SE538598C2 - Ceramic cutting plate with chip breaking surface for cutting hard work - Google Patents

Abstract

Summary A ceramic or mixed-ceramic cutting plate for cutting hard machining of a rotating workpiece, having a rake angle γ having a value of s 0 °, a rake-adjoining chip-breaking surface in a direction away from a cutting edge of the cutting plate being steeper to the tool reference plane. 14

Description

The invention relates to a ceramic carbide insert for cutting hard machining of a rotating workpiece according to the preamble of claim 1.

Machining of workpieces in lathes is done with a cutting tool that clamps a tool carrier. This is designed in the form of a carbide insert or a cemented carbide indexable insert. For the chips produced during cutting or turning of the processed material, the requirement is that on the one hand they are easy to dispose of and that they do not assume too great lengths and on the other hand do not endanger the machinery or personnel. Due to these requirements, particularly long chips or random chips should be avoided. Preferred chip shapes are cylindrical or have a helical spiral shape. Discontinuous shavings are also preferred.

In the soft machining of workpieces during rotation, carbide inserts are known for this purpose with a recess-like depression in relation to the tool. This is arranged near a cutting edge and leads away from the chips from the cutting edge. On the one hand, it can lead to chip breaking and, on the other hand, positively affect the shape of the chip. A disadvantage of this geometry of cemented carbide cutters, however, is that it is suitable only for soft machining and finishing treatments, since the cemented carbide insert due to the calving effect of the trough-like depression, in a hard machining or in rough machining with a higher chip thickness than 2-8 mm tends to crack.

Due to their high temperature strength and hardness, in particular ceramic or mixed ceramic carbide inserts are used in hard machining. To enable hard machining with the hard, but also relatively brittle ceramic carbide insert, its cutting edge must be protected against breakage.

In turning technology, carbide inserts are therefore used without a clearance angle and with a chip angle of 0 ° and a chip surface bevel that connects directly to the cutting edge. Although this geometry has a so-called T-chamfer which provides the necessary edge protection for the ceramic carbide insert for hard and rough machining, the chip formation of this cutting geometry is still disadvantageous. Still occurs as a function of the operating parameters of the rotating machine part and partly random / or long shavings.

In contrast, the invention is based on the task of creating a ceramic cemented carbide insert for cutting hard machining of a rotating workpiece, warp forming is improved. This object is achieved by a ceramic cemented carbide insert according to claim 1. Advantageous embodiments of the invention are described in the patent claims.

A ceramic or mixed-ceramic carbide insert for cutting hard machining of a workpiece rotating specifically around a center of rotation has an antenna insert direction in accordance with DIN 6851, which is supported perpendicular to a tool reference plane of the carbide insert. In addition, it has a cutting edge, through which a chip surface is limited, which is arranged with a chip angle s 0 ° to the reference plane of the tool.

According to the invention, it has a chip-breaking surface adjoining the chip surface, which is arranged in a direction away from the cutting edge which is steeper arranged to the reference plane of the tool than the chip surface.

Since the chip-breaking surface as a consequence and with reference to the chip surface has a steeper slope, a chip-breaking step is formed over the two surfaces, which results in improved chip formation and chip departure. Tests have shown that the cemented carbide insert thanks to this geometry, especially when using cemented carbide inserts of mixed ceramics, has an optimized chip formation and less tendency 2 for long or random chips. As a mixed ceramic material, HC7 from the manufacturer NTK is particularly suitable. This is an advantage especially when turning long-chip materials such as CrNiNo16 / 18, which are used especially for PTO shafts, gear shafts or solar wheel shafts. With the chip surface thus formed and chip breaking surface, the reliability of the processes increases and the operating time of the equipment is extended because no more interruptions for chip removal are necessary.

Similarly, the life of the cemented carbide insert is increased compared to conventional cemented carbide inserts for turning hard machining. This results in savings in operating costs and improves quality and reduces waste in production. The reference plane of the tool is preferably arranged in parallel with a support surface for the cemented carbide insert, which is arranged to lie on a tool holder.

In case a rake angle γ is 0 °, the rake surface is parallel to the Tool Reference Plane or not arranged against it. Thus, the strength and stability of the cemented carbide insert are increased compared to a structure reinforced with a positive chip or with a pointed wedge angle. In the case of the rake angle y of 0 °, a single wedge angle ß of up to 90 ° is thus possible. The wedge angle is defined over the chip surface and a clearance surface of the cemented carbide insert adjacent to a single machining surface. In the case of a negative rake angle, the rake surface is so arranged against the reference plane of the tool that the abrasive effect of the cutting edge is obtained, whereby the stability of the cutting edge is further increased. In this embodiment, an obtuse wedge angle of> 90 ° is enabled which is preferred to increase the stability.

