Abstract: Firstly, the physical and chemical properties ofenameled aluminum wire are analyzed, and then the process and key point control of theenameled aluminum wire motor stator with a diameter below 1.0 mm are explained in detail.

Keywords: small wire diameter; aluminum wire motor; wiring technology; paint stripping powder; double-wall heat shrinkable tube

Introduction

Motor windings used in the household appliance industry generally use copper enameled wire orenameled aluminum wire.enameled aluminum wire motors occupy an irreplaceable position in the motor industry due to their material cost advantages. Aluminum has the characteristics of low hardness and being easily oxidized in the air, resulting inenameled aluminum wire motors having very strict processing technology requirements. This article mainly studies and analyzes various key quality control processes in the production ofenameled aluminum wire motors with a diameter of less than 1.0 mm. Through the rational application of welding materials and new welding processes, problems such as deformation and oxidation can be effectively solved, making the performance of aluminum wire motors both reliable and safe.

1 Analysis ofenameled aluminum wire

1. 1 Physical properties

As can be seen from Table 1, the tensile strength and elongation of aluminum are low.enameled aluminum wires are more susceptible to damage during processing than copper enameled wires. If a small gap occurs, the aluminum wire will also be oxidized. Over time, the aluminum wire will be easily damaged. Overheating will burn out, and the service life will be shortened; the paint adhesion of theenameled aluminum wire is worse than that of the copper wire, and the paint will be easily peeled off after folding a few times, which is prone to turn-to-turn defects; the tensile strength of the aluminum wire is small, and the tension is used when the machine is winding. Easily broken, easily damaged thinning; aluminum has a low melting point and is prone to burning during welding.

Figure1   Comparison of properties of copper and aluminum

1.2 Chemical properties

Aluminum metal is very reactive and easily oxidized. Especially at high temperatures, Al2O3 will be generated, which will lead to difficulties in tin application, poor welding, and virtual soldering. Therefore, the key to the success ofenameled aluminum wire applications lies in how to solve the problem of joint welding.

Many aluminum fluxes currently on the market are acidic and severely corrode the aluminum wire itself, causing the solder joints to corrode and turn into powder after the aluminum wire motors are shipped. In addition, copper wire and aluminum wire connectors should not be directly connected for the following reasons:

(1) Copper and aluminum belong to different elements. The metal inertness of copper is greater than that of aluminum, that is, the chemical activity of copper is much lower than that of aluminum. In this way, after the two metals are connected, an electrochemical reaction will occur, causing the aluminum wire to be gradually oxidized. , reducing the mechanical strength and electrical conductivity of the aluminum wire. (2) Copper wires and aluminum wires will generate heat when passing current, and their resistivities are different (copper 1.7 × 10-8 Ω ·m, aluminum 2.7 × 10-8 Ω ·m). When the same current passes, the aluminum wire The heat generated by copper wire is large, and the heat generated by copper wire is small, so it is easy for failure points to occur at the joints. (3) Copper wires and aluminum wires have different hardnesses. If they are directly connected, the bonding force will not be very good. If the wire is stressed, it will be easily disconnected from the connection between the copper wire and the aluminum wire.

2 Stator assembly process and key point control

2.1 Winding process

Aluminum wire has poor tensile strength and is easily broken, damaged and stretched, which affects temperature rise and lifespan.When winding this wire, the winding tension must not exceed the standard safe winding tension range of aluminum wire.It is recommended to rely on the force of the rotating arm of the winding machine for natural tensioning, and adjust the tension and winding speed.It is advisable to make it 70% of the copper enameled wire.

2.2 Embedding process

Before embedding the thread, check the drop-off cup for burrs, deformation and other defects, and hang the remaining threads.The process is the same as the copper wire motor wiring process. Inlay machine push head cycle time for ≥10 s, use a flexible material pusher.

2.3 Rough shaping process

For rough plastic surgery, it is recommended to use a rough plastic machine with an outward-retracting and an internal-opening type, and facial spacers (aluminum wire electric

After the machine separator paper process is the same as the copper wire motor separator paper process), use bamboo sticks to separate the loose wires and after sorting out the random lines and flying vertical lines, put them into the shaping mold.

2.4 Wiring process (the most critical process)

enameled aluminum wire wiring is specifically divided into two processes: one is the paint removal process, and the other is welding process.

(1) Paint removal methods forenameled aluminum wires: chemical paint removal powder and direct welding paint removal. 1)Chemical paint stripping powder for paint removal (applicable to QZ enameled wire): ①The temperature of the paint stripping furnace is controlled as required set at 350°C for about 2 s. ② Use special cleaning agent for aluminum wires to soak and clean wash and wipe off the detergent with a pure cotton cloth. ③Experimental requirements: Test cleaning pH value of liquid, flux, and paint stripper powder, and record it as required. 2) Direct welding and paint removal(Applicable to QA enameled wire): ① Use soldering furnace high temperature for paint removal, paint removal temperature 400 ℃, paint removal time 2 s. ②Wipe directly with a clean rag after taking off.

