Contenido

El material es arrancado o cortado con una herramienta dando lugar a un desperdicio o viruta. La herramienta consta, generalmente, de uno o varios filos o cuchillas que separan la viruta de la pieza en cada pasada. En el mecanizado por arranque de viruta se dan procesos de desbaste (eliminación de mucho material con poca precisión; proceso intermedio) y de acabado (eliminación de poco material con mucha precisión; proceso final cuyo objetivo es el de dar el acabado superficial que se requiera a las distintas superficies de la pieza). Sin embargo, tiene una limitación física: no se puede eliminar todo el material que se quiera porque llega un momento en que el esfuerzo para apretar la herramienta contra la pieza es tan liviano que la herramienta no penetra y no se llega a extraer viruta.

cutting movements

Two movements are involved in the material removal machining process:

Each of these two movements can have the part or the tool depending on the type of machining.

Manual machining

It is carried out by a person with exclusively manual tools: saw, file "Lima (tool)"), chisel, chisel (electroerosion); In these cases the operator machines the part using one of these tools, using his skill and strength.

Machine tool machining

Machining is done using a machine tool, manual, semi-automatic or automatic, but the machining effort is carried out by mechanical equipment, with the necessary motors and mechanisms. Classic machining machine tools are:.

For some time now, computing applied to industrial automation has made machine tools evolve towards numerical control. So we are talking about 5-axis machining centers and multifunction lathes, which allow us to obtain a complex, fully finished part, starting from a billet or a metal bar and all in a single clamp.

These numerically controlled machines offer versatility, high production and preparation capacities, offering very high precision of the order of microns.

The production costs of a series of parts in a machine tool are divided into fixed costs and costs per production unit.

where C (n) is the production cost of a series of n pieces, C (n) is the non-productive cost of the process for n pieces, c is the unit operating cost and n is the number of pieces produced. The value of these variables depends on the number of pieces in the series.

Taking into account the process times, the production cost can be analyzed using the following expression:

where C is the hourly cost, including the cost of direct labor, amortization of facilities, maintenance, etc.; t is non-productive time, which includes machine setup times (phase time); t is the operation time, C is the cost of the cutting edges, which is the cost of the inserts in the case of using interchangeable inserts, or the cost of the entire tool in the case of integral tools; t is the replacement time of the cutting edges; t is the machining time, that is, the time during which the tool is cutting; and T is the duration or lifetime of the tool.

The hourly cost will be higher the higher the depreciation cost of the machine and the qualification of the workforce. Processes that use numerically controlled machine tools have a higher hourly cost than processes that use conventional machines, but lower than processes that use special machines, such as transfer machines (transfert). In the same sense, the preparation times for a batch are longer in a numerical control machine than in a conventional machine, since it is necessary to prepare the numerical control programming of the process operations.

Operation times are shorter in a numerical control machine than in a conventional machine, which is why, starting from a certain number of pieces in a batch, machining is more economical using numerical control. However, for large batches, the process is more economical using special machines, such as transfer machines.

Contenido

El material es arrancado o cortado con una herramienta dando lugar a un desperdicio o viruta. La herramienta consta, generalmente, de uno o varios filos o cuchillas que separan la viruta de la pieza en cada pasada. En el mecanizado por arranque de viruta se dan procesos de desbaste (eliminación de mucho material con poca precisión; proceso intermedio) y de acabado (eliminación de poco material con mucha precisión; proceso final cuyo objetivo es el de dar el acabado superficial que se requiera a las distintas superficies de la pieza). Sin embargo, tiene una limitación física: no se puede eliminar todo el material que se quiera porque llega un momento en que el esfuerzo para apretar la herramienta contra la pieza es tan liviano que la herramienta no penetra y no se llega a extraer viruta.

cutting movements

Two movements are involved in the material removal machining process:

Each of these two movements can have the part or the tool depending on the type of machining.

Manual machining

It is carried out by a person with exclusively manual tools: saw, file "Lima (tool)"), chisel, chisel (electroerosion); In these cases the operator machines the part using one of these tools, using his skill and strength.

Machine tool machining

Machining is done using a machine tool, manual, semi-automatic or automatic, but the machining effort is carried out by mechanical equipment, with the necessary motors and mechanisms. Classic machining machine tools are:.

For some time now, computing applied to industrial automation has made machine tools evolve towards numerical control. So we are talking about 5-axis machining centers and multifunction lathes, which allow us to obtain a complex, fully finished part, starting from a billet or a metal bar and all in a single clamp.

These numerically controlled machines offer versatility, high production and preparation capacities, offering very high precision of the order of microns.

The production costs of a series of parts in a machine tool are divided into fixed costs and costs per production unit.

where C (n) is the production cost of a series of n pieces, C (n) is the non-productive cost of the process for n pieces, c is the unit operating cost and n is the number of pieces produced. The value of these variables depends on the number of pieces in the series.

Taking into account the process times, the production cost can be analyzed using the following expression:

where C is the hourly cost, including the cost of direct labor, amortization of facilities, maintenance, etc.; t is non-productive time, which includes machine setup times (phase time); t is the operation time, C is the cost of the cutting edges, which is the cost of the inserts in the case of using interchangeable inserts, or the cost of the entire tool in the case of integral tools; t is the replacement time of the cutting edges; t is the machining time, that is, the time during which the tool is cutting; and T is the duration or lifetime of the tool.

The hourly cost will be higher the higher the depreciation cost of the machine and the qualification of the workforce. Processes that use numerically controlled machine tools have a higher hourly cost than processes that use conventional machines, but lower than processes that use special machines, such as transfer machines (transfert). In the same sense, the preparation times for a batch are longer in a numerical control machine than in a conventional machine, since it is necessary to prepare the numerical control programming of the process operations.

Operation times are shorter in a numerical control machine than in a conventional machine, which is why, starting from a certain number of pieces in a batch, machining is more economical using numerical control. However, for large batches, the process is more economical using special machines, such as transfer machines.