The Ancient "Bow Lathe" with Pulleys and Bow-shaped Rods
As early as ancient Egypt, people had already invented the technique of turning wood by rotating it around its central axis and using cutting tools. Initially, two upright logs were used as supports to hold the wood to be turned. A rope was wound around the wood, and the elasticity of tree branches was utilized. By pulling the rope with hands or feet, the wood would rotate, and cutting was performed using handheld tools.
This ancient method gradually evolved and developed into the "bow lathe," where a rope was wound around pulleys for two or three loops. The rope was supported by a flexible rod bent into a bow shape. The bow was pushed and pulled back and forth to rotate the workpiece for turning.
Medieval Foot-operated Lathe with Crank and Flywheel
By the medieval period, someone designed a "foot-operated lathe" that used a pedal to rotate a crankshaft and drive a flywheel, which in turn transmitted the rotation to the main spindle. In the mid-16th century, a French designer named Bézons created a lathe for screw cutting, in which the tool could slide using a screw, but unfortunately, this lathe was not widely adopted.
The Birth of Headstock and Chuck in the 18th Century
In the 18th century, another design emerged using a foot pedal and connecting rod to rotate the crankshaft. This design allowed the rotational energy to be stored in a flywheel on the lathe. The development progressed from directly rotating the workpiece to the introduction of a rotating headstock. The headstock was equipped with a chuck used for clamping the workpiece.
The Invention of the Slide Rest Lathe by Henry Maudslay (1797)
In the history of lathe invention, one notable figure is Henry Maudslay, an Englishman who invented the revolutionary slide rest lathe in 1797. This lathe featured precise lead screws and interchangeable gears.
The Birth of Various Specialized Lathes for Advancing Mechanization and Automation
To enhance the level of mechanization and automation, various specialized lathes were developed. In 1845, an American named Fitch invented the turret lathe. In 1848, the wheel lathe was introduced in the United States. In 1873, an American named Spencer created a single-axis automatic lathe, followed by the development of a three-axis automatic lathe. In the early 20th century, lathes with separate motor drives and gearboxes with variable speeds emerged. With the invention of high-speed tool steel and the application of electric motors, lathes continued to improve and eventually reached the modern level of high speed and high precision.
After the First World War, various efficient automatic lathes and specialized lathes developed rapidly due to the needs of the arms, automotive, and other mechanical industries. In order to improve the productivity of small-batch workpieces, by the late 1940s, lathes with hydraulic copying devices were widely promoted. At the same time, multi-tool lathes also saw advancements. In the mid-1950s, program-controlled lathes with features such as perforated chucks, pin plates, and indexing discs were developed. The use of numerical control (NC) technology in lathes began in the 1960s and experienced rapid development after the 1970s.
Lathes are classified into various types based on their purpose and functionality.
Engine lathes have a wide range of processing capabilities. They can adjust the spindle speed and feed rate and can process the inner and outer surfaces, end faces, and internal and external threads of workpieces. These lathes are mainly operated manually by workers, resulting in low production efficiency. They are suitable for single-piece production, small-batch production, and repair workshops.
Turret lathes and capstan lathes are equipped with turret tool holders or capstan tool holders that can accommodate multiple cutting tools. Workers can use different tools in sequence to complete various operations on a workpiece in a single clamping. They are suitable for mass production.
Automatic lathes can automatically perform multi-process machining on small and medium-sized workpieces according to a predetermined program. They can also handle automatic loading and unloading and repetitive processing of the same batch of workpieces. They are suitable for large-scale and high-volume production.
Semi-automatic multi-tool lathes are divided into single-axis, multi-axis, horizontal, and vertical types. The layout of a single-axis horizontal lathe is similar to that of an engine lathe, but two sets of tool holders are installed in front of or behind the main spindle or above and below it. This type of lathe is used for processing disk-shaped, ring-shaped, and shaft-like workpieces, and its productivity is 3 to 5 times higher than that of an engine lathe.
Copy lathes can automatically replicate the shape and size of a template or sample, completing the machining cycle of a workpiece. They are suitable for small-batch and mass production of complex-shaped workpieces, with productivity 10 to 15 times higher than that of an engine lathe. There are various types, including multi-tool, multi-axis, chuck-type, and vertical copy lathes.
Vertical lathes have a spindle that is perpendicular to the horizontal plane, and the workpiece is clamped on a horizontal rotary table. The tool holder moves on a crossbeam or column. They are suitable for processing larger, heavier workpieces that are difficult to install on an engine lathe. They are generally divided into single-column and double-column categories.