(2)enameled aluminum wire welding method: pierce the terminals, rivet and weld with solder wire. 1)Terminal riveting is used for enameled wires with larger diameters. Enameled wires with too small diameters are physically.The magnetic needle of the terminal can easily break the enameled wire, and the potential difference between copper and aluminum is large. Electrochemical corrosion will definitely occur gradually, the resistance of the connection point will gradually increase, and the temperature rise will increase.High, eventually leading to no power supply. 2) The temperature of the soldering iron is uneven when welding the solder wire.

It is easy to produce overlay welding and false welding. The surface looks full, but in fact it is a false weld inside; In addition, the flux cannot be vaporized in a short time, so there will be a lot of flux in the solder joints. Carbonized flux residue. Therefore this method is not reliable either.

To sum up, using the original copper wire welding process and materials, tin application is not easy at all.

Possible, so the connection must use special soldering materials and processes forenameled aluminum wires. Under it is recommended to use the welding process specially used for small diameter aluminum wire motors - first use the above mentioned the paint stripping powder process removes the paint, then dips it in tin and then seals it. Connect copper leads it is directly wrapped and then immersed in tin in a furnace with aluminum flux and tin liquid, and then used with a high shrinkage ratio. The glued double-layer heat shrinkable tube has solidified colloid in the tube to completely eliminate the problem of oxidation. according to tradition calculated, using this welding process, the comprehensive failure rate of aluminum wire motors is about 1‰. This process it is the most reasonable and reliable and worthy of promotion.

The detailed process operation process is as follows: (1) Wire wrapping: 1) Material requirements: Power cord. The incoming material requires that the stripped end be tinned first. 2) Operation requirements: Wear protective finger gloves when winding the wire, and wrap the enameled wire evenly around the tinned end of the power cord for 5 to 7 turns. (2) Soldering: The soldering temperature is required to be 300 ℃, and it is required to solder twice (apply flux for the first soldering, lift it up and apply flux again for the second soldering), and the soldering time is controlled at about 2 s. After two weldings, use an ultrasonic cleaning machine with alcohol for cleaning, and the time should be controlled to more than 2 seconds. (3) Solder joint quality inspection: It is required that there are no false welds, false welds, or incomplete solder joints. The surface of the solder joints must have no burrs, whiskers, knives, or holes. The tin enameling must be uniform and bright, and there must be no knurling or agglomeration. , The insulation should not have any abnormalities such as overheating or yellowing. (4) Heat-shrouded double-wall tube: Use special heat shrink tooling and use time saver to control the heat shrink time. Make sure the solder joint is in the middle of the heat shrink tube, leaving ≥ 15 mm at the front and rear. Tape tape should be used to fix the tap wire where it meets the temperature control wire to ensure the sealing of the heat shrink tube. During heat shrinkage, the heat shrink tube needs to be rotated continuously to allow it to be heated and shrink evenly.(5) Crimping: Use a special crimping tool to clamp the 15 mm heat shrink tube reserved at the front end to ensure that the hot melt glue in the tube can fill the gap. (6) Quality inspection of heat shrink tube crimping: Check whether the heat shrink seal is good, and then use 3.5 mm white silicon tube to cover the heat shrink tube. (7) Related experiments and requirements: Select a number of solder joints from each batch for metallographic analysis. Take the crimped solder joints and perform a 10-minute boiling test in boiling water to dissect whether the solder joints are sealed and free of water leakage.

2. 5 Lead positioning process

Before positioning the leads, wrap the tap wire around the rubber of the power cord for 1 to 2 turns. Place the thermostat on the winding surface of the main wire. Two layers of tape should be placed under the large bushing. After positioning the stator leads, the stator winding must be vertically aligned. Use bamboo skewers to organize.

2. 6 Wire binding process

Before tying the wires, check whether the equipment is operating normally, check whether the binding needles are smooth and have no burrs, whether the windings are well wrapped, and use bamboo skewers to check and organize the flying vertical wires.

2.7 Fine shaping process

Use a nylon shaping mold for shaping. After shaping, check whether the relevant dimensions of the inner and outer circles of the stator meet the requirements.

2. 8 Appearance finishing process

Use bamboo skewers for cosmetic repairs.

2. 9Repairprocess of defective products

Aluminum wire motor stator wire breakage (except tap wire breakage), short circuit, and defective turns are not allowed to be repaired and will be scrapped directly.

2. 10 Full performance inspection process

The inter-turn voltage standard is calculated at 2.1 kV.

3 Conclusion

The above description is the processing technology of the stator winding of the aluminum wire motor. The rotor processing and final assembly process are the same as those of the copper enameled wire motor. All in all, changing copper wire to aluminum wire is not a simple replacement, especially small-diameter aluminum wire motors. The above reliable and guaranteed process support is needed to effectively ensure the life of the aluminum wire motor.

With the reduction of raw material costs and technological advancement, light alloys will have broader application prospects. Light alloy forming manufacturing is one of the important future needs in my country's manufacturing and equipment fields, and the continuous development of aerospace, transportation, weapons manufacturing and other fields will also put forward new requirements for light alloy forming technology, high performance, high precision, Highly reliable large-size integral component forming technology, high-efficiency, automated forming equipment and systematic numerical simulation research methods will be important development directions of light alloy forming technology.