When installing the motor assembly line, how to ensure that the precision control meets the requirements?

In the process of motor assembly line installation, precision control directly determines the qualification rate, operation stability and overall efficiency of the production line of subsequent motor assembly. It is necessary to establish a whole process control system from four core links: benchmark calibration, component installation, equipment debugging and testing and verification, which can be realized by the following measures:

First, pre-preparation: define the accuracy standard and tool calibration, and lay the foundation.

The premise of precision control is that "standards are available and precision tools are available", and two key tasks need to be completed before installation:

Define the accuracy benchmark and technical parameters.

It is necessary to sort out the core accuracy requirements of the motor assembly line in advance and form a quantitative standard (refer to industry specifications and equipment manuals), which mainly includes:

Linearity accuracy: straightness (≤0.5mm/m) and parallelism (interval error between adjacent tracks ≤ 0.3 mm) of conveying tracks;

Positioning accuracy: the repeated positioning error of assembly station (≤±0.1mm) and the coaxiality of fixture and conveying line (≤ 0.2 mm);

Vertical accuracy: verticality of columns and supports (≤0.1mm/m), so as to avoid assembly deviation caused by inclination;

Transmission accuracy: the tension uniformity of conveyor belt/chain (error ≤5%) and the meshing clearance of transmission gear/synchronous belt (≤0.05mm).

Calibrate measuring tools and equipment

All tools used for precision testing must be calibrated in advance to ensure their own precision meets the requirements. The commonly used tools and calibration standards are as follows:

Calibration cycle is required for tool type and purpose calibration.

The measurement error of straightness and parallelism of laser collimator track is ≤±0.01mm/m/m every 3 months.

Precision level (0.02 mm/m) table/track levelness detection zero error ≤ 0.01 mm/m per month.

The indication error of digital micrometer component size and clearance measurement is ≤±0.001mm every 6 months.

Torque wrench bolt tightening torque control torque error ≤ 3% every month.

Coordinate measuring machine fixture positioning accuracy detection space accuracy ≤±0.02mm every six months.

Second, the core installation link: control the accuracy step by step to avoid accumulated errors.

The precision error of motor assembly line is prone to "cumulative transmission" (for example, track precision deviation will lead to subsequent fixture positioning deviation), so it is necessary to control the key links one by one in the order of "from benchmark to component, from whole to part":

1. Foundation and foundation frame: control "bottom accuracy" to avoid settlement/deviation.

The foundation is the "foundation" of the assembly line. If the accuracy of the foundation is not up to standard, there will be deviations in all subsequent installations:

Foundation flatness calibration: use a precision level to detect the foundation surface to ensure that the flatness error within each square meter is ≤ 2mm; If the deviation exceeds the standard, it should be leveled with epoxy mortar, and the leveling layer should be tested again after curing (curing for more than 7 days) to avoid late settlement.

Foundation frame fixing: Before the frame is installed, it should be positioned according to the elastic line of the design drawing (pop up the center line and reference line), and the method of "subsection fixing+overall calibration" should be adopted: firstly, connect the frame sections with the embedded parts of the foundation (do not tighten the bolts temporarily), then use a laser collimator to detect the straightness and parallelism of the frame, and after the error is adjusted to ≤0.3mm/m, tighten the anchor bolts symmetrically in three times (the torque is as required by the design, such as M20 bolt torque).

2. Conveying track and transmission parts: Control the "motion accuracy" to avoid jamming/deviation.

The conveying track is the core channel for the circulation of motor components, and the transmission components directly affect the running stability, so it is necessary to focus on management and control:

Track installation: Before laying the track, it is necessary to clean the supporting surface of the frame (remove oil stains and impurities), and adopt "subsection docking+real-time calibration": for each section of track (2-3m in length), use a micrometer to detect the deviation between the track and the reference line (≤0.1mm/m), and at the same time use a feeler to detect the joint gap of the track (≤0.05mm) to avoid the jamming at the joint; After all the laying is completed, the track straightness (total length error ≤1mm/10m) will be detected by laser collimator to ensure no "wave" deviation.

Transmission parts assembly:

Conveyor belt/chain: during installation, it is necessary to adjust the coaxiality of the driving wheel and the driven wheel (error ≤0.1mm) to avoid the deviation of the conveyor belt caused by the deviation of the gear train; The tensioner should be adjusted evenly (the tension difference between the two sides is ≤5%), and the tension should be detected by a tensiometer (in line with the requirements of the equipment manual, such as the tension of synchronous belt is ≥500N) to prevent slipping or overstretching.

