Injection Molding Technician Process Summary

First, the raw materials are dry:
1. ABS (MBS): drying temperature 80~85°C, drying time 2~4 hours, material layer thickness 30~40mm;
2, HIPS and PS: raw materials that are not added with water-filled materials and are tightly packed, generally do not need to be dried;
Adding nozzle material: drying temperature 70~75°C, drying time 1.5~2 hours, material layer thickness 30~40mm;
3, PMMA (acrylic): drying and drying temperature 70 ~ 80 ° C drying time 2 ~ 4 hours, material layer thickness 30 ~ 40mm;
4, PC: drying temperature 120~130 °C, drying time 2~4 hours, material layer thickness 25~30mm;
5, PPO: raw materials without added water and tight packaging, generally do not need to dry; add water nozzle: drying temperature 100 ~ 120 ° C, drying time 2 ~ 3 hours, material layer thickness 25 ~ 40mm;
6, POM (Saigang): drying temperature 80 ± 5 ° C, drying time 2 ~ 3 hours, material layer thickness 25 ~ 30mm;
7, PA: drying temperature 90~100, drying time more than 4 hours, material layer thickness 25~30mm;
8, PP: Generally do not need to dry.
Second, the melting temperature (one of the most important factors in injection molding):
The actual melt temperature should be the temperature of the plastic measured at the nozzle with a temperature probe, which is typically about 10 to 20 ° C higher than the temperature of the front of the barrel normally displayed on the machine computer.
The principle of setting the temperature of the rice cylinder is as follows: the rear part of the hopper is set to be 30~40 lower than the recommended melting temperature, and then the temperature is increased step by step, and the recommended melting temperature can be set at the nozzle.
1. Ordinary ABS (T700, etc.): The melting temperature range is 200~250°C, and it is recommended to be 210~225°C;
2, fire ABS (PA765A, etc.): melt temperature range of 200 ~ 240 ° C, recommended 200 ~ 210 ° C.
According to the above setting principle, the barrel temperature of PA765A is set as follows:
Front section: 180~200°C, middle section: 190~205°C, rear section: 195~210°C, nozzle: 200~210°C
3, HIPS: melting temperature range: 200 ~ 250 ° C, recommended 200 ~ 230 ° C;
4, PMMA: melting temperature range: 210 ~ 270 ° C, recommended 240 ~ 250 ° C
5, PC: melt temperature range: 280 ~ 320 ° C, recommended 300 ~ 310 ° C
6, PPO: melt temperature range: 260 ~ 310 ° C, recommended 280 ° C
7, POM: melt temperature range: 180 ~ 230 ° C, recommended 205 ° C
8, PA6: melt temperature range: 230 ~ 280 ° C, recommended 250 ° C
9, PA66: melt temperature range: 260 ~ 300 ° C, recommended 280 ° C
10, PP: melt temperature range: 200 ~ 275 ° C, recommended 230 ° C.
Third, the resin color temperature and start-up shutdown notes:
1. Ordinary ABS (T700, etc.): Although the decomposition temperature of ABS is as high as 270 °C or higher, the resin tends to change color at around 250 °C due to the influence of other process conditions. If it is below 20 °C but is made of light-colored high-gloss products, if it needs to stop for 15 minutes or more, the temperature of the barrel should be lowered to 120 °C first.
2. Fireproof ABS (PA765A, etc.): In the process of starting or stopping the flame retardant ABS, in order to prevent the decomposition of the flame retardant, it is required to clean the cylinder (using general-purpose ABS) and then process it. . For shutdowns that require more than 15 minutes, the cylinder temperature must be reduced to below 100 °C on the one hand before the shutdown. On the other hand, the material in the cylinder is drained and the cylinder is stopped by general-purpose ABS.
All common and fire-resistant ABS require a slightly lower barrel temperature, and special attention should be paid to the stability of the front section of the barrel and the temperature of the nozzle, otherwise it will cause poor appearance.
3, HIPS: PS is generally resistant to heat, but it will turn yellow when heated in the barrel for too long. The cylinder residence time of 250 ° C can not exceed 5 minutes. If the temperature is 275 ° C, the residence time should not exceed 1 to 2 minutes. Signs of overheating of the resin can appear twill or streaks (as wet). After a short shutdown (up to 5 minutes), it is best not to have the first batch of products; if the downtime is long (up to 1.5 to 2 hours), the temperature should be reduced to 150 °C. If this time is exceeded, it must be completely cooled.
