EP4263129B1

EP4263129B1 - Sanding system with damping feature

Info

Publication number: EP4263129B1
Application number: EP21827431.4A
Authority: EP
Inventors: Joseph B. Eckel; Orlin B. Knudson; Erin D. Spring; Nathan J. HERBST; Rufus C. Sanders
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2020-12-17
Filing date: 2021-12-08
Publication date: 2025-08-20
Anticipated expiration: 2041-12-08
Also published as: EP4263129A1; WO2022130129A1; US20240051082A1

Description

BACKGROUND

Manual and powered hand tools are known for sanding operations. Some powered tools include rotary, orbital, or random orbital sanding tools that move an attached abrasive article against a surface, abrading the surface.
Power tools, and in particular random orbital sanders are used by a variety of professionals to perform sanding functions for their craft. Operation of sanding tools often causes vibrations. WO 2020/084523 A2 discloses a a robotic paint repair system comprising a compliant accessory actuator capable of applying a desired force and a desired stiffness to the consumable abrasive product in response to sensed data collected between the tool and the substrate. US 2013/092408 A1 and DE 10 2007 047077 A1 disclose the use of rheological materials for dampening.

SUMMARY

According to the present invention, a sanding system is defined according to independent claim 1, and a method of mechanically sanding a surface according to independent claim 6. Preferred embodiments are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

FIGS. 1A-1B illustrate sanding tools in which embodiments of the present invention may be useful.
FIGS. 2A-2B illustrate a ball bearing based compliance feature for a sanding tool.
FIGS. 3A-3B illustrate a magnetic fluid-based compliance feature for a sanding tool.
FIGS. 4A-4B illustrate a telescoping drive shaft.
FIG. 5 illustrate a fluid-based compliance feature for a sanding tool.
FIG. 6 illustrates an electronic control system that may be useful in embodiments herein.
FIG. 7 illustrates a diagrammatic view of a sanding system in accordance with embodiments herein.
FIG. 8 illustrates a method of providing damping to a sanding operation in accordance with embodiments herein.
FIG. 9 illustrates an exploded view of the components of a robotic abrasive process stack.

