This news article was originally written in Spanish. It has been automatically translated for your convenience. Reasonable efforts have been made to provide an accurate translation, however, no automated translation is perfect nor is it intended to replace a human translator. The original article in Spanish can be viewed at Centros de Mecanizado
Machining centres
by Lorenzo Solano
Area of Industrial quality of AIMME30/04/1999
Area of Industrial quality of AIMME30/04/1999
The machining center has been the result of the logical evolution of the "tool milling machine" in a context where stated increase productivity, flexibility and accuracy, at the time which were improved conditions of safety of workersall logically accompanied by the incorporation of electronics.
1 ORIGIN AND CONCEPT OF THE MACHINING CENTER
The machining center has been the result of the logical evolution of the "tool milling machine" in a context where stated increase productivity, flexibility and accuracy, at the time which were improved conditions of safety of workersall logically accompanied by the incorporation of electronics.
What was said so far may enable us introduce the concept of "machining center". A machining center is first and foremost a machine tool of consisting of startup material (that is, a non portable machine, operating with the help of an external source of power, is able to modify the shape of the material or piece to machine through the boot of small portions of the same or shavings)(, either continuous or discontinuous).
However, the essential features of a machining center and that therefore they should serve to differentiate it from other types of machines are as follows:
- It is equipped with numerical control
- You can perform other operations in addition to milling machining
- It has an automatic tools changer
It is equipped with numerical control
The first of these so-called essential or defining properties means that machining centres are the product of the technological revolution which has resulted in the introduction of the numerical control technology in the world of mechanization. There are no centres prior to the technology of numerical control machining (in the sense supported currently for this expression).
You can perform other operations in addition to milling machining
The transformation of the classical milling in a machining center has occurred as a result of give it the potential to develop operations of work that were traditionally performed in other types of machines. It is the case of the drilling, and the threaded fundamentally. Indeed, such operations are not kinematics and speaking conceptually distinct from the milling operations, given that even if they have different mechanical and technological implications, all them are run by a movement of court circular, with the help of a rotary tool. This is what made it possible that at any given time such operations are integrated in one machine which is known as machining center. Therefore, and so far, a machining center is a machine tool with numerical control that allows to perform various operations as milling machining, drilling and Threading. In this sense must tell the difference between machining centers and milling machines with numerical control, given that these are machine tools as if they are equipped with numerical control but are only designed to carry out operations of milling.
It has an automatic tools changer
The above-mentioned essential characteristics II implies the existence of a system to facilitate the automatic change of the tools that would allow for the different possible operations virtually to the third, in the sense that is almost unavoidable. Logically, the tool change system is governed by the numerical control of the machine. Tool change systems respond to structural concepts, requirements and different design solutions, but in any case must ensure the possibility of a change in the course of execution of a program part, without the need for intervention by the operator.
Finally and with respect for other possible views, we can define a machining center as a machine tool of numerical control who can perform other operations of machining and milling and you have an automatic tools changer.
A machining center is a machine tool of numerical control who can perform other operations of machining and milling, and which has an automatic tool changer.
A preparation more and more complete machine that in the medium-sized or large operators is necessary in micro and small enterprises. It could happen that all tasks had to be performed by one person.
2 MACHINING centers and centers of milling front to centres of TORNEADO
The concept of "Centre of milling" is very similar to "numerical control milling". However it should be a distinction that could go unnoticed, and that sometimes, on a voluntary or involuntary basis is not. The "numerical control milling" themselves, do not have an automatic tool changer. Said another way, if added you an automatic tools changer own numerical control of machine-controlled to a milling machine numerical control, the result is a Centre for milling.
The Centre of turning is something quite different, and that not to be confused is in any case with the previous two. A center of turning is a machine tool of numerical control which may perform operations of turning and milling. To explain more clearly the type of machine to which we refer we will say that a centre of turning is a numerical control lathe which has endowed with the ability to perform operations of milling. This is achieved with the addition of one or more positions for motorized tools.
In summary, a center of turning appropriate and maintains a large formal similarity with a lathe of CNC, while machining centres and centres of milling are product of the evolution of the conventional milling machines (although external fairing and the presence of other elements make that their appearance is quite different to the of the) (classic or conventional milling).
Rotating tools store. Possibly the system most used in machining centres. Sometimes the own store performs the movements that allow to realize the change of the tool from the spindle to a position of the store or vice versa (picture Kondia)
3 TYPES OF MACHINING CENTRES AND CRITERIA OF CHOICE
Difficult issue. For the moment, we can conclude that it is a complex problem for the number of variables involved and the diversity of factors to consider.
In any case, there are some key factors:
- The typology of the parts to produce (size, complexity)
- The size of the batches
- Technical specifications (tolerances of parts)
- The environment where it has to be located and working the machine.
In effect, all these factors and other derivatives, related and even additional to those involved in a decision that may be of importance for the company. In any case, let's go by parts, if the first question is:
What kind of machine do I need?
The answer may be trivial: lathe, milling machine, drill, etc. From here (and assuming that a machine is required to carry out operations of milling) we can ask ourselves the following option:
With or without NC?
The answer will come basically conditioned by three aspects:
- The size of the batches of production: for medium and long runs the CNC may be the most profitable option.
- The complexity of the pieces: on many occasions the numerical control is unavoidable for the manufacture of parts of some geometric complexity.
