JP2003025099A - Powder pressing apparatus and powder pressing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder pressing apparatus and a powder pressing method by which the quality and yield of a molded body can be improved. SOLUTION: The powder pressing apparatus 10 contains a die 22 having a through hole 20 elongating in upper and lower directions, a lower punch 24 previously inserted into the through hole 20, and an upper punch 26 capable of inserting into the through hole 20. A lubricant 68 is fed from a feed port 70 provided on the side face 24a of the lower panch to the side face 20a of the through hole in the die 22. A lubricant feed path 74 connected to the feed port 70 is connected with a three way valve 80 which freely opens and closes a part of the lubricant feed path 74, and a recovery tank 82 is connected to the three way valve 80. On powder compression, by the operation of the three way valve 80, powder 34 in a cavity 27 is degassed, and the lubricant 68 in the lubricant feed path 74 is recovered to the recovery tank 82.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder pressing apparatus and a powder pressing method, and more specifically to a powder pressing apparatus and a powder pressing method for compressing a rare earth magnet alloy powder filled in a cavity to form a compact. Regarding

[0002]

2. Description of the Related Art One example of this type of prior art is Japanese Patent Laid-Open No. 2000-2000.
-197997. The powder pressing device disclosed herein includes a die having a through hole extending in the vertical direction, an upper punch configured to be insertable from above into the through hole of the die, and a die in the through hole of the die. And a lower punch that is movably fitted. Then, a cavity is formed in the through hole of the die by the die and the lower punch, the powder is filled in the cavity, and then the powder in the cavity is compressed by the upper and lower punches to form a compact. Further, in order to prevent seizure on the side surface of the through hole of the die and to easily remove the molded body from the through hole, the lubricant is sprayed from the side surface of the punch to the side surface of the through hole to supply the lubricant in a desired direction. In addition, a seal portion is provided on the side surface of the punch that sprays the lubricant.

[0003]

When the powder is, for example, an alloy powder for rare earth magnets, the average particle size is 3 μm.
It is very small, ~ 6 μm (MMD average particle size), and contains a large amount of gas in the powder (molded body density 3.9 g / cm).
³ to to 5.0 g / cm ^3, the powder packing density 1.8 g / c
m ^{3 to} 3.0 g / cm ³ ), a large amount of gas is squeezed out when the powder is compressed. As described above, since the seal portion is provided on the side surface of the punch for injecting the lubricant, a very small amount of the gas squeezed out by the compression is discharged from the gap between the side surface of the other punch and the side surface of the through hole. However, the other gas has no place to go except to flow backward through the lubricant supply port connected to the lubricant supply port.

However, when the powder is compressed, both the lubricant supply valve and the compressed gas supply valve provided in the lubricant supply passage are closed, and the gas cannot flow back through the lubricant supply passage and be discharged. , It remains in the cavity.
Although it is possible to suck the gas in the cavity under reduced pressure when filling the powder, if the powder is an alloy powder for rare earth magnets with high abrasiveness and activity, the powder is sucked between the punch side surface and the die through-hole side surface by vacuum suction. If the powder is sandwiched, the side surface of the punch and the side surface of the through hole of the die are worn by the powder, and there is a risk of ignition due to frictional heat. For this reason, vacuum suction is refrained from. Therefore, since the powder in the cavity is compression-molded without being sufficiently deaerated, cracks, cracks and the like may occur in the molded body, and there is a problem that the quality and yield of the molded body are reduced. Therefore, a main object of the present invention is to provide a powder pressing apparatus and a powder pressing method capable of improving the quality and yield of molded products.

[0005]

In order to solve the above-mentioned problems, the powder pressing apparatus according to claim 1 is a powder pressing apparatus for compressing powder to form a compact, which is a through-hole extending vertically. A die having a hole, first and second movable in each through hole in the vertical direction relative to the die, and for compressing powder in a cavity formed in the through hole.
A supply means for supplying a lubricant to at least one of the punch, the side surface of the through hole of the die and the side surface of the first punch, and a deaeration means for discharging the gas generated from the powder during compression to the outside of the cavity.

