Machine tool

The term machine tool means all machines that are used among others in mechanical engineering and tool for machining workpieces with tools. And mating machine called Machine Tools: In practice, however, only be transformative and separating ( zerteilende, cutting and abrasive that is, essentially). There are the standards DIN 8580 ff (method) and DIN 69 651 Part 1 (machine tools for working metal ), take the content relate to each other.

In addition to the machines described in this article, serving for the machining of workpieces with tools, there are a number of facilities that meet this description, such as hand drilling and grinding machines, hand operated, electric or pneumatic, hand-held, motor-driven hammers u. v. a..

Shaping the workpiece, the machine tool produces a relative movement between tool and workpiece. A distinction is made between the main motion ( on cutting machines, the " average motion ", for example, the rotation of the spindle ) and the feed or feed motion, which is superimposed on the cutting motion and continuous processing (eg chip removal ) allowed.

Forming machines are usually the machining of metals, such as steel or aluminum and plastics, zerteilende and cutting machine tools are obvious, but the processing of other materials, such as wood. The abrasive machine tools include, for example, EDM machines and laser machines.

The machining accuracy ( precision) of cutting machine tools is, depending on the machine, in the range of 1 mm to 1/1000 mm ( 1 micron ). Ultra- precision machines achieve accuracies of less than 1:1,000,000 mm (1 nm) (for example, for the processing of the laser optics ).

For metal forming and machining of high-performance editing tools are mostly needed. Way as to meet the high demands they exist today mostly made of coated or uncoated cutting materials such as high-speed steel, carbide, cermet, ceramic, diamond or boron nitride ( CBN).

2.1 Geometric Accuracy
2.2 Static stiffness
2.3 Dynamic behavior
2.4 Thermal behavior

3.1 serial kinematics
3.2 Parallel Kinematics

5.1 kinds of metal-forming and separating machine tools
5.2 kinds of cutting machine tools
5.3 Types of abrasive machine tools
5.4 Types of abrasive and building machine tools

Assemblies of machine tools

Frame

The machine frame absorbs the machining forces and secures the position of all modules to each other. Typical versions are made of cast iron ( rare cast steel ) welded steel structures, light metals, cement concrete, mineral cast (polymer concrete) or composite plastic. In ultra precision machines can also be found frame components made of granite. Meanwhile, foamed light metals are used. For smaller machines, the racks are designed as table and Konsolbauform. For heavier machine bed designs in open (stator ) or closed (Portal ) configuration can be used. The frame is the basis for the static and dynamic stiffness of the machine tool.

Foundation

Especially for large machines are special foundations, usually cast in the classic sense of the construction of concrete in a ground form, very important because this in their typical suitable construction as machine base with 70 to 90 % of the total mass of a machine due to the high inertial mass of a high Gesamtverwindungssteifigkeit guarantee and provide quiet of a machine running the necessary accuracy. Especially with extremely heavy workpieces and / or with correspondingly high labor or under shock load a suitably massive interpretation of the machine foundation is extremely important, because otherwise it inevitably leads to partial reductions of the machine and thus the usual today geometric accuracies no longer be achieved in the whole workspace. An exception to this rule is for machines with three-point line-up because their accuracy is independent of the foundation.

Guides

Guides are used to test limiting the movements on one or more (see wave guide ) degrees of freedom. There are hydrostatic, hydrodynamic, aerostatic guides and rolling guides. Originally predominantly hydrodynamic sliding guides were used, because of their dynamic properties ( no stick -slip effect, high movement speeds, etc.) use in recent times more and more by the rolling guides. However, since special manufacturing know-how is required for the production of anti-friction guides, today they are mostly procured as part of the purchase from suppliers.

Drives

Previously machine tools were driven by a transmission, that is, with a common shaft and belt drives from a central machine. All auxiliary drives supplied over transmission also from this mechanical energy distribution.