DETAILED DESCRIPTION

Many sanding and repair operations are increasingly being done by robotic repair units. One of the last areas to be automated includes sanding and polishing operations, which often benefit from an experienced user applying pressure at a desired amount to achieve the desired finish.
One particular area where robots are lacking behind their human counterparts is adaptability of changing pressure when sanding over non-flat part features. Generally, this is handled today by using compliant abrasive products (such as abrasive nonwoven wheels or bristle products) that 'give' when unit pressure increases over the radius or edge of a part. This prevents changing part dimensions but at the expense of cut rate and abrasive selection. By moving the compliance mechanism into the abrasive tool itself, it could allow for any abrasive to be used. Furthermore, if the tool compliance is adjustable in real-time, this could allow for maximizing cut rates during sanding of the part.
Embodiments herein disclose several variable compliance damper systems that change the amount of compliance in the tool as it interacts with the part being sanded. This can allow for real-time adjustability of the compliance in the tool. Variable compliance damping systems provide significant benefits for robotic abrading systems. The ability to control the force applied depending on given abrasive application parameters is incredibly useful. Variable force control systems described herein allow for both real-time adjustment of applied force in a system, for example based on feedback received during an operation, as well as pre-programmed force application cycles. Systems and methods herein can include active controls to monitor abrasion and adjust applied force accordingly.
Systems and methods herein can also be coupled with a vision system, or based on known trajectories of a repair path. For example, when an abrading system is approaching a corner, a viscosity of a magnetorheological fluid-based damper could be increased, providing more compliance. A vision system, or a known trajectory, can provide cues as to when to increase or decrease compliance based on an anticipated path.
A vision system may also detect a material being abraded to determine initial compliance settings. For example, a robotic sander may be sanding an airplane and may approach a window and round a corner. If the robotic system can detect the window coming, compliance can be adjusted accordingly.
Compliance changes are needed based on a variety of factors, including orientation changes, which adjust the application of gravitational forces on an abrasive article, as well as the need for more or less force based on features of the worksurface. Today this is done based on feedback from sensors that know the tool angle / weight and vary force from a force compliance tool accordingly. Systems and methods herein can also adjust compliance by adjusting viscosity of compliant dampers.
Currently, a single sanding tool may interface with a plurality of backup pads based on operation parameters. For example, some operations require a low compliance foam backup pad while others require a firmer backup pad. Systems and methods herein envision a compliance system built into a backup pad that can provide variable compliance without the need to swap out backup pads. Such a backup pad may have an interface that connects to a sanding tool. The interface may allow for power to be drawn from the tool. Some backup pads may be powered by an internal power supply.
Many of the figures systems and methods herein are illustrated as implemented in hand tool embodiments. However, this is for ease of understanding only and it is expressly contemplated that any or all may be implemented in a robotic abrading system.
FIGS 1A-1B illustrate an orbital sanding took in which embodiments of the present invention may be useful.
FIGS. 1A and 1B illustrate a random orbital sander 10 with a housing 14 having a hand grip 12 at a first end. While the housing 14 is shown as cylindrical, it can be formed in other configurations while still keeping within the scope of this disclosure. Connected to the second end of the housing, in some embodiments, is a lock ring that is adapted to secure a motor 20 within the housing 14. The random orbital sander 10 may also include a particulate matter collection skirt 22 that is coupled to the lock ring 18. The particulate matter collection skirt 22 is adapted to contain particulate matter created by the sander and, when used with a vacuum attachment, can be used to allow the dust the be collected by a vacuum unit. Located adjacent the particulate matter collection skirt 22 is a sanding pad 16 that is coupled to the motor 20. The housing 14 also includes a valve assembly 26 that is adapted to be connected to a pressurized air supply. The valve assembly 26 is operated by depressing actuation lever 28. While the housing 14 is preferably made from plastic it can also be manufactured metal, such as aluminum, or other materials.
FIG. 1B illustrates a cutaway view of random orbital sander 10.
FIGS. 1A and 1B relate to pneumatically powered sanding tools. However, it is expressly contemplated that systems and methods herein may also be applicable to electric and battery powered handheld or robotic systems. 1C illustrates a cutaway view of an electric rotary sander.