According to a second aspect of the present invention, there is provided a powder pressing apparatus according to the first aspect, wherein the supplying means includes a lubricant supply passage and the deaeration means can open and close a part of the lubricant supply passage. It is characterized by including an opening / closing means for opening. Claim 3
The powder pressing apparatus according to claim 2 is characterized in that, in the powder pressing apparatus according to claim 2, the powder pressing apparatus further includes a lubricant recovery means connected to the opening / closing means for recovering the lubricant in the lubricant supply passage. .

A powder pressing apparatus according to a fourth aspect is the powder pressing apparatus according to any one of the first to third aspects, wherein the first punch side surface is formed so as to seal the gap between the first punch side surface and the through hole side surface. And a seal portion provided on at least one of the side surfaces of the through hole. The powder pressing apparatus according to claim 5 is the powder pressing apparatus according to any one of claims 1 to 4,
The average particle diameter of the powder is 3 μm to 6 μm, and the distance between the side surface of the second punch and the side surface of the through hole is 10 μm to 40 μm.

A powder pressing apparatus according to a sixth aspect is the powder pressing apparatus according to any one of the first to fifth aspects, wherein the packing density of the powder in the cavity is 40% to 60% of the density of the compact. It is characterized by being. A powder pressing apparatus according to a seventh aspect is the powder pressing apparatus according to any of the first to sixth aspects, wherein the powder is an alloy powder for rare earth magnets.

The powder pressing method according to claim 8 is a powder press for compressing powder by a first punch and a second punch in a cavity formed in a through hole extending in a vertical direction of a die to form a compact. A method, comprising: a first step of supplying a lubricant to at least one of a side surface of a through hole of a die and a side surface of a first punch; a second step of filling a powder in a cavity; and a gas contained in the powder in the cavity. Is discharged, the powder is compressed by the first punch and the second punch to form a molded body. The powder pressing method according to claim 9 is the powder pressing method according to claim 8, wherein in the first step, the lubricant is supplied through a lubricant supply passage, and in the third step, inside the lubricant supply passage. The method is further characterized by further including the step of collecting the lubricant.
The powder pressing method according to claim 10 is the powder pressing method according to claim 8 or 9, characterized in that the powder is an alloy powder for a rare earth magnet.

In the powder pressing apparatus according to the first aspect, the lubricant can be surely applied to the side surface of the through hole of the die and the side surface of the first punch, and the powder in the cavity is degassed so that The powder can be compressed and the moldability can be improved. Therefore, the quality and yield of the molded product can be improved. The same applies to the powder pressing method according to claim 8.

In the powder pressing apparatus according to the second aspect, when the powder is compressed by the first punch and the second punch in the cavity, the powder in the cavity can be easily passed through the lubricant supply passage only by opening the opening / closing means. You can escape. In the powder pressing apparatus according to the third aspect, the lubricant remaining in the lubricant supply passage can be collected. Therefore, the next supply of the lubricant is not hindered by the lubricant remaining in the lubricant supply passage, so that the lubricant can be supplied vigorously. The same applies to the powder pressing method according to claim 9.

When the seal portion is provided on at least one of the side surface of the first punch and the side surface of the through hole of the die, deaeration cannot be performed from the gap between the side surface of the first punch and the side surface of the through hole of the die. In the powder press device described in
Even when such a seal portion is provided, the powder in the cavity can be degassed. In the powder pressing apparatus according to claim 5, the average particle diameter of the powder is very small, 3 μm to 6 μm, and the powder easily contains a large amount of gas, and the gap between the side surface of the second punch and the side surface of the through hole of the die is small. The powder in the cavity can be degassed even if the gas in the cavity is very small and difficult to be discharged.

In the powder pressing apparatus according to the sixth aspect, even if the powder packed in the cavity has a small packing density and the packed powder contains a very large amount of gas, it can be sufficiently degassed. The alloy powder for rare earth magnets is very fine and difficult to deaerate, and if it is sucked under reduced pressure, it is easily ignited by frictional heat. However, in the powder pressing device according to claim 7, the powder is such an alloy powder for rare earth magnets. But you can safely degas. The same applies to the powder pressing method according to claim 10. In this specification, the term "lubricant" means a mold lubricant applied between the side surface of the die through hole and the side surface of the punch, and a mold release agent applied to the side surface of the through hole of the die and releasing the molded body from the die. It is a concept including a release agent that improves the sex.

