JPS594730B2 - Load compensation method for table feed mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel load compensation method for a table feed mechanism of a machine tool, etc., which enables highly accurate positioning by compensating for the load applied to the table feed mechanism.

Conventionally, table feeding mechanisms that require high positioning accuracy often employ rolling guide surfaces or static pressure guide surfaces that have low sliding resistance.

However, since rolling guides and static pressure guides have low dynamic rigidity in the feed direction, chatter vibrations often occur and impair the functionality of the machine tool itself. On the other hand, the flat guide has a large sliding resistance, which causes stick-slip and reduces positioning accuracy, but the dynamic rigidity in the feeding direction is greater than the above-mentioned two and five guide systems. An ideal feeding mechanism can be obtained if the stick-slip that occurs in the tentative guide can be eliminated. Therefore, the present invention compensates for the sliding resistance of the guide surface, that is, the sliding resistance of the guide surface on the feed mechanism of the base guide system, that is, the loads such as the cutting force and grinding force associated with machining, and achieves high-precision positioning. The following is a detailed description of the drawings showing the embodiments. Fig. 1 shows a feeding mechanism for a table (hereinafter referred to as a movable object) that realizes the load compensation method of the present invention, and 151 indicates a fixed object. A movable object 2 is mounted on a sliding guide surface 1a of this fixed object 1.

On the movable object 2 are bearing members 3, 3' and a feed nut 4.
is attached, and a feed screw 5 is rotatably supported by the bearing members 3, 3'. Further, the above-mentioned feed nut 4 is screwed into this feed screw 5. A worm wheel 6 is attached to one end of the feed screw 5, and the worm wheel 6 meshes with a worm gear 8 rotatably supported by a bearing member 7 attached to the fixed object 1. A hydraulic motor (not shown) is connected to one end of the worm gear 8 . A bearing member 10 that rotatably supports the feed screw 5 is mounted on the fixed object 1 near the worm wheel 6 described above. A pressure-responsive device, such as a piston head throat 12a of a hydraulic cylinder 12, constituting a load compensation mechanism 1130 is connected to the side end of the movable object 2, and a supply/discharge boat (not shown) of the hydraulic cylinder 12 is connected to the side end of the movable object 2. Above mentioned servo valve 9
is connected. The load compensation mechanism 3511 including the above-mentioned hydraulic cylinder 12 includes a servo amplifier 13 and a D
C amplifiers 14 are connected in series, and one DC
A strain gauge 15 attached to the feed nut 4 is connected to the input end of the amplifier 14.

With the above configuration, when the hydraulic motor (not shown) is driven, the worm gear 8 connected thereto rotates.

This rotation of the worm gear 8 causes the feed screw 5 to rotate via the worm wheel 6. When the feed screw 5 rotates, the movable object 2 moves while sliding on the sliding guide surface 1a of the fixed object 1 by the feed nut 4 screwed thereto. At this time, the force or load required to move the movable object 2 is electrically detected by the strain gauge 15. This detected electric signal is sent as a feedback signal to the servo valve 9 via the DC amplifier 14 and the servo amplifier 13. The servo valve 9 that receives the signal operates the hydraulic cylinder 12, so that the piston rod 12a of the hydraulic cylinder 12 connected to the movable object 2 always reduces the force required to move the movable object 2, that is, the load applied to the feed nut 4 to zero. make it work so that Therefore, most of the force required for driving when positioning the movable object 2 is applied to the load compensation mechanism 11.
is compensated for, so no load is applied to the positioning mechanism, ie, the feed nut 4. As a result of experiments on the present invention having a load compensation mechanism as described above and a conventional one without a load compensation mechanism under the conditions described below, the results shown in Figures 2 to 7 were as follows.
We obtained the results shown in the figure. Note that the above conditions are as shown below. , Drive source: Hydraulic motor with speed feedback, Worm gear/worm wheel reduction ratio: 39, Feed screw: Trapezoidal screw, outer diameter 40φ, P = 6m'IIL, Feed nut rigidity: 1.89k1m1 Guide surface: v flat sliding guide system Pressure receiving area: 700Ci1i,. Movable object weight: 845kf
1 surface pressure: 1.2kVIim, feed speed of movable object V):
30μm/Iin, 35μm/I, 3OOμ5cm, that is, the above-mentioned Figures 2 to 4 show the measurement of the displacement of the movable object 2 and the positioning mechanism, that is, the force applied to the feed pin 4, when the load compensation mechanism is not used. This is the result.

As can be seen from these three figures, as the movable object 2 slides, a sliding resistance of about 80 kf is applied to the feed nut 4, and the movable object 2 slips by about 100 μm, as shown in Fig. 2. The results show that noticeable stake slip occurs during low speed feeding. 5 to 7 show measurement results of the present invention when a load compensation mechanism is used.
As can be seen from these three types of figures, the force applied to the positioning mechanism, that is, the feed nut 4, shows a value of less than 0.3k7, and there is almost no stick slip on the movable object 2, and the low speed feed shown in Fig. Even at times, no states-slip phenomenon is observed. From the above experimental results, the present invention provided with a load compensation mechanism can compensate for 99% or more of the load applied to the positioning mechanism, that is, the feed nut 4, so that highly accurate positioning can be achieved. Since the present invention employs the above-described load compensation method, it is possible to easily achieve high-precision positioning, which was conventionally considered difficult, and has the effect of significantly improving the functionality of the machine tool itself.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram showing the table feeding mechanism used in the present invention, Figs. 2 to 4 are graphs showing the results of conventional implementation, and Figs. 5 to 7 show the results of implementation of the present invention. FIG. 1... Fixed object, 2... Movable object, 3
・3'・7・10...Bearing member, 4...
・Feed nut, 5...Feed screw, 6. ．． ．． ．． ．．
．． Worm wheel, 8... Worm gear, 9
...Hobo valve, 11...Load compensation mechanism, 12...Hydraulic cylinder, 12a...
・Piston rod, 13...Servo amplifier, 1
4...DC amplifier, 15...Strain gauge.

Claims (1)

[Claims] 1. When a movable object on a sliding guide surface is moved by a screw feed mechanism connected to a hydraulic motor, the load on the screw feed mechanism that receives the sliding resistance reaction force of the movable object is electrically detected. and controlling the servo valve according to the electric signal input thereto, and according to the control content, operates a load compensation mechanism connected to the movable object to compensate the load applied to the screw feeding mechanism to zero. A load compensation method for a table feeding mechanism, characterized in that: