water injection molding makes hollow parts faster, lighter.

by:INDUSTRIAL-MAN     2019-08-30
Taking out thick slices with cooling water is not only faster than gas --
Auxiliary molding, but it makes the wall thinner and the interior of the part smoother.
The technology is very new, but it is developing to a wider range of commercialism. Water-
Auxiliary injection molding is the latest method of forming hollow or partial hollow parts.
Basically similar to gas.
Assist in forming as a means of the thick part of the core. But water-
Injection Technology (WIT)
There is a big advantage: direct cooling inside the part.
The thermal conductivity of water is 40 times that of gas, and the thermal capacity of water is 4 times that of gas.
\"With the cooling capacity of WIT, the cooling cycle time can only be reduced to 25% of the gas,\" said Helmut Eckardt, technical director of low-
Injection molding technology for injection molding of maynetz GmbH Battenfeld, Germany.
But the potential to accelerate the cycle is only part of the story.
\"There are a lot of reasons why this technology is attractive,\" said fridrish Westfall, project management engineering director (PME)
Supplier of WIT systems in Germany.
If done correctly, wit can produce thinner, more uniform part walls, which increases material savings, he said.
WIT is able to produce a smooth internal part surface, which is much more difficult with gas assist, making injection molding more competitive with blow molding.
Some sources also believe that WIT can produce more void space and longer hollow parts than gas.
A Schulman in Germany helped produce a prototype PP shopping cart with a 3-meter-long waterway!
At the K 2001 show in duseldorf, Germany last fall, the injection molding appeared on site in a huge way.
Some European suppliers of injection molding machines and independent manufacturers of natural gas are conducting R & D of this process
Assist in equipment, resin company, etc.
Most of the motivation for this activity is the 1998 witty research report of the fur kunstoffverarbeitung Institute (IKV)
German Center for the development of plastic processing.
IKV continues to actively develop this process.
WIT has limited commercial use in Germany and several projects are under active development.
But as wisdom is so new, many technical questions remain to be answered.
The researchers are seeking to determine the appropriate water temperature, pressure and flow rate, as well as the effect of internal water quenching on the properties of resin crystals and molded parts.
There are also many hardware problems.
\"The injection molding machine and processing have not changed in all aspects until the time of water injection,\" said Jorg Dassow, applied technology manager, Ferromatik Milacron, Germany.
\"At this point, there is a question of how and where to inject water, and the tools and control techniques involved in achieving this goal.
\"Other issues focus on pin, valve design and mold modification.
All of this is a quick indication by knowledgeable parties that tact should not be considered a reason for the decline --
To replace gas assist.
Who is involved in many suppliers that provide natural gas systems
Assist modified their device for use.
Currently, seven companies offer WIT technology.
These systems include three systems from news vendors: Aquamold from battonfield, Watermelt from Engel, and Aqua-
Reporters from Ferromatik Kelon Europe.
Independent sources of WIT equipment are Alliance gas systems, Cinpres Gas injection, Maximator in Germany and project management engineering (PME)in Germany.
Rodia engineering plastics, Germany is a material supplier that has developed its own material intelligence system
The purpose of the test, but not intended to be commercially available.
At present, all smart R & D is carried out in Europe, but suppliers expect a lower cycle time to attract users in North America.
\"Water is now a niche process, so it\'s important that no one promises too much,\" warned Oliver panschmidt, head of the IKV injection molding department.
He recalled when gasoline
Assisting with the initial arrival at the scene, the latency of the processor was difficult, and when they tried to bring the technology into the new field of molding, the processor had little technical help.
The main difference between water and gas is that gas is compressed, and water is non-compressed.
When injected into the melt, the front edge of the water forms a solid boundary or a highly viscous membrane.
The membrane forces the molten material to move forward, not the polymer forces the water to move to the side.
The main reason for this action is that water has a higher viscosity and non-compression compared to gas.
This sticky front is ram as a core part.
The front also pushes the melt down through the water pressure to cool in the mold cavity. \"Gas-
Assist works at pressure from 300 to 2500 psi while water-
\"Assist usually operates in a range of up to 4350 psi,\" said Kai Jacobsen, machine sales and technical manager at Engel . \".
\"The gas can be migrated to the solution through the polymer.
\"Water is a different story,\" Jacobson notes . \".
If the gas penetrates into the polymer, it can make the inner surface of the part rough when the gas moves out again.
However, Steven Van Hawkp.
The sales of Alliance Gas Systems believe that the rough inner surface may be due to excessive Gas pressure or the long placement of some gases ---
These two causes the gas to start acting as a foaming agent.
The supplier agreed on several other differences between gas and water injection.
Unlike water, the gas can branch into a smaller flow inside the part, resulting in poor finger-pointing effects.
The unpredictable behavior of the gas makes it very difficult to control the wall thickness, while water makes the wall thickness uniform and repeatable.
It has been noted that the gas does not cool the part. (
However, there is a new gas
Kotechnology, known as KoolGas, was developed by Warwick Manufacturing Group, part of the Advanced Technology Center of Warwick University, UK.