Gear hobbing lathes, while turning, cyclically move the tool holder radially to form gear surfaces for gear hobbing, gear milling, and other operations. They usually have hobbing attachments and small grinding wheels driven by separate motors for hob grinding.
Specialized lathes are designed for machining specific surfaces of certain types of workpieces, such as crankshaft lathes, camshaft lathes, wheel lathes, axle lathes, roll lathes, and steel ingot lathes, among others.
Combination lathes are primarily used for turning operations. However, with the addition of special components and attachments, they can also perform boring, milling, drilling, threading, grinding, and other operations. They have the characteristic of "one machine, multiple functions" and are suitable for repair and assembly work in engineering vehicles, ships, or mobile repair stations.
Although manual craftsmanship may be considered relatively outdated, it has trained and produced numerous skilled workers. While they may not be experts in machine manufacturing, they are capable of producing various hand tools, such as knives, saws, needles, drills, chisels, grinders, as well as shafts, sleeves, gears, and bed frames. In fact, machines are assembled from these components.
The Early Designer of Boring Machines - Leonardo da Vinci. The boring machine is known as the "mother of machinery." When it comes to boring machines, we must first mention Leonardo da Vinci. This legendary figure may be one of the earliest designers of boring machines used for metalworking. The boring machine he designed was powered by hydraulics or foot pedals. The cutting tool for boring was pressed against the rotating workpiece, which was fixed on a moving table driven by a crane. In 1540, another painter created a painting called "Pyrotechnics," which also depicted a boring machine. At that time, the boring machine was specifically used for precision machining of hollow castings.
The First Boring Machine Born for Cannon Barrel Machining (Wilkinson, 1775). By the 17th century, due to military needs, the development of the cannon manufacturing industry was rapid. The production of cannon barrels became a major challenge that needed to be solved. The world's first true boring machine was invented by Wilkinson in 1775. Strictly speaking, Wilkinson's boring machine was a drilling machine that could precisely machine cannon barrels. It consisted of a hollow cylindrical boring bar installed on bearings at both ends.
Wilkinson was born in America in 1728 and moved to Staffordshire at the age of 20, where he built the first iron furnace in Bilston. Therefore, he was known as the "Iron Master of Staffordshire." In 1775, at the age of 47, after continuous efforts in his father's factory, Wilkinson finally manufactured this new machine capable of drilling cannon barrels with rare precision. Interestingly, after Wilkinson's death in 1808, he was buried in a cast iron coffin that he designed.
Boring Machines' Significant Contribution to Watt's Steam Engine. Without the steam engine, the first wave of the Industrial Revolution would not have been possible. The development and application of the steam engine itself, besides the necessary social opportunities, also relied on certain technical prerequisites. This is because manufacturing the components of the steam engine is not as easy as a carpenter shaping wood. Metal needs to be formed into specific shapes, and the machining precision requirements are high. Without the corresponding technical equipment, it would not be possible. For example, in the manufacturing of the steam engine's cylinder and piston, while the outer diameter precision required for the piston can be measured and cut from the outside, it is not easy to achieve the precision required for the cylinder's inner diameter using conventional machining methods.
Smethwick was the most outstanding mechanical technician of the 18th century. He designed a total of 43 waterwheel and windmill devices. When making steam engines, Smethwick encountered difficulties in machining the cylinders. It was quite challenging to turn a large cylinder's inner circle into a perfect circle. To solve this problem, Smethwick created a special machine for cutting the inner circle of the cylinder at the Carron Ironworks. This boring machine, powered by a waterwheel, had a tool installed at the front end of its long shaft. This tool could rotate inside the cylinder, allowing for the machining of its inner circle. However, due to the tool's installation at the front end of the long shaft, issues such as shaft deflection arose. Therefore, it was extremely difficult to machine a truly circular cylinder. As a result, Smethwick had to repeatedly change the cylinder's position for machining.
In tackling this problem, the boring machine invented by Wilkinson in 1774 played a significant role. This boring machine utilized a waterwheel to rotate the cylindrical workpiece and advanced the fixed tool aligned with the center. Due to the relative movement between the tool and the workpiece, the material was bored to create a cylindrical hole with high precision. At that time, cylinders with a diameter of 72 inches were bored using this machine, with an error of no more than the thickness of a sixpence coin. From a modern technology standpoint, this is a significant error, but achieving this level under the conditions of that time was already quite remarkable.
