• 2023-08-14
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• 5 Comments

Die mold polishing method and working principle

Die mold polishing usually uses the whetstone strip, wool wheel, sandpaper, etc., so that the surface of the material has plastic deformation and remove the convex part of the workpiece surface to get a smooth surface, which is generally based on manual operation. High surface quality requirements can be used by super finishing polishing method, super finishing polishing is the use of special abrasive tools, in the polishing liquid containing abrasive, tightly pressed on the workpiece to be processed on the surface, for high-speed rotation. A surface roughness of Ra0.008μm can be achieved by polishing.

1. Tools and specifications commonly used in mold polishing

The common tools for polishing molds are: sandpaper, whitetstone, felt wheel, grinding paste, alloy file, diamond sharpening needle, bamboo, fiber whitetstone, round rotating sander.

Sandpaper: 150#, 180#, 320#, 400#, 600#, 800#, 1000#, 1200#, 1500#;

Oil stone: 120#, 220#, 400#, 600#;

Felt wheel: cylindrical, round, square beak;

Grinding paste: 1# (white) 3# (yellow) 6# (Orange) 9# (green) 15# (blue) 25# (brown) 35# (red) 60# (purple);

File: square, round, flat, triangular and other shapes;

Diamond needle grinding: generally 3/32 handle or 1/8 handle, with round waveform, cylindrical, long straight column shape, long round vertebral shape;

Bamboo: various shapes suitable for the operator and mold shape, the role is to press sandpaper, grinding on the workpiece, to achieve the required surface roughness;

Fiber stone: 200# (black) 400# (Blue) 600# (White) 800# (Red)

2. Polishing process

(1) Rough throwing

The surface after finishing milling, EDM, grinding and other processes can be polished by a rotating surface polishing machine with a rotating speed of 35000 ~ 40000 r/min. Then there is the manual grinding of the whetstone, a strip of whetstone with kerosene as a lubricant or coolant. The order of use is 180#→240#→320#→400#→600#→800#→1 000#.

(2) Semi-fine throwing

Semi-finish polishing mainly uses sandpaper and kerosene. The number of sandpaper is: 400#→600#→800#→1000#→1200#→1500#. In fact, #1500 sandpaper is only suitable for hardened Die mold steel (52HRC or more), and is not suitable for pre-hardened steel, because it may cause surface damage to the pre-hardened steel and cannot achieve the desired polishing effect.

(3) Fine throwing

Fine polishing mainly uses diamond grinding paste. If diamond grinding powder or paste is mixed with a polishing cloth wheel, the usual grinding sequence is 9μm (1800#) →6μm (3000#) →3μm (8000#). A 9μm diamond abrasive paste and polishing cloth wheel can be used to remove hairmarks left by 1 200# and 1 500 # sandpaper. It is then polished with sticky felt and diamond paste in the order of 1μm (14,000 #) →1/2μm (60,000 #) →1/4μm (100,000 #).

(4) Polishing working environment

The polishing process should be completed separately in two working locations, that is, the rough grinding processing site and the fine polishing processing site are separated, and attention should be paid to cleaning the sand remaining on the surface of the workpiece in the previous process.

Generally, after rough polishing with oil stone to 1200# sandpaper, the workpiece needs to be transferred to a clean room for polishing to ensure that no dust particles in the air stick to the surface of the mold. The polishing process requiring accuracy above 1μm (including 1μm) can be carried out in a clean polishing room. For more precise polishing, it must be done in an absolutely clean space, because dust, smoke, dandruff and drool can destroy the highly polished surface.

After the polishing process is completed, the surface of the workpiece should be protected against dust. When the polishing process stops, all abrasive agents and lubricants should be carefully removed to ensure that the surface of the workpiece is clean, and then a layer of mold anti-rust coating should be sprayed on the surface of the workpiece.