JPS5916641B2 - Maximum displacement position detection device - Google Patents

Description

[Detailed Description of the Invention] 5 The present invention is a maximum displacement method that detects the recoil, deflection, distortion, etc. of round bars, plate materials, etc. (hereinafter collectively referred to as objects to be measured), and the maximum displacement position of the machined surfaces of these materials. The present invention relates to a position detection device.

Conventionally, this type of device is known to extract the amount of displacement of the object to be measured as an electrical signal and process this signal with a data processing device to detect the maximum displacement position. In this case, the price is extremely high, and the setup change when changing the type or size of the object to be measured is troublesome, so it is not practical.

Therefore, the present invention eliminates the above-mentioned drawbacks and provides a simple method that can easily detect the maximum displacement position of the surface to be measured that will fall on the object even when the type and size of the object to be measured is variously changed. It aims to provide a maximum displacement position detection device,
A detection rod is slidably supported on the measurement block, the detection rod is urged toward the surface to be measured and is brought into contact with a stopper to regulate its position, and the air nozzle of the air micrometer is slid on the measurement block. The measuring block is brought close to the surface to be measured of the object to be measured, and the detection part of the detection rod is brought into elastic contact with the surface to be measured, and the measurement surface of the air nozzle is brought into contact with the detection rod. By moving the surface to be measured with respect to the detection rod in this prone state, the air nozzle is slid to the maximum extent through the detection rod to the maximum displacement part of the surface to be measured, and then the surface to be measured is When the detection rod moves away from the air nozzle and approaches the air nozzle again, and the back pressure inside the air nozzle increases, this back pressure is detected by the detection switch and the maximum displacement position of the surface to be measured is determined. It is characterized by the fact that it can be detected.

The present invention also provides a measuring block moving device that moves the measuring block close to the surface to be measured and brings the detection rod into elastic contact with the surface to be measured, and a setting device that slides the air nozzle and brings it into contact with the detection rod. The device is characterized in that it is equipped with a device to automatically detect the maximum displacement position of the surface to be measured. Next, an embodiment in which the maximum displacement position detecting device of the present invention is used as a maximum strain position detecting device for a round bar will be described in detail with reference to the drawings.

Figure 1 is a plan view showing the outline of the automatic strain relief machine.
B is a pair of rotary drive devices that rotatably support both ends of a round bar (hereinafter referred to as round bar m) as the object to be measured m, and B is a press that presses the center of the round bar m to correct distortion. device, C.
l, C2, C3 are the three positions that divide the round bar m into approximately four equal parts.
D is a permissible strain amount detection device that measures the amount of strain (displacement amount) of the round bar m and determines whether this amount of strain is within the permissible strain amount (permissible displacement amount). Each maximum strain position detection device is a maximum displacement position detection device that detects the maximum strain position (maximum displacement position) at the center and stops the rotation of the round bar m with this maximum strain position facing toward the press device B side. The round bar m is transferred as shown by the arrow 4 and @ by an appropriate transfer means (not shown) to the rotary drive device Al,
The round bar that has been supplied onto A2 and has undergone strain detection or strain correction is transferred as shown by arrow 0 and rotates 4.
・A normal round bar m (taken out from above the drive device Al, A2)
Acceptable products) are discharged as shown by the arrow @, and abnormal round bars m (rejected products) are discharged as shown by arrow 3 to distinguish them.

Note that various methods can be considered as this distinguishing means. Conveyors, cylinders, autoloaders, etc. are used as the above-mentioned transfer means, but since these have been widely known in the past9, their explanation will be omitted here, and below, rotation,
Drive devices Al, A2 and allowable strain detection devices Cl, C2, C
3 and the maximum strain position detection device D will be explained in detail. First, the rotary drive device A1 on the discharge side (left side in FIG. 1)
To explain this in detail with reference to Figures 2 and 3, 1 is a holding frame whose one end is pivotably pivoted up and down to a support arm 3 fixed to the machine base 2, and the machine is connected to a support plate 4 fixed to the other end. This plate 4 is biased upward by a spring 5 compressed and interposed between the bases 2, and is received by a stopper screw 7 screwed into a support arm 6 fixed on the machine base 2 to regulate its position. There is. Reference numerals 8 and 9 denote a pair of receiving roller shafts rotatably supported by the holding frame 1 at approximately the same height, and receiving rollers 10 and 11 are fixed to one end of each shaft.