It can improve the cooling effect of gas by cooling at low temperature
292 F and/or circulating gas through the component at a high rate of up to 75 liters/min. )
Mold can be pre-made to reduce shrinkage and sinking
Pressurize with gas before injecting the molten, or introduce gas between non-molten
The appearance side of the parts and molds.
However, water is likely to become the surface of the part in March and cannot be used for this purpose.
\"Overall, we don\'t see the competition between natural gas.
Assistance and water
\"Assist,\" said Mark paddock. p.
And the general manager of Cinpres.
\"Generally speaking, the auxiliary effect of thicker parts and longer flow paths on water may be good.
\"Trying to apply wisdom to a large number
The supplier warned that cavity tools should be cautious.
They recommend the process of tools that do not exceed four to six cavities.
\"Molders should not consider using 12-or 16-
Because process control will be more difficult, \"said Jacobson of Engel.
Many companies expect the first users of WIT to be natural gas --
Help to seek molds that capture potential in a lower cycle time.
Tubular parts, automotive fuel lines and other fluid systems, handles, top racks, sheets, bumpers, door handles, clutch and steering-
Column support is some of the areas where suppliers want the technology to gain the first major foothold.
Other products under consideration include baby carts, kitchen supplies handles, office furniture, shovels, brackets and general purpose accessories.
Thilo Stier, technical director of
The first commercial use of wisdom, says Schulman of Germany, is
Plastic shopping cart produced by Germany Herford Sulo Co. , Ltd.
The project started in 1998.
It uses Shulman\'s PP and PME\'s WIT technology with three waterway mold parts ranging from 20 to 60mm in diameter and 800 to 1500mm in length.
The PP trolley was previously molded with gas.
Assist for 280 seconds while WIT only took 68 seconds.
Jacobson of Engel said,
Saw handle made of 30% glass-
WIT vs for filling nylon in 30 seconds
Gas assist 61 seconds.
Ferromatik reports that PP parts are in one production
Mold cavity test the mold takes 60 seconds as a solid part and 40 seconds with gas
Assist and have 30 seconds with tact. At IKV, a two-
The material sports racket was made using the Aquamold craft of battonfield. It is a three-
The process of shooting with two materials plus water.
The flow path is split from the racket frame to the core.
The handle and frame of the first gun mold 20% glass-
PP of Shulman.
The second photo is the net that is not filled with PP.
The third shot injected water into the picture.
Battenfeld\'s Eckardt notes that uncompressed water supports hollow frames when the network is injected.
PME 6 core-8 mm diam. glass-
Nylon pipes filled with gas and water.
Wall of gas-
The auxiliary part is two to three times thicker than water.
\"WIT trimmed the walls to about 2mm in a shorter cycle,\" Westphal said . \".
The witty part, he added, shows that the mechanical properties have improved even if the material is less.
The early success of technology has been somewhat successful.
PME seems to lead all the other vendors: in 2001, there were 12 systems running in a commercial or advanced project for PME.
The company received an order from a Dutch company asking the system to produce 960,000 electrical handles and use WIT to convert the production of another hollow handle from steel to plastic.
The latter project involves 360,000 units.
PME is also testing for BMW to convert the car pipeline from gasolineassist to WIT.
Rupprecht of Maximator said that in the coming weeks, molder will consider serious applications for its first water molding.
\"But we will consider using gasoline first,\" he added . \".
There are 8 to 10 candidates in the alliance.
\"We only chose two or three to further evaluate the wit, and the rest may cheer up --
\"Help,\" said Van Hawk.
The alliance has conducted witty trials with manufacturers of individual water craft. The 2-ft-
The wide part has a large number of internal parts hollowed out with gas.
Assist, but the gas will leave 1-in, wall.
\"With water, we can cut the wall thickness significantly and shorten the cycle time by 2 minutes,\" Van Hoeck said . \".
Battenfeld has about 10 Aquamold projects in the works and 8 to 10 Engel projects in the trials.
There are five projects in Cinpres and Factor that are going commercial.
These are tubular products in the automotive industry.
Each gas or water is being evaluated.
One of the four processes can apply four process methods.
These sequences, similar to the process changes seen by the gas
The injection technique varies depending on the filling of the polymer, the introduction of water, and the evacuation of water through gravity or air.
* Short shot: Also called bubble or blow-
During the Up process, it is performed by filling the cavity with the molten part.
Before the end of the molten injection, the water is injected into the mold, pushing the material to the end of the cavity for final packaging.
The valve closes the melt from the injection device and the water from the pin.
The release valve of the water is opened, allowing the water to be discharged from the part.
Valves installed at or near the end of the filler can use compressed air to promote the discharge of water.
This method is considered good for very thick parts.
It does not involve wasted material and re-grinding.
Entry and exit points of water (and air)
Can be in/near the same location.
The downside is the need for strict control.
Too little material can cause to burst by melting into the mold.
The water injection pressure must be higher than the melting pressure in order to push it to the end of the filling.
The switching point from resin injection to water injection may cause hesitant marking on the surface of the part, so class a finishes may not be feasible.
In addition, the material at the end of the short lens may form a thicker part, thus extending the cycle time.
