Aochuang Machinery’s Specialised Solution for ABS Rotational Fusion Welding

I. General Provisions

1.1 Purpose of Compilation

To standardise the operational procedures for the entire ABS plastic rotary fusion welding process, unify process parameters, joint structures, operating procedures and quality assessment requirements; to address common issues in ABS welding such as cold welds, bubbles, cracks, uneven flash and insufficient strength; to ensure the sealing performance, structural strength and visual consistency of welded joints; and to meet the requirements of mass production, finished product inspection and after-sales warranty.

1.2 Scope of Application

This specification applies to the rotational friction fusion welding of circular, rotating ABS plastic components, covering circular joint structures such as cylindrical butt joints, tubular socket joints and annular end-to-end joints. It is widely used in the welding of ABS plastic products such as household appliance components, water purification components, automotive plastic piping and industrial sealing housings. This specification applies solely to the rotational friction fusion welding process for thermoplastic ABS materials and is not applicable to modified flame-retardant ABS or glass-fibre reinforced ABS, nor to other specially modified materials.

1.3 Process Principle

Rotational friction welding of ABS plastics is a rotational friction welding process. It utilises the equipment's spindle to drive two sets of circular ABS workpieces-one upper and one lower-to rotate at high speed relative to one another. Under constant axial pressure, continuous frictional heat is generated at the welding end faces of the workpieces. When the end face temperature reaches the ABS melting temperature range (210–260°C), the plastic at the contact surface rapidly melts and plastifies;rotation is then stopped, and a constant forging pressure is maintained whilst the assembly is held under pressure and cooled, allowing the molten plastic molecules to diffuse fully, intertwine and fuse. After cooling and solidification, a high-strength, high-seal integrity integrated welded joint is formed.

II. Material and Equipment Requirements

2.1 Technical Requirements for ABS Base Material

1. Material: Pure ABS thermoplastic. The workpiece must be free from ageing, moisture and impurities. The use of mixed materials is prohibited to prevent delamination and poor fusion during welding.

2. Workpiece Appearance: The welding end faces must be flat and smooth, free from burrs, flash, oil, dust, scratches or deformation. The flatness tolerance of the end faces must be ≤0.05 mm to ensure a tight fit.

3. Moisture Content: ABS workpieces must be dried prior to welding, with a moisture content of ≤0.02%, to prevent the formation of bubbles or porosity defects caused by high-temperature friction.

2.2 Core Welding Equipment

A fully automatic rotary fusion welding machine for plastics is used. The equipment must be equipped with automated control functions including adjustable rotational speed, controllable pressure, precise timing and stable pressure maintenance. The core configuration requirements are as follows:

1. Spindle system: Speed adjustment range 200–3000 r/min; speed stability error ≤ ±5%; operation free from vibration and eccentricity to prevent workpiece displacement and uneven welding.

2. Hydraulic/Pneumatic Pressurisation System: Pressure adjustment range 1.0–6.9 MPa; smooth pressure output with no transient fluctuations during upsetting and pressure holding.

3. Control System: Supports segmented parameter settings (friction stage, upsetting stage, pressure holding stage, cooling stage), with a time accuracy of 0.01 s. Capable of storing multiple sets of ABS-specific process programmes, suitable for batch production.

4. Dedicated tooling and fixtures: Customised ABS workpiece positioning fixtures ensure workpiece concentricity of ≤0.03 mm, providing secure clamping and precise positioning to eliminate welding eccentricity and misalignment.

2.3 Auxiliary Tools and Consumables

Lint-free wipes, anhydrous ethanol, hot-air drying equipment, callipers, dial gauges, tensile testers, leak testing fixtures, and temperature-controlled cooling equipment.

III. Pre-welding Preparation

3.1 Workpiece Pre-treatment

1. Drying: Place the ABS workpieces in a constant-temperature drying oven and dry at a constant temperature of 70–80°C for 2–3 hours to remove internal moisture. After drying, store in a sealed container to prevent re-moisture.

2. Surface cleaning: Wipe the welding ends and mating surfaces with anhydrous ethanol to thoroughly remove oil, dust and release agent residues. Allow to air dry naturally after wiping; do not touch the welding ends with bare hands.

3. Workpiece Re-inspection: Inspect the workpiece for dimensions, roundness and flatness. Reject any non-conforming workpieces that are deformed, damaged or have defective end faces.

3.2 Equipment Commissioning and Inspection

1. Equipment Inspection: Check the operational status of the spindle, pressure system, control system and cooling system. Ensure the equipment produces no abnormal noises, has no oil leaks, and that the air/hydraulic pressure is stable.

2. Fixture Calibration: Install the specialised clamping fixture, calibrate its concentricity and levelness, and perform a test fit of the workpiece to confirm precise positioning and reliable clamping, with no looseness or misalignment.

3. Parameter Presetting: Based on the thickness of the ABS workpiece, pipe diameter and joint structure, preset the basic welding parameters; run the machine idle 3–5 times to confirm that the equipment parameters are executed accurately.

3.3 Requirements for the working environment

The operating environment temperature should be 18–28°C, with humidity between 40% and 60%. The area must be dust-free, draught-free and free from airborne particles to prevent environmental contaminants from adhering to the welding surfaces and affecting the quality of the fusion. The work surface must be kept clean and free of clutter to ensure sufficient space for equipment operation.

