Some manufacturers are troubled by many quality problems in the production process of resin grinding wheels. Today, the editor specially found some common problem analysis and solutions, hoping to exchange and learn with you~

1 The particle size and hardness of the material do not match.

Strictly calculate the ingredients according to the ingredient list, review is the key procedure

2 inclusions

Before and during the mixing process, clean up the tooling and equipment. Before batching, check the various raw materials for impurities

3 uneven mixing

According to the process requirements, the mixing time is mixed. Replace mixer parts that are too worn at any time. The powdered resin material should be sieved according to the screen number and times specified in the process

4 Uneven structure, uneven hardness and unbalanced

Adjust the dry humidity of the mixture to make it have good formability. Carry out spreading and scraping operations according to process requirements. According to the process requirements, first use the pad iron to maintain the precision of the press; when feeding, the material is unevenly spread and scraped, the mixed material is wet, or the material is agglomerated, the feeding is uneven, the mold is worn, and the leakage is serious, so the mold needs to be replaced

5 Formed body cracks

If the hot pressing temperature is too high, the product will be cooled and heated rapidly. When the core is removed, the temperature is too low. The core should be removed in time.

The following four crack prevention measures:

Adjust the speed to ensure the plasticity of the mixture. The forming tools and molds must not exceed the specified wear standard. The formwork and pad iron should maintain good flatness. The thickness of the pad iron should be consistent, and the elasticity of the spring pad iron should be consistent.

6 Cracks on the end face

The plasticity of the molding material is poor, and the method of unloading the mold and taking the blank is improper. The bottom plate of the forming mold is not flat or the backing plate is not parallel too much

7 Peripheral cracks

The mold sleeve is seriously worn, and when the mold sleeve is removed, it is too deflected

8 Aperture cracks

The strength of the blank is low, the vibration is too large when unloading the mold, the mandrel wears too much or the taper is too small, and the unloading sequence does not conform to the process regulations

9 diagonal cracks

The selected spring pad iron has inconsistent elastic force, which causes the mold to be deflected and compressed to produce diagonal lines. The pressing speed of the fine material grinding tool is too fast, the pressure maintenance time is short, and the mold fit clearance is too large

10 The two ends are not parallel

Maintain the precision of the pressing table of the press and operate according to the process regulations

11 uneven surface

Maintenance of tooling equipment within the required accuracy range

12 Forming hardness does not match

The first piece to be pressed must be inspected, and each batch of blanks is not less than 30%, and the weighing unit weight is often checked, and the pressure is often observed for changes.

13 The bridge is uneven

The cooling needs to be uniform; the surface of the workpiece is "warped" and there is no flat plane called bridge flute. This is caused by uneven shrinkage of the workpiece due to uneven cooling or unevenness of the backing plate for the furnace. Most of them come from thin slice grinding wheels and fine-grained thin products. Flake grinding wheels are prone to bridging waste when the cooling rate is too fast

14 Blistering

Carry out controlled temperature hardening according to the hardening curve of the product specification, and strictly control the quality of the compounding process; if the molding temperature is too high or too low, the temperature needs to be adjusted. The curing temperature is too high, and the temperature of the curing oven is out of control. The binder is mismatched; the local surface of the superhard abrasive tool is convex and deformed or the entire surface is swollen, and it has a resinous luster, and some have turtle-like cracks.

Causes:

1 If the heating rate is too fast or the temperature fluctuates greatly, it is easy to cause foaming and expansion of the parts with fine particle size, high hardness and tight structure. Because this type of product contains a lot of binder or has small pores, if the temperature control is not accurate and the heating rate is too fast, it will cause the binder to react violently, the amount of volatiles will increase sharply, and the gas pressure inside the green body will cause foaming and expansion of the product.

2. The molding material is not mixed evenly, and there are binder lumps or more solvents with lower boiling points (such as ethanol, acetone) in the material.

3 Due to errors in the mixing and molding process, the combined dosage of the part increases, the unit weight increases, and the pressure increases.