Reference numeral 12 denotes an intermediate shaft supported by the holding frame 1 between the receiving roller shafts 8 and 9. A gear 15 is fixed to this intermediate shaft 12 and meshes with gears 13 and 14 fixed to the other ends of the receiving roller shafts 8 and 9. has been done.

A brake motor 16 is fixed to the holding frame 1, and a gear 17 that meshes with the gear 14 of the receiving roller shaft 9 is fixed to the drive shaft 16a of the brake motor 16.

Reference numeral 18 denotes a swinging rod which is swingably pivoted to the upper end of a support arm 19 fixed on the machine base 2, and is operated by a spring 20 stretched between it and the support arm 19, as shown in FIG. A roller 21, which is normally rotatably provided at the lower end, is received by an actuating plate 22 fixed to a swing shaft of a maximum strain position detecting device to be described later, and its position is regulated.

Reference numerals 23 and 24 designate a pair of press rollers corresponding to the rollers 10 and 11, which are rotatably mounted on a support plate 25 that is swingably mounted on the upper end of the swinging rod 18.

Therefore, the support plate 25 hangs down b due to the weight of the press rollers 23, 24, and the press rollers 23, 24 are located on the lower side. A portion between the receiving rollers 10 and 11 of the holding frame 1 and a portion between the pressing rollers 23 and 24 of the support plate 25 is cut out so as not to interfere with the round bar m when the latter is gripped. Reference numeral 26 denotes a pedestal that receives the end of the round bar m when the press device B presses the round bar m, and the receiving rollers 10 and 11
He died near the machine and is fixed on the machine base 2.

The receiving surface 26a of this pedestal 26 is provided slightly lower than the round bar m placed on the receiving rollers 10, 11. Next, Figure 4 shows the rotation and drive of the supply side (right side in Figure 1)! Although the device A2 is shown, this rotary drive device A2
is the brake motor 16 and gear 1 of the rotational drive device A1.
It is almost the same as that except for 3, 14, 15, 17 etc.
The same reference numeral as that of the rotary drive device A1 is appended with an alphanumeric letter "e" to omit repeated explanation. Next, the allowable strain amount detecting devices Cl, C2, and C3 will be described. Since these devices have the same structure, only the intermediate allowable strain amount detecting device C2 will be described below with reference to FIGS. 5 and 6.

Note that the present application is not limited to the number of allowable distortion amount detection devices Cl, C2, and C3. Reference numeral 27 denotes a measuring head consisting of a mounting plate 27a and a measuring block 27b that are fixed to each other as one unit, and is pivotally connected to a holding arm 28 fixed at a predetermined position on the machine base 2 via a pivot bolt 29. .

Further, the measuring head 27 is held by the holding arm 28 by force (a spring 32 compressed between a bearing 30 fitted on the pivot bolt 29 and a nut 31 screwed together). Therefore, although the measuring head 27 can be easily swung by a force greater than the frictional holding force, it is normally held at that position by friction. 33 is Natsuto 31's Rock Knight.

Next, 34 is a reference surface of the measuring head 27 that comes into contact with the surface to be measured (hereinafter referred to as the outer circumferential surface) of the round bar m when the measuring head 27 is swung toward the round bar m. In FIG. 5, the left oblique upper surface of the measurement block 27b also serves as the measuring block 27b. A groove 35 is cut into this reference surface 34 . Reference numeral 36 denotes a detection lever whose intermediate portion is slidably pivoted in the groove 35 by a pin 37, and is configured such that a detection surface 38 on the lower end surface can protrude and retract from the reference surface 34.

Incidentally, the reference surface 34 and the detection surface 38 are brazed with cemented carbide. Reference numeral 39 denotes a detection switch fixed to the mounting plate 27a of the measurement head 27, and the detection portion 39a faces the contact surface 40 on the lower surface of the upper end of the detection lever 36.

In this embodiment, a contact switch is used as the detection switch 39, and the amount of protrusion of the detection portion 39a is adjustable. 41 connects the detection lever 36 to the detection surface 3.
8 is a spring biased in the direction of protruding from the reference surface 34, and is compressed and sealed between the pusher 43 loosely fitted in the storage hole 42 of the measuring block 27b and the screw plug 44 screwed together.