4. PMMA: If the temperature is 260 °C, the retention time of the barrel should not exceed 10 minutes at most. If the temperature is 270 °C, the residence time should not exceed 8 minutes.
The hopper and barrel of the formed PMMA should pay special attention to the cleaning condition. If other materials are left in the barrel, the barrel should be cleaned first (the cleaning material can be recycled with PMMA), and the PVC, POM, etc. are left in the barrel. When materials are used, care should be taken to clean the cylinders with materials such as PS and then clean them with recycled materials instead of directly using the recycled materials of PMMA.
5. PC: To increase the activity of the melt, it is not to increase the injection pressure but to increase the injection temperature. It does not decompose in the cylinder for a long time at 300 °C, such as when it exceeds 340 °C. The PC will decompose in the ground, the color of the product will become darker, and defects such as silver wire, dark stripes, black spots and bubbles will appear on the surface, and the physical and mechanical properties will also be significantly reduced.
When starting up, if the material stored in the barrel is PVC, POM, etc., when the molding temperature is lower and the thermal stability is slightly worse, the PC cannot be used to push the cylinder, and the barrel temperature should not be raised, but should be low. At the temperature, the barrel is cleaned with a resin with good thermal stability such as PE or PS. Then raise the temperature of the barrel to the processing temperature of PC, and then clean the barrel with PC recycled material, and empty other resin before processing with new material.
Temporary shutdown for more than 20 minutes requires the cylinder temperature to be reduced to below 160 °C, so as to avoid degradation of the material due to excessive downtime.
6. PPO: When the machine is turned on, when the raw materials in the barrel are PA, PC, PP, etc., it can be directly cleaned with PPO. For PVC, POM or other heat-sensitive materials that are susceptible to thermal decomposition, these materials must be replaced by PS or PE first, and then processed at PPO processing temperature with PPO. When the material is discolored and degraded in normal processing, the temperature is lowered and the material in the barrel is immediately drained. Then, the material is cleaned with PS, PE, etc., and the new material is processed after the process adjustment.
When the downtime is less than 15 minutes, the normal processing temperature can be maintained. If the downtime exceeds 15 minutes, the barrel temperature must be reduced to below 200 °C. If the downtime is 2 hours, the barrel temperature must be reduced to 100 °C. Below, if the downtime is more than 4 hours, the cartridge must be cleaned with PS.
7. POM: The lower molding temperature and shorter molding cycle should be selected as much as possible. The molding temperature of POM should not exceed 200 °C, and the homopolymer should not exceed 220. At this temperature, the material will be decomposed within a few minutes; The residence time in the cylinder above 190 °C is too long, otherwise it will cause the material to decompose. When starting up, first open the nozzle to heat the power supply, so that the nozzle is preheated, and then turn on the barrel to heat the power.
Before processing the POM, if there is material in the barrel that has a processing temperature exceeding the processing temperature of POM, the barrel must be cleaned with other resin such as PE, and the temperature is lowered below the POM processing temperature, and then the barrel is cleaned with PE, then Add POM for molding processing operations.
In the molding, if there is a serious pungent formaldehyde smell, and the product is accompanied by a yellow-brown strip, it means that the material has been overheated and degraded (sometimes the moisture is too high, but the color strip is light), and should be used immediately. The injection method empties the material in the barrel and cleans the barrel with PE. After the temperature drops to normal (or the material is dry), it is processed.
8. PA: If the temperature of the melt is above 300 °C, avoid the residence time is too long (such as more than 15 minutes), otherwise it will degrade and make the product fade or brittle. If the plastic is too hot, it needs to be cleaned up. If the residence time must be extended, the temperature should be reduced to 200 °C.
Fourth, the basic process of debugging products and the basic methods to improve defects:
1. After the mold is put up, borrow two copies of the Forming Condition Table (for production and test molds) and follow the water transport method on the Forming Condition Table (for test molds).
Connect the water and set the mold temperature.
2. Set the barrel temperature.
3. After the mold temperature comes up, it can be officially started.
4. First set the total stroke of the shot with reference to the forming condition table.
5, first debug out the first stroke, that is, the rubber material has just crossed the nozzle for a short distance;
6. Debug the second stroke, that is, the journey of about 95%~98% of the product.
7. Debug the last leg of the journey, that is, just fill the product's itinerary, pay attention to the accuracy of 1~2mm, and not leave a little bit unfilled or overcharged.
