Overview
A workpiece’s cylindrical, conical, or other shaped wire surface is machined to form an inner bore surface, which is then ground using a grinder.
Internal grinding machines can be classified into common internal grinding machines, planetary internal grinding machines, centerless internal grinding machines, coordinate grinding machines, and special purpose internal grinding machines.
Based on the grinding wheel shaft configuration, internal grinding machines can be classified as either horizontal or vertical.
① Common:
The workpiece is held in place by a chuck that is mounted on the main shaft of the head frame, allowing for circular feed motion.
The worktable drives the grinding wheel frame to move longitudinally along the guide rail of the bed.
The head frame moves laterally along the sliding saddle for feeding.
The headstock can also be rotated around a vertical axis to grind tapers.
② Planetary:
During operation, the workpiece remains fixed while the grinding wheel rotates around the axis of the machined hole, achieving circumferential feed in addition to its own high-speed rotation.
This type of machine is suitable for grinding large workpieces or workpieces that cannot rotate, such as cylinder blocks for internal combustion engines.
③ Centerless:
The outer circumference of the workpiece is supported on a roller or support block during operation.
The end face of the workpiece is held in place by a magnetic chuck and is rotated while slightly floating to ensure concentricity of the inner and outer circles.
The grinding wheel speed of small-sized internal grinding machines can reach up to hundreds of thousands of revolutions per minute.
Internal grinding machines used in high-volume production require a high degree of automation.
During the grinding process, the size can be automatically controlled using a plug gauge or micrometer.
Structure
The internal grinding machine is typically categorized into a common internal grinding machine and a universal internal grinding machine, with the latter being the most widely used.
The universal internal grinding machine can grind the inner cylindrical surface, inner conical surface, and stepped shaft end surface of various shaft and sleeve type workpieces.
The main component of the grinding machine is the bed, which serves as the fundamental support for the machine and is equipped with a grinding wheel frame, worktable, head frame, tailstock, and lateral sliding saddle to maintain their exact relative positions during operation.
The inside of the bed is used as an oil pool for hydraulic oil.
The head frame is used to mount and hold the workpiece, which is driven to rotate. The headstock can be rotated 90° counterclockwise in the horizontal plane.
The inner grinding tool supports the grinding wheel spindle for grinding the inner hole. The inner grinding tool spindle is driven by a separate motor, while the wheel carrier supports and drives the grinding wheel spindle at high speed.
The wheel frame is mounted on the sliding saddle and can be adjusted to a certain angular position within the horizontal plane by ±30° when grinding a short conical surface.
The tailstock and the top of the headstock together support the workpiece, while the sliding saddle and infeed mechanism rotate the lateral feed handwheel. The infeed mechanism drives the saddle and the wheel frame for lateral feed motion.
The workbench consists of two layers, with the upper table capable of rotating by an angle (±10°) around the horizontal plane of the table to grind a long conical surface with a small taper. The head frame and tailstock are mounted on the upper workbench, which can be reciprocated longitudinally along the bed rails along with the workbench.
The general precision class universal internal grinding machine has an accuracy level of IT6 or IT7, with a surface roughness value Ra of the machined surface controlled within the range of 1.25 to 0.08 μm.
The universal internal grinding machine is used for finishing the inner and inner cylindrical surfaces, despite its low productivity. Its versatility makes it widely used in single-piece small batch production workshops, tool workshops, and machine repair workshops.
Characteristics
★ The machine tool employs two transmission mechanisms for feed and compensation, which do not interfere with each other.
The feed system includes a fixed-point grinding function, which can be either manual or hydraulic.
★ A fast-jumping mechanism is included, eliminating the need to retool after exiting the grinding wheel for measurement or trimming.
★ The workbench is equipped with a medium stop device, allowing for adjustable rewind distances to reduce assistance time.
★ The workbench starting handle features a safety interlock for secure loading, unloading, and measuring work.
★ The maximum speed of the grinding wheel is 24,000 rpm to enhance grinding efficiency.
★ The electric spindle can be modified with variable frequency speed for grinding small diameter inner holes upon request.
★ The machine is equipped with an end grinding device to ensure verticality of the workpiece hole and end face.
