EP0219825A2 - Process, machine and tool for honing work pieces - Google Patents

Abstract

In the honing process, which is suitable in particular for blind holes or stepped bores, a honing tool (11) is moved into the bore (40) with retracted, that is non-expanded, honing layers, is expanded to the finished size in or behind the bore and performs its working stroke during the return stroke (direction 39). Chip removal takes place in a cutting zone (33) and the calibration to the finished size takes place in the finishing zone (34). The tool has pivotably arranged honing sticks. In a variant, guide strips firmly arranged between the adjustable honing sticks and having an anti-wear layer can be provided. Provision is also made to work with oscillating short strokes to machine the bottom area of a blind hole. <IMAGE>

Description

The invention relates to a method, a honing machine and a honing tool for honing workpieces.

A method according to the preamble of claim 1 has become known from DE-A1 24 60 997. In most machining areas of workpieces, in particular through holes and holes with webs, this method works extremely well and advantageously. However, it is difficult to machine blind holes, bores with inwardly projecting collars, or machining areas where it is difficult to guide the tool with a guide zone in the tool.

For machining blind holes, it has already become known from DE-C3 25 06 243 to make honing stones in such a way that their machining diameter at the tool end, ie in the region of the bottom of the blind hole, is somewhat larger than in the rest of the region. However, like conventional honing tools, this tool works with an oscillating axial drive. The greater widening in the lower area is intended to compensate for the missing overflow of the honing tool. In this honing tool, two different groups of honing stones can be provided, which can be turned on one after the other by means of a rotating mechanism. The optional expansion of various groups of honing stones can also be carried out according to DE-c3 24 50 686 by axially displacing an expansion body in two different directions (back and forth).

The object of the invention is to provide a method, a honing machine and a honing tool with which blind holes or stepped bores can also be machined with only one or a few honing strokes.

This object is solved by the features of claims 1, 7 and 12, respectively.

In the case of workpiece bores in which the machining area is the bore, the tool is thus inserted into the bore with the honed linings drawn in, then the expansion to the finished size is carried out and the working stroke is then carried out in the form of a return stroke. The vast majority of the material removal takes place in this single working stroke, in the area of an expanding cutting zone, which can be followed by a finishing or calibration zone, which ensures the final dimension. This calibration zone can be quite short.

The invention can also be used for honing operations other than drilling operations, for example for external honing. The method can also be advantageous for machining through bores because the guidance of the tool which is pulled in the working stroke in the bore is very good. In this case, the tool would at least be moved through the bore and advantageously out of it with the large part, ie with the calibration and cutting zone, then the widening would take place and the machining to the final quality would then be carried out in the return stroke. However, it is also possible to carry out strokes with largely unchanged tool settings, for example if a certain surface structure (cross-cut) is desired. The use of a guide section arranged in front of, ie on the side of the cutting zone facing the machine spindle is advantageous, but is not absolutely necessary due to the good self-guidance. Could also be slightly conical, which makes it even more self-centering. A guide zone downstream of the calibration zone in the working direction, which would then lie towards the end of the tool, can be provided, but is particularly not necessary if the tool leaves the bore after the working stroke and does not return to it. This post-lead zone, if featured can be seen in the manner known from DE-B 24 60 997 connect continuously to the calibration zone in order to facilitate re-entry into the bore after the calibration zone has been moved out of it. During machining, the tool with the calibration zone is pulled all the way over the machining area.

The results with regard to surface quality, dimensional and dimensional stability, tool wear and the need to readjust the tool are as good as with the tool according to DE-A1-24 60 997, to which reference is also made in particular. With a very substantial machining allowance of up to a few hundredths or tenths of a millimeter, surface, dimension and shape accuracies, and especially straightness of bores, can be achieved that are below one µm. Here, too, the main advantage is that bore edges, for example in the area of webs, do not experience any funnel-shaped widenings.

