Internal hole peeling machines are used to remove coatings, residues, or defective materials from the inner holes of workpieces. The operating method directly determines the processing quality and efficiency. Understanding the principles and applicable conditions of different methods allows for the selection of the most suitable process route in actual production, ensuring both substrate protection and ideal peeling results.
Mechanical cutting is the most basic method. The equipment uses an adjustable-speed rotating cutter or drill bit to cut the target layer along an axial or helical trajectory within the inner hole. The cutter shape can be customized according to the hole diameter and the nature of the residue; for example, flat-end mills are used for flat removal, and pointed drills are used for point peeling. This method is suitable for removing carbon deposits, welding slag, or coatings from materials of moderate hardness such as metals and engineering plastics. Its advantages include direct force application and simple equipment structure, but it requires high precision in cutter coaxiality and feed rate; improper operation can easily produce burrs or damage to the substrate.
Grinding and polishing methods focus on improving surface quality. Using a slender grinding wheel, nylon brush, or diamond grinding head, the oxide or hardened layer is gradually removed by rotating and reciprocating at low speed within the inner hole. This method is suitable for workpieces requiring high surface finish, such as oil passage holes in precision molds and the inner cavities of catheters in medical devices. Coolant can be used during grinding to remove debris and reduce temperature rise, preventing thermal damage. The disadvantage is relatively low efficiency, and the need to select an appropriate grit size based on the material hardness.
Laser abrasion is a non-contact, high-precision process. A high-energy laser beam is focused onto the surface of the inner hole, causing the coating material to vaporize or peel off through photothermal effects without direct contact with the substrate. This method allows for precise control of the depth of action, avoiding deformation caused by mechanical stress, and is particularly suitable for brittle materials or easily deformable thin-walled parts. It shows advantages in removing oxide films from pin holes in electronic components and removing sintering residues from ceramic parts. However, the equipment investment is high, and appropriate wavelength and pulse parameters need to be set for different materials.
Electrochemical abrasion utilizes the action of an electrolyte and electric current to dissolve specific metal coatings. The workpiece is used as the cathode or anode, and a short-term current is applied to a specific solution to selectively dissolve the attached metal or oxide layer. This method causes minimal damage to the substrate and is suitable for fine cleaning of complex-shaped internal holes and high-alloy materials, commonly used in the repair of aerospace components. However, strict control of solution composition and current density is required, as well as proper waste liquid treatment.
High-pressure airflow or water jet methods achieve peeling through kinetic energy impact. High-speed airflow carrying abrasive particles or high-pressure water jets impact the target layer, breaking it down and carrying it away. This method is suitable for softer or less adhesive residues, such as plastic spills and rubber shavings. This method is environmentally friendly, leaving no cutting chips, but its effectiveness is limited by the aperture and depth-to-diameter ratio, and it has limited effectiveness on dense, hard layers.
In practice, the above methods are often combined based on aperture size, material properties, precision requirements, and production targets. For example, most of the coating may be removed by mechanical cutting first, followed by grinding and polishing to improve surface quality. The versatility of internal hole peeling machines allows them to flexibly address different process challenges in fields such as electronics, automotive, medical, mold making, and aerospace.