Since the invention and widespread use of electric motors could move on to the individual drive of the machine tools - each machine had now its own electric motor; the energy distribution was thus electrically and was much less susceptible to wear and also hazardous. Increasingly, separate electric motors were used for all auxiliary drives. The drive units are the main drive and the feed drives and power take-offs. The main drive was previously usually consists of a motor ( usually an electric motor ), a transmission, a safety clutch (in the simplest case of a V-belt slips in case of overload ) and the main spindle as a carrier of the tool or workpiece. Today's machine tools usually have a direct drive in which the rotor of the electric motor directly to the spindle sits (motor spindle). Due to the large capacity of the drive, especially in the use of motorized spindles, it is important to selectively remove the waste heat in order to avoid inaccuracies in the machine due to thermal expansion of the frame. In metal-forming machinery in addition to mechanical transmissions ( Toggle Presses ) come and hydraulic drives are used.

The bearing of the moving parts come to 90% rolling bearing for use, but also hydrodynamic, hydrostatic slide bearings, air bearings and magnetic bearings.

Previously, the feed motion derived via a gear from the main drive. Today, in general, all moving axes have their own feed drives. These generally consist of an electric motor, a ball screw and a measurement system for determining the position of the movable frame elements ( machine slide, table or stand). More rarely the rotary motor movement are used in a translational slide or stand movement known as " rack -and-pinion systems " for translation. As with linear direct drives high positioning accuracy and high dynamics can be achieved at the same time, these drives are to be found more frequently. The drive units (main and feed drives ) are generally CNC controlled today.

In the measuring devices, a distinction direct and indirect measuring systems. Both measuring systems the periods scale sections are counted sensors and from this number the distance traveled is then calculated. In indirect displacement measurement systems, however, the scale is arranged in a circle, so that the system, the change in angle of the screw shaft measured, and then calculates the pitch of the thread on the path change. At the precise direct measuring scale mounted parallel to the direction of movement, so that the length of the sections ( multiplied by the number of sections counted ) directly corresponds to the distance traveled.

The drives of supply aggregates, such as the coolant device are referred to as auxiliary drives

Control

See Computerized Numerical Control and cabinet

Tool storage and changer

Modern CNC machine tools are often equipped with fully automatic tool store, from which, depending on the requirements and tools can be exchanged directly or via a tool changer into the work spindle (eg milling ) or tool holder (eg, vertical lathes, machining centers ). Lathes often have only one or more so-called turret that does not change the tool you need, but only turns to the working level. They are so into slices, crowns, or star shape tool storage for up to twelve tools. As a tool storage (also: tool magazines ) for borers, drilling and milling machines, there are discs, chain, basket, shelf, flat or pallet storage that can hold up to 100 tools. With modern machine even after the expiry of a programmed life or after the actual tool wear (measured via the spindle motors ( cutting force ) ) is increasingly independently substituted in a provided replacement tool, so that such machines then can largely unsupervised machine workpieces in combination with automatic workpiece changer.

Tool holders

To ensure a fast tool changes with high accuracy, the tool holders (interface tool spindle) are standardized. Previously, mainly so-called taper were for rotating tools (SK), earlier known as Morse taper (MK ) was used. Today HSK are increasingly used because of their technological advantages. For HSK ( hollow taper shank ), and others carried out the margins on the inner contour so that the system is suitable for higher speeds.

For all recording systems are each adapter to the other systems to allow the often mixed machinery rational tool use.

Workpiece changer

Modern milling machines and drilling machines often have two or more pallets for clamping the workpieces that can be alternately brought into the work area. This allows to make tensioning operations outside the work area, while the processing can take place at the previous range. If the workpieces replaced together with the pallet as described Speak of the pallet changer. Modern lathes and milling machines for smaller work pieces often have a bar feeder ( diameter usually up to about 60 mm). Larger workpieces can be with robots, and replaced. The time required to switch the workpieces called workpiece exchange time.