Bearings and shafts: Before assembly, clean the bearing seat and shaft neck (oil stain ≤5mg/㎡), and adopt hot installation (heating temperature ≤120℃ to avoid bearing annealing) or cold installation (cooling temperature ≥-40℃). After assembly, rotate the shaft by hand to ensure no jamming and abnormal noise, and use a dial indicator to detect the radial runout (≤0.02mm) of the shaft.

3. Fixture and positioning parts: control the "assembly accuracy" to ensure the accurate alignment of parts.

Fixture is the positioning core of motor components (such as stator, rotor and end cover), and its accuracy directly determines the assembly quality of motor;

Fixture installation: Before fixing the fixture, the flatness of the fixture positioning surface (≤0.05mm) and the coaxiality of the locating pin (≤0.03mm) shall be detected by a coordinate measuring machine to ensure that the fit clearance with the motor parts meets the design requirements (such as the clearance between the locating pin and the hole ≤ 0.02 mm); During installation, the fixture shall be positioned according to the reference line, and the parallelism between the fixture and the conveying track (≤0.1mm) shall be detected with a dial indicator. After fixing, the repeated positioning error (≤±0.05mm) shall be detected with three coordinates again to avoid batch assembly deviation.

Auxiliary positioning parts: such as guide rod and limit block, the verticality of the guide rod (≤0.05mm/m) and the parallelism between the positioning surface of the limit block and the positioning surface of the fixture (≤0.03mm) shall be ensured, and the parts shall be tested with trial parts (standard motor parts) after installation, so as to ensure that the parts can be put in smoothly without forced clamping.

Third, the debugging stage: dynamic precision control to eliminate the deviation in operation.

After the static installation accuracy reaches the standard, it is necessary to verify the "accuracy stability in running state" through dynamic debugging to avoid static qualification but dynamic deviation:

No-load trial operation and debugging

First carry out no-load operation (speed from low speed to high speed, such as 0.5m/min→ design speed 2m/min), and focus on monitoring:

Track deviation: use a displacement sensor (accuracy ≤0.01mm) to detect the real-time deviation of the conveying track during operation, so as to ensure that the maximum deviation is ≤0.2mm and there is no periodic deviation.

Transmission stability: use a vibration tester to detect the vibration value of transmission parts (such as the vibration speed at the bearing ≤2.8mm/s), and use a noise meter to detect the running noise (≤70dB) to avoid precision deviation caused by vibration.

Positioning accuracy: the fixture is controlled to run to each assembly station, and the deviation between the actual position of the fixture and the set position (≤±0.05mm) is detected by a laser locator, and it is continuously tested for 50 times to ensure the stability of repeated positioning error.

Load commissioning and debugging

Simulate the actual production conditions (standard motor parts are placed on the fixture, and the load weight is according to the design value, such as 50kg), run for 24 hours, and focus on monitoring:

Accuracy retention: check the track straightness and fixture positioning accuracy every 4 hours to ensure that the deviation does not increase significantly (cumulative error ≤0.1mm).

Transmission reliability: check the wear of the conveyor belt/chain (measure the tension every hour, the change is ≤3%), the bearing temperature (≤70℃, the ambient temperature is 25℃), so as to avoid the deformation of parts and the decrease of accuracy due to load.

Iv. acceptance and curing: inspection and verification+document retention to ensure traceability of accuracy.

The last step of precision control is "acceptance confirmation+solidification standard" to avoid the loss of precision caused by later maintenance:

Accuracy inspection and acceptance

According to the accuracy standard formulated in the previous period, the "all-item detection+sampling verification" is adopted:

All-round inspection: the core indicators such as foundation flatness, frame straightness, track parallelism and fixture positioning accuracy are inspected one by one to form a Precision Inspection Report, and all indicators need to reach the standard 100%.

Sampling verification: randomly select 10 assembly sites, and try to assemble with standard motor components (assemble for 3 times), and check the motor coaxiality (rotor and stator coaxiality ≤0.05mm) and end cover fit (gap ≤0.03mm), and the pass rate of trial assembly should be 100%.

Document retention and maintenance standards

Keep all accuracy inspection records (tool calibration report, installation and debugging record, acceptance report), and specify the person in charge of each link for later traceability.

Formulate the Precision Maintenance Manual, and specify the daily maintenance requirements, such as checking the track levelness with a level every week, calibrating the fixture positioning accuracy every month, and checking the clearance of transmission parts every quarter to ensure the long-term stability of the accuracy.

summary

The precision control of motor assembly line should follow the principle of "standard first, step-by-step control, dynamic verification and long-term maintenance", and the core is to avoid "local deviation accumulating into overall error" —— from the bottom accuracy of foundation, to the movement accuracy of track, to the assembly accuracy of fixture, each link needs to use quantitative standards, precise tools and repeated verification to ensure the standard, and finally realize the high quality and stability of motor assembly.