• Fig. 1 einen mittigen Längsschnitt durch ein Hon­werkzeug bei der Bearbeitung einer strich­liert angedeuteten Bohrung, wobei rechts daneben stark überhöht das Profil der Honbeläge angedeutet ist,
• Fig. 2 einen Längsschnitt durch ein Leisten-Honwerkzeug mit Führungsbelägen,
• Fig. 3 einen Querschnitt nach der Linie III in Fig. 2,
• Fig. 4 einen schematischen Längsschnitt und
• Fig. 5 einen Querschnitt nach Linie V durch Teile eines Honwerkzeugs und einer Honmaschine mit zwei Gruppen von Honbelägen.

These and further features of preferred developments of the invention also emerge from the subclaims and the description and drawing, the individual features being able to be advantageously realized individually, alone or in the form of subcombinations in embodiments of the invention and also in other fields . Execution and application examples of the invention are shown in the drawing and are explained in more detail below. Show it:

• 1 shows a central longitudinal section through a honing tool during the machining of a bore indicated by a broken line, the profile of the honing pads being indicated greatly to the right of it,
• 2 shows a longitudinal section through a ingot honing tool with guide linings,
• 3 shows a cross section along the line III in FIG. 2,
• Fig. 4 is a schematic longitudinal section and
• Fig. 5 shows a cross section along line V through parts of a Honing tool and a honing machine with two groups of honing pads.

The honing tool 11 shown in FIG. 1 has an essentially tubular tool body 12 with a bayonet mounting device 13 for a machine spindle 14 of a honing machine 15, indicated by dash-dotted lines. The spindle is rotatably and displaceably mounted in the axial direction and contains an adjusting device 16 in the form of a Spindle 14 and relative to this axially displaceable expansion rod.

The tool body has from its lower end 17, extending in the longitudinal direction of the tool, parallel-surface slots 18 which are broken through in the region of the tool end to the central bore 19 of the tool body. In these slots, of which, for example, six are provided on the circumference, honing stones 20 are guided, which are provided at their lower ends adjacent to the tool end 17 with very wear-resistant honing pads 21. for example with diamond honing. From the upper end of the honing layer, the honing stone extends upwards over a large length of the tool body and has an outwardly open recess 22 at its upper end, so that a hook-shaped head is formed which is suspended in a bolt 23 projecting through the slot and thus the honing stone 20 is articulated at its upper end.

The honing stones, which are held together by a tubular spring 24 running around their circumference, can be turned on by an adjusting mechanism 25, i. be expanded. This consists of a bolt-like adjusting body 26 with an adjusting cone 27 at its end and leads into the central bore 19. A screw bolt 28 screwed into it and loaded by a return spring 29 creates the connection to the adjusting device 16.

The adjustment cone 27 acts on inclined adjustment surfaces 30 on the honing stones and can thus pivot the honing stones outwards about the hinge pin 13. It can be seen that the honing stones are not only radially expanded by the employment, but also pivoted obliquely by a small amount, so that they in their lower area are expanded more than in the upper.

From the profile contour 31 of the honing pad 21 drawn to the right of Fig. 1 it can be seen that the honing pad has a front (upper) guide section 32, which lies on a circle of smaller circumference, a subsequent, widening towards the tool end 17, i.e. has a bevelled cutting zone 33 and a subsequent finishing or calibration zone 34. The sections or zones 32, 34 can be essentially cylindrical. They can be relatively short, depending on the use of the tool, and the front guide section 32 can possibly. are completely absent or consist of a section of slightly less taper than the cutting zone 33. The slope of the sections changes with the expansion. Since the wear of the honing linings 21 is usually extremely low, the conditions are very constant.

The tool according to FIG. 1 is particularly suitable for machining blind holes 40. This bore has a recess 37 near its base 36.

