I. Injection molding foundation
Plastics are polymer materials that can be molded and processed after being heated and pressurized. Plastics are natural resins and synthetic resins, generally pointing out synthetic resins made of oil.
One of the specialties of plastics is that it deforms after heating, so it can be easily mass-produced for various shapes.
Plastics are roughly divided into thermoplastic resins and thermosetting resins. Most products are made of these two plastics.
The properties of the thermoplastic resin are melted after heating, and cooling in the mold will solidify the product, reheat it, and dissolve the property.
The property of the thermosetting resin is that although it is heated and dissolved like a thermoplastic resin, it will solidify after reheating. Once it is solidified, it will no longer form a melting.
2-2 Injection molding
It means that the resin is heated and melted in the heating cylinder, then it is fired into the mold, and then the dissolved resin is cooled in the mold. Through this project to manufacture products.
2-3 Things required for injection molding
1. Formed material(resin)
2. Material dryer(hot air, desiccant, vacuum)
3. Injection molding machine
5. Mold temperature regulator(media: water, oil, heater)
7. Smash machine
8. Forming technology
Five Factors of Injection Forming Conditions
Temperature material drying, heating tube temperature, resin temperature, mold temperature, product extraction temperature, indoor temperature, executive oil, cooling water temperature
Time material drying time, measuring time, filling time, holding time, cooling time, period
Location(quantity) The amount of material placed in the Hopper, the starting position of injection molding, the most advanced position of injection molding, the end position of injection molding, the starting position of measurement, the amount of decompression, and the amount of injection molding
Speed measurement speed(screw rotation), injection molding speed, opening mode speed, top out speed, decompression speed
Pressure locking pressure, filling pressure, holding pressure, measuring load pressure, screw back pressure
2-5 forming conditions
The forming conditions should confirm how the five factors are set and the results obtained, and confirm that the forming product can be obtained within the set range and the result range.
What you need on the forming schedule.
1. The range of settings and the final settings should be clearly recorded.
2. The scope of the outcome and the final outcome should be clearly documented.
3. The non-producing parts of the product should be clearly recorded.
2 Forming Condition Setting Procedure
Before the 2-1 forming condition is set
What matters is what kind of resin, products, and molds are used.
1. Confirmation of resin properties.
How much temperature, how much time, how to dry
A number of dryness deficiencies, not only produce poor forming, but also produce a reduction in the physical properties of the product.
The temperature of the resin can be formed in what temperature range
Understand how much temperature will melt and how much temperature will decompose.
The temperature of the mold can be formed in what temperature range
What is the temperature of thermal deformation.
2. What kind of products(molds)
Is it thick or thin?
You can determine the injection time, cooling time, resin temperature, mold temperature required.
• De-moulding when filling is insufficient
Can judge the injection molding speed, injection molding pressure, the amount of resin required.
• Temperature adjustment methods for molds
Make sure to use water temperature, oil temperature or heater temperature.
2-2 Forming Preparation
1 Resin drying
Re-confirm temperature, time, method.
2 mold installation
Confirm the upper and lower direction of the die and the position of the top rod(number of roots, size), tighten the corner from the fixed side.
3 adjustment and confirmation of the action of unlocking die(top)
In order to avoid periodic waste and speed and mold protection, pay attention to position and pressure.
4 Mold temperature(warming)
The mold temperature method should be connected in the same way at a time. In addition, after heating up, you need to confirm the action of opening the mold again.
5 Cleansing in the heating cylinder
When replacing the material in the heating cylinder with the material to be formed, please clean it.
When the melting temperature of the resin to be used is higher than that of the previous resin, it is set to the lower limit temperature of the resin to be used.
When the forming temperature field is different, it is temporarily replaced with a stable resin with the same forming temperature of both resins, and then cleaned again.
When using a hot channel mold, cleaning in the mold manifold is required after the die is opened.
3 Forming condition setting
With regard to temperature, changes in setting values will not change immediately, so according to the resin data, product data directly associated with the temperature data, basically fixed setting values.
• Mold temperature
Heating tube temperature(including the amount of water flowing under the hopper)
• Screw rotation → 100r.p.m
• Screw back pressure → oil pressure: 5 to 10 kg/cm2
(resin pressure: about 50 to 150 kg/cm2)
(1) Measurement setting
In principle, the state that has never been filled begins to form.
○ Temporary Condition Setting
• Less measurement(SM)
• The pressure relief(SD) is about 3 to 5
No need to shoot with Valve
• Pressure holding conversion position is 10mm(same degree of pressure holding as back pressure)
NC9300T set at V-P
NC9000 F • G set at S5
• Injection speed, injection pressure setting(based on the same speed and 2 types of pressure)
Injection speed = V
Injection pressure NC9300T set in Pv
NC9000 F • G set at P1
• Pressure protection NC9300T set at Pp
NC9000 F • G set at P2, P3
Injection molding screen is set to show the state of the screw position.
○ Fill the resin in the mold in manual mode. When the screw does not advance, it immediately returns to the empty gear.
Please confirm which position the screw is advancing to.
After a certain cooling time, open the mold, check it as a shape, and operate according to the chart. Use these actions to set the measurement setting.
Status screw position treatment of forming product
(not filled) Advance to below 5mm to increase measurement
Stop between 5 and 10 mm and increase the holding pressure.
Stop above 10mm to increase speed, injection pressure
Thorn, whitening, rifts.
(Overfill) Advance below 5mm to reduce speed, injection pressure
Stop between 5 and 10 mm to reduce the holding pressure.
Stop above 10mm to reduce measurement
○ The screw forward position is about 5 to 7 mm to manufacture a good shape(not allowed to fill and Burr).
At this time, there is no problem with the appearance of poor appearance(injection marks, flow marks) on the forming product.
○ Enter semi-automatic mode
Reference chart 2, temporarily set injection molding time, cooling time, semi-automatic operation.
○ Enter fully automatic mode
It is true that the product is demolded, and after setting the intermediate time, it is fully automatic.
Injection molding time cooling time of forming product thickness
Up to 1mm 5.0 SEC 10.0 SEC
Below 5mm 15.0 SEC 20.0 to 30.0 SEC
Above 5mm 30.0 SEC 40sec
According to the different shapes of resins and products, the above figure is only for reference.
○ Set the injection pressure to 99(MAX).
NC9300T set in Pv, NC9000F • G set in P1
In order to confirm the speed condition amplitude in the next project, the speed is compensated, so the maximum value is set.
The injection pressure setting value is increased to every 10 <UNK>, and the condition is changed according to the chart 3 and set to 99 <UNK>.
Treatment of forming condition
Thorn generation reduces V during filling
Generate P2, P3 reduction during the filling period
If there is no Burr, etc., in order to adjust the filling time to the same degree, the injection molding speed is reduced and the injection molding pressure is set to 99.
In the future, the final setting value of stable forming can be determined only by understanding the condition range.
(2) Injection speed setting
Change the injection speed to confirm the good value of the product, and then determine the final speed setting value. (About filling time and weight of product)
1 Injection pressure(Pv or P1) = 99 <UNK> conserved pressure conversion position(V-P or S5) = 10mm
Fixed as a holding pressure(Pp or P2, P3)
2 Firstly, the poor appearance(burrs, insufficient filling, bleeding marks, etc.) was observed, and 5 to 10 data were sampled in order to obtain good conditions.
3 The number of samples is calculated based on N = 5.
4 Replace the set data with a chart.
The following figure shows