[0014]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 1, a powder pressing device 10 according to an embodiment of the present invention includes a frame 12 having a housing shape. A punch fixing table 14 and a plate 16 are arranged horizontally in the lower and upper portions of the frame 12, respectively. Further, a mold 18 for compression molding is provided in the frame 12. The mold 18 is used to form a molded body (not shown) of a rare earth magnet used in, for example, a voice coil motor.

The mold 18 includes a die 22 having a through hole 20.
It includes a lower punch 24 that is inserted into the through hole 20 in advance and an upper punch 26 that can be inserted into the through hole 20. Die 2
A cavity 27 is formed in the second through hole 20 by the die 22 and the lower punch 24. The distance between the upper punch side surface 26a and the through hole side surface 20a (see FIG. 2) is, for example, 10
It is set within the range of μm to 40 μm.

The die 22 is set in the die sets 28 and 30, and the feeder box 3 is placed on the die set 30.
2 is placed. A powder 34 such as an alloy powder for rare earth magnets having an average particle size of 3 μm to 6 μm is housed in the feeder box 32, and the feeder box 32 is connected to a hydraulic cylinder 38 via a cylinder rod 36. Therefore, the feeder box 32 can be moved back and forth with respect to the through hole 20 by the hydraulic cylinder 38. The powder 34 of the feeder box 32 is in contact with the upper surface of the die 22, and when the feeder box 32 is located above the cavity 27, the powder 34 of the feeder box 32 falls and is filled in the cavity 27.

Die set connecting plates 42 are attached to the lower surfaces of the die sets 28 and 30 via guide posts 40, respectively. The die set connecting plate 42 is the cylinder rod 4
4 is connected to the lower hydraulic cylinder 46. Therefore, the die 22 and the die sets 28 and 30 can be moved in the vertical direction by the lower hydraulic cylinder 46. The expansion / contraction amount of the cylinder rod 44, that is, the position of the die 22 is measured by the linear scale 48, and the operation of the lower hydraulic cylinder 46 is controlled based on the measured value.

The lower punch 24 is provided on the base plate 50, and the base plate 50 is arranged on the punch fixing table 14 via the columns 52. In this way, the lower punch 24 is fixed. The upper end of the upper punch 26 is attached to the upper punch plate 54. Upper punch plate 5
4 is an upper hydraulic cylinder 58 via a cylinder rod 56.
Connected to. The upper hydraulic cylinder 58 is arranged on the plate 16. Guide posts 60 are inserted near both ends of the upper punch plate 54. Therefore, the upper punch plate 54 is vertically movable by the upper hydraulic cylinder 58 while being guided by the guide post 60. The position of the upper punch plate 54, that is, the position of the upper punch 26 is measured by the linear scale 62, and the operation of the upper hydraulic cylinder 58 is controlled based on the measured value. A pair of pole pieces 64 and a coil 66 wound around the pole pieces 64 are provided in the vicinity of the die 22 so that an orientation magnetic field can be applied to the powder 34 filled in the cavity 27.

Referring to FIG. 2, in the circumferential direction near the upper end of the lower punch side surface 24a, the die 2 is inserted from the inside of the lower punch 24.
A large number of supply ports 70 capable of jetting and supplying the lubricant 68 are provided to the side surface 20a of the second through hole 2. An annular seal member 72 that seals a gap between the lower punch side surface 24a and the through hole side surface 20a of the die 22 is provided immediately below each supply port 70 on the lower punch side surface 24a. As the seal member 72, for example, an O-ring made of nitrile rubber or felt having a high sealing property is used.
By providing the seal member 72, it is possible to prevent the lubricant 68 from being sprayed downward of the lower punch 24 and to reliably spray it upward.

Inside the lower punch 24, a lubricant supply passage 74 whose one end is connected to the supply port 70 is provided. The lubricant supply passage 74 extends downward in the central portion of the lower punch 24 and comes out to the outside while being inclined and descending at a substantially intermediate portion. Lower punch 2
The other end of the lubricant supply passage 74, which is exposed to the outside of the No. 4, is connected to a pressure feed pump 76 for sending air to the lubricant supply passage 74 side via an air valve 78.

