US20230085096A1

US20230085096A1 - Loose abrasive bodies and method of abrading a workpiece using the same

Info

Publication number: US20230085096A1
Application number: US17/793,608
Authority: US
Inventors: Polly H. R. Keen; Helen E. Pearson
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2020-02-06
Filing date: 2021-02-01
Publication date: 2023-03-16
Also published as: CN115052714A; WO2021156730A1

Abstract

A method of abrading a surface of a workpiece comprises agitating a vessel containing loose abrasive bodies and the workpiece. At least most of the loose abrasive bodies have a maximum dimension of 0.25 to 3 centimeters. On a respective basis, each loose abrasive body comprises abrasive particles secured to an organic substrate by a binder material. The vessel is agitated with sufficient energy such that at least some of the loose abrasive bodies contact and abrade at least a portion of the surface of the workpiece. A plurality of chopped loose abrasive bodies, wherein, on a respective basis, the chopped loose abrasive bodies each comprise abrasive particles secured to a substrate and have a maximum dimension of 0.25 to 1.5 centimeters is also disclosed.

Description

TECHNICAL FIELD

The present disclosure broadly relates to abrasives and methods of abrading.

BACKGROUND

Additive manufacturing of metals, polymers, composites and ceramics for both prototyping and manufacturing has increased in importance in recent years. Additive manufacturing methods such as, for example. Direct Metal Laser Sintering (DMLS) often produce parts with unacceptable surface roughness for the parts' intended function. Most users require post-processing techniques to reduce the roughness of the surface of the part before use. Examples of such post-processing steps include vibratory tumbling and abrasive flow machining. In vibratory tumbling abrasive media are tumbled with a part to smooth its surface.
The manufacture of various abrasive articles (e.g., coated abrasive articles and nonwoven abrasive articles) can generate substantial amounts of scrap during converting to forms such as, for example, abrasive discs. The scrap is typically disposed of by incineration or in a landfill.

SUMMARY

According to the present disclosure, the present inventors have discovered that scrap generated in the conversion of various abrasive articles is either already of a desired size (e.g., in the form of a punch out resulting from a perforating operation) or can be chopped to a desired size range and used as abrasive media for vibratory finishing. Not only does this provide a recycling opportunity for the scrap, but it is also unexpectedly discovered that the recycled abrasive media may actually perform in a superior fashion as compared to an equivalent amount of loose abrasive particles.
In one aspect the present disclosure provides a method of abrading a surface of a workpiece, the method comprising:
providing a vessel containing:

- loose abrasive bodies, wherein at least most of the loose abrasive bodies have a maximum dimension of 0.25 to 3 centimeters, and wherein, on a respective basis, each loose abrasive body comprises abrasive particles secured to an organic substrate by a binder material; and
- the workpiece; and

agitating the vessel with sufficient energy such that at least some of the loose abrasive bodies contact and abrade at least a portion of the surface of the workpiece.
In another aspect, the present disclosure provides a plurality of chopped loose abrasive bodies, wherein, on a respective basis, the chopped loose abrasive bodies each comprise abrasive particles secured to a substrate and have a maximum dimension of 0.25 to 1.5 centimeters. The chopped loose abrasive bodies are useful, for example, for practicing methods according to the present disclosure.
As used herein:
the verb “chop” means to cut into pieces, for example, by a blow by a sharp instrument, slicing, or cutting with scissors, die cutting, perforating, cutting with a laser, characterized by clean cuts, and explicitly excludes shredding operations that tear or rip;
the adjective “chopped” means cut into pieces, for example, by blows, slicing, perforating, or cutting with a sharp implement or laser, characterized by clean cuts, and explicitly excludes torn or ripped shreds;
the term “loose packed”, means compacted using only agitation and gravity; and
the term “vessel” refers to a hollow or concave container used for holding liquids or other contents.
Features and advantages of the present disclosure will be further understood upon consideration of the detailed description as well as the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 . is a schematic process diagram of an exemplary method 100 according to the present disclosure.

