Facing the boring lathe, the machine tool is mainly designed for turning. There is almost no rotation on other types of machine tools, and no one can do it in the same facility. The versatility of the lathe also allows drilling and reaming, allowing multiple operations to be performed in a single setup of the workpiece. Compared with other machine tools, this allows various types of multiple lathes to be used in manufacturing.
The key components of a lathe are the bed, headstock assembly, tailstock assembly, guide plate and feed rod. The bed is the pillar of the lathe. Usually made of well-normalized or aged gray cast iron or ductile iron, it provides a heavy-duty rigid frame to which all other basic components can be installed. The bed usually contains two parallel vertical ways at the top, inside and outside. Some manufacturers use an inverted V in all four methods, while others use an inverted V and a flat method in one or two sets. Most modern lathes have hardened surfaces to withstand wear and tear, but care must be taken when operating the lathe so as not to damage the path. These inaccuracies usually mean that the accuracy of the entire lathe is destroyed.
The spindle is usually installed in a position on the internal channel at the left end of the machine. It basically consists of a hollow main shaft mounted on precision bearings and a series of transmission gears similar to a truck transmission. The main shaft can be rotated at different speeds through these gears. Most lathes usually provide speeds of 8-12 with geometric ratios, while modern lathes only need to move 2-4 levers to get all speeds. The growing trend is to provide continuously variable speed ranges through electrical or mechanical drives.
Since the accuracy of the lathe is highly dependent on the spindle, it is a heavy-duty structure, usually installed on pre-loaded tapered rollers or ball-type heavy-duty bearings. The main shaft has a hole extending in the length direction through which long rods can be fed. The largest bar size that can be processed when the material needs to be fed into the spindle.
The assembly basically consists of three parts. The lower casting is installed in the aisle inside the bed, it can slide vertically on it, and provides a way to clamp the entire assembly to any desired position. The top casting cooperates with the bottom casting and moves laterally on the bottom casting in some type of keying to allow alignment of the assembly 28 (ie the tailstock quill). This is a hollow steel cylinder, usually about 51-76 mm (2-3 inches) in diameter, and can be moved to the upper casting within a few inches using a hand wheel and screws.
The dimensions of the lathe are displayed in two dimensions. Originally called a swing. This is the maximum diameter of the workpiece that can be rotated on the lathe. This is approximately twice the distance between the center of the lathe and the line connecting the nearest point on the road. The second dimension dimension is the maximum distance between centers. The center distance represents the maximum length swing of the workpiece that can be installed between the centers and therefore represents the diameter of the largest workpiece that can be rotated on the lathe.
Engine lathes are versatile and very convenient, but they are not suitable for mass production because it takes time to replace and set tools and measure workpieces. In many cases, the actual chip production time is less than 30% of the total cycle time. In addition, all tasks require skilled machinists, who are expensive and often in short supply. However, most of the operator’s time is spent on simple, repetitive adjustments and chip manufacturing. Therefore, turret lathes, screw machines and other types of semi-automatic and automatic lathes have been highly developed and widely used in manufacturing to reduce or eliminate the number of skilled workers required.
One of the most basic concepts in the field of advanced manufacturing technology is numerical control (NC). Before the advent of numerical control, all machine tools were manually operated and controlled. Of the many restrictions associated with manually controlled machine tools, perhaps none are as prominent as the operator’s skill restrictions. With manual control, the quality of the product is directly related to the skill of the operator, and there is a limit. Numerical control is the first step away from human control of machine tools.
CNC is the use of pre-recorded and written symbolic instructions to control machine tools and other manufacturing systems. NC engineers create programs to provide operating instructions to the machine tool instead of operating them. In order to numerically control the machine tool, it is necessary to connect a device called a reader to receive and decode program instructions.
The development of digital control is to overcome the limitations of manual operation. CNC machines are more accurate than manual machines, can produce parts more uniformly, faster, and have lower long-term mold costs. The development of CNC has led to several other innovations in manufacturing technology, such as electrical discharge machining, laser cutting, and electron beam welding.
CNC makes the machine tool more versatile than its predecessors in terms of manual operation. CNC machine tools can automatically generate a wide range of parts, including various parts and complex machining processes. Digital control allows manufacturers to use manually controlled machine costs and processes to produce products that are not economically viable.
Like many advanced technologies, NC was born in a laboratory at the Massachusetts Institute of Technology. The concept of NC was funded and developed by the US Air Force in the early 1950s. In the early stages, CNC machine tools can efficiently perform straight cutting.
However, curved paths are a problem because the machine tool must be programmed to perform a series of horizontal and vertical steps to create the curve. The shorter the straight lines that make up the steps, the smoother the curve. I have to calculate each segment of the step.
Because of this problem, the Automatic Programming Tool (APT) language was developed in 1959. It is a special programming language for NC. It uses English-like sentences to define the shape of parts, describe the tool configuration and specify the required operations.
The development of the APT language is an important step towards further development from the currently used language. This machine has a built-in wiring circuit. The teaching plan was written on perforated paper, which was later replaced by magnetic plastic tape. I use a tape reader to interpret the instructions written on the machine tape. In short, all of these represent a big step forward for machine tool control. However, at this point of NC development, NC has some problems.
The main problem is the fragility of the punched tape media. Paper tapes containing program instructions are often broken or torn during processing. The fact that the paper tape containing the programming instructions must be re-executed on the reader each time the machine tool continuously manufactures parts makes the problem even more serious. If I need to make 100 copies of a given part, I must also pass the paper tape through the individual tines on the Reader 100. The fragile paper tape cannot withstand the harsh outdoor environment and this repeated use.
This led to the development of special magnetic plastic tapes. The paper uses a series of holes on the tape to carry the programming instructions, while the plastic tape uses a series of magnetic dots to carry the instructions. Plastic tape is much stronger than paper tape and solves the problem of frequent tearing and breakage. However, there are still two problems.
Most importantly, it is very difficult or impossible to change the description entered on the tape. In order to make the smallest adjustments in the instruction program, the machining process must be interrupted and a new belt created. We also had to pass as many tapes as the number of parts to be produced through the reader, but fortunately, computer technology became a reality and quickly solved the NC problems associated with perforated paper and plastic tape.
The development of the direct digital control (DNC) concept has solved the paper tape and plastic tape problems related to digital control, and only needs to eliminate the tape as a medium for carrying program instructions. In direct numerical control, the machine tool is connected to the host computer through a data transmission link. The program used to operate the machine tool is stored in the host computer and provided to the required machine tool through the data transmission link. Direct digital control represents an important step beyond perforated tape and plastic tape. However, it is subject to the same limitations as any technology that relies on the host. When the host machine fails, the machine tool will also stop. This problem led to the development of computer numerical control
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