A method for removing wax from a precision micro stepping motor

Abstract

The present application relates to a kind of precision micro stepping motor wax removal methods, comprising the following steps: 1) after organic solvent water bath is heated to constant temperature, stator is immersed in organic solvent ≥30min;2) take new organic solvent water bath and heat to constant temperature, use circulating pump to flush the inner hole of stator, and each stator flushing time ≥1min;3) using anhydrous ethanol along the inner hole of stator axial reciprocating wash ≥20 times, then room temperature is placed ≥10min;4) stator is placed into high-low temperature test chamber and is treated at high-low temperature, first at high temperature and is kept ≥20min, then temperature is changed to low temperature and is kept ≥10min, repeat high-low temperature treatment at least 4 times, low temperature recovers to normal temperature and is taken out;5) repeat step 1) to step 3) or step 2) to step 3);The present application improves the effect of paraffin wax cleaning under the stator winding structure, improves production efficiency, and reduces the amount of solvent used.

Description

Technical Field

[0001] This invention belongs to the field of precision micro stepper motor processing and manufacturing, especially the processing and manufacturing of stators for military precision micro stepper motors, and specifically relates to a method for dewaxing precision micro stepper motors. Background Technology

[0002] During the stator machining process of miniature precision motors, due to the small air gap between the stator and rotor, small foreign objects generated during the machining of the stator's inner bore can enter the stator, causing step loss, jamming, or even damage after stator assembly. To prevent foreign objects from entering the stator, a wax-filling sealing process is adopted during stator machining, and the wax is removed by cleaning with organic solvents after stator machining and before motor assembly.

[0003] There are two main existing dewaxing techniques: conventional organic solvent immersion and rinsing, and ultrasonic cleaning using a specially formulated water-based dewaxing solution. Based on the principle of "like dissolves like," immersion and rinsing with organic solvents, which have similar polarity to paraffin, is effective at dissolving and cleaning paraffin under high-temperature conditions. However, because this process involves the continuous dilution of paraffin, residues are easily left in fine structures due to poor liquid exchange. Water-based dewaxing solutions primarily consist of surfactants, mainly emulsifiers. These surfactants emulsify paraffin, reducing its adhesion to the part surface. Combined with ultrasonic cleaning, this allows the paraffin to detach from the part surface. This process is effective at cleaning surface paraffin, but despite the addition of surfactants, their surface tension is generally still greater than that of organic solvents. Therefore, their desorption effect on paraffin in fine structures is not ideal, and there is a risk of corrosion caused by residual surfactant decomposition products.

[0004] Patent CN111650018A discloses a novel dewaxing method in the preparation of pathological sections. The method involves first pouring xylene of the same concentration twice: the first time for ten minutes, and the second time for ten minutes. Then, different concentrations of anhydrous ethanol are poured in, in the following order: 100% anhydrous ethanol for one minute; 100% anhydrous ethanol for one minute; 95% anhydrous ethanol for two minutes; 95% anhydrous ethanol for two minutes; and 80% anhydrous ethanol for two minutes. Finally, the section is rinsed with running water. This method significantly shortens the dewaxing time, but it is not suitable for dewaxing motor stators.

[0005] The existing stator paraffin cleaning process is roughly as follows: first, the stator is immersed in an organic solvent at 100°C for ≥2 hours; then the organic solvent is replaced and the temperature is raised to 100°C in a water bath, and the inner hole of the stator is rinsed with a circulating pump for ≥5 minutes per stator; finally, the stator is left to stand at room temperature for ≥1 hour, and then placed in an 80°C oven for ≥4 hours; the above operation is repeated at least twice. However, the existing cleaning method has the following drawbacks: (1) Considering that the immersion and baking are done in batches, the average total time for a single motor stator to undergo paraffin cleaning is about 30 minutes; (2) The pass rate for a single cleaning (no paraffin precipitate is considered as qualified during subsequent debugging and testing) is less than 30%; (3) On average, each stator needs to be cleaned to pass the test, and the number of rework cleanings is no less than 2 times, with a total cleaning time of about 90 minutes for 2 times; (4) If the entire motor is to be repaired, the cleaning efficiency is even lower and the cost is higher.