8. After debugging the three-stage large stroke, the first section can be set to the slow point, and the second section of the pressure and speed can be set to high pressure and fast, and the maximum can be more than 90% (provided that various appearance defects cannot occur in a large area) ), the last paragraph needs to lower the speed and pressure again.
9. If there is a local trapped gas, flow pattern and other speed-related defects in this process, it is necessary to measure the cause of the defect and estimate the position of the stroke where the defect is located, and then find it by means of filling and analysis. Actual position, add a slow or fast small stroke to the first few mm and a few mm behind the position to debug, and improve the forming defects with this kind of push
10, hold pressure (the first paragraph is recommended to set to slow and short time), pay attention to check whether there is no pattern after the pressure.
11. In order to prevent the rubber material from staying in the barrel for too long, the amount of residual glue is 3~8mm. Therefore, after the above actions are completed, the strokes of each section should be added or subtracted, and the amount of residual glue should be adjusted to this range. .
12. The pressure and speed of the above paragraphs can refer to the existing Forming Conditions Table.
13. The basic setting principle of the cooling time of each set of molds is as follows: in the case that the long bone position or long column position of the product is not deformed, and the appearance is not white or top height, the flow channel is just cooled to be taken out. The cooling time should not be too long.
14. The screw speed does not need to be set too fast or too slow, and its swing time is slightly shorter than the cooling time.
15. In order to speed up the forming cycle, it is necessary to shorten the time of opening and closing the mold as much as possible. However, when the mold is closed, there is no loud sound and the nozzle that can be dropped by itself can be safely dropped. When debugging the manipulator, it is also necessary to speed up the robot to drop the middle of the mold. In order to ensure that the intermediate cycle of forming is controlled between 4 and 6 seconds.
16. After the commissioning, check the appearance of the samples provided by the quality department (check whether there are any slight shrinkage, defects, flow lines, gas lines, water lines and colors, and whether there are any differences on the appearance. Injury or pitting rust, etc.), but this process needs to be controlled within 10 minutes; if self-checking appearance NG, continue to improve with reference to Article 9 above;
If the appearance of the self-test is OK, then 15 beer will be formed under this condition. On the one hand, observe whether there is any change in appearance. If not, take the 8th beer, and after cooling it, refer to the sample and the "Inspection Standard Book" to measure the size of the control. OK, the processing board is signed to the production team leader, and the first inspection is sent.
5. Provisions for daily maintenance and mold-down maintenance of molds in production:
1. In order to prevent foreign matter (such as glue, draping, etc.) on the surface of the mold, the mold is crushed, and at the same time, the oil and dust on the surface of the mold are prevented from being badly formed during the forming, and the technician must use it every 4 hours. Clean the PL surface of the mold with a clean cotton cloth and record it;
2. In order to prevent the guide column and the thimble and the row from ablation after the lubricating oil is dried up, the original lubricating oil of the guide post and the row position should be wiped and coated with new oil every 4 days, the thimble is completely ejected, and the clean cotton cloth is used. After wiping off the water vapor and the original lubricating oil on each of the cylinders and the inclined top, the ejector plate is returned, and an appropriate amount of thimble lubricating oil is sprayed on the square of the stool, and then the ejector action is repeated 3 to 4 times. And make a record.
3. If a set of molds has not been moulded for 25 days in a row, it is necessary to drop the mold to arrange a maintenance section of the biotechnology class maintenance team or the mold department maintenance team for a comprehensive maintenance.
Sixth, the work at the end of the formation:
1. After the end of the specified production, close the baffle under the hopper, and repeatedly rotate the screw and shoot until the resin in the barrel will be completely discharged. Note (If the inside of the cylinder is not in the high-speed return, it will be easily damaged, so Rotate at low speed).
2. The resin used for molding is a highly viscous resin that is easily decomposed by thermal decomposition. It must be replaced with PS or PE. The resins that must be placed are PVC, PC, POM, etc.
3, the oil on the mold is first blown with a wind gun, and then wiped clean with a clean cotton cloth, sprayed with a thin layer of anti-rust oil (not excessive).
4. Use low-pressure clamping (no manual high pressure is allowed), retreat the screw drive, turn off the cooling water, and cut off the power.