The method according to the invention works as follows:
The tool according to FIG. 1 is inserted into the bore with the adjusting mechanism withdrawn. In this case, the diameter covered by the honing linings is less than the diameter of the bore 40 in the workpiece 38 indicated by dashed lines on one half of the drawing. The retraction can take place at an increased lifting speed, since no machining takes place when retracting. When the tool is inserted into the bore, ie the tool end 17 is short of the base 36 of the bore, the honing pads 21 are set to a fixed value. In contrast to conventional honing tools, the tool is adjusted by axially downward displacement of the adjusting device 16 and the adjusting mechanism 25 and the effect of the adjusting cone 27 on the adjusting surfaces 30 in that the honing stones 20 are pressed outwards in their lower region with pivoting about the bolts 23 . In contrast to conventional honing tools, this setting is carried out practically before the start of machining, ie before the working stroke, ie the return stroke in the direction of arrow 39 starts. The position of the tool remains essentially unchanged during the working stroke. The peripheral speed of the honing pads is in the range of normal cutting speeds for honing, for example in the range of 20 to 30 m / min. However, the lifting speed is considerably lower and is approximately one tenth to one thirtieth of the peripheral speed.

Zones 32, 33, 34 of honing coating 21 pass through the bore in succession in a single stroke and are processed simultaneously, but in succession in the axial direction from start to finish. The main cutting work is carried out in the area of the oblique cutting zone 33, while the calibration zone 34 creates the calibration to the exact finished dimension and the desired surface quality.

In the case of blind bores with very little turning at the end of the bore, the honing pads with the three successive zones would have to be very short, which could result in the cutting and calibration zones 33, 34 being too short despite the excellent self-guidance of the tool. In this case, it would also be possible to adjust the honing linings in such a way that the calibration zone 34 is not immediately set to the exact finished dimension when the machining begins. In this case, the lower edge 41 of the machining surface 40 of the bore 40 would be in a central region of the cutting zone or possibly. are even in the area of the calibration zone 34. However, the final adjustment would then take place in such a way that the expansion to the final finished dimension has ended before the calibration zone 34 has swept over the edge 41. There, too, the condition is met that the adjustment to the finished dimension and the blocking of this dimension is carried out by the adjusting mechanism before the tool with the calibration zone 34, which is decisive for the finished dimension, is completely moved into the machining surface 40 in the working direction 39.

When machining is carried out with sufficient supply of cutting fluids, for example honing oils, excellent dimensional and shape retention and surface quality are achieved in a single pass. The tool leaves the processing area 35 at the upper bore end 42. Because of the rigid Support and the blocked employment the honing pads do not have the tendency to "press in" elastically, the bore is not widened even more in the area of the upper bore end than in the rest of the processing area, so that the shape accuracy extends over the entire processing area. In this case, it is not necessary to connect a further joining zone to the calibration zone 34 at the bottom. However, it could be provided and have a profile as indicated by dashed line 43. It should connect continuously to the calibration zone 34 and makes it possible, if necessary, to retract the tool into the bore for a leveling stroke following the working stroke, without the bore edge 42 or the tool being damaged. This leveling stroke can be important, for example, in order to create certain surface properties, for example for cross grinding on the surface, ie a surface with intersecting machining marks.

At the lower end of the tool, a stop 44 in the form of an adjusting screw is also indicated, with which the downward movement of the adjusting mechanism can be blocked. It could be adjusted according to the finished size and ensures that regardless of the exact setting of the adjusting device in the honing machine, the widening of the honing pads takes place exactly to the finished size. An adjustment can then be made there depending on wear, but this is usually only necessary after several hundred workpieces. Such a readjustable finished dimension stop could, however, also be provided in the honing machine or the spindle and, if necessary, could be automatically readjusted step by step.

The basic structure of the tool shown in FIG. 2 corresponds to that of FIG. 1, to the description of which reference is made. The same reference numerals designate the same or comparable parts.

