*2.2. Research Objects*

The "SM" motor production lines in Vietnam are mainly divided into engineering, coil, and motor assembly production lines. The engineering production line is mainly focused on the assembly of rotors, sleeves, bearings, and other components, as well as magnet production. The coil assembly line is primarily responsible for winding, spot welding, cutting of commutators, washer assembly, bearing assembly, and distance inspection as well as voltage, insulation, and impedance testing. The motor assembly line deals with coils, brushes, washer, and motor assembly, as well as visual inspection. The layout of the "SM" motor production line in Vietnam is shown in Figure 2. In total, there are three production lines and two assembly lines. Each rectangle represents one workbench, each person is assigned to a workbench and is responsible for handling 1–2 operating procedures.

**Figure 2.** Production line layout.

The operation processes of the coil and motor assembly lines are shown in Figures 3 and 4, respectively.

**Figure 3.** Coil assembly line.

The coil assembly line in Figure 3 is composed of eight main operating procedures as follows.

	- (1) Check if the rotor is rusty and there is a mounting sleeve; there must be five grooves. After confirmation, ensure that the machine is inserted according to the direction.
	- (2) Press the button for the machine to start winding.
	- (3) Use a wooden shaft to number the parts.
	- (4) Ensure that the copper wire is not cracked. The diameter of the rotor should not exceed those of the casing and spot welding of the rotor.

**Figure 4.** Motor assembly line.

	- (1) Place the coil into the machine according to the direction.
	- (2) Press the button to allow the machine to start the spot welding.
	- (3) Check whether the appearance of parts is complete and if there are five grooves. The NG product is placed in the NG box, and good products proceed to the next step.
	- (4) Photographs are taken and saved for every 1000 products.
	- (1) Place the parts of the machine according to the direction.
	- (2) Start the button to allow machine cutting.
	- (3) Check whether the appearance of parts is intact; put the NG product in the NG box.
	- (4) Install the bolt gauge tool to the commutator after cutting.
	- (1) Place the parts in the machine.
	- (2) Clean the parts with a brush.
	- (3) Use a magnifying glass to check the appearance of parts and for foreign objects. Put the NG product into the NG box; the good products proceed to the next step.
	- (1) The parts are placed into the machine and aligned with the air-jet holes for air-jet cleaning.
	- (2) Check the parts for foreign matter and whether the parts appear complete and bright. Place the NG product in the NG box; the good products proceed to the next step.
	- (1) Place the washer into the machine.
	- (2) Press the switch to initiate the washer punch.
	- (3) Put the parts into the machine for voltage withstand, absolute resistance, and impedance tests. Put the NG products into the NG box; good products proceed to next step.
	- (1) Place the bearing and coil in the machine in the same direction.
	- (2) Press the switch to initiate punching.
	- (3) Check whether the parts are intact and correctly aligned. Place the NG product into the NG box; good products proceed to the next step.
	- (1) Place the parts of the inspection machine as directed.
	- (2) Press the button to initiate machine check.
	- (3) Check if the parameters are within range. Put the NG product into the NG box; good products proceed the next step.

The motor assembly line in Figure 4 is composed of nine main operating procedures as follows.

	- (1) Align the iron frame with the coil cut groove and place it in the dispenser.
	- (2) Press the switch to dispense the machine.
	- (3) Check whether the parts have a sufficient amount of glue. The NG product is placed into the NG box, and the good products proceed to the next step.
	- (1) Place the parts of the machine according to the direction.
	- (2) Clip the iron frame into the coil with the white assistive device and take it out.
	- (3) Check whether the parts are installed. Place the NG product into the NG box; good products proceed to the next step.
	- (1) Align the red part of the brush with the machine.
	- (2) Press the switch to open the terminal.
	- (3) Assemble the parts and coils into the finished product according to the working procedure.
	- (4) To provide a gap in the iron frame, check the positioning point. The base assembly must be accurately positioned. The NG product is placed in the NG box; good products proceed to the next step.
	- (1) Assemble the machine parts.
	- (2) Inspect the parts for damage through closed-circuit television. The NG products are placed in the NG box, and the good products proceed to the next step.
	- (1) Put the small and large washers on the machine and install the parts.
	- (2) Press the button to connect the washer.
	- (3) Put the parts into the machine according to the indicated direction, and capture image.
	- (4) Ensure that no washer is missing based on the image. Put the NG product into the NG box, and good products proceed to the next step.
	- (1) Check whether the size of the washer is correct, and the iron frame cover must fully fit the iron frame.
	- (2) Align the machine parts.
	- (3) Press the button to initiate pressing.
	- (4) After installation, ensure that there are eight cut-outs in the parts. Place the NG product into the NG box; good products proceed to the next step.
	- (1) Place the parts of the inspection machine.
	- (2) Press the button for the machine to detect the gap. Place the NG box out of the specification range; the good products proceed to the next step.
	- (1) Align the parts of the inspection machine.
	- (2) Press the button for the machine to transport the parts until they touch the terminals.
	- (3) Press the switch to start measurement and check the 88 items of motor performance data.
	- (4) Check if the data are within range. Put the NG product into the NG box; good products will be automatically engraved with a number. Proceed to the next step.
	- (1) Use a tool to check if the screw pattern is correct.
	- (2) Use a tool to check whether the laser marking (seal) is sufficient.
	- (3) Check if the motor rotation direction is correct.
	- (4) Put the motor into the machine to check whether the terminal is defective. Put the NG product into the NG box and put the good product into the box according to its number. Finally, pack and ship.