The cemented carbide insert according to the invention is particularly suitable for hard machining of and I or rough machining, ie for engaging depth or chip thickness, of about 2 to 8 mm. Thus, a sum of the rake angle, the wedge angle and a clearance angle as formed between the assumed machining plane and the clearance surface delimited by the cutting edge is defined to be 90 °. The wedge angle is always positive and can also be blunt, or show a value> 90 °. The clearance angle is always 20 ° and preferably about 0 °. To guarantee a constant angle sum of 90 °, the rake angle γ is so defined that it has negative values, if the rake surface extends starting from the cutting edge in a direction towards the rake departure away from the tool reference plane or rises away from it.

Admittedly, similar chip breaker steps for ceramic cemented carbide inserts are pre-hardened in the milling technique known as shown in, for example, US-A-7,837,41? is B2. However, there is in lathe technology, the technical prejudice, that such geometry with a chip breaker step is not suitable for turning. Reasons for this include the fundamentally different types of interventions in milling and turning.

Another aggravating circumstance of the invention is that until recently it was only with great difficulty to use non-standard cutting geometries, which in that case required a manual readjustment of the cutting edge to the rotational center of the workpiece. However, since the chip switching step of the present invention has a lower height of the cutting edge. the support surface of the cemented carbide insert, than on a comparable standard cemented carbide insert, this readjustment process would not be absolutely necessary.

Only with modern three- or four-axis lathes, this readjustment is possible automatically. The required manual readjustment until then thus constituted a considerable resistance to using cemented carbide inserts according to the invention with a reduced cutting edge or chip breaker step when turning.

In a preferred embodiment of the invention, the chip breaking surface is provided with a chip breaking angle v to the tool reference plane whose value is preferably 2 -90 ° and is less than 0 °, the chip breaking angle with respect to the tool reference plane being steeper than the chip angle according to the invention.

Analogous to the definition of the rake angle, the rake-breaking angle assumes negative values when the rake-breaking upper surface, starting from the rake surface, extends or rises in the direction of a rake departure away from the tool reference plane.

For feed speeds of up to about 0.1 mm / revolution, especially for fine machining, a value of the chip breaking angle av of about -90 ° to -75 ° is preferred, in order to achieve a high resistance force at a low feed force over the chip breaking angle. against removal and consequently affect the fracture and the chip and its shape and in a beneficial manner.

For a medium-sized machining at feed speeds from 0.1 mm / revolution to 0.25 mm / revolution, a chip-breaking angle av of about -75 ° to -60 ° is preferred, for rough machining with feed speeds of between 0.25 and 0.5 mm / chip breaking angle of about -60 ° to -45 ° is preferred. At feed speeds of less than 0.5 mm / revolution, especially in a tongue machining, a chip breaking angle av avca -45 ° to less than 0 ° is preferred.

Preferably the value of the rake angle y is 0 ° and z - 25 °, more preferably about s 0 ° and z -2 °. The latter range is preferably applied in the general processing. Chip angle with values less than -2 ° is preferred for heavy cutting, especially for a cutting depth ap of more 2 4 mm in radius or 2 8 mm in circumference of the workpiece, as an increasing stability of the cutting edge is achieved with a smaller value of the chip angle.

In a particularly preferred and advantageous embodiment of the cemented carbide insert, the chip surface has a chip surface chamfer adjacent to the cutting edge so that a small, immediate connection to the cutting edge adjacent area of the chip surface is more strongly arranged towards the tool reference plane than the rest of the chip surface. Also through this measure, the stability of the cutting edge is increased, since the cutting edge is protected against breakage due to the abrasive effect of the chip chipping surface. Thus, the rake angle as described above is defined as the slope of the remaining chip surface against the reference plane of the tool, ie not on the slope of the chamfer.

In order to optimize the chip departure, a preferred embodiment of the invention shows that the chip breaking surface has a concave transition surface as the delimiting chip surface. This has, in the direction of the chip departure, preferably a transition radius RZ 2 0.5 and s 1 mm. This transition radius Rg increases the stability of the chip breaker stage, as the calving action is reduced due to it. In this way, the tendency to a fracture indication at the transition from the chip surface to the chip-breaking surface is reduced. For rough machining, the transition radius R has; preferably a value of about 0.5 to 0.8 mm, for heavy machining a value 2 0.8 mm.

In a particularly preferred and advantageous embodiment, the cemented carbide insert is designed as a cemented carbide indexable insert and preferably has an A- or B- or C- or D- or E- or H- or K- or L- or M- or O- or R- or S- or T- or V- or W-shape.

In a particularly preferred embodiment of the cemented carbide insert or the cemented carbide indexable insert, the chip surface and / or the chip breaking surface is formed along the circumference of the cemented carbide insert or the cemented carbide indexable insert.