FIG. 2 is a schematic cross-sectional side view of an exemplary coated abrasive article 200.

FIG. 3 is a schematic cross-sectional side view of an exemplary coated abrasive article 300.

FIG. 4A is a schematic perspective view of an exemplary nonwoven abrasive article 400.

FIG. 4B is an enlarged view of region 4B in FIG. 4A.

FIG. 5 is a schematic perspective view of an exemplary convolute abrasive wheel 500.

FIG. 6 is a schematic perspective view of an exemplary unitized abrasive wheel 600.

Repeated use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the disclosure. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the disclosure. The figures may not be drawn to scale.

DETAILED DESCRIPTION

Referring now to FIG. 1 , exemplary method 100 of abrading a surface 112 of a workpiece 110 comprises the steps of providing a vessel 120 containing loose abrasive bodies 130 and at least a portion of the workpiece 110, and then agitating the vessel 120 with sufficient energy such that at least some of the loose abrasive bodies 130 contact and abrade at least a portion of the surface 112 of the workpiece 110. At least most (and preferably all) of the loose abrasive bodies 130 have a maximum dimension of 0.25 to 3 centimeters; for example as shown in FIGS. 2-6 . Respectively, each loose abrasive body 130 comprises abrasive particles secured to a substrate by a binder material. In some embodiments, the loose abrasive bodies may be constructed of the same or different materials, although they need not be the same size and/or shape. For example, they may be recycled scrap from a common abrasive article.
The vessel may be capable of retaining any volume of material, and may be partially or completely filled with loose packed abrasive bodies, preferably completely filled if compressible loose packed abrasive bodies are used. In either case, there should be sufficient mobility of the loose packed abrasive bodies or the workpiece so that there is relative motion between the bodies and workpiece during agitation. In some embodiments, the loose packed abrasive bodies fill at least 10 volume percent, at least 20 volume percent, at least 30 volume percent, at least 40 volume percent, or even at least 50 volume percent of the maximum retaining capacity (i.e., excluding overflow) of the vessel. In some embodiments, including any of those mentioned in the preceding sentence, the loose packed abrasive bodies fill less than 90 volume percent, less than 80 volume percent, or less than 70 volume percent of the maximum retaining capacity of the vessel. Lesser and greater amounts of the loose abrasive bodies may also be used. Typically, the greater the mass of each loose abrasive body, the less important the percentage fill of the vessel, although this is not a requirement.
In some embodiments, in addition to the workpiece and loose abrasive bodies, the vessel may further contain additional optional items such as, for example, loose abrasive particles, if desired. In other embodiments, the vessel may be free of such additional optional items.
Any suitable means to agitate the vessel and hence also the loose packed abrasive bodies may be used, including, for example, shaking, vibrating, and/or tumbling. Motion of the vessel may comprise linear, arcuate, elliptical, or random oscillations, for example. In some preferred embodiments, the motion comprises linear reciprocating motion. The process of abrading the workpiece may be batch-wise or continuous.
Methods according to the present disclosure may be carried out, for example, using a vibratory system that includes a vessel. The vessel may be hermetically sealed or in some embodiments it may have one or more openings (e.g., an opening through which the workpiece extends into the vessel). The system may further include an actuator (e.g., a mechanical actuator) capable of vibrating the vessel. Preferably, a control module controls the actuator such that the vessel vibrates under resonant or near-resonant conditions (e.g., resonant acoustic conditions) throughout the surface modification process. Use of vibrationally resonant conditions ensures high efficiency use of the supplied energy. Commercially available mixing devices capable of accomplishing the above are marketed by Resodyn Acoustic Mixers, Butte, Mont. Laboratory-scale devices include LabRAM I and LabRAM II controlled batch mixers. Large scale devices are marketed under the trade designations OmniRAM. RAMS, and RAM 55. These devices typically operate at resonant vibrational frequencies from 20 to <1 kilohertz (kHz), preferably 40 to 100 hertz, more preferably 40 to 80 hertz, and more preferably 55-65 hertz, although this is not a requirement. The vibrating mixers are also characterized by actuator displacements that are on the order of 0.5 inch (1.3 cm), that may be accompanied by an acceleration g-force, where g=9.8 m/s², of at least 20-g. 30-g, 40-g, 50-g, or even at least 60-g, although this is not a requirement. Further details concerning suitable resonant acoustic mixers can be found, for example, in U.S. Pat. No. 7,188,993 (Howe et al.) and U.S. Pat. No. 9,808,778 (Farrar et al.).