However, Wilkinson's invention was not patented, and people began to imitate and install it. In 1802, Watt also mentioned Wilkinson's invention in his book and replicated it in his Soho Ironworks. Later, Watt also applied this marvelous machine by Wilkinson in the manufacturing of steam engine cylinders and pistons. For pistons, measurements could be taken on the outside while cutting, but for cylinders, it was not as simple, and a boring machine was necessary. Watt used a water wheel to rotate the metal cylinder, while a fixed tool pushed forward to cut the interior of the cylinder. As a result, cylinders with a diameter of 75 inches had an error of less than the thickness of a coin, which was considered highly advanced at that time.
The Birth of the Table-Lifting Boring Machine (Hetherington, 1885). In the following decades, many improvements were made to Wilkinson's boring machine. In 1885, Hetherington in England manufactured the table-lifting boring machine, which became the prototype of modern boring machines. A milling machine refers to a machine tool primarily used to process various surfaces on a workpiece using milling cutters. Usually, the main motion is the rotation of the milling cutter, while the movement of the workpiece (and the milling cutter) is the feed motion. It can process flat surfaces, grooves, as well as various curved surfaces, gears, and more. A milling machine is a machine tool used to mill workpieces with various shapes using milling cutters. In addition to milling flat surfaces, grooves, gear teeth, threads, and keyways, it can also process relatively complex profiles. It is widely used in mechanical manufacturing and repair departments.
In the 19th century, the British invented boring machines and planers for the needs of the Industrial Revolution, while Americans focused on inventing milling machines to produce a large number of weapons. A milling machine is a machine with various-shaped milling cutters that can cut workpieces into special shapes, such as spiral grooves and gear profiles.
As early as 1664, the British scientist Hooke created a machine for cutting using rotating circular tools, which can be considered as the primitive form of a milling machine. However, at that time, society did not respond enthusiastically to it. In the 1840s, Pratt designed the so-called Lincoln milling machine. Of course, Whitney and Pratt can only be said to have laid the foundation for the application of milling machine inventions in machine manufacturing. The real credit for inventing a milling machine suitable for various operations in factories should be attributed to the American engineer Joseph Brown.
The First Universal Milling Machine (Brown, 1862). After a period of silence, milling machines became active again in the United States. In comparison, Whitney and Pratt can only be regarded as laying the groundwork for the invention and application of milling machines. The true achievement of inventing a milling machine suitable for various operations in factories should be attributed to the American engineer Joseph Brown.
In 1862, Brown in the United States manufactured the world's first universal milling machine, which was a groundbreaking innovation with its universal dividing head and comprehensive milling cutters. The worktable of the universal milling machine could rotate at a certain angle in the horizontal direction and was equipped with accessories such as a vertical milling head. When his "universal milling machine" was exhibited at the 1867 Paris Exposition, it achieved great success. Additionally, Brown also designed a formed milling cutter that would not deform even after grinding. He then manufactured a grinding machine for milling cutters, bringing milling machines to the level we see today. In the process of invention, many things are often interconnected and interdependent: the manufacturing of steam engines required the assistance of boring machines, and after the invention of steam engines, the demand for planers emerged from the process requirements. It can be said that the invention of the steam engine led to the design development of the "mother machine" from boring machines and lathes to planers. In fact, a planer is a "plane" for planing metal.
Machining Large Flat Surfaces - Planer (1839). Due to the need for machining steam engine valve seats, many technicians began researching this area from the early 19th century. Among them were Richard Roberts, Richard Pratt, James Fox, and Joseph Clement, who independently manufactured planers over a span of 25 years, starting in 1814. These planers fixed the workpiece on a reciprocating table and used a cutting tool to machine one side of the workpiece. However, these planers did not have a tool feed mechanism and were still in the process of transitioning from "tools" to "machines." In 1839, a person named Bodmerd in England finally designed a planer with a tool feed mechanism.
Planer for Machining Small Flat Surfaces. Another British individual, Nasmyth, invented and manufactured planers for machining small flat surfaces from 1831 to 40. These planers fixed the workpiece on the bed, while the tool moved back and forth.
Afterward, with tool improvements and the emergence of electric motors, planers developed towards high-speed cutting and high precision on one hand, and towards larger sizes on the other. Grinding is an ancient technique known to humans since ancient times. In the Paleolithic era, this technique was used to grind stone tools. Later, with the use of metal tools, the development of grinding technology was promoted. However, the design of true grinding machinery is a more recent development. Even in the early 19th century, people still used rotating natural grindstones to come into contact with the workpiece for grinding.
