Analysis and Processing of Special-shaped Sheet Metal Parts

Analysis and Processing of Special-shaped Sheet Metal Parts

Ⅰ. The Structure of the Work Piece

Figure 1 shows the metal skeleton on a fitness equipment. The shape is irregular and the material is Q235. Each fitness equipment needs a metal skeleton, which is mainly formed by welding the five parts shown in the figure.

Figure 2 shows the main support. The profiles that need to be used are mainly 36mm × 36mm × 3mm angle steel and φ32mm × 2mm steel pipe.

It is required that after processing and forming, it can be properly installed with supporting parts without interference.

Panel skeleton

Figure 1 Panel skeleton

 

  • Left angle steel
  • The main support
  • Conversion Card
  • Heart rate tube
  • Right angle steel

Main support

Figure 2 Main support

Ⅱ. Analysis of Process Plan

Graphically, the difficulty of part processing lies in the processing of the main support and the welding of the main support to the left and right angle steel.

(1) Main support: The designer originally considered the use of 36mm × 36mm × 3mm angle steel profiles for tailor welding. In the actual processing process, the angle steel needs to be machined first, and the individual parts are processed and formed, and then the tailor welding is performed.

Due to the large number of tailor-welded angle steels and the difficult to control the angle during the tailor-welding process, it is difficult to guarantee the size. Therefore, it is not recommended to use angle welding in the process, but to use other processes.

Considering the company’s actual processing capacity, the company has a laser cutting machine that can cut steel plates up to 6mm thick, with high processing efficiency. The bending and forming after the steel plate is staked out can improve the processing efficiency and accuracy, so the laser cutting of the 3mm steel plate and the inner hole are bent and welded.

Through the calculation and analysis of the unfolded material, it is found that the unfolded material of the adjacent bent parts on the main support will interfere, so it is necessary to remove three folds at intervals, and the welding process is used to form it. It is found through the discharge that if one stake out is adopted, the surplus material will be wasted seriously.

Considering that the main support is a left-right symmetrical structure, it can be disconnected from the middle, saving waste loss during discharge. In the later stage, tooling welding is adopted, which does not affect performance and strength.

The unfolded material is shown in Figure 3.

Main support unfolding material 1

Figure 3 Main support unfolding material 1

The forming of the main support can be completed by the lofting bending and welding process.

(2) Welding of main support and left and right angle steel:

The main difficulty is that the twist angle of 1.2 ° needs to be considered when welding the left and right angle steel to the main support. The position of the twist point is at 1mm as shown in Figure 1.

Welding must be performed after precise positioning through the tooling to meet the requirements for use. The difficulty lies in the production of the welding tooling.

Ⅲ. Tooling Design

It can be known from the process analysis that the tooling design mainly considers the positioning and clamping of the main support and the left and right angle steels, and the forming of the panel skeleton also includes the welding of the adapter plate and the heart rate tube.

Therefore, the design of the welding tool needs to take into account the welding forming of the entire panel framework.

(1) Positioning and clamping of the main support:

The shape of the main support and the location of the positioning pin holes can be used to completely position the main support, and the edges to be welded can be aligned with the end faces.

(2) Positioning of left and right angle steel:

Add one wedge on each side and the height is 36mm, which is consistent with the main support. Position the wedge with the main support as the reference, plan the left and right angle steel twist angles on the wedge, and locate the twist angle between the left and right angle steel and the main support through the forming angle of the wedge.

Another inclination angle between the left and right angle steel and the main support is achieved by using a pad support to achieve the inclination angle of the left and right angle steel.

(3) Positioning of the heart rate tube:

Adding a U-shaped plate to the outer circle of the heart rate tube on the tooling can realize the positioning of the heart rate tube. The part that interferes with the heart rate tube is removed by machining.

(4) Positioning of the conversion card:

Welding the positioning plate on the tooling to position the adapter plate to move laterally, and welding the positioning plate in the square hole to move the conversion card longitudinally, can achieve complete positioning of the adapter plate.

Panel framework welding tooling

Figure 4 Panel framework welding tooling

Left Angle Steel Positioning Tooling

Figure 5 Left Angle Steel Positioning Tooling

Positioning Pin

Figure 6 Positioning Pin

Ⅳ. Processing Technology

(1) Left angle steel as well as right angle steel:

Discharging → Punching, Blanking → Bending

(2) Rotating bracket connection plate:

Discharging → Laser cutting → Bending forming

(3) Heart rate armrest tube:

Use pipe bender and pipe bending tool (see Figure 7) for pipe bending → Drilling and milling to form the total length

Pipe Bend Tooling

Figure 7 Pipe Bend Tooling

(4) Main support:

① Discharging → Laser cutting the shape and inner e-hole of the unfolded material 1 (see Figure 3), unfolded material 2 (see Figure 8), the quantity is cut according to 2: 1 → Bending the unfolded material 1, both sides of the hem, symmetrical left and right, parts need to be folded symmetrically.

② The shearing machine cuts the steel plate into 3mm × 33mm × 157mm, the number is the same as the number of unrolled parts.

Main support unfolding material 2

Figure 8 Main support unfolding material 2

Ⅴ. Final Assembly Welding

The final assembly effect is shown in Figure 9.

Final assembly effect

Figure 9 Final assembly effect

(1) Main support welding:

Welding tooling and positioning pins are used to fix the left and right two parts of the unfolded material 1 → Spot welding into one → Positioning missing parts are aligned to form the main support

(2) Left and right angle steel welding:

Use the left (right) angle steel positioning tool to locate the main support and left (right) angle steel, and then spot-weld.

(3) Welding of heart rate tube and conversion card:

Position and install the heart rate tube and the conversion card, then spot-weld.

(4) Fully welded, shaped and polished welding slag.

(5) Paint:

The outer surface paint is coated with yellow zine epoxy primer HG / T2239-91, fine silver car paint YZW-9172, acrylic-urethane clear lacquer HG / T2454-06.

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