In practice, the loose abrasive bodies and the workpiece(s) are disposed within the vessel. The workpiece may be loose within the vessel or fixed in a given position relative to the vessel (e.g., mounted to a wall of the vessel). The latter configuration may be desirable in instances where selective modification of a portion of the workpiece surface is desired. The latter configuration may also be desirable if the workpiece has a large mass and/or is delicate, so that collisions between the workpiece and the vessel walls are prevented. Advantageously, the loose abrasive bodies may ricochet off the sides and top of the vessel during vibration such that the workpiece is bombarded from all angles.
Mixtures of two or more types, compositions, shapes, and/or sizes of loose abrasive bodies may be used. Examples of suitable loose abrasive bodies include coated abrasive articles (e.g., having make and size layers or a slurry layer), nonwoven abrasive articles (e.g., surface finishing abrasive articles including a lofty open fiber web), convolute abrasive wheels, and unitized abrasive wheels. Such abrasive articles are well-known in the art.
Referring to FIG. 2 , an exemplary coated abrasive article 200 has backing 220 and abrasive layer 230 according to the present disclosure. Abrasive layer 230, in turn, includes abrasive particles 240 secured to major surface 270 of backing 220 by make layer 250 and size layer 260.
Referring to FIG. 3 , exemplary coated abrasive article 300 has backing 320 and abrasive layer 330. Abrasive layer 330, in turn, includes abrasive particles 340 and binder 345 according to the present disclosure.
Further details regarding coated abrasive articles having make and size layers and/or structured abrasive article, and methods of their manufacture can be found, for example, in U.S. Pat. No. 4,734,104 (Broberg); U.S. Pat. No. 4,737,163 (Larkey); U.S. Pat. No. 5,203,884 (Buchanan et al.); U.S. Pat. No. 5,152,917 (Pieper et al.); U.S. Pat. No. 5,378,251 (Culler et al.); U.S. Pat. No. 5,436,063 (Follett et al.); U.S. Pat. No. 5,496,386 (Broberg et al.); U.S. Pat. No. 5,609,706 (Benedict et al.); U.S. Pat. No. 5,520,711 (Helmin); U.S. Pat. No. 5,961,674 (Gagliardi et al.), and U.S. Pat. No. 5,975,988 (Christianson).
Referring now to FIGS. 4A and 4B, exemplary nonwoven abrasive article 400 comprises a lofty open low-density fibrous web 410 formed of entangled filaments 410. Abrasive particles 440 are secured to fibrous web 410 by binder 420.
Convolute abrasive wheels may be made, for example, by winding a nonwoven abrasive article 510, as described above, under tension around a core member 530 (e.g., a tubular or rod-shaped core member) such that the nonwoven abrasive article is compressed, then impregnating with a curable binder precursor and curing. A convolute abrasive wheel 500 is shown in FIG. 5 .
Similarly, unitized abrasive wheels can be made, for example, as with convolute wheels, except that instead of winding the size layer precursor coated web, it is stacked and compressed prior to curing. A unitized nonwoven abrasive wheel 600 is shown in FIG. 6 having a plurality of nonwoven abrasive layers 610.
Further details concerning nonwoven abrasive articles, abrasive wheels and methods for their manufacture may be found, for example, in U.S. Pat. No. 2,958,593 (Hoover et al.). U.S. Pat. No. 5,591,239 (Larson et al.); U.S. Pat. No. 6,017,831 (Beardsley et al.); and in U.S. Pat. Appl. Publ. 2006/0041065 A1 (Barber, Jr.) and 2018-0036866 (Alkas et al.).
The workpiece may be any object, typically fabricated, where abrading of the workpiece surface is desired. Examples include camshafts, crankshafts, and turbine blades. Exemplary workpieces include metal components (e.g., which may be sintered metal parts manufactured by rapid prototyping/3-D printing). Examples of workpiece materials include metal and metal alloys (e.g., aluminum and mild steel), exotic metal alloys, ceramics, glass, wood, wood-like materials, composites, painted surfaces, plastics, reinforced plastics, stone, and/or combinations thereof. The workpiece may be flat or have a shape or contour associated with it.
The loose abrasive bodies may be obtained by chopping corresponding abrasive material involved in the manufacturing process such as, for example, converting manufacturing waste (e.g., weed) or scrap abrasive goods. While not required for practice of aspects of the present disclosure; in some embodiments, it may be desirable to provide the loose abrasive bodies according to a predetermined specific size distribution (e.g., monomodal or polymodal) and/or compositional specifications (e.g., two different coated abrasive loose bodies or a combination of coated abrasive loose bodies and nonwoven abrasive loose bodies). It may also be desirable to provide the loose abrasive bodies as random shapes or specified shapes.