The First Grinding Machine (1864). In 1864, the United States produced the world's first grinding machine, which involved mounting a grinding wheel on the slide rest of a lathe and equipping it with an automatic transmission device. Twelve years later, Brown in the United States invented the universal grinding machine, which approached the modern grinding machine.
The Birth of Artificial Grinding Stones - Grinding Wheels (1892). The demand for artificial grinding stones also arose. How to develop grinding stones that are more wear-resistant than natural grindstones? In 1892, an American named Acheson successfully experimented with silicon carbide made from coke and sand, which is now known as C abrasive, an artificial grinding stone. Two years later, another abrasive called A abrasive, primarily composed of aluminum oxide, was successfully developed. With these advancements, grinding machines found wider applications.
Subsequently, with further improvements in bearings and guide rails, grinding machines achieved higher precision and specialized in various types, including internal cylindrical grinders, surface grinders, cylindrical grinders, gear grinders, universal grinders, and more. Ancient Drilling Machine - "Bow Drill." Drilling technology has a long history. Archaeologists have discovered that humans invented drilling devices for hole-making around 4000 BCE. Ancient people would place a rotating cone suspended from a beam that was supported by two columns. They would then use a bowstring to rotate the cone, allowing for drilling in wood or stone. Soon, people also designed a drilling tool called the "hand drill," which utilized an elastic bowstring to rotate the cone.
The First Drilling Machine (Whitworth, 1862). Around 1850, the German Matignoni first produced a twist drill for metal drilling. In 1862, at the International Exhibition held in London, an Englishman named Whitworth showcased a power-driven drilling machine with a cast-iron frame, which became the prototype of modern drilling machines.
Afterward, various types of drilling machines appeared, including radial drilling machines, drilling machines equipped with automatic feed mechanisms, and multi-spindle drilling machines capable of drilling multiple holes simultaneously. With improvements in tool materials and drill bits, along with the adoption of electric motors, large-sized, high-performance drilling machines were finally manufactured. CNC stands for Computer Numerical Control, which is an automated machine tool equipped with a program control system. This control system can logically process programs specified by control codes or other symbolic instructions, decode them, and control the movements and machining of workpieces. The control unit of a CNC machine tool completes all the operations and monitoring, serving as the "brain" of the CNC machine tool.
High machining accuracy and stable processing quality;
Ability to perform multi-axis coordinated movements and process complex-shaped parts;
When the machined part changes, only the CNC program needs to be modified, saving production preparation time;
The machine tool itself has high precision and rigidity, allowing for optimal machining parameters and high productivity (generally 3 to 5 times that of conventional machine tools);
High level of automation, reducing labor intensity;
Requires higher qualifications for operators and higher technical skills for maintenance personnel.
A CNC machine tool generally consists of the following components:
Host: It is the main body of the CNC machine tool, including the machine bed, columns, spindle, feed mechanism, and other mechanical components. It is responsible for completing various cutting processes.
CNC device: It is the core of the CNC machine tool, including hardware components (printed circuit boards, CRT display, keyboard, paper tape reader, etc.) and corresponding software. It is used to input digitized part programs, store input information, perform data transformation, interpolation calculations, and various control functions.
Drive device: It is the driving component of the CNC machine tool's execution mechanism, including the spindle drive unit, feed unit, spindle motor, and feed motor. It realizes spindle and feed drive under the control of the CNC device through electrical or electro-hydraulic servo systems. When multiple feeds are coordinated, it can perform positioning, linear, planar curve, and spatial curve machining.
Auxiliary devices: These are necessary supporting components of the CNC machine tool to ensure its operation, such as cooling, chip removal, lubrication, lighting, monitoring, etc. It includes hydraulic and pneumatic devices, chip removal devices, exchangeable worktables, CNC rotary tables, CNC indexing heads, as well as tooling and monitoring and detection devices.
Programming and other ancillary equipment: These are used for off-machine programming and storage of part programs.
Explanation of CNC Machine Tool Processing Flow
CAD: Computer-Aided Design, which refers to the use of computers to assist in the design of 2D or 3D workpieces or solid models.
CAM: Computer-Aided Manufacturing, which involves using CAM software to generate G-Code.
CNC: CNC Machine Tool Controller, which reads the G-Code and initiates the machining process.
Explanation of CNC Machine Tool Programming
CNC programs can be divided into main programs and subprograms (subroutines). For repetitive machining operations, subprograms can be used to simplify the design of the main program.