Modern machine tools have measurement systems, which is used for detecting the position of, for example, the tool or the axis slide. The required angle and length measurements are made mainly opto - electronically, for example, with incremental encoders or absolute encoders on rotating shafts and directly the position measuring glass scales. Furthermore, resistive, inductive, capacitive, magnetic or electromagnetic active principles of transducers common.

Supply and disposal facilities

Machine tool cutting processes nowadays are usually equipped with a cooling lubricating devices. This usually promote a water -oil emulsion in the working area of the tool, be it via spray nozzles on the machine, the spindle head or nozzles in the respective tool. The coolant is filtered in circulation. As part of an environmentally - friendly manufacturing and job- but now switched increasingly to the so-called minimum quantity lubrication ( MQL or MMS ). In this case, a very small amount of coolant is atomized with air and sprayed on to the active site.

The supply and disposal facilities also include the chip conveyor, which conveys the removed chips from the work area out into a container.

Machine housing and safety devices

Machine tools today usually have a machine housing. This serves to protect the operator from flying chips, coolant before and before the resulting noise pollution and to protect against injury to the moving parts and for burst protection ( for example, if a tool breaks ). Larger machines and plants are protected by light barriers and grid.

Properties of machine tools

In addition to properties that affect the efficiency of machine tools, such as power, traversing, tool change time, etc. There are also properties that affect the quality of the manufactured product. These are:

Geometric accuracy

The attainable geometric accuracy will be obtained primarily from the production quality, the game's engine and design. Accordingly, for example, results in a portal design as it is but often implemented with large measuring machines in quality assurance in the production at the portal milling machines, the high accuracy of 1 to 5/ 1000 mm (1-5 microns ) for a large working area.

The geometric accuracy of machine guides produced today for larger CNC machines often additionally switches per axis, a correction profile by software, which is aligning input from the foreman of the machine manufacturer after setting up the machine and increases the geometric accuracy accordingly.

Static stiffness

The static rigidity or stiffness results from the inside constructed in a machine geometric structural ( wall thickness, cross-sections ) and the properties of the materials used. Further particularly location, shape and number of joints and guides ( fixed and mobile connections of machine elements ) are crucial for the achievable stiffness

Dynamic behavior

The dynamic behavior of machine tools is a highly complex issue. Key factors are the static stiffness of machine foundation and the workpiece and the tools, the location and distribution of masses and their vibration options (recovery effect), and the type, design and quality of the guides ( guided tours: Accuracy of the rollers, hydrostatic / hydrodynamic bearing, linear guides: roller guides, air tours, Hydrostatic / hydrodynamic guides )

Thermal behavior

The thermal behavior of a machine tool is significantly influenced by the action of heat sources and sinks on the quantity of heat and its position or arrangement. One differentiates between the thermal stress between internal and external influences.

To increase the accuracy and to keep despite the effort temperature fluctuations small, it is advantageous to build thermal Symmetric machines. Thermal symmetry means that cancel each other expansions. Here, the expected temperature distribution in the components of influence, and the length and the expansion coefficient ( a rule of thumb in steel: 1 m → heating → 1K 0.01 mm growth).

With the knowledge of the temperature behavior of the machine tool, the thermal expansion can be compensated for in the CNC part.

Kinematics

Serial kinematics

Classic, serial construction of the individual feed movements of the series after successive building.

Example console milling machine: The machine frame to the spindle housing moves, with a front mounted swivel head as a carrier of the mill, in a guide back and forth in the machine axis Y. The chuck moves on the console to the left and right of the machine axis X. The console moves up and down with the worktable resting on the machine frame and forming the machine axis Z.