This spring 41VC. As a result, the detection lever 36 is biased in the clockwise direction as shown in FIG.
The position is regulated by coming into contact with 9a. At this time, the size is determined so that the amount of protrusion of the portion of the detection surface 38 that comes into contact with the outer peripheral surface of the round bar is the allowable amount of strain on the outer peripheral surface of the round bar m. The detection switch 39 is connected to the reference surface 3 of the measurement head 27.
4 is pressed against the outer circumferential surface of the round bar m, and after the round bar m rotates at least once, the force is such that it becomes a movable prone state, and when the rotation of the round bar m is stopped, it becomes an inactive prone state. When the contact surface 40 of the detection lever 36 comes into contact with the detection part 39a in this last movable state, a signal is transmitted. Reference numeral 45 denotes a setting device for bringing the reference surface 34 of the measuring head 27 into contact with the outer peripheral surface of the round bar m prior to performing the measurement, and is constructed as follows.

Reference numeral 46 denotes a swing shaft whose both ends are rotatably supported by bearings 47, 47a fixedly installed on the machine base 2. A leaf spring 48 is attached to the mounting member 49 at a position of the swing shaft 46 corresponding to the measurement head 27. It is fixed by.

A swinging arm 50 is wedged near the end of the swinging shaft 46, and an air cylinder whose head side end is pivotally connected to a fixture 51 on the machine base 2 is connected to the tip of the swinging arm 50. The tip of the piston rod 52a is pivotally connected so that the plate spring 48 is swung by a predetermined amount by the force of the air cylinder 52 and the forward movement of the air cylinder 52. The piston rod 52a of this air cylinder 52 is normally recessed, and the round rod m is connected to the receiving rollers 10, 11, 10e, 11 of the rotary drive device Al, A2.
e so that it is ejected after being completely placed on top. Next, the maximum strain position detection device D will be explained with reference to FIGS.
5, 55a are fixed at appropriate intervals, and 56 is a support arm 57 fixed at a predetermined position on the machine base 2.
A swinging rod serving as a measuring block moving device is pivotally attached to the upper end of the swinging rod 56.
3 is fixed in a predetermined direction. The swinging rod 56 is biased clockwise in FIG. It is received by the moving plate 61 and its position is regulated. The swing shaft 60 is connected to the machine base 2.
Both ends of the shovel are rotatably supported by bearings 62, 62a fixedly provided above. A swinging arm 63 is wedged near the end of the swinging shaft 60, and an air cylinder 65 whose head side end is pivotally connected to a fixture 64 on the machine base 2 is connected to the tip of the swinging arm 63. The tip of the piston rod 65a is pivoted, and the swing shaft 60 is rotated by the operation of the air cylinder 65.
is configured to be oscillated by a predetermined amount. The piston rod 65a of the air cylinder 65 normally protrudes as shown in FIG. Send upwards to 10e and 11e,
After that, the conveying roller descends and the round bar m is transferred to the receiving rollers 10, 1.
1, 10e and 11e, the measuring block 53 is retracted and released from the lifting position. Next, a fitting hole 66 and a spring housing hole 67 having a larger diameter are continuously provided in the lower holding body 55a of the measuring block 53. A detection rod 69 with a collar 68 is fitted inside. This detection rod 6
9 is placed in the storage hole 67 and is biased downward by a spring 71 compressed and sealed between the collar 68 and a locking tool 70 fixed to the holder 55a, as shown in FIG. Storage hole 67
The position is regulated by coming into contact with the stepped part (stopper 1).
A roller 72 is rotatably attached to the lower end of the detection rod 69, and the outer periphery of the roller 72 serves as a detection portion 72a, and the end surface of the detection rod 69 serves as a reference surface 73. On the other hand, the soil-side holder 55 of the measuring block 53 is provided with a sliding hole 74 at a position corresponding to the insertion hole 66, and has a measuring surface with an air hole opened at one end and the other end. An air nozzle 76 having a supply hole for supplying compressed air and communicating with a compressed air source is slidably fitted into the slide hole 74. Further, a notch 77 is cut in the upper holding body 55 toward the sliding hole 74, and a pressing member 78 is fitted into the notch 77. This pressing member 78 is pushed by a screw 79 attached to the mounting plate 54, and presses a leaf spring 80 interposed between it and the air nozzle 76.
Therefore, the air nozzle 76 is frictionally held by the leaf spring 80 and is held in the slidable position. The air nozzle 76 is an air nozzle of an air micrometer (not shown), and the air nozzle 76 and the detection rod 6
9, a measuring block 53, and the like constitute a measuring head 81. The air nozzle 76 is
A detection switch (not shown) is connected that measures the back pressure inside and issues a signal when the back pressure exceeds a predetermined set value, and this detection switch and air nozzle 76 constitute an air micrometer. ing. The setting value of this detection switch is set to the magnitude of the back pressure when the air hole 75 of the air nozzle 76 is substantially closed, and this detection switch is set to the magnitude of the back pressure when the air hole 75 of the air nozzle 76 is substantially closed. When one of the lice detection switches 39 is moved to 0N, it is in the operable prone state.When all the lice detection switches 39 are in 0FF (/l) movement, that is, when the strain on the surface to be measured is smaller than the allowable strain amount, it is in the inoperative prone state. Further, when the detection switch issues a signal, the drive of the rotary drive device A1 is stopped. Reference numeral 83 denotes a stopper for regulating the swinging position of the swinging rod 56. It is fixed to the arm 57.

