#rough machining

Drum brake is one of the main parts of the automotive, and belong to consumables, the surface roughness require about Ra1.6.We can choose a suitable insert to get better surface roughness while not affect the manufacture benefit. 

Part 1 Machining drum brake process

In current times, the brake drum brake main materials are gray cast iron. Gray cast iron has good shock absorption and wear resistant, and low noisy, it need simple process.

General process as follows:

Casting-Roughing-Semi-Finishing-Finishing-Drilling-Test.

(1)  Casting: when machining the drum brake, need control the charge mass, also the chemical composition of the molten iron, the pouring temperature, proper ingredients, avoiding casting defects, such as clip sand, porosity, white and so on.

(2)  Roughing: Manufacturers usually use CNC lathe machining the drum brake. Advantages(1.reduce the rejection rate of the work piece, 2.improve the processing efficiency. )

Roughing brake drums need about 0.5mm working allowance for subsequent semi-finishing and finishing guarantee finish requirements.

Part 2 The insert selection of rough machining drum brake

Process the drum brake need three steps,rough machining allowance within 3mm, and the brake drum need a high demand. In the process, it is important to ensure dimension, but improve processing efficiency,

Insert selection required:

1.High-speed cutting

2.Reducing processing time and improving processing efficiency.

First, manufacturers will use carbide insert, but its linear speed is low ,can not satisfy the requirements. So when meet machining gray cast iron with high speed, manufacturer will choose cbn insert which will not only improving the working efficiency, but also save the processing cost.

 Especially Halnn BN-S30 and BN-K20 CBN insert, will be more effective for machining drum brake.

Part 3 Select the most suitable cbn insert for different process

(1) Roughing:When the working allowance within 3mm, select BN-S30 CBN insert, which not only has high hardness and high strength, but also has better wear-resistance and impact-resistance. Following show the figure on BN-S30 CBN insert machining brake drum:

Cutting parameters: ap=1-10mm,Fr=0.2-1mm/r,Vc = 200-800m/min. Processing effect: BN-S30 CBN insert lifetime with one cutting edge will be15 times than the coated carbide insert.

(2)Semi-finishing: Working allowance within0.5mm, BN-S30 CBN insert Cutting parameters: ap≤1mm, Fr = 0.05-0.3mm / r, Vc = 300-1500m / min.

(3)Finishing: within margin of 0.3mm, select BN-K20 CBN insert ,which will be more economical, can make sure the braking surface finish and mouth stop finish and dimension tolerances.

Following is the figure of BN-K20 CBN insert machining surface and mouth stopper .

Cutting parameters: ap≤1mm, Fr = 0.05-0.3mm / r, Vc = 300-1500m / min. Processing effect: BN-K20 CBN insert finish turning to ensure roughness Ra1.0, the single cutting edge lifetime is about 2 times than other PCBN insert.

Halnn is the most famous cbn insert brand in China, and always devote to researching new cbn insert to satisfy customers’ requirements.