A three-way valve 80 for opening and closing a part of the lubricant supply passage 74 is connected to the supply passage of the lubricant supply passage 74. A recovery tank 82 for recovering the lubricant 68 in the lubricant supply passage 74 is connected to the three-way valve 80. The recovery tank 82 is arranged below the three-way valve 80. A branch pipe 84 is connected between the three-way valve 80 and the air valve 78. The branch pipe 84 is connected through a lubricant valve 88 to a supply tank 86 that stores the lubricant 68. Electromagnetic valves are used for the air valve 78, the three-way valve 80, and the lubricant valve 88, for example.

The pressure pump 76 operates when the die 22 moves upward before the powder 34 is filled in the cavity 27, and when the pressure pump 76 operates and the air valve 78 is opened. The lubricant valve 88 is opened so that the lubricant 68 is dripped from the supply tank 86 into the lubricant supply passage 74. Then, the lubricant 68 can be atomized by dropping the lubricant 68 into the compressed air (for example, a pressure of about 0.7 MPa) that is pressure-fed by the pressure pump 76. Atomized lubricant 6
8 is supplied from the supply port 70 to the side surface 20a of the through hole through the lubricant supply passage 74. Therefore, the supply port 70, the lubricant supply passage 74, the air valve 78, the pressure pump 76, the branch pipe 84, the lubricant valve 88, and the supply tank 86 constitute a supply unit that supplies the lubricant 68 in a mist state. When the lubricant 68 is supplied to the side surface 20a of the through hole, the three-way valve 80 is located on the upstream side (pressure pump 76
Side) is opened and the recovery tank 82 side is closed. Details will be described later. In FIG. 2, arrow A indicates the supply direction of the lubricant 68, and arrow B indicates the degassing direction.

Next, referring to FIG. 3, the powder pressing apparatus 1
The electrical configuration of 0 will be described. Powder press machine 10
Are controlled by the control unit 90. The control unit 90 includes a CPU 92 for calculating various information and controlling processing operations.
RA as a work area via BUS94 for 92
An M96, a ROM 98 storing a control program and the like and an I / O port (not shown) are connected.

The lower hydraulic cylinder 46 is attached to the I / O port.
And a hydraulic cylinder drive circuit 100 for linearly driving the upper hydraulic cylinder 58, linear scales 48 and 62,
A feeder box drive circuit 102 for expanding and contracting the hydraulic cylinder 38, a valve drive circuit 104 for opening and closing a three-way valve 80, an air valve 78, and a lubricant valve 88,
And a coil drive circuit 1 for generating a magnetic field in the coil 66
06 is connected. Further, the BUS 94 is connected with an operation panel 106 for inputting various information. Therefore, the control unit 90 controls a series of molding operations.

Next, referring to FIG. 4, the powder pressing apparatus 1
The main operation of 0, that is, the timing of the open / closed states of the three valves 78, 80 and 88 will be described. When the die 22 starts to rise in a state where the powder 34 is not filled in the cavity 27, at the same time, the upstream side of the air valve 78, the lubricant valve 88, and the three-way valve 80 are opened, and the recovery tank 82 side of the three-way valve 80 is opened. In the closed state, the lubricant 68 is sprayed on the side surface 20a of the through hole.
Is applied.

When the die 22 reaches the highest point,
Air valve 78, lubricant valve 88 and three-way valve 8
0 is closed on the upstream side, and the three-way valve 80 on the recovery tank 82 side is opened, so that the powder 34 is stored in the cavity 27.
Is supplied (powder packing density 1.8 g / cm ^{3 to} 3.0 g
/ Cm ³ ) It is compressed by the upper punch 26 and the lower punch 24. At this time, the lower punch side surface 24a and the through hole side surface 20a
The gap between and is sealed by the seal member 72,
The gas squeezed out from the powder 34 is the side surface 26a of the upper punch.
Except for discharging a very small amount from the gap between the side surface 20a of the through hole and the side surface 20a of the through hole, the lubricant flows back to the lubricant supply path 74 via the supply port 70,
It is discharged from the three-way valve 80. As a result, the powder 34 in the cavity 27 is degassed. In addition, the lubricant 68 accumulated in the lubricant supply passage 74 is recovered in the recovery tank 82. Since the lubricant supply passage 74 descends toward the three-way valve 80, the lubricant 68 in the lubricant supply passage 74 is smoothly recovered in the recovery tank 82.