15 Deformation and collapse

Carry out furnace loading and temperature control operations according to the process regulations. The ratio between fillers should be strictly controlled and adjusted, and there is interaction between fillers. When the cutting discs are stacked, the pressure will be insufficient and they will be deformed.

The reasons for the deformation and collapse of superhard abrasive tools during the hardening process are as follows:

1. When the furnace is loaded, the green body is exposed outside the hardened backing plate or the green body is squeezed together, and the green body is tilted due to the uneven backing plate.

2 The high-thickness parts were not filled with paper and sand according to the process regulations.

3 The natural drying time is short or it is hardened directly into the furnace without drying at low temperature.

4. If the heating rate is too fast, the binder will melt sharply, causing the green body to soften and then collapse.

16 hearts

The exhaust system of the hardening furnace needs to be unimpeded, and the hardening operation should be performed according to the hardening curve of the product specification, and should be controlled correctly. For the blank of the liquid resin material, a porous backing plate or a ceramic backing plate should be used; Are easy to break.

cause:

1 The exhaust system of hardening equipment is poor, and exhaust gas is difficult to discharge.

2 The hardening curve is unreasonable, and the heating rate is too slow.

3 The backing plate of the liquid resin blank has poor air permeability.

4 The resin free phenol content of the liquid resin material is too high and the solid content is too low.

17 Hardening hardness discrepancy and rotary fracture

According to the correct temperature control operation according to the hardening curve, the hardening of powdery resin blanks must be covered or buried with sand. During the process of loading and unloading, the blanks should not be shaken. The superhard grinding tool breaks during the test rotation, which is caused by low bonding strength or cracks in the grinding tool.

The reason is:

1 If the hardening temperature is too high, the bonding agent has been partially carbonized, which reduces the strength of the abrasive tool.

2 The compounding error, such as the addition of too much abrasive, the lack of bonding agent, or the poor quality of the bonding agent itself reduces its strength.

3 Violent vibration during mold unloading, transportation, and furnace loading will cause mechanical damage to the workpiece and dark cracks inside.

4 The structure of the grinding wheel is uneven, and the number of unbalanced grams is too large.

5 The grinding wheel is seriously eccentric or the hole diameter is too large.

18 Cutting discs come off the grid during use

The quality of the resin powder, resin solution and mesh should be qualified, and the process formula should be reasonable, so that the above-mentioned problems basically do not exist. In some fractures, the abrasive grains are coarse, the structure is loose, and the binder is missing. The mesh cloth will be pulled off a little. These defects are related to the improper manufacturing process.

19 The hardness and strength of the finished product do not match

1 The quality of the resin is unstable, and the free phenol content of the resin fluctuates from high to low. The so-called free phenol is the phenol remaining in the resin. The molecular formula is C6H5OH. Long-term heating can crack the hardened resin and affect the strength of the grinding wheel.

2 The mixture of resin powder and urotropine is uneven. The scientific name of urotropine is hexamethylenetetramine ((CH2)6N4). As a hardener for resin, the amount of urotropine added is insufficient, and the resin hardens incompletely. , affecting the strength and hardness of the grinding wheel; if the content is too high, the excess urotropine will not combine with the resin, and will decompose and volatilize during the hardening process, increasing the pores of the grinding wheel and reducing its strength and hardness.

3. The particle size of the binder is too coarse, and the particle size of the binder should be finer, which is conducive to the uniform distribution of the binder and the full contact of the hardener. If the particle size is too coarse, the molding material is not easy to mix evenly, which will affect the hardness and strength of the grinding wheel. Even for resin flake cutting wheels and cymbal-shaped grinding wheels with relatively coarse particle sizes, the particle size of the selected binder (resin powder) should be finer than 320#. To manufacture fine-grained grinding wheel products, the particle size of the bond is required to be several microns.

20 Dropped edges and corners

Care should be taken after molding and until hardening to ensure that the edges of the workpiece are intact and avoid mechanical damage. Dropped edges and corners are mostly caused by careless handling during furnace loading and transportation. For unskilled workers, training should be strengthened to improve their skills. The green body of the resin abrasive tool has low wet strength and should be transferred or picked up by the flip method, and the green body cannot be moved directly by hand.