Home > FAQ > INDUSTRY KNOWLEDGE >

Machining center and configuration selection

Machining center and configuration selection
Update Time:2019-03-12
Machining center and configuration selection
1. Selection of processing objects
According to the experience of Nuojin Seiki technicians for many years, before you determine the object of purchase, you must first clearly define the objects to be processed. In general, parts with the following characteristics are suitable for machining in machining centers: Multi-process intensive type workpieces require many tools to be machined on one workpiece.
Positioning cumbersome workpieces, for example, has a porous machining process with a positioning hole pitch accuracy requirement, and is highly convenient to implement by utilizing the high positioning accuracy of the machine tool.
Repetitive production of workpieces is suitable for single-piece, small-volume production. Small batches refer to 1-100 pieces, each batch is not much, but it needs to be repeated. In addition, even if the shape and size of the workpiece are different, they are similar workpieces, and it is easy to realize the parts of the group processing (gt) process.
Complex shape parts such as complex shape parts and aerospace parts can be processed into various shaped parts on the machining center by means of automatic programming technology.
The box type and the plate type parts use a rotary table on the horizontal machining center to perform multi-face machining on the box parts, such as a spindle case body, a pump body, a valve body, an internal combustion engine cylinder block, and the like. If the top surface is to be machined in one setup, a pentahedral machining center is available. The vertical machining center is suitable for processing the lid cylinder head and flat cam. The gantry machining center is used to process large cabinets and plate parts, such as diesel engine block, machining center column, bed, and printing wall machine.

2. Selection of machine specifications
According to the determined size and size of the machined workpiece, the table size of the required machine tool and the stroke of the three linear coordinate systems are determined accordingly. The size of the table should ensure that the workpiece can be smoothly clamped on the workpiece. The machining size must be within each coordinate stroke. In addition, the space of the tool change and the interference of each coordinate interference zone should be considered.

3. Selection of machine tool accuracy
The precision of the machining center is classified into standard type and precision type. The main precision items are as follows:

Machining center main precision project

Precision project

Standard type (mm)

Precision type (mm)

Linear positioning accuracy

±0.01/full range

±0.005/full range

Repeatability

±0.006

±0.002

Milling accuracy

0.03-0.04

0.015


According to the machining accuracy requirements of the workpiece, the user selects the machine tool with the corresponding accuracy grade, and the mass-produced parts may have a precision value of 1.5-2 times of the positioning accuracy. Ordinary machine tools batch processing 8-level precision workpieces, precision machine tool processing accuracy can reach 5-6, but there must be constant temperature and other process conditions, so the precision machine tools are strict and high price.

4. Tool magazine capacity selection
Manufacturers of machining centers usually have 2-3 different capacity magazines for the same type of machine tools. For example, vertical machining centers have 16, 21, and 24 capacity magazines.
When the user selects, the required quantity can be determined according to the process analysis result of the workpiece to be processed. Usually, the capacity of the tool magazine is determined by the number of tools required for one part in one setup, because when another part is processed The tool needs to be rearranged, otherwise the tool management is complicated and error-prone.
From the statistical data, it is advisable to use a 16-knife knife magazine for the vertical machining center. Of course, it must be finalized according to actual needs.

5. Machine selection function and selection of accessories
When selecting the machining center machine tool, in addition to the basic functions and basic components, there are also functions and accessories that the user selects according to their own requirements, which are called selection functions and optional accessories (optional accessories). With the development of numerical control technology, more and more content is available for selection, and the proportion of its constituent price in the mainframe is also increasing. Therefore, it is uneconomical to use a large number of accessories without clear purpose. The so-called "prepared" Ordering guidance is essentially a waste. Therefore, a comprehensive analysis should be made at the time of selection, and long-term factors should be properly considered.
The selection function is mainly for the numerical control system, but the price increase is not much, but it has many convenient functions for use, and should be properly configured. For accessories that can be shared by multiple machine tools, one machine can be considered for multi-purpose. But you must consider that the interface is generic.

6. Processing beat and machine number estimation
Based on the selected workpieces, and then analyzing the routing, the processes to be processed on the machining center are selected in this routing, and the hourly beat estimates are made for these processes.
The cutting time of each process is estimated based on the current process parameters, and the auxiliary time is usually 10%-20% of the cutting time. In addition, each tool change time of the small and medium-sized machining center takes about 10-20 seconds, so the single process time is: t single order = t cut + t auxiliary + (10-20s) = t cut + (10% - 20%) t cut + (10-20s).
With a single process time, it is not difficult to calculate the annual output. 300 working days a year, the machine starting rate is calculated from 75%-85%. If the calculation result does not reach the target value, but the process is similar, modify the process parameters; if the gap is large, you should consider increasing the number of machine tools.
cnc machining center