Necessary repair and strengthening methods for bi-alloy screw
Nov 03, 2021
The injection equipment of screw injection molding machine consists of barrel, screw of injection molding machine, nozzle, Hopper, metering equipment, screw transmission equipment, injection barrel, injection table moving barrel and other components.
The working quality of double alloy screw has an important influence on material plasticization, product quality and production efficiency. These working qualities are related to manufacturing precision and assembly clearance. When the parts wear seriously and the output of extruder decreases, necessary repair and strengthening methods should be applied to the twin alloy screw.
1. Arrangement of appearance
Before spraying the welding screw, the residual plastic attachments on the appearance of the screw must be sorted out and cleaned. The finishing method is to install the screw on the sprayer and rotate it, bake it with the neutral flame of the spray gun, and remove it with a cutter after plastic. After that, use sand-blasting gun to finish the appearance and further remove the oxide layer.
2. Preheat
When preheating, use coating machine or vibration welding machine to clamp screw head. Make the rotating speed of the machine tool below 15r/nin, neutral flame, preheat the whole screw from muzzle to screw 100mm to about 270, reduce the thermal stress of the shaft and ensure the quality of thermal spraying layer.
3. Jet welding
Single trigger welding technology, select SPH-1/h spray gun, No. 2 nozzle, oxygen pressure 0.25MPa, acetylene pressure 0.06MPa.
During rotation, the screw wear part is corrected by spraying welding, and the screw wear amount is about 2-3mm. In one operation, sufficient size should be sprayed, and the processing space should be considered. If the spray does not work once, pay attention to the preheating temperature and preheating uniformity when re-welding next time to prevent the welding layer from cracking.
4. Trimming and correction
Due to the skill requirements of the Screw, namely straightness, appearance of the screw and vibration of the Screw working face of screw shaft lines, the screw must be trimmed after welding. The trimming method is to process mandrel of the center hole and press it into the bearing hole of the screw head.
5. Preheating of the workpiece before painting
Preheating the workpiece before coating has great practical significance, which can remove the appearance moisture and reduce the stress concentration of the coating, especially the oxide scale shaft parts like our factory, the preheating temperature is appropriate at about 100C. Outside the treated Journal, aluminum coated nickel composite powder F505 is sprayed as adhesive layer. The thickness of the bonding layer can be 0.10-0.15. Since this layer is only used as a combination, it can not be sprayed too thick.
After spraying the binding layer, spray G101 powder working layer. G101 powder must be preheated at a temperature of 105-250 before application, and fired to ensure the flowability of the powder and prevent blocks from blocking the spraying channel. Strictly control the pressure of the ejected medium and gas, flame temperature, ejected interval, ejected angle and moving speed to make the coating even and flat, and the bonding is firm. The preheating temperature is 100-200C degrees Celsius. Spray Distance 180-200mm; Spray angle 90; Spray gun moving speed 12mm/min; Roller linear speed is 8-12m/min.
If neutral flame is used when spraying the working layer, the powder can be observed from the flame, and the powder at the end of the flame is white. This means that if the temperature is high, the temperature will not work if it is dark red or red. At this time, it is better to adjust the size of the powder feeding airflow and the flame energy rate to heat the powder into white. Now the powder has high temperature, fast speed and good accumulation effect.
6. Metal processing after coating
After the painting is finished, the coating part is wrapped with asbestos in multiple layers to cool it to avoid cracks. After cooling to room temperature, rough car is carried out, and grinding allowance can be left for grinding. The required scale and specified roughness of grinding drawings. The role modification ends here.
