Supporting plate for motor and gear box:
As the shaft of the motor and that of the gearbox are not concentric, we needed to manufacture a set of components to support the motor and the gearbox so that they would be concentric. However the front plane of the motor is not flat, there is a circular bar protruding from the motor, therefore the plate for supporting the motor should be a circular cave for fitting the motor and holding the motor to stand horizontally.
Because of the limitation of the cutting depth of boring tool, the cave cannot be made by conventional milling machine. To solve this, we used lathe. First of all, we needed to change the original jaw to a jaw specialized for clamping the rectangular plate and then aligned the centre of rotation with a concentric alignment tool and a dual gauge. Finally, by using a suitable speed and following the use of lathe, the required cave was obtained.
In the previous planning for manufacturing, we intended to make the keyholes by milling. However, later we found that the milling tooling cannot reach the required depth to make the keyholes. So we changed to use wire cut of Electro-Discharge Machining to do so. Moreover, as the system is monitored by a CNC system, higher degree of machining precision could be obtained while compared with that of the milling machine.
Due to the deformation of L-bars caused in welding, the base and vertical bars are not right angle. To solve this, during assembly of the L-bars with the base, the inclined pad of the L-bars needed to be cut and be welded again so that we can adjust the vertical bar to fit the stands of the frame.
- Posture of the four stands of the mainframe:
Similarly because of the deformation of L-bars, while fixing the L-bars and the four stands of the mainframe together with the screws, the four stands could not stand vertically even though we welded the L-bars again. It is because due to insufficient experience and more importantly the method of welding, the L-bars cannot be perfectly at 90o. Therefore, we used hammer to adjust to the right position.
Initially we used milling machine and then grinding machine to make the keys, however, as the exact tolerance of each components are not the same, some of the keys did not fit the keyholes and the keyways. To solve this, we use sand paper for grinding the keys very gently to reduce their sizes gradually.
and motor alignment:
After assemble the gearbox with the motor, we found that the clearance between the aluminum couple, which joins their shafts together, and the shafts is little more than expected. As a result, a much larger vibration and more noise were produced while running the motor. Due to the shortage of the machines available for the MU project and better absorption of noise, we changed to use a rubber couple instead of the aluminum one.
The holes on the stands do not fit those on the horizontal bar of the mainframe. It is because we drilled the holes according to the CAD drawings, but due to the deformation of L-bars and the changed position of the stands, the holes are then not fitted. To solve this, we drilled some new and larger holes for adjustment of the position of the components and add washer to fix all these components with screws.