1. The material granularity does not match and the hardness does not match.
Calculate the ingredients strictly according to the resinoid grinding wheel ingredient list, and review is a key procedure.
2. Mixed.Before mixing and during the mixing process, clean the tools and equipment. Before batching, check the raw materials of various resinoid grinding wheels for impurities.
3. Uneven mix.
Mix according to the mixing time required by the process. Replace mixer parts that are too worn at any time. Powdered resin materials must be sieved according to the screen mesh number and frequency specified in the process.
4. The structure is uneven and the hardness is uneven and unbalanced.
Adjust the dryness and humidity of the mixture to ensure good formability. Carry out spreading and scraping operations according to process requirements. Use the pad iron first according to the process requirements to maintain the accuracy of the press; when feeding, the scraping of the material is uneven, the mixture is too wet, or the material is agglomerated, the feeding is uneven, the mold is worn, and material leakage is serious, the mold needs to be replaced.
5. Cracks in the molding body.
The hot pressing temperature is too high, the product is cooled and heated rapidly, the temperature is too low when removing the core, the core should be removed in time, the raw material of the resinoid grinding wheel is affected by moisture and deteriorates, or the compounding materials are wrong.
5.1 End cracks. The molding material has poor plasticity and the mold removal method is improper. The bottom plate of the forming mold is uneven or the backing plate is too non-parallel.
5.2 Peripheral cracks. The mold sleeve is severely worn and is too skewed when removing the mold sleeve.
5.3 Aperture cracks. The strength of the blank is low, the vibration is too great when unloading the mold, the mandrel is too worn or the taper is too small, and the order of unloading the mold does not comply with the process regulations.
5.4 Diagonal cracks. The selected spring pad iron has inconsistent elasticity, causing the mold to deviate and be compressed to produce diagonal lines. The pressing speed of the fine-grained abrasive tool is too fast, the pressure maintenance time is short, and the mold fitting gap is too large.
5.5 The above crack prevention measures: adjust the speed to ensure the plasticity of the mixture, the molding tool and mold must not exceed the specified wear standards, the template and pads should be kept in good flatness, the thickness of the pads should be consistent, and the elasticity of the spring pads should be consistent. The process stipulates the order of mold removal.
6. The two end faces are not parallel.
Maintain the accuracy of the press pressing table and operate according to the resinoid grinding wheel process regulations.
7. The surface is uneven.
Work equipment is maintained within the required accuracy range.
8. The molding hardness does not match.
The first pressed piece must be inspected, and no less than 30% of each batch of blanks shall be randomly inspected. The unit weight shall be checked and weighed frequently, and pressure changes shall be observed frequently.
9. The bridge is uneven.
The cooling needs to be uniform; the "warped" surface of the workpiece without a flat surface is called a bridge. This is caused by uneven cooling that causes the parts to shrink inconsistently or the furnace pad is uneven. Mostly come from thin grinding wheels and fine-grained thin products. Thin disc grinding wheels can easily produce corrugated waste products when the cooling rate is too fast.
10. Blister.
Temperature hardening is controlled according to the hardening curve of the resinoid grinding wheel product specification, and the compounding process is subject to strict quality control; if the molding temperature is too high or too low, the temperature needs to be adjusted. The curing temperature is too high and the curing oven temperature is out of control. The bonding agent is mismatched; the local surface of the superhard abrasive tool is convex and deformed or the entire surface swells and becomes resinous, and some have turtle-like cracks. Causes:
10.1 If the heating rate is too fast or the temperature fluctuation is large, it is easy to cause foaming and expansion of parts with fine particle size, high hardness and tight structure. Because this type of product contains a large amount of binder or has small pores, if the temperature control is inaccurate and the heating rate is too fast, the binder will react violently, the amount of volatile matter will increase sharply, and the gas pressure inside the green body will be high, causing the product to bubble and expand.
10.2 The molded material is mixed unevenly, and there are lumps of binder in the material or it contains a lot of solvents with lower boiling points (such as ethanol, acetone).
10.3 Due to errors in the mixing and molding processes, the bonding dose of the part increases, the unit weight increases, the pressure increases, etc.