A motor can be seen and is designated generally by reference numeral 30. The motor 30 includes an armature 32 having an output shaft 34 associated therewith. The output shaft or drive spindle 34 is coupled to a combined motor cooling and dust collection fan 36. In particular, fan 36 comprises a disc-shaped member having impeller blades formed on both its top and bottom surfaces. The impeller blades 36a formed on the top surface serve as the cooling fan for the motor, and the impeller blades 36b formed on the bottom surface serve as the dust collection fan for the dust collection system. Openings 18a formed in the platen 18 allow the fan 36b to draw sanding dust up through aligned openings 19a in the sandpaper 19 into the dust canister 16 to thus help keep the work surface clear of sanding dust. The platen 18 is secured to a bearing retainer 40 via a plurality of threaded screws 38 (only one of which is visible in FIG. 1C) which extend through openings 18b in the platen 18. The bearing retainer 40 carries a bearing 42 that is journaled to an eccentric arbor 36c formed on the bottom of the fan member 36. The bearing assembly is secured to the arbor 36c via a threaded screw 44 and a washer 46. It will be noted that the bearing 42 is disposed eccentrically to the output shaft 34 of the motor, which thus imparts an orbital motion to the platen 18 as the platen 18 is driven rotationally by the motor 30.
FIGS 2A-2B illustrate a ball bearing based compliant damping feature for a sanding tool. Illustrated in FIG. 2A is a rotary sander 210 that is part of a sanding system 200. However, while a rotary sander 210 is illustrated, it is expressly contemplated that other sanding tools, such as orbital, linear and random orbital may be used, in other embodiments. Sanding tool 210 is coupled to a backup pad 250, which has a tool connecting feature 254, which connects to a drive shaft of tool 210. Backup pad 250 also has an abrasive article attachment surface 252, which receives an abrasive article for a sanding operation, such as an abrasive disc.
Between backup pad 250 and tool 210 is a damping system that includes a pair of ball bearings 260 that ride in a groove 262 (illustrated in FIG. 2B). Each ball-bearing 260 is coupled to a compliant damper 264, which are also coupled to tool 210. As illustrated in FIGS. 2A and 2B, compliant damper 264 is a magnetorheological shock absorber. Compliant damper 264 is a variable compliance damper, for example allowing a range of compliance options when actuated. While backup pad 250 is illustrated at a significant distance from tool 210 for ease of understanding, it is expressly contemplated that, in at least some embodiments, the compliance dampers264 are condensed such that the tool 210 and the backup pad 250 are in close proximity to one another, for example on the order of one or more millimeters apart.
Compliant dampers 264, in the embodiment illustrated in FIG. 2A, are magnetorheological shock absorbers with a magnetorheological fluid that causes springs to expand and contract to absorb vibrations caused by operation of tool 210 during a sanding operation. However, other suitable shock absorbing mechanisms may be used in other embodiments.
FIGS 3A-3B illustrate a magnetic fluid-based compliant damping feature for a sanding tool. FIG. 3A illustrates a top-down view of a backup pad 300 modified with a damping system. The backup pad includes a tool connector 302, which connects to a drive shaft of the tool, and which is on an opposite side from an abrasive article receiving surface 304.
Backup pad 300 includes a damping system with a first contact ring 310 and a second contact ring 320. As illustrated in FIG. 3B, a flexible fluid container 330 is present within a housing of backup pad 300. Fluid container 330 is filled with a magnetorheological fluid, in one embodiment, with a viscosity that can be altered when a current is applied to the wire coils that encircle, or are embedded within the fluid container 330. In the embodiment illustrated in FIGS. 3A-3B, a current can be applied by one of spring-loaded mobile arms 340 making contact with either or both of contact rings 310 or 320. As the viscosity of the fluid within container 330 changes, the firmness of backup pad 300 also changes.
In some embodiments, a second set of arms 340 are also needed, such that arms 340 and the second set of arms both contact a coiled conducting wire in order for sufficient current to flow and cause an electromagnetic field.
In another embodiment, a single coil is positioned within the magnetic fluid and receives a current that adjusts the viscosity of the magnetic fluid.
Alternatively, as illustrated by coils 360, in one embodiment the fluid container 330 is encircled and current is applied using contacts 340. Windings 360 are illustrated as used in conjunction with contacts 340, and instead of contact rings 310, 320.
Using any of the systems illustrated in FIGS. 3A-3B may allow for adjusting a viscosity of a magnetorheological fluid in fluid container 330 such that it becomes more or less stiff. Viscosity can be adjusted by varying current, and thus the strength of the resulting electromagnetic field, or by varying the number of windings 360.
FIGS 4A-4B illustrate a telescoping drive shaft for a sanding tool. As illustrated in FIG. 4A, a telescoping driveshaft 450 couples tool 410 to backup pad 420, in one embodiment of a dampened sanding tool 400. Backup pad 420 includes a tool connecting side, which receives drive shaft 450 through a threaded portion 480 of shaft 450 coupling to threading of backup pad 420 (not shown in FIGS. 4A-4B). Backup pad 420 also includes an abrasive article connecting side 422, which receives an abrasive article for a sanding operation.
Telescoping drive shaft 450 is capable of collapsing up and down such that a magnetorheological damping feature 470 can collapse or expand within shaft 450. In the embodiment illustrated in FIG. 4B, telescoping drive shaft has a plurality of grooves such that the telescoping sections can rotate together as tool 410 rotates backup pad 420 and an abrasive article coupled to side 422.
Telescoping drive shaft 450 also has a connection feature 480 that interlocks tool 410 to backup pad 420. As illustrated in FIG. 4B, in one embodiment, the connection feature is a threaded shaft.