While the die 22 descends to take out the molded body in the cavity 27, the recovery tank 82 side of the three-way valve 80 is closed. And again the cavity 27
The die 22 when the powder 34 is not filled in the die 22.
At the same time, the upstream side of the air valve 78, the lubricant valve 88, and the three-way valve 80 are opened, the recovery tank 82 side of the three-way valve 80 is closed, and the lubricant 68 is applied to the side surface 20a of the through hole. It is sprayed and applied. In FIG. 4, the lubricant valve 88 and the air valve 78 are always open when the lubricant is applied.
Actually, opening and closing are alternately repeated in a short cycle (for example, every 0.5 seconds).

By repeating such a series of operations, the lubricant 68 is applied to the side surface 20a of the through hole at a predetermined timing, and the gas in the cavity 27 is discharged from the three-way valve 80 through the lubricant supply passage 74. The lubricant 68 accumulated in the lubricant supply passage 74 is collected in the recovery tank 82.
Will be collected. By this, the density of 3.9 g / cm ³ ~
A molded body of 5.0 g / cm ^{3 with} no cracks or cracks is formed.

According to the powder pressing apparatus 10, the lower punch 2
The lubricant 68 can be reliably applied from the supply port 70 of No. 4 to the side surface 20a of the through hole of the die 22. Further, when the powder 34 is compressed by the upper punch 26 and the lower punch 24 in the cavity 27, the upstream side of the three-way valve 80 is closed and the recovery tank 82 side of the three-way valve 80 is opened. The gas inside 27 can escape through the lubricant supply passage 74. Therefore, the powder 34 filled in the cavity 27 can be easily degassed, the moldability can be improved, and the quality and yield of the molded body can be improved.

A recovery tank 82 is connected to the three-way valve 80, and the lubricant 68 remaining in the lubricant supply passage 74 can be recovered in the recovery tank 82. Therefore,
Since the next supply of the lubricant 68 is not hindered by the lubricant 68 remaining in the lubricant supply passage 74, the lubricant 68 can be vigorously injected, and the lubricant can be reliably applied to the side surface 20a of the through hole. 68 can be applied. Also,
The recovered lubricant 68 can be reused.

Furthermore, since the sealing member 72 is provided on the lower punch side surface 24a during powder compression, the gas in the cavity 27 cannot be discharged from the gap between the lower punch side surface 24a and the through hole side surface 20a of the die 22. ,Also,
Even if the gap between the upper punch side surface 26a and the through hole side surface 20a of the die 22 is very narrow and the gas in the cavity is difficult to be discharged from this gap, the gas in the cavity 27 is allowed to escape through the lubricant supply passage 74. You can

As described above, the average particle size of the powder 34 is 3 μm.
m to 6 μm, and the packing density of the powder 34 into the cavity 27 is about 40% to 60% of the compact density.
Therefore, even if the powder 34 in the cavity 27 contains a very large amount of gas, such a gas is supplied to the lubricant supply path 7
It can be thoroughly degassed through 4. Further, even if the powder 34 is a rare earth magnet alloy powder, it can be safely degassed. Further, when a value of (filling depth ÷ unit weight) of the cavity 27 is large, for example, when a vertically long block-shaped molded body is obtained, the quality of deaeration greatly affects the moldability. The present invention is particularly effective when it is obtained.

The supply port 70 is provided on the side surface 26a of the upper punch.
It may be provided on the through hole side surface 20a of the die 22 or the punch side surface 24a or 26a and the through hole side surface 2
0a may be provided. In this way, the lubricant 68 can be applied from the supply port 70 to at least one of the through hole side surface 20a and the punch side surface 24a or 26a. At this time, it goes without saying that the lubricant supply path is appropriately provided depending on the location where the supply port 70 is formed. Further, the lubricant 68 may be injected when the die 22 descends, and may be injected during both ascending and descending.

The seal member 72 may be provided on the upper punch side surface 26a or the through hole side surface 20a of the die 22, or the punch side surface 24a or 26a and the through hole side surface 20.
It may be provided in both a. The upper punch side surface 26
When the supply port 70 and the seal member 72 are provided in a, the seal member 72 is provided above the supply port 70.

