RU2003938C1 - Bridge-type coordinate measuring machine - Google Patents

Description

The invention relates to a bridge type coordinate measuring machine (SMM) for measuring workpiece dimensions.

A known coordinate-measuring machine of the bridge type consists of a bed, a bridge, a portal, movably mounted on a bed, a carriage arranged to move on the upper part of the bridge, a probe (measuring head), movably mounted on the carriage, and a measuring and computing system, responsive to the probe for measuring the size of the workpiece located on the upper surface of the bed

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In a coordinate measuring machine, accuracy and repeatability can be adversely affected by vibration and relative movement between the struts of the bridge. Poor bridge stiffness allows relative movement between the bridge struts, while height, distance and stiffness can affect the resonant frequency, which, if low, makes the measuring probe mounted on the bridge more sensitive to vibration.

One of the technical solutions to reduce or dampen the effect of vibration on the coordinate of the measuring machine

consisted in installing a coordinate measuring machine on an air cushion device, either on a large concrete platform, or increasing the weight of the bridge struts. These technical solutions are expensive, require a large working area and exclude only external vibrations, i.e. soil vibration. Internal vibrations, for example, caused by electromechanical servomechanisms mounted on the machine, would not be excluded or damped.

One technical solution to reduce the effect of relative movement between the bridge struts is discussed in the patent, where a position indicator is mounted on each strut. However, this increases the cost of positioning and measuring the coordinate measuring machine, but the problem of the undesirable low resonant frequency that may be present in the bridge structure, for example, a resonant frequency below 20 Hz, can have a negative effect on the accuracy of the measurement of the coordinate measuring machine.

Also known is a coordinate measuring machine comprising a bridge in the form of a bracket, i.e. portal formed by racks

connected together by an upper element and a lower element forming a bridge that surrounds the desktop 2.

An object of the invention is: to improve the accuracy of a coordinate measuring machine used to measure bulky workpieces, such as car engine blocks and car body parts;

0 improving the rigidity of the bridge coordinate measuring machine;

reduction in relative movement between the struts of the bridge coordinate measuring machine, especially when

5 height of racks over 1 m;

reducing the influence of vibrations on the probe mounted on the bridge of the coordinate measuring machine by increasing the resonant frequency of the bridge;

0 reducing the need for an expensive system to protect the measuring probe of the coordinate measuring machine from external vibrations. Elimination of the deflection effect which

5, the workpiece, placed on the upper surface of the bed, is provided with guides.

The proposed bridge-type coordinate measuring machine has a bridge configuration in the form of a closed bracket that surrounds the upper surface of the bed of the measuring machine on which the workpiece for measurement is placed, and characterized in that the guide rail 5 is located on each side of the bed and there are supports which interact upward, downward and inward opposite the guides.

In one embodiment of the invention, it is preferable to have a lower bridge member that connects to racks placed above the rails on the bed along which the bridge moves. When the lower horizontal connecting element of the bridge is placed above the rails, and not below the rails, the distance between the upper and lower horizontal bridge elements decreases without changing the working space.

0 between the top of the bridge and the top of the bed.

1 and 2 show the proposed coordinate measuring machine; in Fig.Z-truncated view coordinate-measured

5 of the body machine, showing the location of the bridge mounted on the bed of the coordinate measuring machine; Figures 4 and 5 show the fastening devices of the bridge on the bed of a coordinate measuring machine.

A bridge-type coordinate measuring machine comprises a bed 1, a portal 2 movably mounted on a bed, a carriage 3 arranged to move on the bridge, and a probe 4 movably mounted on the carriage 3. The bed includes an upper surface 5 of the table on which the measurement is located removable workpiece (not shown) and guides 6.7. The bed 1 is divided into the upper part of the table 8, separated from the bottom by the legs 9. The rubber bearings tO at the bottom of the bed reduce the effect of external vibrations on the coordinate measuring machine. This arrangement of guides 5, 6 and legs 9 provides space for the engine and the corresponding drive mechanism to move the portal 2 to be located in the center of the bed. The portal 2 contains two racks 11, 12. connected together by the upper 13 and lower 14 elements. The carriage 3 is movably mounted on the upper element 13 of the portal 2 has a probe pin 15 which is movably attached to it and has a probe (measuring head) at one end 4. The probe 4 is usually of the type that when it touches the workpiece being measured, it gives a signal to the corresponding computational device. The portal 2 is mounted on the frame 1 with the possibility of moving along the guides 6, 7, the surfaces of which are in contact with the bearings 16 installed in the respective channels 17 of the portal 2. Air bearings 16 are preferably used to improve the movement of the portal 2 along the guides 6.7 of the frame 1. Moving the bridge, carriage, and pins 15 of the probe allows the probe to move and measure in three dimensions. Electrical or mechanical means that respond to the movement of the probe indicate the position of the probe in three coordinates and calculate the measurements.

The carriage 3 is mounted on the upper element 13 of the portal 2 with the possibility of movement along the guides 18, 19,

Claims (2)

1. BRIDGE TYPE COORDINATE MEASURING MACHINE, comprising a bed, a table mounted thereon for accommodating the measured part, and a portal made in the form of a closed bracket surrounding the table and formed by two posts and elements connecting the ends of the posts to each other, guides mounted on opposite sides of the bed, the surfaces of which are in contact with bearings 20 in the respective channels 21, 22, 23 of the carriage 3. The probe 4 is mounted on the portal 2 for movement in two axes and can move to the third axis when the bridge moves. Mechanical or air bearings 20 are used to improve the movement of the carriage 3 relative to the portal 2. Upper and lower bearings 16 of the portal 2 interact with the surfaces of one of the bed guides 6. The air bearings 16 located in the channels 17 of the portal 2 are in contact with the surfaces of the guides 6, 7 of the bed. In this position, the lower element of the bridge is located below the bearings 16 and part of the table 8 of the bed. The top of the bed table is supported by only three legs 9. This provides better isolation from vibration and deflection compared to four legs, that is, one in each corner of table 8, In another embodiment of the invention, the portal 2 has two lower connecting elements 14, 24 with bearings 16 interacting with the guides 6, 7 of the frame 1 located between the two lower elements 14, 24 of the portal 2. Fig. 5 shows how the air bearings 16 located in the channels 17 of the portal 2 are in contact with the surfaces of the frame guides 6, 7. In this position, the lower element 14 of the portal 2 located above the guides 6, 7 and below the part of the bed table 8, The upper part of the bed table is supported by only three legs 9. This provides better insulation. vibration and deflection compared to four legs, i.e. one in each corner of the table 8. (56) U.S. Patent No. 3,749,501, CL 356-169. USSR copyright certificate Mg621955, cl. G 01 B 5/02, 1978. four bearings mounted on the frame, one of which is located on the side of one guide and is designed to interact with one of its surfaces, and the other three are on the side of the second guide and are designed to interact with its three surfaces, carriage mounted an element connecting the upper ends of the uprights, with the possibility of moving along it in a direction perpendicular to the guides, and a quill with a measuring head mounted on the carriage with the ability to move along an axis perpendicular to system of movement of the carriage, characterized in that, in order to increase the measurement accuracy by 1, it is equipped with two additional bearings located on the side of the first rail and designed to interact with their respective other surfaces each the pillar has a groove in which the end of the corresponding guide is placed to form the channel, the open end of each channel is facing the table, and in each knee of the channel there is a corresponding bearing. 2. The machine according to claim 1, characterized in that the bearings located in the opposed, positive bends of the channel are located on one axis. fie. 2 thirteen  tpt / g 5