We should also know that products are generally manufactured by machinery,

Do you know about CNC machinery? 

Of course, the machinery used in this industry is not the same, so the machinery used in various industries The names are also different, and their functions are different at the same time, but one thing is the same. 

They are composed of different parts. Although the parts are just a trivial item in the machine, they have a large amount. It is also possible to form a complete machine. And parts are also quite important. We can also understand non-standard parts in this way, there is no certain uniform standard, only the manufacturers need to make their own. 

Can non-standard parts be processed by hand? This impossible, you must use machinery to complete, after all, most of the parts on the machinery are metal, and can not be completed by hand alone.