The position of this stopper 83 is determined such that when the swinging rod 56 is received, the detection portion 72a of the detection rod 69 comes into contact with the road surface of the outer peripheral surface of the round bar m. 84 is a setting device that slides the air nozzle 76 to bring the measurement surface into contact with the reference surface 73 of the detection rod 69;
Most of the setting device 45 of C2 and C3 is also used, and a long leaf spring 85 is connected to the swing shaft 46 by a mounting member 86.
is fixed to.

An engagement piece 87 is fixed to the rear end of the air nozzle 76 and is pressed at a predetermined time by the leaf spring 85. 8
8 is a hydraulic press of press device B.

The present embodiment is constructed as described above, and a series of previous effects will now be described.

First, the round bar m as the object to be measured is transferred as indicated by the arrow A and is supplied to the upper position of the rotary drive devices Al and A2.
Thereafter, the conveying roller serving as the conveying means is lowered, and both ends of the round bar m are placed on the receiving rollers 10, 11, 10e, and 11e. When this conveyance roller descends, the air cylinder 65 of the maximum strain position detection device D operates, and the piston rod 6
5a retracts, the swinging rod 56 of the maximum strain position detecting device D is swung by the spring 58 and comes into contact with the stopper 83, and the detection part 72a of the detection rod 69 of the measuring head 53 detects the outer peripheral surface of the round bar m. It comes into contact with the upper surface of the approximately central portion. In this case, the detection rod 69 compresses the spring 71 by an appropriate amount, but the present invention is not limited to this. Also, the piston rod 6 of the air cylinder 65
5a is retracted, the swinging rods 18, 18e of the rotary drive devices Al, A2 are swung by the springs 20, 20e, and the press rollers 23, 24, 23e, 24e press both ends of the round bar m. Receiving rollers 10, 11, 10e, 11e
A round bar m is held between. Next, when the piston rod 65a of the air cylinder 65 is completely retracted, the air cylinder 52 of the setting device 45, 84 is
is activated and the piston rod 52a is projected. As a result, the swing shaft 46 is rotated by a predetermined amount, and the leaf spring 48 of the husband pushes down the mounting plate 27a of the corresponding measuring head 27 to swing the measuring head 27 clockwise in FIG.
The reference surface 34 of each measuring head 27 is brought into contact with the outer peripheral surface of the round bar m. At this time, the detection lever 36 is swung against the spring 41 until the detection surface 38 comes into contact with the outer solid surface of the round bar m, and this detection surface 38 becomes flush with the reference surface 34, and the contact surface 4
0 leaves the detection section 39a of the detection switch 39. Further, due to the rotation of the swing shaft 46, the leaf spring 85 presses the engagement piece 87 of the air nozzle 76 to swing the air nozzle 76 downward, and the measurement surface of the air nozzle 76 is moved to the detection rod 6.
9 is brought into contact with the reference surface 73 of No. 9. However, the piston rod 5 of the air cylinder 52 of the setting device 45, 84
2a is retracted, and the respective leaf springs 48, 85 are returned to their original positions as shown in FIG. And this leaf spring 48,8
5 is completed, the brake motor 16 of the rotary drive device A1 is driven, and this causes the round rod m to connect both ends to the receiving rollers 10, 11, 10e, 11e and the pressing rollers 23, 2.
4, 23e, and 24e, it is rotated in a prone position. By at least one rotation of this round bar m, the measurement heads 27 of the allowable strain amount detection devices Cl, C2, and C3 are swung as the reference surface 34 is pushed by the maximum distance part of the outer peripheral surface of the round bar m from the center of rotation. , is frictionally held at this maximum swing position.
Further, the detection lever 36 is swung so that the detection surface 38 is always in pressure contact with the outer peripheral surface of the round bar m, and the detection surface 38 projects beyond the reference surface 34 in accordance with the distortion of the outer peripheral surface of the round bar m. and,