[0006] The stator windings of miniature precision stepper motors have small internal gaps, resulting in extremely poor liquid flow and exchange during immersion and rinsing. This makes it difficult to dissolve and clean residual paraffin wax. Furthermore, subsequent temperature changes during motor use can cause the paraffin wax to agglomerate and precipitate, blocking the air gap and causing step loss. There has long been no effective process for removing paraffin wax from the stator windings and other internal structures of small-gap precision motors. The only method available is repeated high-temperature immersion and rinsing, which is often ineffective and difficult to clean completely in one go. Moreover, the motor jamming caused by paraffin precipitation has a time lag, often appearing after the motor has been assembled and adjusted. Once this occurs, the motor must be disassembled and re-cleaned and re-adjusted. These factors present significant challenges to the production and processing of small-gap precision stepper motors. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies by proposing a method for dewaxing precision micro stepper motors.

[0008] Specifically, this is achieved through the following technical solutions:

[0009] A method for dewaxing a precision micro stepper motor includes the following steps:

[0010] 1) Organic solvent immersion: After heating the organic solvent water bath to a constant temperature, immerse the stator in the organic solvent for ≥30 min;

[0011] 2) Organic solvent rinsing: After heating the new organic solvent to a constant temperature in a water bath, use a circulating pump to rinse the inner hole of the stator. The rinsing time for each stator is ≥1 min.

[0012] 3) Anhydrous ethanol washing: Use anhydrous ethanol to wash back and forth along the inner hole of the stator ≥20 times, and then let it stand at room temperature for ≥10 minutes;

[0013] 4) High and low temperature treatment: The stator is placed in a high and low temperature test chamber for high and low temperature treatment. First, it is kept at a high temperature for ≥20 minutes, then the temperature is changed to a low temperature and kept at a low temperature for ≥10 minutes. The high and low temperature treatment is repeated at least 4 times. The stator is taken out after the low temperature is restored to room temperature.

[0014] 5) Repeat steps 1) to 3) or steps 2) to 3).

[0015] In steps 1) and 2), the amount of motor loaded in the organic solvent ensures that the maximum residual amount of paraffin in the motor is ≤ 1 / 2 of the saturated solubility of paraffin in the organic solvent.

[0016] In steps 1) and 2), the constant temperature is 70℃~80℃.

[0017] In step 4), the high temperature is 120℃±1℃.

[0018] In step 4), the low temperature is -20℃±1℃.

[0019] In step 4), the rate of temperature change is 2℃ / min.

[0020] The organic solvent is an organic reagent that is compatible with paraffin.

[0021] The organic solvent is either kerosene or a hydrocarbon cleaning agent.

[0022] Technical principle:

[0023] Existing dewaxing techniques can be broadly categorized into two principles: one uses organic solvents for cleaning, with the principle of "high-temperature melting → dissolution → dilution"; the other uses water-based dewaxing liquids in ultrasonic cleaning, with the principle of "emulsification → desorption". The dewaxing principle in this invention is similar to that of organic solvents, but it also utilizes the physical properties of paraffin wax—its low melting temperature, high saturated vapor pressure, and ease of vaporization—as well as the small and dense gaps in the stator windings, which facilitate capillary condensation. This allows the paraffin wax to repeatedly approach the surface through continuous high and low temperature cycles, forming a skin effect that promotes its dissolution. The principle is "melting → vaporization (approaching the surface) → capillary condensation (becoming solid) → melting → dissolution → dilution". By incorporating high and low temperature cycles, not only can the paraffin wax precipitate to the surface for easier cleaning, but the increased liquid exchange rate near the paraffin wax accumulation also reduces the driving force for dissolution, thus lowering the cleaning process temperature and improving safety.

[0024] Beneficial effects:

[0025] (1) Considering that soaking and baking are done in batches, the average cleaning time of a single motor stator with paraffin wax is about 20 minutes.

[0026] (2) Single cleaning pass rate: 100%.