For the cemented carbide indexable insert in accordance with the invention, a radius R is preferably suitable on the cutting edge which has a value of 0.1 and s 1 mm. Thus, a value of about 0.1 mm is preferably preferred for precision machining, a value of about 0.3 mm is preferred for preferably medium and rough machining, and a value of 0.3 mm is preferred for heavy machining.

For the depth of the chip surface and the chip breaking surface, which is measured in the tool reference plane and perpendicular to the cutting edge, the following preferred values are obtained: A chip breaking surface depth B preferably has a value of 2 l and s 5 mm.

A chip surface depth L preferably has a value of 2 1 mm and s 5 mm.

Thus, the chip-breaking surface depth B is preferably adapted to or dependent on the transition radius R2.

A method according to the invention for manufacturing a ceramic or mixed ceramic hard metal insert or cemented carbide indexable insert as described above includes the steps of: sintering a basic geometry of the insert, and laser machining and / or grinding the basic geometry to generate the chip surface and / or the chip breaking surface.

Below are two embodiments of a cemented carbide insert according to the invention which are further illustrated by four schematic figures. The figures show: Figure 1 shows a first embodiment of a carbide insert in a plan view; Figure 2, the carbide insert according to Figure 1 in a longitudinal section; Figure 3 shows a second embodiment of a carbide insert in a top view, and Figure 4 shows the carbide insert according to Figure 3 in a longitudinal section.

The first embodiment according to Figures 1 and 2 shows a mixed ceramic hard metal insert 1 formed in an S-shape (square). It consists of the material HC7 from the manufacturer NTK. This has a high hardness so that the cemented carbide insert is particularly suitable for turning hard materials of hard materials. In this first embodiment, a cross section 2 of the cutting plate 1 measures 15 mm. The corners 4 of the cemented carbide insert 1 are rounded with a corner radius Ropå 1.6 mm. The rounded corners 4 have, in a plane facing the viewer in Figure 1, a peripheral cutting edge 6. To illustrate the relevant geometries of the cemented carbide insert 1, a description of Figure 2 now follows.

Figure 2 illustrates the first embodiment (cf. figure 1) in figure 1 along the cross section AA. The carbide insert 1 has a tool reference plane 8, which is defined so that it is arranged perpendicular to an assumed cutting direction 10 (according to DIN 6851) the carbide insert 1. Furthermore, a cutting point (not shown) of the cutting edge 6 arranged in the tool reference plane 8. The cemented carbide insert 1 has a support surface 11 for resting on a tool holder (not shown). The support surface 11 is thus parallel to the tool reference plane 8.

In a normal operation of the cemented carbide insert 1 according to the determination, the workpiece is moved parallel to and opposite to the cutting direction 10 past the cemented carbide insert 1. The cemented carbide insert 1 is thus in engagement with the workpiece with a certain depth of engagement, via which the chip thickness is determined. The cemented carbide insert 1 is configured so that a clearance surface 12 is parallel to an assumed machining plane of the cemented carbide insert 1.

It follows that a clearance angle α between the assumed working plane and the clearance surface 12 has a value of 0 °. Furthermore, the cemented carbide insert 1 is designed so that the wedge angle ß between the clearance surface 12 and a chip surface 14 has a value of 90 °.

Thus it appears that a rake angle γ which spans between the rake surface 14 and the tool reference plane 8 is 0 °. The clearance surface 12 is delimited against the chip surface 14 by the cutting edge 6. The cutting edge 6 has a radius Rj of 0.3 mm. Due to the right-angled wedge angle ß, the cutting edge 6 is well protected against breakage during hard machining.

In a direction of the chip departure, which follows from left to right according to Figure 2 along the left chip surface 14, adjacent to the chip surface 14 is a transition surface 16 which has a transition radius Rz of 0.5 mm. This transition surface 16 is part of a chip breaking surface 18, which extends from the chip surface 14 along its chip breaking depth B. The chip breaking surface 18 is thus arranged with a chip breaking angle δ of -37 ° towards the tool reference plane 8.

Thus, the chip-breaking angle according to the previous description is defined on the basis of the tool's reference plane 8.

The steep slope of the invention of the chip-breaking surface 18 towards the chip surface 14 and the tool reference plane 8 leads to the intended improved chip formation during the rotary machining of the workpiece.

It increasingly comes from advantageous cylindrical or helical helical chips. Continuous shavings are also increasingly being observed. The formation of bands and / or random chips is reduced compared to conventional forms of cemented carbide inserts, especially T-bevel carbide inserts.

Figures 3 and 4 show a second embodiment of a cemented carbide insert 101 according to the invention which is designed as a cemented carbide indexable insert. With respect to the material and the geometric parameters such as the cross section 2, the corner radius Ro, the chip depth L, the chip breaking surface depth B, the clearance angle α, the cutting edge radius R1, the wedge angle ß, the chip angle γ, the transition radius Rz and the chip breaking angle identically constructed with the first embodiment shown in Figures 1 and 2. At this point, therefore, the description of Figures 3 and 4 is limited only to the functions different from the first embodiment.