The honing stones 20a are not pivotable in this tool, but are guided in a radially displaceable manner and are supported, each with two spacing surfaces 30 arranged at a distance from one another, on axially successively arranged cones 27a, which are provided on two positioning bodies 26a likewise arranged one behind the other. These are connected to each other by a connecting bolt 50 bound and, if necessary, adjustable in their distance from each other, so that the axis parallelism of the honing stones can be adjusted. The honing stones 20 are guided in slots 18 and are resiliently loaded inwards with upper and lower hose springs 24. The receptacle 13 and the rest of the adjustment mechanism 25 are comparable to FIG. 1.

In Fig. 2 left and in Fig. 3 it can be seen that between the total of six honing stones 20, a guide bar 51 is fixedly arranged on the tool body 12a. The guide coating 52 of the guide bar 51 has approximately the same length as the honing coating 21 of the honing bar 20a. The guide coating 52, which can also be referred to as armor coating or wear protection coating, consists, like the honing coating 21, of particles of great hardness and wear resistance, for example diamond particles or similar materials, which e.g. are galvanically bound. However, the grain size is much smaller here, so that there is no significant cutting effect and, accordingly, no wear on the coating.

From the profile 31 of the honing coating 21 indicated on the right in FIG. 2 and the substantially axially parallel, ie cylindrical section-shaped contour 53 of the guiding coating, it can be seen that the front guiding zone 52 forms the front guiding zone 32 as a result of the (stronger drawing) superimposition of the two contours then the adjustable honing stone 20a takes over the cutting work in the area of the cutting zone 33 and the calibration zone 34 is formed by flattening this stone. 1, the bevel of the cutting zone 33 can either be formed by appropriate profiling of the honing coating on the bar or by the inclined position of the bar, which results automatically in FIG. 1 and in FIG. 2 by mutual adjustment the adjusting body 26a can be achieved. In this case, the calibration zone 34 would be designed as a rear bevel, which in turn results in an essentially cylindrical contour when the honing stone is inclined. Since this also grinds itself in again during operation, the readjustment for wear could also be carried out by mutual adjustment of the two adjusting bodies 26, 26a. The contours 31, 53 indicated in FIGS. 1 and 2 are idealized. In practice, there are rounded transitions especially if you consider that the diameter differences shown in the drawing are exaggerated in practice in the range of hundreds and thousandths of a millimeter. Also in Fig. 2 is indicated by a dashed line 43 that a rear guide zone could be provided, which connects to the calibration zone 34 essentially steplessly and possibly leads back to the level of the guide pad 52, which then with its wear protection pad for the rear guide for a possible reintroduction of the honing tool.

The honing process to be carried out with FIG. 2 is the same as that described with reference to FIG. 1 with the difference that the guiding tasks are partially taken over by the guide strips 51. It should be noted, however, that this tool, like the one shown in FIG. 1, is also suitable for through holes, the tool preferably being moved through the hole so far that the lower end of the machining area is in the area of Guide zone 32 is located and then the processing takes place in the return stroke after the employment.

FIG. 4 shows a honing tool which corresponds to that of FIG. 1 except for the changes described below. The honing stones arranged pivotably in slots 18 of the tool body 12 form two groups, namely honing stones 20b with a honing coating 21, which extends upwards longer from the tool end 17 than a honing coating 61 of short-stroke honing stones 60, each alternating with the honing stones 20b on the tool body are arranged. Except for the other type of honing pads, the honing stones 20b and 60 correspond. The short-stroke honing pad 61 is considerably shorter and, in the state adjusted to the finished size, has an essentially cylindrical or slightly widening shape, while the honing pad 21 of the honing stones 20b can be profiled according to FIG. 1. In the example shown, a pronounced front guide zone 32 is missing, which is possible in many applications due to the good self-centering of the tool drawn during the working stroke.