FIG. 5 illustrate a fluid-based damping feature for a sanding tool. FIG. 5 illustrates a sanding tool 500 with an external housing 502 that houses a motor, as illustrated. Within housing 502 is a fluid-filled bladder 510. Fluid 520, in one embodiment, is a magnetorheological fluid that can change viscosity when affected by a magnetic field. A magnetic field can be applied by running a current through a current-conducting medium, such as a wire 530 wrapped around bladder 510. Current conducting element 530, in some embodiments, is an insulated coil to prevent shorts.
One end of element 530 couples to a positive lead, and the other couples to a negative lead. The strength of the applied magnetic field can be varied by the amount of current and / or the number of windings of wire 530. A single wire 530 on an exterior is illustrated in FIG. 5, However, wire 530 may be within bladder 510, in some embodiments. In another embodiment, a second wire 530 is present on an interior of bladder 510, between bladder 510 and a motor.
While a single fluid bladder 510 is illustrated in FIG. 5 surrounding the entire motor, it is expressly contemplated that, in some embodiments, fluid bladder 510 may only be substantially between the top of a motor and the top of the housing 502. Such an embodiment may limit the ability of the motor to move to just along axis 540. In other embodiments, instead of a single fluid bladder 510, a plurality of fluid bladders 510, each surrounded by a current conducting element 530, are present within housing 502. The plurality of fluid bladders 510 may allow for at least some angular movement of the motor within housing 502, as illustrated by axis 542.
FIG. 6 illustrates an electronic control system which may operate in concert with damping systems described herein. Systems using compliant damping systems, such as rheological-based fluids or other shock absorbers under the control of an electronic control system can product damping as selected or specified by a program memory 620 stored in, or accessible by, the device.
A set of system operating conditions 610 are monitored by a control system of a sanding tool and are input to an electronic analog to digital converter (A/D) 614 that converts analog signals to a digital representation, which is then provided to a computing engine 614. Operating conditions 610 may include RPM, temperature, axial acceleration, etc. Also input to the A/D is a force or displacement measurement sensed by a sensor 640 associated with a rheological damping element 650. Sensor(s) 640 may be an accelerometer, force and/or displacement sensor or other sensors that determine the system operating conditions. Computing engine 614, therefore, takes as inputs: the algorithm(s) of the program memory 620, system operating conditions 610 and measurements from sensor(s) 640.
In some cases, A/D 612, program memory hardware 620, and digital to analog converter (DAC) 616 are integrated into computing engine 614. Computing engine 614 may be, in some embodiments, a microprocessor, microcontroller or other suitable computing device.
Program memory 620 programs the response of the computing engine 614, for example setting parameters around how fast to respond, under what conditions as determined by the system operating conditions, etc., and this is output to digital to analog converter (DAC) 616 that converts the multiple inputs, using program memory algorithm 620, through an amplifier 630 into a controlled current signal that controls the magnetic field provided by compliant damper 640.
While only one rheological damper 650, and one amplifier 630, are illustrated in FIG. 6, and discussed with respect to FIGS. 2-5, it is expressly contemplated that, in some embodiments, multiple dampers are present within a sanding system. In such system, program memory 620 may contain an algorithm that adjusts compliance of each damper based on sensed information from sensor 640. In some embodiments the output of the computing engine 614 to the amplifier 630 may be an analog signal, in which case the DAC 616 is not required.
FIG. 7 illustrates a diagrammatic view of a sanding system in accordance with embodiments herein. The sanding system 800 includes a sanding tool 802 which couples to a backup pad 850, which connects to an abrasive article 804, such as an abrasive disc. The sanding tool 802 may be a linear sander, a rotary sander, an orbital sander or a random orbital sander. Sanding tool 802 includes a housing with an internal cavity that houses a motor 820. The motor includes an output shaft that couples to backup pad 850, or directly to an abrasive disc 804.
In some embodiments, sanding tool includes a particulate collector 816 that, for example, applies a vacuum or otherwise collects particulates created during a sanding operation. In embodiments where sander 802 includes a particulate collector 816 that operates based on a vacuum, an air supply connection 818 may be present.
As illustrated in FIG. 7, in different embodiments, either tool 802 and / or backup pad 850 may have a damping feature 822, 852. In some embodiments, damping features 822, 852 are each components of a damping system that spans a connection between tool 802 and backup pad 850. However, in some embodiments, the damping system is wholly contained within either sander 802 or backup pad 850, such that one or the other of features 822, 852 are either not present, or not active, during a sanding operation. For example, system 400 described herein wholly contains the damping system within the sanding tool 802, while system 300 contains the damping system wholly within the backup pad 850. In contrast, system 200 contains features 822, 852 that are either part of tool 802 or backup pad 850.
Sanding tool 802 has an actuator 812 that, when actuated, causes motor 820 to move abrasive disc 804 to move in a pattern for a sanding operation. In some embodiments, actuator 812 is only actuatable when sanding tool 802 has been plugged in or otherwise powered. In other embodiments, actuator 812 serves to power on and actuate motor 820. In some embodiments, motor 820 directly causes movement of backup pad 820, which then causes abrasive disc 804 to move.