Parallel kinematics

Work, similar to the rod kinematics of the telescopic leg construction to a freely movable in all directions platform for a professional flight simulator, all feed drives in parallel to each other simultaneously to the desired movement of a tool in so-called hexapod ( walking Hexa Greek numbers: Six, pod greek) in space and at the same time to produce a desired inclination of the tool holder or the tool. The realization of this principle in kinematic machine tools is because of the promising geometric properties for over 20 years the focus of research projects for machine tools. To date, there is no significant use in the production, which is traditionally dominated today by machines with serial kinematics. Advantage of parallel kinematics is usually higher dynamics due to the low mass of the guide elements, which, in contrast to a serial kinematics, the loads evenly (s), split on all guiding elements.

Order according to increasing level of automation

A conventional machine tool generates the cut and the feed motion via a motor and gearbox, as well as by hand wheels.
A vending machine controls the feed motion, for example, using cams. ( inflexible )
A CNC machine tool performs an automatic working cycle of a manually clamped workpiece. The tool change is usually performed automatically.
A machining center integrated in general, in addition to the workpiece and the tool change control system.
The flexible manufacturing cell includes several machines with their tool magazines, a larger workpiece storage and partly integrated measuring equipment.
Flexible manufacturing systems have a machine- cross automatic workpiece flow connection with a production control or of a production planning system.

Rigid transfer line have a very low degree of flexibility. Only by consuming Upgrade small changes in the product range can be produced. The rigid transfer line follows the line of principle and has no options, grinding or bifurcations to follow a rule.

Types of machine tools

Types of metal-forming and separating machine tools

Guillotine shears
Bending machine
Press
Press brake

Types of cutting machine tools

Lathe Universal Lathe ( Lathe, CNC Universal Lathe )
Turret lathe (single-and multi- turret lathes)
Lathe ( single and multi- spindle automatic lathe, automatic lathe )
Nachformdrehmaschine
Vertical Turret Lathe
Facing lathe
Facing Lathe
Precision lathe, ultra-precision lathe
Turning cell
Special Lathes

Drill bench Drilling Machine
Upright Drilling Machine
Jig Boring Machine ( Single Column, portal, CNC )
Pillar Drilling / radial drilling machine (boom drill )
Line boring machine
Deep Hole Drilling Machine
Revolver drill
Multi-spindle drilling machine
A precision drill
Jig
Special drilling machine ( floor type, tube sheet drilling machine, pcb drilling machine )

Milling Machine Console and universal milling machine (horizontal, vertical)
Bed milling machine (horizontal, vertical, cross table, traveling column )
Portal milling machine
Multi-spindle milling machine
Milling / boring machines
Tool Room Milling Machine
Special milling machine ( crankshaft milling machine, Milling Machine, rolling ingot milling machine, plate edge milling machine )
CNC machining center
HSC milling machine (High Speed Cutting )
Hobbing machine for producing gear wheels
Jig (horizontal, vertical)

Planer Slotting Machine
Table planer
Stamp planer
Keilnutenhobelmaschine

Broaching broaching
Außenräummaschine
Kettenräummaschine
Screw and Rundräummaschine
Drawing machine
Sonderräummaschine

Sawing machine circular saw machine
Band Saw Machine
Jigsaw ( hacksaw, jigsaw, reciprocating saw )
Formsäge
Sondersäge

Filing, brushing, shaving machine Vertical filing machine

Grinding machine Surface and profile grinding machine
Cylindrical grinding machine ( external cylindrical grinding machine, internal cylindrical grinding, roll grinding machine )
Jig Grinding Machine
Roll grinding / gear grinding machine
Belt sander
Tool Grinding
Cylinder head grinding machine ( Combined machine for turning and grinding )
Special grinding machine ( crank, camshafts and spline shaft grinding machine )

Lapping machine

Honing Machine

Types of erosive machine tools

EDM EDM machine
Wire EDM

Laser processing machine - see laser cutting

Water jet cutting machine

Types of erosive and constructive machine tools

Laser processing machine

The machine tools can be manually or automatically loaded with robots (loaded with workpieces ). For precise positioning and fixing of the workpiece on the machine table is used in automated machines, a palletizing. Similarly, the editing tools by hand or with the aid of a tool changer can be automatically inserted into the tool holder.