L20 Processing / Seperating

Name three different applications of shearing.

Cutting sheet metal in automotive manufacturing, electrical enclosures, and appliance casings.

What are the main differences between conventional shearing and fine blanking?

Fine blanking uses additional tools (e.g. counterholder, vee ring), smaller shearing gap (0.2-0.5%), and results in smoother edges with little post-processing needed.

What type of material is predestined for shearing?

Ductile materials like mild steel and aluminum are well-suited for shearing due to their ability to plastically deform before fracture.

What are the advantages of Shearing / Fine Blanking in terms of industrial usage?

High-speed mass production, good dimensional accuracy, smooth cut surfaces, and minimal material loss.

How is the shear resistance ks defined?

ks = c × Rm, where c is the relative shear resistance and Rm is the ultimate tensile strength.

What are approximate values for the relative shear resistance for a) Aluminium and b) ductile materials?

a) Aluminum: c ≈ 0.6-0.65, b) Ductile materials: c ≈ 0.8-0.9.

Name at least 4 measures to decrease the maximum cutting force

Use beveled punch, plane grind, convex/concave punch shapes, reduce shearing gap appropriately.

Draw the effect of three different impact factors on the shear resistance (qualitatively) - e.g.: Shearing Gap, max. Tensile stress, Elongation at break, ...

(Verbal summary:) Increasing shearing gap reduces Fs_max but worsens edge quality; higher tensile strength increases ks; greater elongation at break generally reduces ks due to improved ductility.

What are some of the problems that can occur during shearing?

Burr formation, punch wear, poor edge quality, material distortion when punching too close to the edge.

Name one advantage and one disadvantage of Wedge Cutting (2 blades) over Shearing

Advantage: Higher cut quality. Disadvantage: Higher wear and cost.

Describe the principle of water jet cutting

High-pressure water (often with abrasives) is focused through a small nozzle to erode material by high-velocity impact.

Name 2 advantages and 2 disadvantages of water jet cutting

Advantages: Cuts hard materials precisely without heat-affected zones; environmentally friendly. Disadvantages: Expensive nozzle materials; slower than laser/plasma cutting.

What are the limitations for using plasma arc cutting, in terms of material and max. thickness?

Only electrically conductive materials; effective up to ~150 mm thick, but most efficient between 4-20 mm.

Name and describe the 3 different laser cutting techniques. Which one has the highest energy consumption?

Laser Flame Cutting: laser + oxygen (burning). Laser Fusion Cutting: laser melts material, assist gas removes it. Sublimation Cutting: laser vaporizes material. Highest energy consumption: Sublimation Cutting.

Why is the purity of the process gas important?

Impurities can affect cut quality, speed, and edge finish by introducing oxidation or turbulence in the gas flow.

What are the OEM's standards for Nitrogen and Oxygen in laser cutting?

Nitrogen: 99.998% (N2 4.8); Oxygen: 99.95% or higher. Even 50 ppm O2 impurity can reduce cut quality.