Based on current processing equipment capabilities, drilling and tapping of small machine bases are performed on vertical drilling machines and tapping machines. Drilling and tapping of medium and large machine bases are performed on radial drilling machines. In batch production, drill jig positioning is used to ensure the consistency and accuracy of hole positions; Ms. [Name] will have a brief discussion with you today.
Different drilling methods for machine bases
A simple drilling jig for the drill rig base end holes uses a clearance fit between the base stop and the drill jig stop. After drilling the first hole, a fixing pin is inserted to prevent relative movement between the drill jig and the base. Then, other holes are drilled. The distance between the foot holes and the center line of the base is one of the main installation dimensions of the motor and must be strictly controlled.
Different machining schemes for the machine base result in different drilling and tapping methods for the machine base.
Option 1
Drilling the base hole is performed after machining the inner circle, end face, and stop. Therefore, the base hole can be positioned based on the inner circle or end face and stop. However, the positioning and machining of the base hole are somewhat difficult because the base plane is not in the same direction as the inner circle and stop face.
There are two common types of drilling jigs for the base holes.
For small drilling bases, during drilling, first place the drill jig on the worktable of the drilling machine, then fit the base onto the inner locating jig and clamp it with tension screws and pressure plates. Finally, use the drill bushing to guide the drill bit to drill the hole. The symmetry of the base holes with respect to the center line of the base is ensured by the jig. However, the mounting and dismounting of the base is relatively difficult.
For medium-sized machine bases, when drilling, first place the machine base on the worktable of the radial drilling machine, and use the stop circles on the front and rear templates to match the stop at both ends of the machine base for positioning. The drill jig handle and eccentric wheel mechanism interact to make the template coincide with the vertical center line of the machine base, ensuring the symmetry of the foot hole with respect to the vertical center line of the machine base. Then, use the tension screw to tighten the front and rear templates and position the axial distance of the foot hole. Finally, use the drill bushing to guide the drill bit to drill. Its disadvantages are: (1) There is a gap between the drill jig and the foot, which makes it difficult to remove chips and affects drilling efficiency; (2) The drill rod is relatively long, and the shaking is large, which makes it easy to hit the machine base wall.
Option 2
First, drill the base holes, then machine the end stops, end faces, and inner circles. The symmetry of the base holes with respect to the machine base centerline is ensured by adjusting the machine tool.
Tapping can be done manually, by machine, or by using a multi-head tap chuck to tap several bolt holes at once. The tap rotates much slower than the drill bit. Some tap holders have a safety device that automatically stops rotating when the tap reaches the bottom or encounters excessive resistance to prevent breakage.
Improve drilling efficiency and accuracy of machine base
For large production batches, to further improve productivity, a multi-axis drive chuck can be added to a conventional drilling machine, or a multi-head drilling machine (combination drilling machine) can be used, allowing several holes to be machined simultaneously in a single setup. The end faces of small machine bases are drilled using a multi-head drilling machine, arranged symmetrically on both sides, allowing simultaneous drilling or tapping of both end faces. The machine base is roughly positioned on the intermediate body; when machining different machine bases, the positioning fixture on the intermediate body must be changed. Drilling and tapping are precisely positioned using left and right tower-type stop jigs. Each end of the drilling machine is equipped with eight drill rods: four for drilling and four for tapping, and their radial distances are adjustable.
Apart from manual loading and unloading of workpieces, the multi-head drilling machine relies on the coordination of hydraulic and electrical systems to make the entire work cycle automatic, with an average production rate of 5 minutes per machine.
Drilling holes for magnetic poles in DC motor base
If the pole holes on the DC motor base are not evenly indexed, it will cause difficulties in pole assembly and affect motor performance. In mass production, the drill jig for drilling pole holes can move left and right within the slide, while the slide can move up and down within the V-groove. The indexing plate is used to evenly divide the positions of the pole holes on the base and is positioned by springs. This type of fixture has high versatility. During drilling, first, the base stop is fitted onto the stop jig, clamped with pressure plates, shafts, and nuts, and the drill jig is adjusted to the appropriate position. Two pole holes are drilled sequentially. Then, the base is rotated through a specified angle using the indexing plate, and the second set of pole holes is drilled. This process continues until all pole holes are drilled.
Some motor manufacturers use self-made specialized internal drilling machines to process the pole holes on the machine base. The workpiece is vertically clamped. A set of drill bits drills from the inside out. After drilling one set of pole holes, the workpiece is rotated at a certain angle before drilling the second set of pole holes. This cycle is repeated until all pole holes are drilled. This processing method results in uniformly spaced pole holes on the inner wall of the machine base, no burrs on the inner wall, good contact between the poles and the machine base, and high efficiency.