In some embodiments, damping feature 822 and / or damping feature 852 are actuated in conjunction with sanding actuator 812, that is the damping starts as soon as sander 802 begins a sanding operation. However, damping actuator 814 may also be mechanically actuated based on another event, such as a minimum counterforce applied by a workpiece against the abrasive disc 804 during a sanding operation, or a minimum vibratory activity.
An amount of compliance provided by damping features 822 and / or 852 is controlled by controller 820. For example, many compliant damping features described herein include a magnetorheological fluid that can change viscosity under an applied magnetic field. Controller 860 may communicate with a damping feature 822, 852 and activate, increase, decrease or deactivate current flow, causing a viscosity of a magnetorheological fluid to change.
FIG. 8 illustrates a method of providing damping to a sanding operation in accordance with embodiments herein. Method 900 may be implemented in any suitable sanding or grinding tool that is expected to produce vibrations during a grinding operation.
In block 910 a sanding tool is prepared. Preparing a sanding tool may include selecting and attaching a suitable backup pad to the tool, and / or selecting a suitable abrasive article for a sanding job. For example, as discussed in FIGS. 2-5, in some embodiments a backup pad 912 has features of a damping system that correspond to damping features on or associated with the sanding tool. Preparing the sanding tool may also include other steps 916, such as attaching a particulate collection system.
In block 920, a sanding operation is conducted. The sanding operation may be conducted using an orbital sander 922, random orbital sander 924, rotary sander 926, or another sanding tool 928, such as a linear sander.
In block 930, a compliant damping feature is actuated. While block 930 is illustrated as following block 920, it is expressly contemplated that, in some embodiments, actuating the sanding tool also actuates the damping feature. However, it is expressly contemplated that the damping feature may be separately actuated, for example when power to the sanding tool is initiated, or when a reaction force is exerted on the sanding system by a worksurface being sanded. The damping feature may be any suitable damping feature, such as a fluid feature 932 containing a magnetorheological fluid that has a manipulatable viscosity, such as that described in FIGS. 3 and 5, a ball-bearing-based damping system 934, such as that described in FIG. 2, a telescoping drive shaft, as described in FIG. 4. Other damping systems 938 may also be possible.
The damping feature activated in block 930 may include components solely associated with the sanding tool, as illustrated in block 952, for example incorporated into the drive shaft or otherwise housed within the housing of the sanding tool. In other embodiments, the components of the damping feature may be solely associated with, or wholly included within the backup pad, as illustrated by block 954.
FIG. 9 illustrates an exploded view of the components of a robotic paint repair stack. As illustrated, the robotic paint repair stack 1106 comprises a robot arm 1200, force control sensors and devices 1108, a grinding/polishing tool 1110 with damping system 1102, a hardware integration device 1202, abrasive pad(s) and compounds 1112, a design abrasives process 1204, and data and services 1206. These elements may work together to identify defect locations and to implement a predetermined repair program using a deterministic policy for the identified defect, such as the policy discussed in co-owned and co-pending PCT Application No. PCT/IB2019/057053, filed on August 21, 2019 .
While human-operated sanding tools are discussed above as example embodiments, providing damping to a robotic grinding / polishing tool 1110 through a damping feature 1104 is also expressly contemplated herein. One area where robots are lacking behind their human counterparts is the ability to identify and adapt to the need for changing pressure of changing pressure when sanding over non-flat part features. Generally, this is handled today by using compliant abrasive products (such as abrasive nonwoven wheels or bristle products) that 'give' when unit pressure increases over the radius or edge of a part. This prevents changing part dimensions but at the expense of cut rate and abrasive selection. Alternatively, compliance is provided through a force control unit 1108, which adjusts a force applied to a sanding tool 1110.
By moving the compliance mechanism into the abrasive tool, itself, it could allow for any abrasive to be used. Furthermore, if the tool compliance is adjustable in real-time, this could allow for maximizing cut rates during sanding of the part. This could also reduce complexity in the robotic system by removing the need for a separate force control unit outside of the sanding tool.
Providing a damping system that can be adjusted and connected without the need for a separate force control sensors and devices 1108 allows for more dynamic sanding systems that can more efficiently conduct grinding and polishing operations.
The components of the illustrative devices, systems and methods employed in accordance with the illustrated embodiments of the present invention can be implemented, at least in part, in digital electronic circuitry, analog electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. These components can be implemented, for example, as a computer program product such as a computer program, program code or computer instructions tangibly embodied in an information carrier, or in a machine-readable storage device, for execution by, or to control the operation of, data processing apparatus such as a programmable processor, a computer, or multiple computers.