The adjusting body 26b is a cylindrical body in which the adjusting bevels 27b, 27c in the form of axially extending grooves inclined groove base are incorporated. Such designs of adjusting bodies are described in principle in DE-OS 24 50 686 and 25 06 242, to which reference is made here. In the present embodiment, however, the inclined surfaces 27c, 27d, for the two different groups of honing stones 20b, 60, each run in the same direction, so that when the adjusting body 26b is moved axially downward, both groups of stones are set, but in accordance with the shape of the bevels at the beginning of the expansion one after the other. For this purpose, the inclined surface 27b is offset in that it begins in its near-end region with an incline-free section, then has a steeper incline and finally changes to the same incline that the inclined surface 27c has over the entire length.

The following method is thus possible: the tool 11c is inserted into a blind hole, and only the group of short-stroke honing stones 60 is started by moving the adjusting body 26b downward. This is shown in the schematically indicated profile A. The honing pads 21 of the groin group 20b do not come into engagement. However, it can be seen that the short-stroke honing pads 61 have approximately the length of the calibration zone 34. With these short-stroke honing bars, a short-stroke honing movement is carried out in several strokes in the area of the bottom of the blind hole. This serves to sufficiently process sections of the machining area that are very close to the bottom of the bore, which would not be possible due to the lack of space during the actual working stroke. A measuring device can be connected to the tool, for example a pneumatic measuring device 68 with a measuring nozzle 65 in the tool body. When the finished dimension has been reached, the adjusting body 26b, which is axially advanced in this part of the machining in accordance with the machining progress, has already advanced so far that the honing pads 21 have already been adjusted by moving the adjusting surfaces 30b out of the incline-free area over the thicker one Hike into the main setting area 66. The honing pads 21 and 61 lie on a common circumferential line in the calibration zone 34, so they work synchronously. When the finished dimension is reached, if necessary controlled by the measuring device, the actual working stroke is initiated, the short strokes being interrupted and the tool being passed through the bore in one operation is pulled.

It is therefore an upstream short-stroke honing that blends in well with the other honing operations carried out in one operation and can be carried out with an integrated tool. The two honing stone groups can also be employed in other ways. For example, in the usual way for two-group honing tools, each group also works for itself, in which case the short-stroke honing bars would not be engaged during the main machining. In the embodiment according to FIG. 4, however, the honing pads 21, 61 can always grind in in the same way during the main working stroke carried out jointly, so that reproducible conditions are always present. In the case of different wear for both tool groups, a corresponding adjustment between the two groups could be provided. The upstream short-stroke honing can also be carried out with the honing stones 20b alone, in which case the calibration zone is effective during short-stroke honing and replaces special short-stroke honing pads. Other adjustment devices, for example the adjustment described in DE-PS 25 06 243 by means of a rotatable adjustment body, can also be provided.

Depending on the workpiece shapes to be machined, a change in the relative lengths of the short-stroke and main honing pads 61, 21 to one another is also possible. It is advantageous when the two groups work together that the calibration zone 44, which is important for good dimensional stability, has a larger proportion of the grinding surface on the circumference than the other zones. This could also be provided for tools with only one group of honing pads by making the grinding pads wider in the area of the calibration zone. This is particularly advantageous for workpieces that come close to the bottom or shoulder of a bore with correspondingly very short calibration zones.

The invention has been described above with the aid of strip tools. It can also be carried out with tools with a self-expandable tool body.

FIG. 4 also shows, in a schematic form, that of the honing machine 15 assigned measuring device 68, which ends the short stroke honing when the finished dimension is reached by blocking the adjusting device 16 and switching the spindle lifting device 69, both of which are shown schematically as hydraulic cylinders, from the oscillating short stroke to the working stroke in the direction 39.