Select Embodiments of the Present Disclosure

In a first embodiment, the present disclosure provides a plurality of chopped loose abrasive bodies, wherein, on a respective basis, the chopped loose abrasive bodies each comprise abrasive particles secured to a substrate and have a maximum dimension of 0.25 to 3 centimeters (cm), preferably 0.3 to 2.6 cm, more preferably 0.5 to 2.5 cm, and more preferably 0.7 to 2.5 cm.
In a second embodiment, the present disclosure provides a plurality of chopped loose abrasive bodies according to the first embodiment, wherein the plurality of chopped loose abrasive bodies has a predetermined size distribution, preferably monomodal or polymodal.
In a third embodiment, the present disclosure provides a plurality of chopped loose abrasive bodies according to the second embodiment, wherein the predetermined size distribution has at least two modes; e.g., bimodal or trimodal.
In a fourth embodiment, the present disclosure provides a plurality of chopped loose abrasive bodies according to any of the first to third embodiments, wherein at least some of the chopped loose abrasive bodies comprise chopped coated abrasive articles.
In a fifth embodiment, the present disclosure provides a plurality of chopped loose abrasive bodies according to any of the first to third embodiments, wherein at least some of the chopped loose abrasive bodies comprise chopped lofty open nonwoven abrasive articles.
In a sixth embodiment, the present disclosure provides a plurality of chopped loose abrasive bodies according to any of the first to third embodiments, wherein at least some of the chopped loose abrasive bodies comprise chopped unitized or convolute abrasive articles.
In a seventh embodiment, the present disclosure provides a plurality of chopped loose abrasive bodies according to any of the first to third embodiments, wherein, on a respective basis, at least some of the substrates comprise resilient foam.
In an eighth embodiment, the present disclosure provides a plurality of chopped loose abrasive bodies according to any of the first to third embodiments, wherein at least some of the substrates respectively comprise metal foil.
In a ninth embodiment, the present disclosure provides a plurality of chopped loose abrasive bodies according to any of the first to eighth embodiments, wherein at least some of the abrasive particles comprise crushed abrasive particles.
In a tenth embodiment, the present disclosure provides a plurality of chopped loose abrasive bodies according to any of the first to ninth embodiments, wherein at least some of the abrasive particles comprise shaped abrasive particles.
In an eleventh embodiment, the present disclosure provides a plurality of chopped loose abrasive bodies according to any of the first to tenth embodiments, wherein, on a respective basis, the abrasive particles are secured to the substrate by a binder material.
In a twelfth embodiment, the present disclosure provides a plurality of chopped loose abrasive bodies according to the eleventh embodiment, wherein the binder material comprises crosslinked organic binder material.
In a thirteenth embodiment, the present disclosure provides a method of abrading a surface of a workpiece, the method comprising:
providing a vessel containing:

