The Pursuit of Precision



Throughout the molding process, different operators and their methods have resulted in a lack of uniformity. This unstandardized way of operating has resulted in a lot of waste. Because of our deep understanding of common operator problems, we were able to strengthen our technical management and staff training to meet the needs of our customers.

The service life of any mold is indicative of its quality. There are three crucial factors which affect service life: abrasion, deformation and rupturing. Our dies are composed of tungsten carbide case and inserts. The link between abrasive resistance and non-destructive die cases are antagonistic, so precision and combination of the case and insert will determine the balance between the two.

Case Study:

The screw bolt of Volkswagen’s stainless-steel door lock

Production challenges: 

This bolt is made of stainless steel. Due to the difficulties of stainless steel’s plasticity, the service life of the punches and the die in the production process is not ideal, and it’s difficult to shape the screw bolt

Solution:  1 →

Choose high-quality stainless-steel materials with good surface alramenting

2 →

Use imported die steel and special stainless-steel alloy to make the mold

3 →

Adopt appropriate die steel heat treatment technology

4 →

The finish of the inner hole of the die reaches mirror level

Currently, this kind of bolt is used in all series models of Volkswagen, with stable life and quality.


High-quality polishing

High-quality die polishing is one of the chief factors affecting the dies’ life. What is the quality of the die polishing? How to polish? What’s the specific method?

High-quality mold polishing is not only to ensure the size of dies but also to guarantee the smoothness of the hole; the basis of the current measurement of smoothness is the wireless scar. Ra values represent the roughness and finished dies need to be between a margin of 0.01mm to 0.02mm for polishing. The Ra value after being polished can reach around Ra0.08mm to Ra0.04mm.

The specific method of polishing: ① rough polishing → ② cleaning → ③ semi-fine polishing → ④ cleaning → ⑤ fine polishing → ⑥ cleaning


Why so much emphasis on cleaning?

Mixing abrasive paste particles with differing degrees of thickness can produce poor polishing results. So, for irregular dies we use a better procedure.

We use an automatic polishing machine (fluid polishing machine) for the products from the LSWEDM machine. For irregular parts which require EDM, we typically use mirror discharge and fluid polishing. After manual polishing is complete, it will clean the 0.005~0.008s(5μ~8μ)electrocorrosion layer which is generated either from LSWEDM or electro-discharge.

Our polishing technology is at the highest level within the industry.


Differences between ordinary EDM and mirror discharge (EDM)

With the diversification of products and an ever-growing demand for irregular dies, these are the main problems:

① The unstable current easily causes carbon deposition (extensive area) in conventional EDM machines.

② The surface roughness of the die is poor after using the typical spark machine, polishing creates deformation, and it is difficult to polish thoroughly.

③ Currently, when the traditional cold forming molds need to process the head, most choose the conventional spark machine. The traditional spark machine requires changing the electrode and continually adjusting and centering it, resulting in highly inefficient processing.

Compared with the standard spark machine, the mirror discharge spark machine has distinct advantages. Currently, for tungsten steel products in the industry, most choose the Japanese mirror spark machine with tungsten steel power supply or the Swiss mirror spark machine which use oil and electricity.

It has the following advantages:

The output of the current is stable and no matter if operating in a large or small area, it will not accumulate carbon. The electrode will become smaller after use, resulting in smoother polishing precision.

Currently, the mirror spark machine can reach Ra0.16 smoothness after discharge. It can achieve a high level of smoothness (easy to polish) in a short time.

The spark machine usually carries a knife storehouse, which can be processed continuously for 24 hours. The efficiency is improved, requiring only a once-through after operation of sub-machining to go from the center back to zero.

Our company has replaced the standard spark machine with the mirror discharge spark machine.

Our certification conforms to GB, ANSI, JIS and DIN standards. JunGu provides products and services that meet customer and regulatory requirements allowing us to be more efficient and improve customer satisfaction.



Company Profile




Ph +86 137 6433 5488

WeChat ID: 137 6433 5488


Feng Lin road 1, Shuangfeng, Taicang,

Suzhou, Jiangsu 215400




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