Claims (14)

1. A method for honing workpieces, in particular workpiece bores with a honing tool, which has expandable honing pads, from which material is removed from a machining area in an expanding cutting zone and which are adjusted to the finished dimension of the workpiece in a finishing zone before machining begins characterized in that the tool is retracted into the machining area with the honed linings drawn in, the honing linings are adjusted there according to the finished dimension and held in this position during the machining and the rotatingly driven tool is moved through the machining area in one working stroke, preferably the tool in the without entering the machining area without a machining area, essentially the entire length of the machining area to be machined is driven and the working stroke is carried out in a return movement of the tool. 2. The method according to claim 1, characterized in that the tool for the working stroke is moved axially more slowly than when retracting and / or at least moved a second time through the machining area with the honing pad permanently attached to the finished dimension and if necessary the honing pads are retracted at the end of the machining process. 3. The method according to any one of the preceding claims, characterized in that the tool is guided on the workpiece when retracting guide covers which cannot be raised. 4. The method according to any one of the preceding claims, characterized in that the tool performs some short strokes before the start of the working stroke, which are preferably carried out in particular at the end of the machining area remote from the machine, preferably by a different honing layer than the working stroke. 5. The method according to claim 4, characterized in that the short strokes take place under the machining progress adapted employment and then, if necessary, dimensionally controlled, the initiation of the working stroke taking place with fixed dimensions is carried out. 6. The method according to any one of the preceding claims, characterized in that the calibration zone is widened to the finished dimension in the processing area. 7. Honing tool, in particular for carrying out the method according to one of the preceding claims, with at least one honing coating (21) which, at least in the employed state, has an expanding cutting zone and a calibration zone (34) which can be adjusted by a setting mechanism (25) and which can be determined in accordance with the finished size , characterized in that the adjusting mechanism (25) the honing coating (2) after the first time, without having carried out substantial processing of the Machining area (35), but before the working stroke traversed in the opposite direction (39), to a position corresponding to a finished dimension, the tool possibly having guide linings (52), which are preferably arranged in the tool axis direction and arranged between the honing linings (21), strips (51) fastened to the tool body (12) are formed from a wear protection material. 8. Honing tool according to claim 7, characterized in that it has two separately adjustable honing pad groups (20b, 60), of which a short stroke honing group (60) can be employed for performing short honing strokes and the other group (20b) is provided with the cutting and calibration zone (33, 34), preferably the short-stroke honing pads (61) for performing the working stroke can be locked together with the other group (20b), preferably in the area of the calibration zone (34) are arranged. 9. Honing tool according to one of claims 7 to 8, characterized in that the expansion of the cutting zone (33) when changing the honing pads (21) is changeable. 10. Honing tool according to one of claims 7 to 9, characterized in that it is designed as a ingot tool and that the honing coating (21) corresponding to the cutting and calibration zones (33, 34) and possibly one in the working direction (39) before the cutting zone (33) and a guide zone arranged behind the calibration zone (34) is profiled, the honing stones (20) preferably being pivotably mounted on the tool body (12) in the manner of a one-armed lever and preferably the pivot axis on the drive side End of the honing stone (20) is. 11. Honing tool according to one of claims 7 to 10, characterized in that the adjusting mechanism (25) contains a stop (44) which can be preset according to the finished size. 12. Honing machine, in particular for carrying out the method according to one of claims 1 to 6, characterized in that it has at least one spindle (14) which accommodates a honing tool (11, 11b) and is rotatable and axially movable in a retracting stroke through the machining region (35). which has at least partially an adjusting device (16) for adjusting the honing pads (21, 61) of the honing tool (11, 11b) to a finished dimension after the retracting stroke through the machining area (35) and for blocking this adjustment during the subsequent working return stroke (39), the adjusting device (16) in particular being designed to employ two different groups of honing pads (21, 61). 13. Honing machine according to claim 12, characterized in that the spindle (14) during the working return stroke (39) can preferably be moved with a lower axial stroke speed than with the retracting stroke, the working axial stroke speed being approximately one tenth to one thirtieth of the peripheral speed of the honing tool ( 11, 11b). 14. Honing machine according to one of claims 12 to 13, characterized in that a measuring device (65, 68) measuring during processing is provided which has a blocking device for the employment device (16) and possibly triggers a triggering of the lifting device (69) for carrying out the working return stroke (39).

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