- The required accuracy: when you narrow the margins of tolerance, the numerical control tends to be the preferable option, especially if it's series of parts where it is required to also make sure that a good repeatability.
Do machining center, Center of milling or numerical control milling machine?
The answer to this question is implicit in the arguments made for the definition of the centres of machining and differentiation with other types of machines.
At this point, if the choice is a machining center, we will have to be pointed to the possible variations within them on the basis of selection:
- worktable size
- pallet changing system
- number of axes
- type and size of the storage of tools
- features of the control to be fitted
- spindle orientation
- adjustable spindle
- divider plate
- communication possibilities
- applications of verification and scanning of parts
- system of the swarf
- "taladrina" projection system
- mechanical robustness
- speed
- power
- pair
- advance force
- range of spindle
- accuracy and repeatability
- dynamic behavior (stability, vibration)
- quality of components and accessories
- the machine safety systems
- issues relating to peacekeeping
- security systems for the operator
- ergonomics
- overall dimensions of the machine
- fairing
- weight
- aesthetic issues
- etc.
The choice of one or another variant will come depending on these "key factors" and other as the preferences of the buyer with respect to a particular manufacturer of machine or control, and the economic and financial possibilities of the company.
Machining center has allowed greatly to diversify the number of operations to perform on a single machine, as well as to increase the number of operations carried out with the same subject of piece, resulting in an increase in the ratio quality/cost of the produced pieces (photo Mikron)
4 FEATURES SPECIFIC CONTROLS OF THE MACHINING CENTERS
From the point of view of its structure and its design concept and inner workings, there are no major differences between the control of a machining center and the other type of machine. Obviously as your application is different, their functions, user-level, are also. The differences lie basically in the specific application that van intended and other factors given by the evolution of the technology.
Logically, in any case, it is desirable that the operator of the machine has a specialization and professional experience to deal with possible eventualities that may arise during the mechanization. If not, the operator of the machine becomes a "changer of pieces" and "apretador of buttons", that does not require any specific preparation beyond the learning of a work process.
Ergonomics and functionality of the controls has been markedly increased by the use of units such as the one shown in the figure, with a size and low weight, and its connection with a tensile cable, allow to control certain functions of the machine with faster response and accuracy while the operator can continue with more detail and comfort the evolutions in the tooling (photo Mikron).
Thus, to find defining characteristics when choosing a control would raise issues such as:
- Number of axis controlled successively
- Number of axes to control simultaneously
- Process speed and calculation capacity
- Memory communication possibilities and and integration in automated environments
- Ease of operation
- Friendly interface for the operator
- Programming language
- Possibility of using various programming languages
- Graphical support for programming
- Visualization of programs
- Information tools and operating parameters of the machine
- Functions to facilitate the use of programs from CAD applications / CAM
- Management tools
- Control of trajectories
- Custom cycles
5 SKILLS REQUIRED TO PROPERLY OPERATE A MACHINING CENTER
The situation will be very different depending on the structure of jobs within the company. In any case it is useful to distinguish several tasks associated with the work with a machining center:
- The programming
- The preparation of the machine and tools
- The loading, unloading, selection and eventual modification of the piece on site programs
- The assistance and monitoring during the implementation of the programme and the change of workpiece machining
- Maintenance mechanical, hydraulic, pneumatic and electrical and electronic (hardware and software)
Because the Division (or structuring of work) is often accentuate in larger enterprises, it could conclude that for micro-enterprises and small business needs (more complete) greater preparation machine that in the medium-sized or large operators. In the first case you can reach the extreme situation in which all the previous tasks have to be developed by the same person. For medium or large it is usual that the operator does not require great knowledge of programming or maintenance, although a few minimum notions can be very useful.
Logically, in any case, it is desirable that the operator of the machine has a specialization and professional experience to deal with possible eventualities that may arise during the mechanization. If not, the operator of the machine becomes a "changer of pieces" and "apretador of buttons", that does not require any specific preparation beyond the learning of a work process.
Logically, in any case, it is desirable that the operator of the machine has a specialization and professional experience to deal with possible eventualities that may arise during the mechanization. If not, the operator of the machine becomes a "changer of pieces" and "apretador of buttons", that does not require any specific preparation beyond the learning of a work process.
6 TRENDS FUTURE IN MACHINING CENTERS
Future trends for machining centers can cover in two lines. On the one hand we have the increase in current benefits or quantitative improvements, and on the other hand, the innovations and qualitative improvements.
Machining center of reference SPT-H500S of high rigidity, designed for applications of machining of high-torque (Hyundai - Delteco)
We can include in a non-exhaustive list of them:
- The use of structures stiquito type
- The development of systems of actuation and control for high speed machining
- The use of touch screens as a means of programming and control
- Automatic correction of the path systems based on variations in temperature, wear and tear on tools or measurement in process of machined parts
- The incorporation of communication functions for the integration of the centres of machining in automated environments: communicating with other machines, robots, manipulators arms, automatically guided vehicles stores centralized tools, computers, etc.
- It's transmission, sync, check and control functions
Machining centres in Spain
In http://www.interempresas.net/MetalMecanica/FeriaVirtual/Centros_de_mecanizado/ the visitor will find all the features of each of the machines, namely: year of launch to the market; total power of the main spindle; number of main spindles; maximum speed; type of table; dimensions; maximum weight of the piece; construction and type for a column; and controls numeric that mounts.
