SI20048A2 - Device for step milling - Google Patents

Abstract

The subject of the invention can be classified into the field of CMC machines, more precisely milling machines. The device for step milling according to this invention solves the problem of milling workpieces with cylinder shaped milling tools, where the ratio between the milling depth a (mm) and the milling tool diameter d (mm) is larger than 1,5 (a/d). It provides better durability of the tool and a very rare or hardly any breaking of the milling tool, minimises the presence of large milling forces which leads to a lesser deviation of the milling tool and a good geometric precision of the processing. The main feature of the device for step milling according to the invention is, that it consists of an input microprocessor based communication module, a step code generator, an appropriate control program (KP) and an output microprocessor based communication module allowing a ratio between the depth and the diameter of the milling tool of up to 5d, which is impossible to achieve with milling machines featuring standard control.

Description

STEERING MACHINE

The subject of the invention belongs to the field of numerically controlled machine tools more precisely milling machine tools

A technical problem is a design solution for such a step-milling machine which, when machining workpieces with cylindrical milling cutters, where the ratio of the milling depth a (mm) to the milling diameter d (mm) is greater than 1.5 (a / d), will make the tool extremely durable and minimal or infrequent milling of the milling cutter, reducing the occurrence of large cutting forces, resulting in less milling deflection and good geometric machining accuracy.

The aforementioned problems preclude the removal of material above the recommendations of the tool manufacturer (more than a / d = 1.5). The recommendations reduce the utilization of the machine, and some machining operations cannot be performed at all.

The inventors are aware of the following patent documents, which are the result of a search by the STEP and MILLING criterion in the European Patent Office database

SU1558573 SU1207651 SU1053983 DE3625234

JP58217211

FACE STEP MILLING CUTTER

FACE STEP MILLING CUTTER

FACE AND END STEP MILLING CUTTER Milling cutter with step-by-step radially displaceable cutting elements, preferably for working wood and similar nonferrous metals

STEP CUTTING MΕ MILLING CUTTER.

The aforementioned documents address the step-by-step milling that is performed with a special tool design. A special shaped tool is used for each form of stepping. In this case, the programmed movement of the tool does not change, only the designed shape, which is influenced by the predetermined stepper shape of the cutter, changes.

US5803683

EP0864121

DIMENSIONAL

AU1478697

VVO9731158

AU1269797

KR9711785

SU1350943

GB2312702

A query with the search criteria MILLING yields the following documents: GR63578 IMPROVEMENTS IN OR RELATING TO MILLING MACHINES

GR58063 REFUSE MILLING APPARATUS ZA8400630 MILLING APPARATUS Milling system

METHOD AND DEVICE FOR MILLING THREEVVORKPIECES

Patella milling instrument PISTE MILLING DEVICE Improvements in milling systems NC MILLING METHOD OF CURVED SURFACES USING THE STEEPEST DIRECTED TREE APPROACH

METHOD OF GROUP LAYOUT OF SHEET BLANKS BY MILLING One trip milling system

The aforementioned milling devices and methods for which patent protection is sought or obtained do not cover the step milling solution. Likewise, the authors have not found a similar solution on any machine, nor are there any data in the literature (UMI, COBISS, SCI, CC databases searched) and no patent files (European Patent Office).

The essence of the step milling device according to the invention is that it consists of an input communication module, a step code generator, a corresponding control program and an output communication module in microprocessor technology, and allows milling depth and diameter ratios of up to 5d, which is not the case with conventionally controlled milling machines achievable.

The step-milling device of the invention will now be described in greater detail by means of figures showing:

Fig. 1 - block diagram of the installation of the milling machine in the CNC control of the milling machine Fig. 2 - block diagram of the KP control program Fig. 3 - movements of the milling cutter with parameters Fig. 4 - flow of the milling movement pulses generated by the milling device

The step milling device consists of an input communication module, a step code generator, a corresponding KP control program, and an output communication module. It is implemented in microprocessor technology. It can be installed on the milling machine in three ways:

- into the control unit of the milling machine, between the position memory and the interpolator as shown in Figure 1,

- to the control unit immediately after the data loading module, and

- in front of the control unit where it intercepts the NC program inputs and processes them accordingly.

The machine reads the CNC program bar for the product, identifies the desired start of the stepping process and its parameters p1 and p2.

The parameter p1 is the feed direction, the parameter p2 is the feed direction and a is the cutting depth. The parameters p1 and p2 have been determined through extensive laboratory and real-world testing and provide all the benefits of stepping. The optimum values found are p1 = 0.2-0.8 mm, p2 = 0.05-0.4 mm, the parameters must satisfy the condition p1 is greater than p2, the delay time is 0.01 -1 s (see Figure 3). The machine then transforms the values of the respective tool positions so that they meet the desired limit values and the requirements of a new, stepping milling method.

The generated path characteristic of the device according to the invention is the cyclic repetition of stepping motion in a programmed trajectory. The tool moves by the parameter p1 in the predetermined (desired) direction, stops at this position by 0.01 - 1s, and then moves by the value of the parameter p2 in the opposite direction. This stepping motion is repeated throughout the given tool trajectory.

Transformation of tool paths and coordinates is performed automatically by controlling the deviation from previously desired positions.

Using a milling machine, depth and diameter ratios of up to 5d were achieved, which cannot be achieved on conventionally controlled milling machines. With this device, therefore, it is possible to process positions that we could not previously. At the same time, studies of the operation of the milling machine show that the same cutting force parameters on the tool are significantly smaller, therefore the wear of the cutting edge of the tool is smaller, the deviation of the milling cutter is smaller and therefore the geometrical precision of machining is higher. These are the side, positive effects of using a milling machine.

The use of the said device is particularly useful in the tool and metal industries, where high material removal is required and the products have complicated shapes.

Claims (3)

1. A stepping milling device that generates a new milling tool path in such a way as to produce shapes that were not feasible with the old tool path, characterized in that it consists of an input communication module, a step code generator, a suitable control program (KP) ) and the output communication module in microprocessor technology and allows milling depth and diameter ratios up to 5d. Step milling device according to claim 1, characterized in that it is mounted in the control unit of the milling machine immediately behind the data loading module. Step milling device according to claim 1, characterized in that it is located in front of the control unit of the milling machine, where it intercepts the input data of the numerical control program and processes it using the KP program.