agitating the vessel with sufficient energy such that at least some of the loose abrasive bodies contact and abrade at least a portion of the surface of the workpiece.
In a fourteenth embodiment, the present disclosure provides a method according to the thirteenth embodiment, wherein the vessel has a maximum retaining capacity, and wherein the plurality of loose abrasive bodies has a total volume that is at least 25 percent of the maximum retaining capacity of the vessel.
In a fifteenth embodiment, the present disclosure provides a method according to the fourteenth embodiment, wherein the plurality of loose abrasive bodies has a total volume that is at least 50 percent of the maximum retaining capacity of the vessel.
In a sixteenth embodiment, the present disclosure provides a method according to any of the thirteenth to fifteenth embodiments, wherein the vessel is agitated by linear displacement.
In a seventeenth embodiment, the present disclosure provides a method according to any of the thirteenth to sixteenth embodiments, wherein the method is continuous.
In an eighteenth embodiment, the present disclosure provides a method according to any of the thirteenth to seventeenth embodiments, wherein the workpiece comprises metal.
In a nineteenth embodiment, the present disclosure provides a method according to any of the thirteenth to eighteenth embodiments, wherein the workpiece comprises plastic.
In a twentieth embodiment, the present disclosure provides a method according to any of the thirteenth to nineteenth embodiments, wherein the loose abrasive bodies comprise the plurality of chopped loose abrasive bodies of any of the first to twelfth embodiments.
Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure.

EXAMPLES

Unless otherwise noted, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight.
The system used for all examples described below was a LabRAM Resonant Acoustic mixer from Resodyn Corporation, Butte, Mont. The machine, which was equipped with a sealed mixing vessel, was run at 100% intensity in the auto frequency mode. Roughness measurements: R_a, were measured using a MarSurf PS 10 stylus profilometer and S_aroughness measurements were recorded using a MikroCAD surface metrology system.

Example 1

This example demonstrates abrading aluminum alloy with cloth-backed electrocoated abrasive bodies.
The workpiece was a machined aluminum alloy (Grade BS EN 755 6082-T6) 16 mm×3 mm×50 mm cuboid. The workpiece had an initial surface roughness R_aof 4.3 microns. The workpiece was placed in a polypropylene container with 55 mm internal height and 80 mm internal diameter. 53 g of 3M 947A 120+ cloth-backed electrocoated abrasive (chopped into 1 cm×1 cm squares) was placed in the container along with the workpiece, and the was container sealed with a lid. The LabRAM was run at 100% intensity in the auto frequency mode for 15 mins. The roughness R_aof the workpiece after 15 mins of processing was 2.1 microns. The mass loss of the workpiece during processing was 0.05 g (0.8% of the total initial mass).

Example 2

This example demonstrates abrading additively manufactured tool steel with a microreplicated cloth-backed abrasive bodies.
The workpiece was an additively manufactured tool steel tube of 20 mm diameter with 2 mm walls printed by DMLS. The initial roughness of the outside of the tube was an R_aof 6.8 microns and 12.0 microns on the inside of the tube. The workpiece was placed in a polypropylene container with 55 mm internal height and 80 mm internal diameter. 50 g of 3M 307EA A100 Trizact belt (chopped into 1.27 cm×1 cm rectangles) was placed in the container along with the workpiece, and the container was sealed with a lid. The LabRAM was run at 100% intensity in the auto frequency mode for 15 mins. After 15 mins, the roughness R_aof the workpiece on outside surface of the tube was 3.0 microns, and on the inside surface the tube was 6.8 microns. The mass loss of the workpiece was 0.17 g (1% of the total initial mass).