[0027] (3) The present invention improves the effect of paraffin cleaning under the stator winding structure, improves production efficiency, and reduces the amount of solvent used.

[0028] Compared with existing cleaning methods, the method of the present invention has the following advantages:

[0029] (1) High processing efficiency, with a single cleaning efficiency increase of over 50% and a full range of qualified cleaning efficiency increase of 350%;

[0030] (2) Paraffin wax has a good cleaning effect, and the pass rate of a single cleaning is increased by more than 70%;

[0031] (3) The processing temperature can be reduced by about 20℃, resulting in a higher safety factor;

[0032] (4) Reduce the amount of solvent used; Attached Figure Description

[0033] Figure 1 External shape and internal structure of a micro precision stepper motor stator;

[0034] Figure 2 The high and low temperature treatment process in the method of this invention;

[0035] Figure 3 Anatomical diagram of the changes in the end of the stator inner winding before high and low temperature treatment in Example 1;

[0036] Figure 4 Anatomical diagram of the changes at the end of the stator inner winding after high and low temperature treatment in Example 1;

[0037] Figure 5 The residual paraffin wax on the stator of a miniature precision stepper motor after paraffin cleaning according to the method of Comparative Example 1;

[0038] Figure 6 The residual paraffin on the stator of a micro precision stepper motor after paraffin cleaning according to the method in Example 2. Detailed Implementation

[0039] The specific embodiments of the present invention will be described in further detail below, but the present invention is not limited to these embodiments. Any improvements or substitutions based on the basic spirit of these embodiments shall still fall within the scope of protection claimed by the claims of the present invention.

[0040] Example 1

[0041] A small-sized precision stepper motor with a diameter of Φ16mm has an operating air gap of only 0.020mm between its stator and rotor. The stator is protected using a wax-filling process during internal hole grinding. The subsequent wax removal and cleaning method includes the following steps:

[0042] (1) Organic solvent soaking: Heat 1L aviation kerosene water bath to 75℃±2℃ and keep it warm, then put 50 stators into the container and soak for 30 minutes; the amount of motor loaded in the organic solvent ensures that the maximum amount of paraffin residue in the motor is not higher than 1 / 2 of the saturated solubility of paraffin in the organic solvent.

[0043] (2) Organic solvent rinse: Take 2L of aviation kerosene again and heat it in a water bath to 75℃±2℃ and keep it warm. Use a circulating pump to rinse each stator inner hole one by one for 1 minute each. The amount of motor loaded in the organic solvent ensures that the maximum amount of paraffin residue in the motor is not higher than 1 / 2 of the saturated solubility of paraffin in the organic solvent.

[0044] (3) One-time brushing with anhydrous ethanol: Hold the two ends of the stator with tweezers, immerse the stator in anhydrous ethanol, and brush back and forth 20 times along the inner hole axis of the stator. Then take it out and let it stand at room temperature for 15 minutes.

[0045] (4) High and low temperature treatment: After washing, 50 stators were placed in a high and low temperature test chamber. They were first kept at a high temperature of 120℃ for 25 minutes, and then kept at a low temperature of -20℃ for 15 minutes. After a total of 5 cycles, the temperature was restored to room temperature and the stators were taken out. The rate of changing from high temperature of 120℃ to low temperature of -20℃ and from low temperature of -20℃ to high temperature of 120℃ was 2℃ / min.

[0046] (5) Secondary rinsing with organic solvent: Heat a 2L aviation kerosene water bath to 75℃±2℃ and keep it warm. Use a circulating pump to rinse the inner hole of each stator piece one by one for 1 minute each.

[0047] (6) Secondary rinsing with anhydrous ethanol: Hold both ends of the stator with tweezers, immerse the stator in anhydrous ethanol, rinse it back and forth 20 times along the inner hole of the stator, and then take it out and let it stand at room temperature for 15 minutes.

