounded off, but the interval between 6.3 and 8.0 is big, is this reasonable?
Reasonable and unreasonable, let us make an analogy. For example, the natural numbers 1, 2, 3, 4, 5, 6, 7, 8, 9 seem to be very smooth. We use this series to pay wages, give Zhang Sanfa 1000, and Li Sifa 2000, both of whom are convinced. Sudden inflation, gave Zhang Sanfa 8000, and Li Sifa 9000. In the past, Li Si’s salary was twice that of Zhang San, and now it’s 1.12 times. You said that Li Si can be willing? He is the supervisor, and sending him 16,000 is almost the same. Zhang San will not complain that the supervisor is 8,000 more than him.
There are two comparison methods for this natural thing, namely "relative" and "absolute"! The priority number system is relative.
Some people say that his product specifications are 10 tons, 20 tons, 30 tons, 40 tons. Now it seems unreasonable. If you take twice, it should be 10 tons, 20 tons, 40 tons, 80 tons. Or keep the head and tail, it should be 10 tons, 16 tons, 25 tons, 40 tons, the ratio is 1.6 is reasonable.
This is "standardization". People often say that "standardization" is said in the forum. Actually, they are talking about "standard parts". The work done is only to sort out the standard parts of the whole machine, which is called standardization. Actually, this is not the case. . For true standardization, you need to serialize all the parameters of your product according to the priority number, and then serialize the functional parameters and dimensions of all components with the priority number.
Natural numbers are endless, but in the eyes of mechanical designers, there are only 10 numbers in the world, which is the R10 priority number. Moreover, the 10 numbers are multiplied, divided, multiplied, squared, and the result is still in these 10 numbers. What a wonderful thing! When you design, don’t know how big the size is, just in this 10 Choose from a few, what is your convenience!
1.0 N0, 1.12 N2, 1.25 N4, 1.4 N6, 1.6 N8, 1.8 N10, 2.0 N12, 2.24 N14, 2.5 N16, 2.8 N18, 3.15 N20, 3.55 N22, 4.0 N24
4.5 N26, 5.0 N28, 5.6 N30, 6.3 N32, 7.1 N34, 8.0 N36, 9.0 N38
Two priority numbers, such as 4 and 2, whose numbers are N24 and N12, respectively, are multiplied, and their sequence numbers are added, and the result is equal to N36 or 8;
Divide, the serial number is subtracted, equal to N12 or 2 is;
2 cube, multiply its serial number N12 by 3 to get N36 or 8 is;
4, the number N24 is divided by 2 to get N12 or 2 is the second power of 2? N12 * 4 = N48, here is not, what should I do? The above list, did not write a number, is 10, its serial number is N40, and if the serial number is greater than 40, only the part larger than 40 is seen.
For example, N48 looks at N8, which is 1.6, and then multiplies by 10 to get 16. If the serial number is N88, look at N8 to get 1.6, then multiply by 100 to get 160, because the serial number of 100 is N80, the serial number of 1000 is N120, and so on.
Do mechanical design, it is enough to use these 20 numbers for a lifetime. But sometimes you need to use the R40 number system, there are 40 numbers, it is more perfect, if not enough, there are R80 series. I have turned the R40 number back down, and I don't need a calculator for general calculations.
Simply speaking, the torsion resistance of the 40-diameter 45 steel is 0.5*π*R^3, the twisting stress is half of the 360, that is, 180 MPa, the pi is 3.15, the left and right hand pinch the decimal point, and the mental arithmetic plus or minus the serial number. Come out in a minute. Some people say that you don't add a safety factor? Say, is it 1.25, or 1.5, or 2? Oh.
The golden section is 0.618, which is 1.618, and there are also 1.6. The square root series is the root number 1, the root number 2, and the root number 3. Is it easy to find it? (The serial number of 3 is N19)
What is the square of π equal to? You are convenient when the pressure bar is stable? The round bar torsion coefficient is about 0.1*D^3. Now you can calculate the torsion coefficient?
Why does the big screw jump directly from the M36 to the M40?
Why is the gear ratio of the gears 6.3 or 7.1?
Why does channel steel have a number 12.6 that is rarely seen on the market?
Why does the outsourcing factory call to say that the 140 square tube is not, but there are 120 and 160?
Because the R5 number is preferred over the R20 number.
Why does the standard component have a first sequence, a second sequence? Generally, the first sequence is the R5 sequence.
Why does Inventor have a M11.2 list of screw holes? Now you know that it is not a number that comes out of it?
There are also steel plate thickness, steel model, gear modulus, all standard parts, functional parameters on all industrial samples, dimensional parameters, standard tolerance tables, etc. Their sources are now clearly clear in our hearts. . It can be said that we have already understood the half mechanical design manual and the industrial products that have not yet been made.
Then, when designing the product, we can design a series at the same time, instead of doing the so-called “standardization” after the design; further, if the product is destined to be serialized, then we can even work on the actual conditions. Design products without understanding
Because the priority number has included all models.
The application of the priority number system, listed above, can be described as a drop in the ocean, and endless applications are waiting for us to develop. Reciting the priority number, this is a once-and-for-all job.
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