Example 3

This example demonstrates abrading aluminum alloy with foam backed electrocoated abrasive bodies.
The workpiece was a machined aluminum alloy (Grade BS EN 755 6082-T6) 16 mm×3 mm×50 mm cuboid. The workpiece had an initial surface roughness R_aof 4.5 microns. The workpiece was placed in a polypropylene container with 55 mm internal height and 80 mm internal diameter. 20 g of 3M P1000 Hookit Flexible Abrasive Foam Disc (foam-backed electrocoated abrasive chopped into 1.5 cm×1.5 cm squares) was placed in the container along with the workpiece. The container was sealed with its lid. The LabRAM was run at 100% intensity in the auto frequency mode for 15 mins. The roughness R_aof the workpiece after 15 mins of processing was 2.5 microns. The mass loss of the workpiece during processing was 0.02 g (0.3% of the total initial mass).

Example 4

This example demonstrates abrading additively manufactured tool steel with double-sided foam-backed coated abrasive bodies.
The workpiece was an additively manufactured tool steel tube of 20 mm diameter with 2 mm walls printed by DMLS. The initial roughness of the outside of the tube was an R_aof 12.2 microns and 12.8 microns on the inside of the tube. The workpiece was placed in a polypropylene container with 55 mm internal height and 80 mm internal diameter. 3M 737U 400+ paper-backed coated abrasive was laminated to both sides of sheet of soft foam (0.5 cm thick), and this construction was chopped into 1 cm×1 cm squares. 18 g of the double-sided foam-backed abrasive bodies was placed in the container along with the workpiece, and the container was sealed with a lid. The LabRAM was run at 100% intensity in the auto frequency mode for 15 mins. After 15 mins. the roughness R_aof the workpiece on outside surface of the tube was 8.7 microns and on the inside surface the tube was 5.2 microns. The mass loss of the workpiece was 0.21 g (1.3% of the total initial mass).

Example 5

This example demonstrates abrading additively manufactured tool steel with unitized wheel abrasive bodies.
The workpiece was an additively manufactured tool steel tube of 20 mm diameter with 2 mm walls printed by DMLS. The initial roughness of the outside of the tube was an R_aof 7.4 microns. The workpiece was placed in a polypropylene cylindrical container with 55 mm internal height and 80 mm internal diameter. 3M Scotch-Brite Debunr and Finish PRO 6C Med+ Unitized Wheel (0.125 inch thickness) was chopped into 0.5 cm×0.5 cm squares. 30 g of the unitized abrasive bodies was placed in the container along with the workpiece, and the container was sealed with a lid. The LabRAM was run at 100% intensity in the auto frequency mode for 15 mins. After 15 mins, the roughness R_aof the workpiece on outside surface of the tube was 2.6 microns. The mass loss of the workpiece was 0.21 g (1.3% of the total initial mass).

Example 6

This example demonstrates abrading aluminum alloy with lofty nonwoven abrasive bodies.
The workpiece was a machined aluminum alloy (Grade BS EN 755 6082-T6) 16 mm×3 mm×50 mm cuboid. The workpiece had an initial surface roughness R_aof 4.1 microns. The workpiece was placed in a polypropylene cylindrical container with 55 mm internal height and 80 mm internal diameter. 30 g of 3M 7446 S-CRS Scotch-Brite (lofty nonwoven abrasive handpad chopped into 1 cm×1 cm squares) was placed in the container along with the sealed. The container was sealed with a lid. The LabRAM was run at 100% intensity in the auto frequency mode for 15 mins. The roughness R_aof the workpiece after 15 mins of processing was 2.2 microns. The mass loss of the workpiece during this time period of processing was 0.02 g (0.3% of the total initial mass).

