A detailed explanation of the machining center

Machining center, do you really understand?

Classification of machining centers
Machining centers are often divided into vertical machining centers, horizontal machining centers, gantry machining centers and universal machining centers according to the state of the spindle in space.
The spindle of the machining center is called a vertical machining center in a vertical state in the space, and a horizontal machining center with the spindle in a horizontal state in the space.

(1) Vertical machining center: The structure is mostly fixed column type, and the worktable is rectangular,
which is suitable for processing plate, sleeve and plate parts. Vertical machining centers usually have three linear motion coordinates,
XYZ axes, and a fourth axis A axis can be installed on the worktable. The vertical machining center is easy to clamp, easy to operate, easy to observe the processing situation, and convenient to debug the program. However, due to the influence of the height of the column and the tool changing mechanism, parts that are too high cannot be processed.
The vertical machining center has a simple structure, small footprint and low price.

(2)Horizontal machining center: Usually a mobile column is used, and the headstock is moved up and down along the guide rail between the two columns.
Horizontal machining centers usually have three linear motion coordinates. Facing the machine tool, the left and right movement is the X axis,
the front and rear movement is the Z axis, and the up and down movement is the Y axis.
The horizontal machining center can also install a fourth axis A axis on the worktable.
Parts such as helical cams and cylindrical cams can be processed. The horizontal machining center is inconvenient to observe when debugging programs and trial cutting pins,
inconvenient to monitor during processing, and inconvenient to clamp and measure parts, but it is easy to arrange pins during processing.
Compared with the horizontal machining center, the vertical machining center has a complex structure, a large area and a higher price.

(3)Gantry machining center: Most of its spindles are vertically set, with ATC system and replaceable spindle head accessories.
The system software has many functions, and can be used for multiple purposes in one machine, which is suitable for processing large parts.

(4)Universal machining center: The universal machining center is a five-sided machining center,
which has the functions of a vertical machining center and a horizontal machining center.
After the workpiece is clamped once, it can complete all the side and top machining except the installation surface.

Common universal machining centers are:
1.The spindle can be rotated 90°, which can work like a vertical machining center or a horizontal machining center.

2. The spindle does not change its direction, and the worktable rotates 90° with the workpiece. Finish the machining of five faces.
In short, according to the number and function of the workbench: there are single workbench machining centers,
double workbench machining centers, and multi workbench machining centers.

The structure of the machining center
(1)Basic components. It is the basic structure of the machining center, which consists of a bed, a column and a worktable.
They mainly bear the static load of the machining center and the cutting load generated during processing,
so it must have sufficient rigidity. These large pieces can be cast iron parts or welded steel structural parts,
and they are the largest and heaviest parts in a machining center.
AKIRA-SEIKI castings are made of high-grade Meehanna castings, which are heat-treated for high stability.

(2)Spindle parts. It is composed of spindle box, spindle motor, spindle and spindle bearing and other parts.
The start, stop and speed change of the spindle are controlled by the numerical control system,
and the cutting tool is involved in the cutting motion through the tool installed on the spindle,
which is the power output component of the cutting process. It is the key component of the machining center,
which determines the machining accuracy and stability of the machining center.

(3)CNC system. The CNC part of the machining center is composed of cNc device, programmable logic controller PLC, servo drive device and operation panel.

(4)Automatic tool change system. It consists of tool magazine, manipulator drive mechanism and other components.
When the tool needs to be changed, the CNC system issues an instruction,
and the manipulator takes the tool out of the tool magazine and loads it into the spindle hole.
It solves the tasks of automatic storage, selection, handling and exchange of tools between processes in the multi-process continuous processing after the workpiece is clamped once.
The tool magazine (tool head) is a device that stores all the tools used in the machining process.
The tool magazine has a disc-type chain and other capacities ranging from a few to several hundred.
The structure of the tool arm also has various forms according to the relative position and structure of the tool magazine and the spindle,
such as: single-arm type, double-arm type, etc.
Some machining centers do not use tool arms but directly use the movement of the spindle box or tool magazine to realize tool change.

(5)Auxiliary devices. Including lubrication, cooling, chip removal, protection, hydraulic, pneumatic and detection systems and other parts. Although these devices do not directly participate in the cutting motion, they play a role in guaranteeing the machining efficiency, machining accuracy and reliability of the machining center,so they are also an indispensable part of the machining center.

(6)APC automatic pallet exchange system. In order to realize the unmanned operation of one part or further shorten the non-processing time,
some machining centers use multiple automatic exchange worktables to reserve workpieces, and install one workpiece on the worktable for processing. At the same time, another one or several worktables can also load and unload other parts.
When the processing of the parts on one worktable is completed, the worktable will be automatically exchanged to process new parts,
which can reduce auxiliary time and improve processing efficiency. .

The main processing objects of the machining center
(1)Box-type parts: Box-type parts generally refer to parts with more than one hole system, a cavity inside, and a certain proportion in the direction of length, width and height.

(2)Complex surface: It is difficult or even impossible to complete complex surfaces by ordinary machining methods.

(3) Special-shaped parts: Special-shaped parts are parts with irregular shapes, and most of them need multi-station mixed processing of point,
line and surface, such as fork and so on.

(4) Disc, sleeve, plate parts: with keyway, or radial hole, or distributed hole system on the end face, curved disc sleeve or shaft parts, such as flanged shaft sleeve, with keyway or square head Shaft parts, etc., as well as plate parts with more holes, such as various motor covers, etc.
Vertical machining centers should be selected for disc parts with distributed holes and curved surfaces on the end faces, and horizontal machining centers with radial holes.

(5) Parts that are put into production periodically: When machining parts with a machining center, the time required mainly includes the basic time and preparation time, of which the preparation time accounts for a large proportion, such as: process preparation, programming, trial cutting of the first piece of parts, etc.
The time is very long, and the machining center can store the content of these times for repeated use in the future.
This saves that time when machining the part later. The production cycle can be greatly shortened.