Using the powder pressing device 10 as described above, the powder 3 in the cavity 27 is controlled by the three-way valve 80.
An experimental example comparing the case of forming a molded body by degassing No. 4 and the case of forming a molded body without degassing is shown below. As the powder 34, an alloy powder for rare earth magnets having an average particle diameter of 3.5 μm (MMD average particle diameter) is used, and 100 mm × 80 mm
300 × 80 mm compacts were produced. The orientation magnetic field was applied at 1.2 MA / m in the direction perpendicular to the compression direction of the powder 34.

When the compacts were produced without deaeration of the powder 34, 93 out of 300 compacts had cracks and cracks, while the compacts were produced by deaeration. There were no cracks or cracks on the surface. As can be seen from this, if the powder 34 in the cavity 27 is degassed according to the present invention, cracks and cracks of the molded body can be very effectively prevented, and the quality and yield of the molded body can be improved. Productivity can be improved.

[0037]

According to the present invention, the lubricant can be surely applied to the side surface of the through hole of the die and the side surface of the first punch,
Further, the powder in the cavity can be degassed and the powder can be compressed in the cavity, and the moldability can be improved. Therefore, the quality and yield of the molded product can be improved.

[Brief description of drawings]

FIG. 1 is an illustrative view showing a powder pressing apparatus according to an embodiment of the present invention.

FIG. 2 is an illustrative view showing a main part of a powder pressing apparatus according to an embodiment of the present invention.

FIG. 3 is a block diagram showing an electrical configuration.

FIG. 4 is a timing chart showing the opening / closing timing of each valve.

[Explanation of symbols]

10 Powder press equipment 20 through holes 20a side surface of through hole 22 die 24 Lower punch 24a Lower punch side 26 Top punch 26a Side of upper punch 27 cavities 34 powder 68 Lubricant 70 Supply port 72 Seal member 74 Lubricant supply path 76 Pressure pump 78 Air valve 80 three-way valve 82 Recovery tank 86 supply tank 88 Lubricant valve

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Claims (10)

[Claims] 1. A powder pressing device for compressing powder to form a compact, comprising: dies having through holes extending in the vertical direction, and moving in the through holes in the vertical direction relative to the dies. First and second punches capable of compressing the powder in the cavity formed in the through hole, and a supply means for supplying the lubricant to at least one of the through hole side surface and the first punch side surface of the die And a depressurizing device for discharging the gas generated from the powder during compression to the outside of the cavity. 2. The powder pressing apparatus according to claim 1, wherein the supply unit includes a lubricant supply passage, and the deaeration unit includes an opening / closing unit that opens and closes a part of the lubricant supply passage. 3. The powder pressing apparatus according to claim 2, further comprising a lubricant recovery unit connected to the opening / closing unit to recover the lubricant in the lubricant supply passage. 4. A seal portion provided on at least one of the first punch side surface and the through hole side surface so as to seal a gap between the first punch side surface and the through hole side surface. 4. The powder press device according to any one of 1 to 3. 5. The average particle diameter of the powder is 3 μm to 6 μm, and the distance between the side surface of the second punch and the side surface of the through hole is 10.
The powder pressing apparatus according to any one of claims 1 to 4, which has a size of μm to 40 μm. 6. The powder pressing device according to claim 1, wherein a packing density of the powder in the cavity is 40% to 60% of a density of the molded body. 7. The powder pressing apparatus according to claim 1, wherein the powder is an alloy powder for rare earth magnets. 8. A powder pressing method for forming a compact by compressing powder with a first punch and a second punch in a cavity formed in a through hole extending in a vertical direction of a die, wherein the die is penetrated. A first step of supplying a lubricant to at least one of the hole side surface and the first punch side surface, a second step of filling the powder in the cavity, and discharging gas contained in the powder in the cavity. A powder pressing method comprising a third step of compressing the powder with the first punch and the second punch to form the compact. 9. The lubricant is supplied through a lubricant supply passage in the first step, and the third step further includes a step of collecting the lubricant in the lubricant supply passage. 8. The powder pressing method according to item 8. 10. The powder pressing method according to claim 8, wherein the powder is a rare earth magnet alloy powder.