5. All technicians need to strictly supervise the relevant upper and lower molds to carry out the upper and lower mold operations in accordance with the “Guidelines for the Upper and Lower Parts of the Injection Molding Department” issued by the company to prevent safety accidents, mold damage, and Please pay attention to the balance of the upper and lower molds and the lower mold when the mold is not properly handled and the mold surface is rusted.
Seven, refueling and color change operations:
1. Close the baffle under the hopper, and repeatedly rotate and eject the screw until all the resin in the barrel is discharged.
2. Remove the hopper, remove the resin in the hopper, and remove the inside of the hopper and the resin drop.
3. Add new resin or intermediate material (refill resin, such as PS, PE, PP, etc.).
4. Carry out the material replacement work of the barrel, set the barrel temperature to be slightly higher than the set temperature of the former resin (+10 ° C or less), and the injection pressure is medium pressure.
5. After the material replacement in the barrel is completed, the metering is set to 5~10mm at the same or slightly lower temperature, and the highest speed and pressure are emitted, in order to replace the material between the head of the barrel and the nozzle.
6. When the above method is not completely replaced, repeat 45, and change the back pressure, the number of revolutions, and the injection speed several times, and it will receive good results.
7. After replacing the old material with new materials or intermediate materials, set the temperature to the forming temperature of the new material or intermediate material.
8. If an intermediate material is used, then the procedure of 1~7 is repeated, and the intermediate material is replaced with a new material.
8. Provisions for the treatment of machines and moulds for the production of special materials:
1. If the plan is to produce transparent or light-colored high-gloss products, and the former material is not light-colored material; and the plan is to produce light-colored products, and the former material is fire-rated material, the technician needs to plan When the order is completed, the machine will be arranged to replace the barrel and screw or the immediate cleaning screw, barrel, nozzle, rubber head and meson and hopper. After the machine is repaired, the technician should carefully check whether it is cleaned or omitted. Lead to repeated loading and unloading and commissioning.
2, the production of fire-resistant materials for 15 days or less than 15 days, but the black spots are not increasing, the technicians need to arrange the disassembly and cleaning after writing the hand-written materials.
3. For the production of transparent or light-colored high-gloss products, the technicians need to arrange the molds for the cleaning and transfer plan about 4~6 hours before the current plan is expected to be completed.
4. After the completion of all work orders, at least 1 beer sample (not processed by hand, including runners and nozzles) should be provided to the biotechnology class, and it is necessary to simply explain which parts of the product are difficult to debug, etc. The mold data is subsequently improved for production.
Nine, other matters needing attention:
1. Note on mold temperature:
The general requirement is that the industrial parts maintain high temperature, and the general-purpose goods are kept at a low temperature. Whether it is heating or cooling, a stable temperature is obtained to obtain a uniform molded product.
2. Always check the gauge of the forming machine:
The instrument installed on the machine is the thing that represents the state of the machine. It must not be ignored. Just like the car driver should always observe the speedometer, water temperature meter and fuel gauge, pay attention to the precision instrument. For the injection molding machine, The pressure gauge is a hydraulic pressure gauge that supervises the highest pressure of the hydraulic line, the load of the hydraulic cylinder (the clamping force for the direct press, the closing force for the toggle machine), the injection pressure, etc. Whether the mechanical force is fully exerted, and the pressure gauge is a vulnerable part. When it is outside the pine tree, it must be closed and well protected.
Thermometer.....When paying attention to the temperature-adjusted batch needle (indicative temperature of the thermocouple), it can be found that the heater disconnection is different from the heating and energization. When the temperature reaches a certain temperature or higher, the temperature abnormality alarm will alarm.
The level meter ..... its role is to investigate the amount of oil, monitor the state of the operating cylinder capacity, in case of ignoring this content, causing all the operating oil to use light, it is necessary to repair, when the amount of oil is too small, it will alarm.
3. It is forbidden to stop for a long time when the clamping force is applied, and the alarm will be issued when the type is placed. When shutting down, the mold should be closed with low pressure.
4. On the bearing bushing of the clamping device, it is necessary to regularly lubricate the oil. The rod bushing and the thickness adjustment section are also regularly supplied with oil (one shot per 500,000 shots). (There is a period of every three months) The injection part of the injection unit must also be lubricated once a month.
5. Before the start of the forming, confirm whether or not the appropriate temperature of the cylinder is sufficiently raised according to the use of the resin.

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