After the round bar m has rotated at least once and the measuring head 27 is frictionally held at the maximum possible swing position, the detection switch 39 is energized at this time and falls into the swinging state. When the minimum distance part of the outer peripheral surface of the round bar m from the center of rotation is rotated to the detection surface 38 position of the detection lever 36, the detection surface 38 of the detection lever 36
protrudes from the reference surface 34 to the maximum extent possible. At this point,
If the amount of protrusion of the detection surface 38 is smaller than the preset allowable strain amount, the contact surface 40 of the detection lever 36 will not contact the detection switch 39, so the detection switch 39 will not be operated, and in this case, the rotation drive The driving of the device A1 is stopped by a preset timer, and then the round bar m is discharged as shown by arrows C and 2 in FIG. 1, and is treated as a passed product.
On the contrary, if the amount of protrusion of the detection surface 38 is larger than the allowable strain amount, the contact surface 40 of the detection lever 36 will come into contact with the detection part 39a of the detection switch 39 and move the detection switch 39,
Detection switch 39 emits a signal. On the other hand, due to the rotation of the round bar m, the detection rod 69 of the maximum strain position detection device D is moved to the round bar m.
The air nozzle 76 is pushed up against the spring 71 in accordance with the strain of the outer circumferential surface with respect to the center of rotation, thereby causing the air nozzle 76 to slide in both directions against the frictional holding force. When the round bar m rotates at least once, the detection rod 69 is pushed to the maximum extent by the part of the outer peripheral surface of the round bar m that is at the maximum distance from the center of rotation, and the air nozzle 76 is slid upward to the maximum extent. Frictionally held in position. Then, due to the rotation of the round rod m, the maximum distance part of the outer circumferential surface from the center of rotation is again detected by the detection rod 69.
When pushed up as much as possible, the reference surface 73 of the detection rod 69 approaches the measurement surface of the air nozzle 76 and almost closes the air hole 75, and the back pressure of the air nozzle 76 reaches the level detected by the air micrometer. The pressure rises above the set pressure of the switch. At this point, if any one of the detection switches 39 of the allowable strain amount detection devices Cl, C2, and C3 is emitting a signal, the brake motor 16 of the rotary drive device A1 is driven by the signal of this detection switch. is stopped, and the round bar m is stopped in a down position with the maximum strain position located on the upper side. Further, the hydraulic press 88 of the press device B moves forward in response to a signal from the detection switch of the air micrometer, and presses the upper surface of the center portion of the round bar m, that is, the maximum strain position, by a predetermined amount, thereby correcting the distortion of the round bar m. In this case, when the round bar m is pressed by the hydraulic press 88, the holding frame 1 of the receiving rollers 10, 11, 10e, 11e,
1e is swung downward against the springs 5, 5e, and both ends of the round bar m are received by pedestals 26, 26e to remove strain. Thereafter, the air cylinders 52 of the setting devices 45, 84 are operated again, and the above-mentioned measurement work and distortion removal work are repeated. If the product passes the measurement process, it will be discharged as shown in C.2 above, but even if this process is repeated a predetermined number of times, the allowable strain amount detection device Cl,C
2. When the detection switch 39 of C3 emits a signal,
After the rotation of the round rod m is stopped, the piston rod 65a of the air cylinder 65 is projected, and the measuring head 81 of the maximum strain position detecting device D is thereby lifted as shown in FIG. The transport rollers are also raised. Thereafter, the round bar m is discharged as indicated by the arrow H shown in FIG. 1, and this round bar m is treated as a rejected product. In the above embodiment, the measurement head 81 is moved to the surface to be measured and the air nozzle 76 is set to the origin automatically, but this may also be done manually. .

