In the mold processing line cutting process is generally the final process, so the processing accuracy is very demanding, if the machine tool's mechanical accuracy is not good, will directly affect the quality of products and mold processing, and ultimately lead to loss of users, loss of market, so online cutting machine tool selection When it comes to type, how to judge the mechanical accuracy and structure, and the merits and demerits are very important.
In general, the accuracy of new machine tools is easy to judge, because there is a national standard GB7926-87 and related general standards for machine tool accuracy, where the new machine can know whether it is qualified or not when commissioning and acceptance. However, the most important factor is the judgment of the accuracy of the maintenance of the machine tool, because the accuracy of the maintenance of the machine tool will only be reflected in the use of the machine after a certain period of time, but the national standard can not be strictly controlled, so It is only when the user selects a type to do a thorough understanding of the machine tool and structure. Do not listen to hearsay and listen to some unfounded rumors, so as not to disturb your judgment.
Here we elaborate on the drive structure, guide rail structure, and drive mode of the machine tool table.
4-1 screw and its installation structure
The accuracy of the screw is important, but if the screw is not properly installed, the screw will not help.
First of all, we must look at the form of the screw and see if it is a ball screw, a triangular thread screw or a trapezoidal thread screw. On the wire cutting machine, the ball screw is superior to the triangular screw thread and the trapezoidal thread screw, and the screw diameter is required to be as large as possible to increase the rigidity.
Followed by the installation structure of the screw, ball screw is a precision transmission components, so to fully play its precision, then the assembly structure of the screw is also higher, must be fixed at both ends, bearing support, for large stroke machine tools Also, the lead screw must be pre-stretched to reduce the deflection of the lead screw, thereby improving the accuracy of the machine table.
4-2 gear transmission structure
(1) Firstly, we must learn more about the number of gears in the gear box. The more gears that participate in the transmission, the greater the transmission resistance, the easy wear of the tooth surface, and the easy transmission of gear gaps. As a result, the larger the system error of the machine table, the more gears. The assembly is not easy but also easy to produce accidental error, so the less the better the transmission gear, the use of a pair of gear transmission error is minimal, so it is very important to understand the gear transmission structure of the table movement during the selection.
(2) Observe the working environment and lubrication performance of the gear box of the worktable. Some manufacturers' early machine tools were designed to be irrational, so that the cutting fluid can easily enter the gear box, so that the gears work in the immersion of the cutting fluid for a long time. This design is very unreasonable. The lighter ones increase the wear of the gears. The heavy ones cause the stepper motor to be flooded, so the user must observe the position of the gearbox of the worktable during the selection to ensure that the cutting fluid must not be immersed. This is critical to the accuracy of the machine tool.
4-3 Rigidity and Overall Structure of Rails
(1) The guide rail is the key to ensure the accuracy of the table, and the user should attach great importance to the selection. First, observe the size of the cross section of the guide rail. Under the same conditions, the thicker the shape is, the better the rigidity is, and the deformation is less likely to occur during processing. Secondly, the material of the guide rail and the heat treatment process are known to the manufacturer. In general, in order to ensure its strength and small deformation, it is better to use a high-carbon alloy steel, an overall quenching or more audio quenching process.
(2) Observe the structure of the guide rail directly. The common guide rail structure on the market is as follows:
1. Inlaid steel ball type rolling guide;
2. Inlaid steel roller type rolling guide;
3, linear rolling guide;
4, elastic bearing cast iron rails.
The difference between the first and the second is on the roller body of the guide rail, one is the ball and the other is the roller. The ball and the guide surface are in point contact, and the roller and the guide surface are in line contact, so its wear resistance and bearing capacity are much better than the ball type. The elastic bearing cast iron guide rail is a kind of simple guide rail and it is eliminated. At present, the second and third structures are used in the machines imported from Japan's Sodick, Japan's Mitsubishi, Swiss Charmilles, and Ruiach. Therefore, the user should consider as many as possible during the selection process. Two and third structures.
4-4 drive method
CNC wire-cutting machine tools are generally driven by stepper motors. In stepper motors, there are also reactive and hybrid-type distinctions to achieve different step angles. The most common type of stepper motors on the market are reactive stepper motors. The stepping motor also has different driving modes such as three-phase three-shot, three-phase six-shot, five-phase ten-shot, and five-phase double-ten. This type of motor has a large step angle and only three-phase windings. With the continuous improvement of market demand and the improvement of the overall level requirements of the machine tool industry by the relevant departments of the Ministry of Machinery Industry, five phases and ten beats will gradually replace three-phase six-shots. This is because the five-phase ten-shot not only further subdivides the step angle of the three-phase six-beat, but also increases the motor winding resistance to five phases, so the transmission is smooth and powerful.
To sum up, the user should choose this structure to ensure the long-term reliability of the machine tool during the selection:
(1) Select a precision ball screw with a diameter as large as possible, and have a fixed bearing support structure at both ends;
(2) The number of transmission gears on the table is small. A pair of gears is preferable, and the position structure of the gear box ensures that the cutting fluid must not be immersed.
(3) Try to use roller-mounted steel rolling guides or linear guides with large cross-sectional area or large aspect ratio;
(4) Select the five-phase ten-step stepper motor drive, if the conditions available to use hybrid subdivision drive or AC servo drive is even more ideal.
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