Claims

A sanding system comprising:
a tool (500, 802) with a motor (820) which, when actuated, drives movement of a drive shaft;

a backup pad (300, 850) coupled to the drive shaft, wherein the backup pad is configured to receive an abrasive article (804), and wherein movement of the drive shaft causes movement of the abrasive article;

characterized in that a compliant damping unit is configured to provide variable compliance for the tool when the abrasive article is contacting a worksurface, wherein the damping unit comprises a magnetorheological fluid (520) that changes from a first viscosity to a second viscosity when an applied current is changed from a first current to a second current, wherein the magnetorheological fluid is housed in the backup pad (300) and wherein the current is applied to a contact ring (310, 320) on a surface of the backup pad; and

an electronic controller that receives a system operating condition, sends a signal to the compliant damping unit based on the system operating condition.
The sanding system of claim 1, wherein the system operating condition is received from a sensor associated with the damping unit, a sensor associated with the motor, an end effector to which the sanding tool is coupled, or a vision system.
The sanding system of claim 2, wherein the system operating condition is a measured reaction force, an orientation of the tool with respect to the worksurface, an indication that the abrasive article has contacted a worksurface, or a vibration threshold.
The system of claim 1, wherein the magnetorheological fluid is contained by a fluid bladder, and wherein the tool comprises a wire wound about the fluid bladder, and wherein the wire is configured to produce a magnetic field when a current is received.
The system of any of claims 1-4, wherein the sanding system is mounted to a robotic arm.
A method of mechanically sanding a surface, the method comprising:
providing a sanding system as defined in any of the previous claims, comprising a sanding tool (500, 802) coupled to an abrasive article (804);

contacting the abrasive article to a worksurface; and

varying compliance of the sanding tool during an abrasive operation comprising the abrasive article contacting a worksurface, wherein varying compliance comprises controlling a compliant damping feature, wherein the compliant damping feature adjusts an applied force of the sanding tool wherein the compliant damping unit comprises a magnetorheological fluid (520) that changes from a first viscosity to a second viscosity when a magnetic field is applied wherein the magnetic fluid is housed in the backup pad (300) and wherein the current is applied to a contact ring (310, 320) on a surface of the backup pad; and

wherein an electronic control system actuates the mechanical damping feature in response to a system operating condition received from a sensor.
The method of claim 6, wherein controlling comprises increasing an applied current which increases the applied force of the sanding tool.
The method of any of claims 6 or 7, wherein controlling comprises decreasing an applied current which decreases the applied force of the sanding tool.
The method of claim 6, wherein actuation of the motor causes actuation of the electronic controller.
The method of claim 9, wherein the system operating condition is received from a sensor associated with the compliant damping feature, a sensor associated with the motor, or a vision system remote from the sanding tool.
The method of claim 9, wherein the magnetic field is applied to a wire (530) coiled around the magnetorheological fluid (520).