DE1913462A1 - Grinding wheel - Google Patents

Description

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N ORTO N C O M P Λ N Y

1 Ilen Jiond Street
Worcester / Hass., USA

Grinding wheel

The invention relates to grinding wheels for with relatively Foundry rough grinding work to be carried out by hand with light pressure.

The normal foundry grinding work requires the implementation of a rough or plaster grinding process to remove of gates, risers and ribs of the castings, how they come out of the molds. Such grinding work are usually done with bench grinders and sometimes with light pendulum grinders. At all During these grinding work, the grinding pressure between the wheel and the workpiece is usually determined by hand, although the disk storage and drive device can of course be used for this purpose, the operator support in generating the required grinding pressure, which is used to press the disc ^ against the casting or other object to be ground.

Whenever rough grinding work, the wheel must be able to withstand a very robust load, but grinding work in the foundry is a particularly rough process. Sometimes have sharp corners of

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Cast the tendency to chisel into the sides of the disks and since the pane is operated by hand, it is exposed to strong impacts on the casting. For these and other obvious reasons, rough grinding wheels for the foundry with a single agent be produced that has a sufficient degree of stability so that it can withstand the stresses that occur during use and the risk of the panes tearing can bring about what stress is caused by the type of grinding wear mentioned.

conventional grinding wheels for this purpose include h abrasive grain made of sintered alumina in resin bonded by a resistance having a pore volume in the disc 26 \ or less, which results in an increased hardness. With a pore volume of 26% , the strength has been found to be about the minimum that can be expected to withstand the harsh treatment to which conventional foundry grinding wheels are subjected, if harder or stronger binders are used, With the conventional abrasives for rough grinding, the grinding effect becomes slower and the labor cost increases, so? the grinding work is less economical, although the wheel has a longer service life. When rough grinding, it is like all grinding work on a large scale usually desirable \ worth to accelerate the softest grade for the disc to be used, which gives a reasonable performance under the prevailing conditions to the completion of the grinding action. However, in all grinding work it is essential to ensure that the wheel used has sufficient strength to withstand the particular grinding action of the grinding work.

For foundry rough grinding work carried out by hand became the best conventional disc so far with a fixed one Form of abrasive grain of sintered aluminum oxide bound in a phenolic resin binder with a pore volume of

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2u 'Ό made, iiiue wheels of this type are ideal for this purpose, as long as the abrasive grain remains sharp * but it was found that the bond λ'οη of the named porosity has a degree of strength that is sufficient for the conventionally sintered and ground aluminum oxide screw to hold in the surface of the disc up to the maximum grinding life of the abrasive grain, ie until it becomes dull. When the abrasive grit becomes dull through use, the wheels lose their grinding efficiency and their surfaces eventually become laxative. Dull abrasive grain and a glazed wheel surface impair the ability of the wheels to lift metal very significantly and therefore greatly reduce the grinding speed. The grinding work must therefore be interrupted and wheels of the type mentioned have to be dressed or sharpened from time to time to expose fresh, sharp grain on the surface of the panes, thereby renewing their steel conductivity. This dressing process requires the use of a comparatively expensive tool set-up and requires an unproductive expenditure of time for the work of such a wheel dressing. The time spent on dressing a wheel also represents non-productive time for the machine system for driving the wheel and for the device for handling a casting to be ground and for carrying out the grinding process.

The subject of the invention is a grinding wheel for foundry coarse grinding, which are made by hand with a relatively light bridge, which grinding wheel consists of resin-bonded abrasive grain and has a pore volume of 22% to 26 l, the abrasive grain being spinel or mullite or a mixture thereof from one The size corresponds to a clear jug width of -1.4I- to 0.74 ram (14 to 24 mesh) and makes up between 44 and 62 percent by volume in the disc, while the remaining disc volume is due to the binder and the. J?, Oren is formed. . . ,. _;

