Ⅰ. The Structure of the Work Piece
Figure 1 depicts the irregularly shaped metal skeleton of a fitness equipment made from Q235 material. The metal skeleton of each fitness equipment is created by welding together five parts illustrated in the figure.
Figure 2 displays the primary support structure, which should be constructed using 36mm × 36mm × 3mm angle steel and φ32mm × 2mm steel pipe.
It is crucial that the finished product is processed and shaped to fit seamlessly with the supporting parts without any interference during installation.
Figure 1 Panel skeleton
- Left angle steel
- The main support
- Conversion Card
- Heart rate tube
- Right angle steel
Figure 2 Main support
Ⅱ. Analysis of Process Plan
Graphically, the difficulty in processing parts lies in both the main support processing and welding the main support to the left and right angle steel.
The designer initially considered using 36mm × 36mm × 3mm angle steel profiles for tailor welding. However, during the actual processing, it was found that machining the angle steel was necessary, followed by processing and forming individual parts before performing tailor welding.
Due to the difficulty of controlling the angle during the tailor-welding process and the large number of tailor-welded angle steels, ensuring size accuracy proved challenging. As a result, using angle welding is not recommended, and alternative processes should be considered.
Taking into account the company’s actual processing capacity, a laser cutting machine capable of cutting steel plates up to 6mm thick and high processing efficiency is available. Bending and forming after the steel plate is staked out can improve processing efficiency and accuracy. Therefore, laser cutting of the 3mm steel plate with bent inner holes is recommended.
Through calculating and analyzing the unfolded material, it was discovered that the unfolded material of the adjacent bent parts on the main support will interfere. To overcome this, it is necessary to remove three folds at intervals and use welding to form the structure. Discharge revealed that one stake-out would lead to serious waste material.
Considering that the main support is a left-right symmetrical structure, it can be disconnected from the middle, thereby reducing waste loss during discharge. In the later stage, tooling welding is adopted, which will not affect performance or strength.
The unfolded material is shown in Figure 3.
Figure 3 Main support unfolding material 1
The main support can be formed by completing the lofting, bending, and welding processes.
(2) Welding of main support and left and right angle steel:
The primary challenge is to take into account the twist angle of 1.2° while welding the left and right angle steel to the main support. As illustrated in Figure 1, the twist point is located at 1mm.
Accurate positioning through tooling is necessary before welding to meet the usage standards. The complexity arises in the production of the welding tooling.
Ⅲ. Tooling Design
Upon analyzing the process, it can be observed that the tooling design mainly focuses on the positioning and clamping of the primary support and the left and right angle steels. Additionally, the formation of the panel skeleton involves the welding of the adapter plate and the heart rate tube.
Therefore, the welding tool’s design must take into consideration the welding formation of the complete 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 utilized to accurately position the main support. This allows for the edges to be welded to be aligned with the end faces.
(2) Positioning of left and right angle steel:
By adding a wedge on each side, the height is increased to 36mm, ensuring consistency with the main support. Using the main support as a reference, position the wedge and plan the twist angles of the left and right angle steel on the wedge. Locate the twist angle between the left and right angle steel and the main support by using the forming angle of the wedge.
In addition, the inclination angle between the left and right angle steel and the main support can be achieved by using a pad support.
(3) Positioning of the heart rate tube:
The tooling can achieve heart rate tube positioning by adding a U-shaped plate to the outer circle of the heart rate tube. Any parts that interfere with the heart rate tube are removed through machining.
(4) Positioning of the conversion card:
Complete positioning of the adapter plate can be achieved by welding the positioning plate onto the tooling to allow for lateral movement of the adapter plate, and by welding the positioning plate into the square hole to enable longitudinal movement of the conversion card.
Figure 4 Panel framework welding tooling
Figure 5 Left Angle Steel Positioning Tooling
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:
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.
Figure 8 Main support unfolding material 2
Ⅴ. Final Assembly Welding
The final assembly effect is shown in Figure 9.
Figure 9 Final assembly effect
(1) Main support welding: To join the left and right parts of the unfolded material 1, welding tooling and positioning pins are utilized. The two pieces are spot welded together and any missing parts are aligned to form the main support.
(2) Left and right angle steel welding: Using the left (right) angle steel positioning tool, locate the main support and left (right) angle steel, and then spot-weld them together.
(3) Heart rate tube and conversion card welding: First, position and install the heart rate tube and conversion card, and then spot-weld them together.
(4) Fully welded, shaped, and polished: Once all welding is complete, the product is fully welded, shaped, and polished to remove any welding slag.
(5) Painting: For the outer surface, apply a coat of yellow zinc epoxy primer HG/T2239-91, followed by fine silver car paint YZW-9172, and finish with acrylic-urethane clear lacquer HG/T2454-06.