[0048] Comparative Example 1

[0049] A small-sized precision stepper motor with a diameter of Φ16mm has an operating air gap of only 0.020mm between its stator and rotor. The stator is protected using a wax-filling process during internal hole grinding. The subsequent wax removal and cleaning method includes the following steps:

[0050] (1) Organic solvent soaking: Heat 1L aviation kerosene water bath to 100℃ and keep it at that temperature. Put 50 stators into the container and soak for 2 hours.

[0051] (2) Organic solvent rinsing: Take 2L of aviation kerosene again and heat it in a water bath to 75℃±2℃ and keep it warm. Use a circulating pump to rinse the inner hole of each stator piece one by one for 5 minutes each.

[0052] (3) Baking: Let 50 stators stand at room temperature for 1 hour, then put them all into an oven and bake at 80°C for 4 hours;

[0053] (4) Repeat steps (1) to (3) to obtain the cleaned product.

[0054] Figure 1 The stator shape and internal structure of a miniature precision stepper motor; Figure 2 This refers to the high and low temperature treatment process in Example 1; Figure 3 This is an anatomical diagram showing the changes at the end of the stator inner winding before high and low temperature treatment in Example 1; Figure 4 This is an anatomical diagram showing the changes at the end of the stator inner winding after high and low temperature treatment in Example 1; Figure 5 The residual paraffin after paraffin cleaning of the stator of a miniature precision stepper motor according to the method of Comparative Example 1; Figure 6 The residual paraffin after the stator of a micro precision stepper motor was cleaned with paraffin according to the method in Example 2.

[0055] Depend on Figure 3 and Figure 4 It can be seen that after the high and low temperature cycle treatment, paraffin wax was precipitated on the outer surface of the winding, indicating that the paraffin wax underwent a vaporization and condensation process, which exposed the paraffin wax in areas that were difficult to clean, thus facilitating the thorough cleaning of the paraffin wax and improving the cleaning qualification rate.

[0056] Depend on Figure 5 It can be seen that: after the rotor was removed from the cleaned product obtained in Comparative Example 1, a large amount of paraffin was visible at the bearing stop, indicating that the cleaning efficiency was low and the paraffin could not be removed in large quantities.

[0057] Depend on Figure 6 It can be seen that: when the rotor was removed after the cleaning test of the finished product obtained in Example 1, there was no visible paraffin at the bearing stop, indicating that the cleaning efficiency was high and a large amount of paraffin was removed.

Claims

1. A method of dewaxing a precision microstepping motor characterized by, The method comprises the following steps: 1) organic solvent soaking: after the organic solvent water bath is warmed to a constant temperature, the stator is immersed in the organic solvent for ≥30 min; 2) organic solvent flushing: after a new organic solvent water bath is warmed to a constant temperature, the inner hole of the stator is flushed by a circulating pump, and the flushing time of each stator is ≥1 min; 3) absolute ethyl alcohol brushing: the absolute ethyl alcohol is used to reciprocally wash the inner hole of the stator axially for ≥20 times, and then the stator is left to stand at room temperature for ≥10 min; 4) high and low temperature treatment: the stator is placed into a high and low temperature test box for high and low temperature treatment, is first warmed at high temperature for ≥20 min, is changed to low temperature and is warmed for ≥10 min, the high and low temperature treatment is repeated at least 4 times, and the stator is taken out after the low temperature returns to room temperature; 5) repeating steps 1) to 3) or steps 2) to 3); In step 4), the high temperature is 120℃±1℃; In step 4), the low temperature is -20℃±1℃.

2. The method of claim 1, wherein the precision micro stepping motor is a brushless DC motor. In steps 1) and 2), the loading amount of the motor in the organic solvent ensures that the maximum paraffin residual amount in the motor is ≤1 / 2 of the saturated solubility of paraffin in the organic solvent.

3. The method of claim 1, wherein the precision micro stepping motor is a brushless DC motor. In steps 1) and 2), the constant temperature is 70℃~80℃.

4. The method of claim 1, wherein the precision micro stepping motor is a permanent magnet motor. In step 4), the rate of temperature change is 2℃ / min.

5. The method of claim 1, wherein the precision micro stepping motor is a brushless DC motor. The organic solvent is any one of kerosene and a carbon hydrogen cleaning agent.

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