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BATH ORIGINAL

In particular, a wheel can be used in which the abrasive grain makes up about 54 percent by volume of the wheel and the preferred grain size is 1.41 mm clear mesh size (14 mesh). The binder can be prepared by at least 75 volume percent phenolic resin with 0 to 25 i cryolite filler and from 0 to 8 i calcium oxide filler, are formed. In this way, a combination of spinel and / or mullite abrasive grain in connection with a phenolic resin-bonded wheel is obtained with the specified porosity, the abrasive grain having just the right degree of chipping to make the surface of the wheel self-sharpening in use. The inventive combination of wheel hardness W and type of abrasive bonded in a coarse grinding wheel of conventional design results in a wheel which can be subjected to the robust treatment of hand-carried foundry grinding work with relatively little pressure in order to benefit from the right degree of bond strength and softness the grinding effect for the special job, but at the same time to get the fastest-acting grinding wheel for this purpose. With such a combination of the hardness of the wheel and the abrasive grain, the undesired defects of the wheel described above are eliminated, which are long characteristic of the currently available conventional grinding wheels for foundry rough grinding work.

The invention is described in more detail below in conjunction with the accompanying drawing, which is a graphic representation gives which curves of typical grinding results of different wheels shows for comparison purposes.

As mentioned, a special combination of bond strength and abrasive grain is provided for the rough grinding work optimally designed for the foundry needs, whereby a relatively light pressure in the hand-controlled grinding work for cleaning the casting and the like is exercised. .

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^ ifksdnie Gfob abrasives for the corners of the invention can be produced by grinding Müllite (3 Al ₂ O _3. '2SiO ₂ ) or Spinel · CIgO .Al ₂ O ₃ ) within the size range of the abrasive grain conventionally used for rough grinding, Larger grain sizes such as 1.4ΐ, 1.19, 0.84 or 0.74 mn clear mesh size (14, "16, 20 Odör-24 neh) are usually provided for this use; (under" mesh "here are the "Greetings from the O.'S. Standard sieve set to understand. Disks that are made from either müilit or'Spinell Korh are preferably used in" conventional cold-pressed phenolic resin coarse grinding wheels with a porosity of 26 % for those with a relatively light weight Pressure, rapidly and manually controlled foundry coarse grinding jobs for which the invention is intended;

The mullite and / or spinel abrasive grain in a phenolic resin bonded wheel with a porosity of 26 proves to have a relatively soft or sharp cutting effect for the grinding of the castings obtained in normal foundry work. The "grinding effect of the wheel according to the invention has the" feel "and * is the equivalent of the effect of the known wheels with a pore volume of 26 % and conventional ^{sharp abrasive particles 1} made of ground, sintered aluminum oxide. '

The resin-bonded disc with a pore volume of 26% and '' made with the! specified. "abrasives is sufficient robust, in order to be able to ständnäiteh bumps or blows and another robust handling, as they normally do in the case of hand-carried Giesseroi rough grinding work occur, whereby it can be established, however, that the mullite and Spineli-Schieifko ^ is slowly breaking out in use, i.e. with a "speed ^ the device" is sufficient, sharp to bieifeeri, uiid when breaking out the oil resin biiidüng ' at the same time eroded and removed; to the Seheibe'Always isicharfiihä schneistnttii ^ iia iö lialten. It leaves Noting that there is no wheel dressing ii

Kind is required, v; hen this is too normal --- carried out by hand- * Foundry rough grinding is used and that the wheel continuously sharpens itself to maintain the fastest cutting speed that: with the use of the discs for rough grinding work at ^ the relatively light pressure that comes with such work is usually applied, is compatible. - ..- ■; '

The traditional Xorh treatment processes are used to produce the spinel and mullite abrasive grain for use in the disks. The grain is then subjected in herkümrili'-cher way a size sorting Tina to select the appropriate the "rough grinding size ranges, Irie mentioned, it is preferable grain in the range of 1.41 to O _f 74 now possible .Maschenweite (14-24 US Standard sieve set} should be used. - - ... ·, - , ■. <: ■:,. :