Example 7

This example demonstrates abrading aluminum alloy with paper-backed electrocoated abrasive bodies.
The workpiece was a machined aluminum alloy (Grade BS EN 755 6082-T6) 16 mm×3 mm×50 mm cuboid. The workpiece had an initial surface roughness R_aof 4.2 microns. The workpiece was placed in a polypropylene cylindrical container with 55 mm internal height and 80 mm internal diameter. 29 g of 3M P500 334U (paper-backed coated abrasive laminated to brushed nylon, chopped into 1 cm×1 cm squares) was placed in the container along with the workpiece and the container was sealed with a lid. The LabRAM was run at 100% intensity in the auto frequency mode for 15 mins. The roughness R_aof the workpiece after 15 mins of processing was 2.8 microns. The mass loss of the workpiece during processing was 0.04 g (0.6% of the total initial mass).

Example 8

This example demonstrates abrading additively manufactured tool steel with paper-backed electrocoated abrasive bodies (waste pips).
The workpiece was an additively manufactured tool steel tube of 20 mm diameter with 2 mm walls printed by DMLS. The initial roughness of the outside of the tube was an R_aof 11.8 microns. The initial roughness of the inside of the tube was an R_aof 12.4 microns. The workpiece was placed in a polypropylene cylindrical container with 55 mm internal height and 80 mm internal diameter. The abrasive bodies were 3M 255P P80 pips. 3M 255P is a paper-backed coated abrasive laminated to brushed nylon. Pips are circular pieces of coated abrasive removed to create dust extraction holes in a coated abrasive disc (in this case with diameters 18 mm. 10 mm and 7 mm). 60 g of the pips was placed in the container along with the workpiece, and the container was sealed with a lid. The LabRAM was run at 100% intensity in the auto frequency mode for 15 mins. After 15 mins, the roughness R_aof the workpiece on outside surface of the tube was 3.5 microns, and the R_aon the inside of the tube was 7.0 microns. The mass loss of the workpiece was 0.29 g (1.8% of the total initial mass).

Example 9

This example demonstrates abrading additively manufactured polymer with lofty nonwoven abrasive bodies.
The workpiece was an additively manufactured FormLabs Clear Resin (methacrylic acid esters with a photoinitiator) tube of 20 mm diameter with 2 mm walls. The workpiece was printed by SLA (stereolithography) (initial roughness S_a=24 microns). The workpiece was placed in a polypropylene cylindrical container with 200 ml volume and 60 mm internal diameter. 25 g of 3M 7447 A-VFN Scotch-Brite (lofty nonwoven abrasive handpad chopped into 1 cm×2 cm squares) was placed in the container along with the workpiece, and the container was sealed. The LabRAM was run at 100% intensity in the auto frequency mode for 20 mins. After 20 mins, the roughness S_aof the workpiece on the surface of the tube was 2.7 microns (89% improvement). The mass loss of the workpiece was 6% of the total initial mass.

Example 10

This example demonstrates the comparison between abrading aluminum alloy with coated abrasive bodies and loose abrasive grains.
The workpiece was a machined aluminum alloy (Grade BS EN 755 6082-T6) 16 mm×3 mm×50 mm cuboid. The workpiece had an initial surface roughness R_aof 4-4.5 microns. The workpiece was placed in a polypropylene cylindrical container with 55 mm internal height and 80 mm internal diameter along with the abrasive media, and the container was sealed with a lid. The abrasive media either comprised 60 g of 3M P80 255P pips (coated abrasive bodies), or 24 g, 60 g or 100 g of P80 semi-friable fused aluminum oxide BRFPL loose abrasive grain (Imerys). The reason for selecting these masses of loose abrasive grain are detailed in Table 1. The LabRAM was run at 100% intensity in the auto frequency mode for 5 mins. The results for mass loss and surface finish improvement are shown in Table 1. The mass loss and surface finish improvements from the coated abrasive bodies were significantly greater than from any mass of the loose abrasive grain.

