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Molding technology of superhard material resin abrasives (3)
- Nov 09, 2018 -

3. Molding


According to the process flow, the following steps are taken:


(1) Preparation of the substrate


The aluminum substrate is contaminated with oil and impurities during processing. The substrate must be cleaned with gasoline or xylene before use. Then, epoxy or liquid phenolic resin is applied to the contact between the substrate and the material to ensure the abrasive and the substrate. a strong combination. In particular, for a substrate without a non-diamond layer, the joint portion has no knurling and grooves, and the adhesive should be applied.


(2) Assembly of the mold


The part in contact with the molding material is evenly coated with a release agent, such as molybdenum disulfide, zinc stearate, soap liquid, silicone grease, etc., so as to prevent the grinding wheel from being stuck by the mold wall and at the same time reducing The external friction of the material layer and the mold wall during molding to avoid pressure loss as much as possible. Then the base body is assembled on the turntable for use.


(3) Non-diamond layer pressing


Put the non-diamond material into the cavity, mix it evenly and tamping it; if it is difficult to feed once, it can be divided into two or three times, and then pressed with the feeding ring; then put on the pressure ring and send it to the press for cold. Pressure. Cups, bowls, saucers, single-sided concave, double-sided concave grinding wheels, pressurized to make the non-diamond layer and the substrate at the same level. The parallel grinding wheel is cold pressed to 1.5 to 2 times the required thickness.


(4) Diamond layer pressing


Remove the non-diamond layer blank, roughen the contact surface of the non-diamond layer and the diamond layer, apply a layer of epoxy-like adhesive, re-mold; then put the diamond layer, stir, flatten, and compact; Put the pressure ring and horn on, put it into the hot press for pre-pressing; after the flattening on the top, remove the horn under the die sleeve, and then pressurize the bottom plate into the mold sleeve. The purpose of adding horn is to make the two sides of the mold evenly pressed, and to ensure that the density of the grinding tools is consistent.


1. Molding pressure Since the adhesive softens and flows during the hot pressing process and fills all parts of the cavity, it does not require too high molding pressure, and the unit pressure is usually 30 to 60 MPa.


2. Pressurization speed Because the particle size of the molding material is fine, the speed is too fast, the air is not easy to run out, and it is easy to cause the layering and foaming waste. Therefore, the pressing speed is usually slow; and after pressing for a period of time, the pressure is released and deflated. Allow air and volatiles to escape sufficiently and then repressurize to the specified size.


3. Hot pressing temperature The phenolic resin is (180 soil 5) ° C; the polyimide resin is (235 ± 5) ° C.


4. Hot pressing time: varies with the specifications of the grinding wheel.


(5) Unloading


After the grinding tool is finished, after it is taken out from the press, it is rapidly cooled, and the mold sleeve, the core rod, the core body, the pressure ring, etc. are removed. This operation should be carried out by mechanical unloading conditions to avoid impact, so as to prevent the grinding tool from being Damaged when unloading the mold. The phenomenon of thermal expansion and contraction of the resin is remarkable, and the shrinkage after cooling is relatively large, which affects the mold release. In order to ensure the quality of the product, some grinding wheels can not be cooled, and hot stamping is required: such as BW2, D2, PSX, PDX. The powder base grinding wheel needs a hot unloading mandrel; B, BW, D, PDA, PSA need to be hot-discharged.


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