The same result can be achieved by bonding a spinel or mullite abrasive grain or mixtures thereof in a rubber bond. In this case, the bond strength must be chosen so that the disk can have the fastest cutting speed, which is compatible with holding the grain for grinding while the bond is raking at approximately the same speed happens, with ₍ with which the grain is broken out in use to make the -t disc self-sharpening; Burning ^{11 of} the rubber results when the Seheibe -hart- is gear part; Furthermore * ^{: i} the rubber binding is more expensive to manufacture ^ than the conventional phenolic resin binding *. ■ '- "-" ■ "" - ■ "'■■^;; ' * "'' ■ '-'- « ^v · - ~ ^;

Although the preferred teaching according to the invention is the use of spinel and abrasive grains with a grain size of 26% for coarse grinding notes, in order to obtain an optimal cutting speed that is compatible with the strength of the abrasive grain for use Giesaarei grinding work is compatible, a harder qualitiij:: 4 bond with

ciner.v pore volume of etua 22 ν vorwendet v.'erden. In this case, however, the harder wheel, which contains a spinel or mullite abrasive grain, may require truing from time to time to allow reuse, but it should be noted that truing is not nearly as frequent as with conventional alumina -Discs must be made.

The erfindunqsgeraassen discs can also be used in the rest of the Manner and using known methods and Abrasives for binding and preparing the mixture can be produced for compression molding and firing of the disc.

The binder "enisch" can be between IOD% and phenolic resin a mixture containing only 75 percent by volume of this resin. It can contain up to 25 percent by volume of cryolite filler can be used, but the grinding aid can be omitted in certain cases. Furthermore, others can conventional grinding aids are combined with cryolite or used in its place, it is proposed between Use 0 to 8 percent by volume calcium oxide to help harden the resin. The abrasive content The disc according to the invention can range from about 44 to 62 percent by volume of the finished disc can be changed. It is suggested to cold-press the green mixture carefully controlled in order to bring about a compaction, which in a finished disc has a porosity of about Results in 20% in the hardened disc. When the porosity increases, the disc becomes too soft and mechanically proportionate weak .. Xenn the porosity far below 22 I in of the finished disc is reduced, the disc will cut slowly and appear harder.

Below are several typical slices of the one according to the invention Structure given for example:

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55.8 7.5 34.5 20th 9.7 5

e i s ρ i e 1

A resin binder composition was made with the following Approach made:

Wt . % Vol

. Piienol resin cryolite calcium oxide

W Where the V.ichte of the mixture was 1.72 and using this binder composition disks were prepared with the following structure in volume percent: 54 i abrasives, 20 i binder and 26% pores,

Three discs were made, one each with each of the abrasives: a conventional one for comparison Disc made of sintered, ground aluminum oxide with a mesh size of 1.41 mm (14 mesh), a disc according to the invention with spinel grain of 1.41 mm clear mesh size and another disc with mullite grain of 1.41 mm clear mesh size » The specification 1.41 mm clear mesh size (14 mesh) for . the grain means, for example, that the grain passed through a sieve of 1.41 mm clear mesh size (14 mesh), however, was held on a 1.19 mm open mesh (16 mesh) screen. All of the aforesaid discs were produced with the specified volume structure by cold pressing in a closed mold, which means that they were pressed to have a "constant volume".

Furfurol was used in the conventional! Heise as a mixture plasticizer 55 ecm per 0.453 kg (each Ib) of the aforementioned dry resin binder were used. For a 16 "χ

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2 "χ 6") the following mixtures were made;

Disc grinding ski with. Weight d. Weight d. No. medium weight binding pellets, in kg in kg per ecm

1 alumina 12.02o 1.941 2.47

2 spinel 10.886 1.941 2.26

3 mullite 10.024 1.941 2.04

The complete mixture was then pressed to form the disc shape 16 "χ 2" χ 6 ") and the "green" disks were then fired to cure the resin binder, peeled off and in the usual way Way subjected to a speed test.

