25 frequently asked questions in the field of mold manufacturing

- Mar 30, 2019-

1) what are * important and * decisive factors in the selection of die steel?


Forming method - two basic material types are available.


A) hot working tool steel, which can withstand relatively high temperatures during die casting, forging and extrusion.


B) cold working tool steel, which is used for blanking and shearing, cold forming, cold extrusion, cold forging and powder compression forming.


Plastics - some plastics produce corrosive byproducts, such as PVC.Corrosion can also result from condensation, corrosive gases, acids, cooling/heating, water, or storage conditions due to long downtime.In these cases, stainless steel die steel is recommended.


Die size - prehardened steel is often used for large die sizes.Integral hardened steel is often used in small die sizes.

Number of die USES - for long term use (>1000000) dies should be made of high hardness steel with a hardness of 48-65hrc.Prehardened steel with a hardness of 30-45hrc shall be used for molds with medium long life (100000 to 1000000 times).Short life (surface roughness) - many plastic mold manufacturers are interested in good surface roughness.When sulfur is added to improve metal cutting performance, the surface quality will decrease accordingly.Steel with high sulfur content also becomes more brittle.


2) what are the primary factors that affect the machinability of materials?


The chemical composition of steel is very important.The higher the alloy content of steel, the more difficult it is to work.When carbon content increases, metal cutting performance decreases.


The structure of steel is also very important for metal cutting performance.Different structures include: forged, cast, extruded, rolled and machined.Forgings and castings have very difficult surfaces to work on.


Hardness is an important factor affecting metal cutting performance.The general rule is that the harder the steel, the harder it is to work.High speed steel (HSS) can be used to process materials with hardness * 330-400hb;High speed steel + titanium nitride (TiN) coating, machinable hardness * 45HRC material;For materials with hardness of 65-70hrc, cemented carbide, ceramics, cermet and cubic boron nitride (CBN) must be used.


Non - metallic impurities generally have adverse effects on tool life.For example, Al2O3 (alumina), which is pure ceramic, has a strong abrasion.


* the latter is residual stress, which can cause metal cutting performance problems.Stress relief procedures after rough machining are often recommended.


3) what are the production costs of mold manufacturing?


Roughly speaking, the cost distribution is as follows:


Cutting 65%

Workpiece material 20%

Heat treatment 5%

Assemble/adjust 10%


It is also very clear that good metal cutting performance and excellent overall cutting solutions are important to the economic production of molds.


4) what are the cutting characteristics of cast iron?


In general, it is:


The higher the hardness and strength of cast iron, the lower the metal cutting performance, and the lower the life expectancy from the blade and cutter.