Characters (numerical data) → Words → Blocks → Machining program.
CNC code can be edited using a text editor, such as Notepad in the Windows operating system. Simulated software can be used to verify the correctness of the tool path based on the written CNC program.
Explanation of Basic Function Instructions for CNC Machine Tools
Functional instructions consist of an address code (alphabetical letter) and two numbers, representing a specific action or function. They can be categorized into seven main types: G-function (preparatory function), M-function (auxiliary function), T-function (tool function), S-function (spindle speed function), F-function (feed rate function), N-function (block number function), and H/D-function (tool compensation function).
Explanation of Reference Points for CNC Machine Tools
When programming CNC machine tools, at least one reference coordinate point is selected to calculate the coordinate values of various points on the workpiece. These reference points are commonly referred to as zero points or origin points. The commonly used reference points include the machine origin, home position, work origin, and program origin.
Machine Reference Point: The machine reference point, also known as the machine origin, is a fixed reference point on the machine.
Reference Points: Each axis of the machine has a reference point, which is pre-set precisely using limit switches as the return points for the worktable and spindle.
Work Reference Points: The work reference point, also known as the work origin, is the origin of the work coordinate system. It is a floating point set by the program designer as needed and is generally set at any position on the worktable (workpiece).
Program Reference Points: The program reference point, also known as the program origin, is the benchmark point for all coordinate values at turning points on the workpiece. This point must be selected when writing the program, so the program designer needs to choose a convenient point for ease of programming.
The steel telescopic guide rail protection cover is made of high-quality 2-3mm thick steel plate formed by cold pressing. It can also be made of stainless steel as required. Special surface polishing enhances its value. We can provide corresponding types of guide rail protection for all types of machine tools (horizontal, vertical, inclined, transverse). However, crankshaft dedicated machine tools have their processing limitations. Only by using suitable machine tools can the high efficiency and specialization of crankshaft machining be achieved, thereby improving the processing efficiency of the process.
1. When the crankshaft journal has a counterweight groove, CNC internal milling machines cannot perform the machining. If the crankshaft journal has a counterweight groove in the axial direction, both CNC high-speed external milling machines and CNC internal milling machines cannot perform the machining. However, CNC turning machines can conveniently perform the machining.
2. When the side of the balance block needs to be machined, CNC internal milling machines should be the preferred choice because the internal milling cutter disc has good external circular positioning and rigidity, especially suitable for machining large forged steel crankshafts. In this case, CNC turning machines are not suitable because when machining the side of the balance block with a CNC turning machine, the side of the balance block undergoes intermittent cutting, and the crankshaft speed is high. Under these conditions, tool breakage is more severe.
3. When the crankshaft journal does not have a counterweight groove and the side of the balance block does not need to be machined, in principle, several types of machine tools can be used for machining. When machining automotive crankshafts, CNC turning machines are used for the main journal, and CNC high-speed external milling machines are used for the connecting rod journal, which is the optimal and efficient machining choice. When machining large forged steel crankshafts, it is more reasonable to use CNC internal milling machines for both the main journal and the connecting rod journal.
Crankshafts can be divided into large-sized forged steel crankshafts and lightweight automotive crankshafts. Forged steel crankshafts generally do not have counterweight grooves on the journals and require machining with larger tolerances. Automotive crankshafts generally have counterweight grooves on the journals and do not require machining on the side. Therefore, it can be concluded that CNC internal milling machines are used for machining forged steel crankshafts, CNC turning machines are used for the main journal of automotive crankshafts, and CNC high-speed external milling machines are used for the connecting rod journal, which is a reasonable and efficient machining choice. Forging machines are equipment used for metal and mechanical cold working, and they only change the external shape of the metal. Forging machines include rolling machines, shearing machines, punching presses, hydraulic presses, oil presses, bending machines, etc.
There are many types of machine tool accessories, including flexible accordion-type protective covers (bellows), tool blades, steel or stainless steel guide rail covers, telescopic screw covers, rolling shutter protective covers, protective curtains, dust-proof folding covers, steel drag chains, engineering plastic drag chains, machine tool work lights, machine tool pads, JR-2 rectangular metal hoses, DGT conduit protection sleeves, adjustable plastic cooling tubes, dust suction tubes, ventilation tubes, explosion-proof tubes, travel groove plates, bumpers, chip conveyors, alignment gauges, platforms, granite slabs, cast iron slabs, and various operating components, etc.