TABLE 1

				SURFACE FINISH
				IMPROVEMENT
		MASS OF	MASS LOSS	OF SUBSTRATE
		MEDIA IN	FROM	SURFACE,
ABRASIVE	DESCRIPTION OF ABRASIVE	CONTAINER,	SUBSTRATE,	ROUGHNESS R_a,
MEDIA	MEDIA	g	g	microns	NOTES

3M P80	Pips (7, 10 and 18 mm diameter discs) of	60	0.052	27%	Example of a coated
255P pips	3M P80 255P coated abrasive (full				abrasive body
	construction with brushed nylon
	attachment system and stearate coating)
P80 BFRPL	P80 grade aluminum oxide loose	24	0.024*	−7%	Approximate mass of
	abrasive grain				abrasive grain on 60 g
					of the coated abrasive
P80 BFRPL	P80 grade aluminum oxide loose	60	0.011	5%	Same mass of abrasive
	abrasive grain				grain as mass of coated
					abrasive
P80 BFRPL	P80 grade aluminum oxide loose	100	0.004	−1%	Approximately same
	abrasive grain				volume of abrasive
					grain as solid volume of
					coated abrasive

*Major mass loss from collisions of workpiece with container.

All cited references, patents, and patent applications in this application are incorporated by reference in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in this application shall control. The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.

Claims

1-20. (canceled)

21. A plurality of chopped loose abrasive bodies, wherein, on a respective basis, the chopped loose abrasive bodies each comprise abrasive particles secured to a substrate and have a maximum dimension of 0.25 to 1.5 centimeters, and wherein, on a respective basis, the abrasive particles are secured to the substrate by a binder material.

22. The plurality of chopped loose abrasive bodies of claim 21, wherein the plurality of chopped loose abrasive bodies has a predetermined size distribution.

23. The plurality of chopped loose abrasive bodies of claim 22, wherein the predetermined size distribution has at least two modes.

24. The plurality of chopped loose abrasive bodies of claim 21, wherein at least some of the chopped loose abrasive bodies comprise chopped coated abrasive articles.

25. The plurality of chopped loose abrasive bodies of claim 21, wherein at least some of the chopped loose abrasive bodies comprise chopped lofty open nonwoven abrasive articles.

26. The plurality of chopped loose abrasive bodies of claim 21, wherein at least some of the chopped loose abrasive bodies comprise chopped unitized or convolute abrasive articles.

27. The plurality of chopped loose abrasive bodies of claim 21, wherein, on a respective basis, at least some of the substrates comprise resilient foam.

28. The plurality of chopped loose abrasive bodies of claim 21, wherein at least some of the substrates respectively comprise metal foil.

29. The plurality of chopped loose abrasive bodies of claim 21, wherein at least some of the abrasive particles comprise crushed abrasive particles.

30. The plurality of chopped loose abrasive bodies of claim 21, wherein at least some of the abrasive particles comprise shaped abrasive particles.

31. The plurality of chopped loose abrasive bodies of claim 21, wherein the binder material comprises crosslinked organic binder material.

32. A method of abrading a surface of a workpiece, the method comprising:

providing a vessel containing:

loose abrasive bodies, wherein at least most of the loose abrasive bodies have a maximum dimension of 0.25 to 3 centimeters, and wherein, on a respective basis, each loose abrasive body comprises abrasive particles secured to an organic substrate by a binder material; and

the workpiece; and

agitating the vessel with sufficient energy such that at least some of the loose abrasive bodies contact and abrade at least a portion of the surface of the workpiece.

33. The method of claim 32, wherein the vessel has a maximum retaining capacity, and wherein the plurality of loose abrasive bodies has a total volume that is at least 25 percent of the maximum retaining capacity of the vessel.

34. The method of claim 33, wherein the plurality of loose abrasive bodies has a total volume that is at least 50 percent of the maximum retaining capacity of the vessel.

35. The method of claim 32, wherein the vessel is agitated by linear displacement.

36. The method of claim 32, wherein the method is continuous.

37. The method of claim 32, wherein the workpiece comprises metal.

38. The method of claim 32, wherein the workpiece comprises plastic.

39. The method of claim 32, wherein the loose abrasive bodies comprise the plurality of chopped loose abrasive bodies of claim 21.