IV. Core Welding Process Parameters (ABS Specific)

Based on the melting characteristics, hardness and flow properties of ABS plastic, standardised process parameters have been established to suit the welding of conventional circular ABS plastic parts:

Principles for Optimising Parameters

1. Thin-walled small parts and small-diameter pipe fittings: Reduce rotational speed, shorten friction time and decrease forging pressure to prevent flash and deformation;

2. Thick-walled large parts and large-end-face joints: Appropriately increase rotational speed and extend friction time to ensure complete melting of the end faces;

3. Workpieces with high sealing requirements: Increase forging pressure and extend pressure holding time to enhance joint density.

V. Standardised Welding Workflow

5.1 Workpiece Clamping

Precision-fit the upper and lower sets of ABS workpieces into the upper and lower clamps respectively. After positioning and alignment, secure the clamps. Verify that the workpieces are coaxially aligned, with no misalignment or looseness. Upon completion of clamping, re-check the positional accuracy of the workpieces.

5.2 Equipment Start-up and Friction Heating

1. Start the equipment programme; the spindle drives the upper workpiece to rotate at a constant speed until the preset stable rotational speed is reached;

2. The spindle descends, bringing the workpiece end faces into contact whilst applying the preset friction pressure; continuous friction between the end faces causes rapid heating, gradually bringing the material into a molten plastic state.

5.3 Forging and Fusion Moulding

Once the set friction time is reached, the equipment brakes instantly to stop rotation and simultaneously switches to high-pressure upsetting. This compresses the molten end face, causing the molten ABS layers on both sides to fuse fully and interlock at a molecular level, thereby completing the fusion moulding.

5.4 Pressure Holding, Cooling and Curing

A constant holding pressure is maintained whilst the workpiece cools at rest, allowing the welded area to fully solidify and set, eliminating internal stresses and preventing cracking, deformation or warping after cooling.

5.5 Unloading and Re-inspection

Once cooling is complete, the equipment resets and releases the clamps; the welded product is removed gently-violent disassembly is prohibited. A preliminary inspection is carried out to check for flash on the exterior and the flatness of the joint, after which the parts are sorted and stored pending further inspection.

VI. Quality Inspection Standards and Acceptance Criteria

6.1 Appearance Quality Standards

1. The welded seam shall be uniform and regular, with no breaks in the weld, no cold welds or gaps around the entire circumference; the misalignment at the joint shall be ≤0.1 mm;

2. The weld bead must be uniform and continuous, with no localised build-up, no defects, no scorching or blackening, and no yellowing or discolouration;

3. The workpiece shall be free from cracks, deformation or warping, and its overall shape shall conform to the dimensional requirements specified in the drawings.

6.2 Structural Strength Standards

1. Tensile test: The tensile strength of the welded joint shall be ≥85% of the base material strength of the ABS; the failure mode under load shall be base material fracture; detachment or tearing of the weld seam is prohibited;

2. Torsion Test: Circular joints must show no loosening or torsional cracking, and must meet the load-bearing requirements for product assembly and use.

6.3 Sealing Performance Standards

For ABS plastic parts intended for sealing applications, air pressure/water pressure sealing tests shall be conducted. Under rated pressure, the pressure shall be maintained for 30 seconds; there shall be no air leakage, water seepage or pressure loss, and the joint shall be deemed to have passed the tightness test.

6.4 Dimensional Accuracy Standards

After welding, the total length, roundness and concentricity of the workpiece shall comply with the dimensional tolerances specified in the drawings; there shall be no dimensional deviations that affect subsequent assembly or use.

VII. Common Defects and Remedial Measures

VIII. Safe Operation and Civilised Construction

1. Operators must wear protective gloves and safety goggles. Do not touch the running spindle or workpieces that have just been welded and are still hot with bare hands, to prevent burns and mechanical lacerations.

2. Do not open the safety door whilst the equipment is running, and do not reach into the machine to touch fixtures or workpieces. In the event of a fault, the machine must be shut down and the power disconnected before repairs are carried out; working on live equipment is strictly prohibited.

3. Strictly adhere to process parameters; unauthorised modification of equipment programmes or overloading of the equipment is prohibited.

4. Keep the work area tidy; store workpieces, semi-finished products and finished goods in designated zones, and clear away scrap material promptly to prevent the accumulation of debris.

5. At the end of each working day, clean the equipment and fixtures, switch off the power and gas supplies, and complete equipment maintenance and operational records.

IX. Protection and Storage of Finished Products

1. Stack and store finished products that have passed welding inspection only after they have cooled to room temperature. Do not stack or compress them whilst hot to prevent deformation.

2. Pack finished products individually to prevent friction, impact or scratches to the welds and workpiece surfaces.

3. The storage environment must be dry, well-ventilated, dust-free and protected from light. Avoid prolonged exposure to high temperatures and humidity, which may cause workpiece ageing and a deterioration in joint performance.

X. Supplementary Provisions

1. This procedure constitutes a generalised standard for ABS plastic rotary fusion welding. For workpieces with special structures or intended for specific applications, parameters may be fine-tuned based on actual test results to create bespoke process documentation for record-keeping.

2. All operators must be familiar with the procedures and parameters outlined in this protocol and may only commence operations after successfully completing pre-employment training.

3. For matters not covered in this procedure, refer to the general industry standards for plastic rotary fusion welding and the equipment operating manual.