A grinding test was carried out on the disks using a pendulum grinder so with weights that was a total force of 45.36 kg (100 lbs) to the Pressing of the disc in rest on the workpiece was obtained,

Starting from the slices in the freshly peeled state The factory delivery included four test runs with each disc carried out. Periodic measurements of wheel wear and the volume of chip removal were made over time equally measured operating periods carried out during the test of each disc. The material of the workpiece was cast steel from the 1020 SAE specification and the disks were measured at 2895 surface meters (9500 surface feet) per minute operated.

The results of this trial are in the form below given in a table as hourly value and the curves shown in the drawing are plotted from these values.

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disc Experimental
run Chip removal
speed.
(kg / h) Disc wear
speed
Ccm3 / n) aluminum
oxide 1 8.345 158.9 Il 2 7.555 118.0 It 3 6,577 90.1 Il 4th 5.216 60.6 Spinel 1 9.299 417.9 Il 2 9.525 431.0 Il 3 9 _p 072 404.8 • 1 4th 9.525 429.3 Mulit 1 9,072 262.2 It 2 9.299 273.7 Il 3 8.845 250.7 Il 4th 9.525 290.0

From these results it can be seen that the alumina disk is initially an economical high-speed cutting disc under the grinding conditions mentioned, while the aluminum oxide curve rejections 2, 3 and 4 show that the Disc quickly becomes dull. After about 20 minutes of operation dulls the aluminum oxide disc to such an extent that the volume of the chip removal decreases radically and the grinding work becomes ineffective to the specified degree when the disc becomes blunt. After the fourth test run, the surface was glassy, so that the disk was no longer operational. The rapid dulling requires dressing that required a period of at least 5 minutes and the removal of approximately 0.5 mm (0.020 ") from the radius of the disc, to restore the initial cutting speed. The dressing of course also leads to a corresponding one Non-productive time of the grinding machine.

Spinel and mullite slices, however, cut as they proceed the grinding work continues continuously and quickly. the end

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the curves for the discs that these abrasives use contained, it follows that the speed of the disc wear and the stock removal for the different periods of use have the aim to approximate that same narrow area of the respective curves for the disks to remain, indicating that the abrasive grain is kept at about its maximum sharpness. The fact that the second and fourth readings had more chip removal and higher disc wear than the first and third Periods of operation indicate that the bond itself is also moving from the surface of the disc at a rate which is appropriate to the breaking out of the grain, so that a fully customized combination of Abrasive grain and bond is obtained when those described in US Pat These discs can be used for rough grinding work carried out by hand.

Patent claims:

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Claims (6)

Patent claims: /l.ischleif disc for manually with a relatively light pressure executed foundry Grobschleifar "BEITEN from a resin bonded abrasive grain, characterized in that the disc has a pore volume of 22 ■ · to 26 I, thereof, the abrasive grain of spinel or mullite, or mixtures consists, the abrasive grain corresponds to a sieve size of 1.41-0.74 mm clear mesh size (14-24 mesh US standard sieve set) and is present in the wheel with 44-62 volume%, while the remainder of the wheel volume through the binder mass and the pores are formed. 2. Disc according to claim 1, characterized in that the abrasive grain is about 54 volume! of the finished disc forms. 3. Disc according to claims 1 and 2, characterized in that that the binder is a phenolic resin. 4. Disc according to claims 1-3, characterized in that the abrasive has a screen size of 1.41 mm clear mesh size (14 mesh U.S. standard sieve set) is equivalent to. 5. Disc according to claims 1-4, characterized in that · .909845 / 090 0- net that the binder is a phenolic resin composition which is used to form a disk with a pore volume of 26% has been hardened. 6. Disc according to the preceding claims, characterized in that that the bond is 75 - 100 volumes phenolic resin, 0 - 25 volume% of a cryolite filler and 0-8 volume * contains a calcium oxide filler. 909845 / 09Gi) / fV Empty soap