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Methods To Reduce The Defect Of Plastic Mold
Oct 24, 2017

Methods to reduce the defect of plastic mold

As an important tool for the manufacture of the workpiece, the mould will inevitably have some defects in the process of processing, which will lead to the production of the workpiece, which cannot be used properly or even used as a waste product.


In order to make the relevant workpiece better, I will give you the seven points of attention, hoping to help you.


1) reasonable selection and dressing of grinding wheel

Use white corundum grinding wheel is better, it is the performance of hard and brittle, and easy to produce the new cutting edge, so the cutting force is small, the grinding heat is small, use medium granularity on granularity, such as 46 ~ 60 mesh is better, on the grinding wheel hardness by using soft and soft (ZR1, ZR2 and R1, R2), namely, coarse granularity, low hardness of the grinding wheel, good self excitation can reduce heat cutting.

Of selecting the appropriate fine grinding wheel is very important, in view of the condition of the die steel with high vanadium high molybdenum, choose GD is suitable for single crystal corundum grinding wheel, when processing hard alloy, high quenching hardness of materials, the priority of using organic binder of diamond grinding wheel, since the organic binder grinding wheel grinding, grinding the workpiece roughness of Ra0.2 microns,

In recent years, with the application of new materials, CBN (cubic boron nitride) grinding wheel shows very good processing effect, in the numerical control molding grinding, jig grinding machine, CNC finishing on inside and outside grinder, grinding wheel is better than other species.

In the grinding process, the grinding wheel should be repaired in time to keep the grinding wheel sharp. When the grinding wheel is passivated, the surface of the workpiece will be skidded and squeezed, causing the surface burns and the strength of the workpiece to be reduced.


2) reasonable use of cooling lubricant

The three functions of cooling, washing and lubrication can be used to keep the cooling and lubrication clean, so that the grinding heat can be controlled to prevent thermal distortion of the workpiece.

To improve the cooling conditions of grinding, such as the use of leaching oil sands wheel or inner cooling grinding wheel.

The cutting fluid is introduced into the center of the grinding wheel, and the cutting fluid can be directly entered into the grinding zone to play an effective cooling role to prevent surface burns of the workpiece.


3) reduce the quenching stress after heat treatment to a minimum

Because the hardening stress and reticular carbonization tissue are under the action of the grinding force, the tissue produces the phase transition easily causing the workpiece to crack.

In order to eliminate the residual stresses of grinding, the high-precision die should be treated with low temperature to improve toughness after grinding.


4)Eliminate the grinding stress

But will die in 260 ~ 315 ℃ of salt bath at 1.5 min, and then in 30 ℃ oil cooling, so can drop 1 HRC hardness, residual stress reduced by 40% ~ 65%.


5)Pay attention to the effect of temperature

For the precision grinding of precision molds within 0.01mm of dimension tolerance, it is important to pay attention to the influence of ambient temperature and require constant temperature grinding.

By calculating, the 300 mm long steel, temperature 3 ℃, the change of the material there are about 10.8 microns, (10.8 = 1.2 * 3 * 3, 1.2 mu per 100 mm deformation mm / ℃), various finishing processes are required to fully consider the influence of this factor.


6) use electrolytic grinding to improve the precision and surface quality of mould

Electrolytic grinding, grinding wheel shaving oxide film: instead of grinding, metal and small grinding force, grinding heat is small, won't produce the phenomenon such as grinding burrs, cracks, burns, surface roughness can be better than general Ra0.16 microns;

In addition, the grinding wheel wear small, such as grinding hard alloy, silicon carbide grinding wheel wear is about for grinding of cemented carbide of the weight of 400% ~ 600%, electrolytic grinding, grinding wheel wear is only hard alloy grinding in addition amount of 50% ~ 100%.


7) reasonable selection of grinding dosage

The fine grinding method with the radial intake is small and even fine grinding.

Such as appropriate to reduce the radial feeding and grinding wheel speed, increase the axial feeding, reduce grinding wheel and workpiece contact area, cooling condition is improved, so as to effectively control the improvement of surface temperature.


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