Further, although the object to be measured m is made to move, it is also possible to use the measurement head by making it move. Furthermore, it goes without saying that the detection work may be performed by linearly reciprocating the measuring head or the object to be measured, if necessary. As described above, in the present invention, the air nozzle of the air micrometer is slidably held by friction on the measuring block, and then the air nozzle is moved to the maximum extent through the detection rod according to the maximum displacement position of the surface to be measured. After sliding it upward, the detection rod is again pushed up by the maximum displacement position of the surface to be measured, and the reference surface of the detection rod almost closes the air hole of the air nozzle, thereby activating the detection switch. Therefore, even if the type or size of the object to be measured changes, it can be used as is, and handling is extremely simple.
Furthermore, since there is no need for the reference surface of the detection rod to come into contact with the tip of the air nozzle again, even if dust or the like is attached to the surface to be measured, there will be no erroneous movement, and reliable detection work can be performed. Furthermore, it has a simple structure, can be manufactured at extremely low cost, and has few failures. Furthermore, the maximum displacement position of the surface to be measured can be continuously and automatically detected, contributing to labor saving.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a plan view schematically showing an automatic strain relief machine, FIG. 2 is a sectional view taken along the line X--X of FIG. 1, and FIG. 4 is a sectional view taken along the Y-Y line of
5 is a sectional view taken along the line P-P in FIG. 1, FIG. 6 is a sectional view taken along the Q-Q line in FIG. 5, and FIG. 7 is a sectional view taken along the line R-R in FIG. FIG. Explanation of symbols of main parts, m...Object to be measured, 53
...Measurement block, 69...Detection rod,
72a...Detection section, 73...Reference plane,
75...Air hole, 76...Air nozzle, 81...Measurement head.

Claims (1)

[Scope of Claims] 1. An inspection machine capable of rotating or reciprocating an object to be measured in a direction along its surface to be measured is equipped with a measurement block that can be moved near and far with respect to the movement locus of the surface to be measured. This measurement block has a detection rod having a detection section on one end side and a reference surface on the other end side, and the detection section of this detection rod is moved in a direction near and far with respect to the above-mentioned movement trajectory when the measurement block approaches the above-mentioned movement trajectory. The detecting rod is slidably supported on the measuring block, and the detecting rod is biased toward the movement trajectory and is brought into contact with the stopper of the measuring block to regulate its position.The measuring block has an air hole opened at one end. Slide the air nozzle of an air micrometer, which has a measuring surface and a supply hole for supplying compressed air at the other end, in a direction in which the measuring surface faces the reference surface and moves toward and away from the reference surface. The air nozzle is frictionally held so as to be movable, and the air nozzle is further provided with a detection switch that issues a signal when the back pressure within the air nozzle exceeds a set value at a predetermined time. Displacement position detection device. 2. An inspection machine capable of rotating or reciprocating the object to be measured in a direction along its surface to be measured is equipped with a measuring block that can move near and far with respect to the movement locus of the surface to be measured, and this measuring block supports a detection rod having a detection section on one end and a reference surface on the other end so that when the measurement block approaches the above-mentioned movement trajectory, the detection section of this rod is slidable in a direction toward and away from the above-mentioned movement trajectory. and urges the detection rod toward the movement trajectory and limits its position by abutting against a stopper of the measurement block, and the measurement block has a measurement surface with an air hole opened at one end. An air nozzle of an air micrometer having a supply hole for supplying compressed air on the other end side is frictionally held so that the measurement surface of the air micrometer faces the reference surface and can slide in the direction of moving toward and away from the reference surface. , A detection switch is connected to the air nozzle to issue a signal when the back pressure inside the air nozzle exceeds a set value at a predetermined time, and the measurement block is moved closer to the movement trajectory at a predetermined time. A measurement block moving device that moves the detection part of the detection rod to come into contact with the surface to be measured against the biasing force, and a measurement block moving device that moves the air nozzle toward the detection rod with the measurement block approaching the movement trajectory. A maximum displacement position detection device comprising a setting device that slides to bring a measurement surface into contact with a reference surface.