Figure 3 shows the cemented carbide insert 101 analogous to the representation of the first embodiment of Figure 1 in a plan view. It should be noted that both a chip surface 114 and a chip breaking surface 118 are formed around the cemented carbide insert 101. Furthermore, the ground on the upper side of the cemented carbide insert 101 shown in Figure 3 forms a cavity 120 suitable for positioning and fixing the cemented carbide insert to the tool carrier. A transition surface 116 is also formed on the circumference of the carbide insert 101.

Other variations of the first embodiment according to Figs. 1 and 2 are shown in Fig. 4, where a section B-B, as shown in Fig. 3, is illustrated. The cemented carbide insert 101 shows below subdivision 122, which in Fig. 4 is shown as a broken line, a second insert geometry. This has a tool reference plane 108 from which a chip breaking surface 218 extends arranged at a chip breaking angle ö 'towards the tool reference plane 108.

The chip breaking angle δ 'is thus larger in value than the chip breaking angle on the top of the cemented carbide insert 101, or the first embodiment according to Figures 1 and 2. In addition, a height H' of the chip breaking step formed by the chip surface 214 and the chip switch surface 218 is less than one reference plane. height H of the chip switch step formed by the chip surface 114 and the chip switch surface 114 above the pitch 122.

Another difference is easy to see, as a chip surface depth L 'and a chip breaking depth B' differ from the chip surface depth L and the chip breaking surface depth B.

Opposite the upper surface of the cemented carbide insert 101, the chip surface depth L 'is larger and the chip-breaking surface depth B' is shorter. The lower side of the hard metal insert 101 in Fig. 4 has a cutting direction 10 on its upper side opposite the cutting direction 110.

The values of the clearance angle α, the wedge angle β and the rake angle γ of the underside of the cemented carbide insert 101 correspond to those of the upper side or those of the first embodiment according to Fig. 2.

The cemented carbide insert according to the invention is also suitable for milling. Surface transitions from the chip surface to the transition surface and from there to the chip-breaking surface are preferably tangentially continuous to minimize calving action, but they can also be diverted tangentially discontinuously (buckling). 11 Reference Number List 1; 101 2 4 6 8; 108 10; 110 11 12 14; 114, 21416; 116, 21418; 118, 218120 122 L; L 'B; B 'cemented carbide cutting cross section corner cutting edge tool reference plane cutting direction support surface clearance surface chip surface transition surface chip breaking surface depression division chip surface depth chip breaking surface depth drop angle wedge angle chip angle breaking angle 12

Claims (1)

Ceramic cemented carbide insert for cutting hard machining of a rotating workpiece, with a cutting direction (10, 110) perpendicular to a tool reference plane (8, 108) of the cemented carbide insert (1, 101), and with a single cutting edge (6), through which a chip surface (14, 114, 214) is limited, which is arranged against the reference plane (8, 108) of the tool with a rake angle (γ) of 0 °, characterized in that a rake-breaking surface (18; 118, 218) connects to the rake surface (14, 114 , 214) in a direction away from the cutting edge (6) which is steeper arranged to the reference plane (8,108) of the tool than the chip surface (14, 114, 214). Cemented carbide inserts according to claim 1, wherein the chip-breaking surface (18, 118, 218) is arranged against the tool reference plane (8, 108) with a chip-breaking angle (δ) which is <0 ° and z -90 °. Carbide inserts according to one of Claims 1 or 2, in which the rake angle (γ) is 0 ° and 2 -25 °. . Carbide inserts according to any one of claims 1 to 3, wherein the chip surface comprises a chip surface chamfer adjacent to the cutting edge. . Carbide inserts according to one of the preceding claims, wherein the chip-breaking surface (18, 118, 218) has a concave transition surface (16,116,216) which delimits the chip surface (14, 114, 214). Cemented carbide inserts according to claim 5, wherein a transition radius (R2) of said transition surface (16, 116, 216) in one direction is a chip gap z 0.5 and s 1.0 mm. Carbide insert according to one of the preceding claims, which is designed as a carbide indexable insert (101). The cemented carbide insert according to any one of the preceding claims, wherein the chip surface (114, 214) and / or the chip-breaking surface (118, 218) is formed around the cemented carbide insert (101). Carbide insert according to one of the preceding claims, wherein a radius (R1) of the cutting edge (6) is>. 0.1 and s 1.0 mm.10. Carbide insert according to one of the preceding claims, wherein a chip-breaking surface depth (B; B ') measured in the reference plane (8, 108) of the tool and perpendicular to the cutting edge (6) is 2 l and s 5 mm. 14