Views:22 Author:Site Editor Publish Time: 2020-09-04 Origin:Site
Ambient condition requirements of plastic extrusion machine:
1. Indoor use only, ambient temp between -20℃ to 40℃.
2. Air humidity≤85%
3. Without conductive dust or corrosive gases that damage metal insulation
4. Avoid vibration and bumps
The function of PVC coating extruder
The purpose of the PVC coating extruder is for melting processable polymer granules, using the rotary shearing and transferring effects of the screw to deliver homogenous molten resin, then pass the viscous plastic under high-temperature pressure through the die runner with a specific cross-sectional shape, final pass through the molds installed on the head to wrap on the copper wire or core wire to achieve the purpose of insulation.
In actual use, pay attention the extruder output should be matched to the use level of the product going to be made. In principle larger screw do not use for smaller diameter cables, for example using a 90mm screw for cable OD 2.0, the extruder output will be much larger than the use level which will make the redundant resins staying in the barrel for a longer time and final causing the burns of resins. This not only reduces the quality of the products but also reduces the service life of the screw.
The plastic extrusion machine is mainly composed of a transmission system, screw and barrel, heating and cooling control system, crosshead, automatic hopper dryer and vacuum loader, optional of stripe or skin extruders.
I. Preparation before start-up
1.1. The granules for the extrusion process should meet the drying requirement before into screw and pre-drying is required when necessary.
1.2. According to the product type and size chose the correct cross-head type and install the cross-head flange, breaker plate, screening, mandrel & matrix in sequence.
1.3. Install the heater & thermocouple then lock the clamp to ensure no leaking.
1.4. Adjust the distance of tooling(if manual centering head) and check the stripe extruder (if have) nozzle if on the same line.
1.5. Turn on the capstan and take-up switch checking if there are working or not, in step speed and monitoring the performance as well as the instrument working status.
1.6. Switch on the heater for cross-head and barrel to warming up and keep it for at least 5 minutes when the actual temp is 10 centigrade higher than the setup temp. To make sure the temperature is evenly at the extruder set.
1.7. When each part reaches the specified temperature, check and tighten the adjusting bolts connected to each part of the PVC extrusion machine head.
1.8. It is strictly prohibited to start up the plastic coating extruder machine in cold conditions in case the high plastic viscosity resin makes the screw breaking.
II. Attentions during operation
2.1. Slowly feeding in a small amount at the beginning and increase it when the cross-head is coming out with melt flow.
2.2. After the plastic is extruded, the core wires of the entire production line are connected from head to tail, and the auxiliary machines are allowed to operate.
2.3. Adjust each part of the PVC extrusion machine according to the indicated value on the control cabinet and the requirements of the products, until the operation reaches its normal state.
2.4. Cut the extruded sample, check whether the appearance and size of the product meet the requirements, and then adjust the extrusion process according to the quality requirements.
III. Operation of shutdown/downtime
3.1. Stop feeding and discharge out all the remaining plastic inside the barrel as much as possible until the wire cannot be made.
3.2. Stop all the auxiliary equipment such as preheater, powder applicator, chiller, etc.
3.3. Discharging out all remaining plastic in the screw barrel and head of the machine. When extruding plastics such as Rigid PVC, the soft PVC granules should be added for cleaning the screw and the barrel.
3.4. Extruding polyolefin plastic, usually shutdown the plastic extrusion machine under the full load of the extruder (stop with the material loaded ), this is to prevent air into the barrel, so as not to oxidize the plastic in the barrel, and continue to produce the quality products.
3.5. Stop the main engine, clean the head, lock the head clamp, and prepare for the next shift production.
3.6. Switch of the general power supply, as well as the air supply and water supply.