* Push back: fully melt the filled cavity.
Open the water needle located near the end of the melt filling and push the excess melt back to the head space of the injection device.
The advantages of this method include the absence of scrap and the ability to reach the following levelsA finish.
As for the disadvantages, it requires a special nozzle and inspection ring to hold the material back in the injection unit.
The user must be careful not to let the water penetrate into the injection top empty (
This could be a big problem with moisture-absorbing materials like nylon).
Each part of the process must be under controlled pressure in order to put the known amount of material back into the molding unit.
The returned material may differ from the temperature or pressure in the barrel, resulting in process variables that may affect the next shot.
Separate air and water delivery systems are required.
* Overflow: the mold cavity is fully filled with molten material and closed with a valve.
The pin is then opened in the mold for water injection, and at the same time, the valve at the end of the cavity filling opens the path from the main cavity to the secondary or overflow cavity.
The incoming water replaces the molten material pushed into the secondary cavity.
In order to keep and pack, the secondary valve is closed.
Water can be drained by gravity or evaporation.
It is reported that this method can provide a class a surface.
It is closest to traditional molding and provides a wider processing window.
It also needs to be lower than the short water pressure. shot method.
The downside is that the replacement materials of the core must be recycled.
Secondary trimming is required to separate the finished product from the excess material in the secondary cavity.
* Process: combination of short processes
To enhance cooling, the fire and overflow methods flush the water over the part.
The cavity is partially filled and then water is introduced to push the material to the end of the filling.
At the end of the filling, a special valve is opened and the water passes through the melt and flows into the water through the valve
Recycling circuit.
The advantage is to save materials and cool fast.
Disadvantages include flaws at the tip of the part.
In addition, low pressure may cause water to penetrate between the inner mold surface and the outer surface.
A common factor in the WIT process is the need to clean the water.
Gravity is valid in some cases, but some suppliers advocate sorting with gasassist.
Alliance Gas Systems says its WIT system includes pressurized Gas purification.
Alliance can provide gas for sensitive materials
Secondary water injection is carried out by the auxiliary system, and then gas purification is carried out.
The entire water injection and drainage process takes only a few seconds, the supplier said.
Available business intelligence systems by Independentalone water-
Conveying hardware with pressure, temperature and flow control.
The controller also operates water and air valves in the tool.
Many systems also have water filtration.
Every company has its own professional water.
Nozzle or pin.
Some syringes can handle water and purify air, and some perform double service by getting water in and out of the mold. Maximum water-
The pressure and flow capacity of different systems are also different.
Most systems need to inject units to signal to start the loop.
* Alliance gas system with HMP-3 multi-
Fluid electronic syringe.
It injects water and gas.
\"Washing water with air is the fastest way,\" Van Hoeck said . \".
The pin is also used for water push back.
Alliance system in 60-70 F.
It has water injection.
Although 5000 to 1000 psi is usually used, the pressure capacity is 3000 psi.
* The Aquamold system of Battenfeld arises from its airmold gas unit.
Touch screen control for mobile devices.
It can also be controlled through the Unilog B4 system on the injection molding machine.
Modular system provides pressure-
A generator set of different sizes capable of withstand water pressure up to 4350 psi and a flow rate of 60 liters/mm.
The water pressure can be described in nine steps.
Compact pressure-
The control module can be installed near the mold.
Water can be injected and purified through the same opening.
The gas injected through another module can also purify the water. One pressure-
The generator set can serve several molding machines.
* Cinpres Gas injection currently offers a WIT system developed by Factor Maschinen & Anlagentechnik GmbH in heinburg, Germany.
CGI is developing its own system and it will have a different design but no details.
The factors of the system provide water pressure and flow rate of more than 2900 psi for 1 liter/min.
* Engel\'s water melting process is designed to cycle the water through the parts.
A new moving water
The maximum pressure of the jet unit is 2900 psi and the flow rate is 7. 9 gal/min.
* Two push from Ferromatik Dragon
Return and overflow process.
Aquapress technology based on the Airpress III system can provide about 4350 psi of water.
The company is evaluating the advantages of pressure up to 14,500 psi.
* Women in Development at Maximator
The flood system is based on GID gas.
Auxiliary technology. The water-
The accumulator system can provide a flow rate of up to 23 liters/minute in the case of up to 7250 psi.
The water pressure can be set at 10-step profile.
Maximator provides a spring
A loaded water injection nozzle opened under hydraulic pressure and closed through a spring. (
The current design is said to be an improvement to the initial model, which is not always completely closed. )
The company is testing new
Hydraulic nozzle design is being developed by Bayer, Germany.
* PME designed a touch screen PC-
Control system based on mold water injection and water circulation
Temperature control.
It also controls heat. runner system.
PME also provides 18 different nozzle designs for water injection.
The standard 27/210 system provides 27 liters/minute at up to 3480 psi, while the 130/150 model can provide 130 liters/minute at 5000 psi.
WIT power module 27/210 control water and compression-air delivery.
Resin companies such as BASF, Bayer, DuPont, Rodia and A are testing and developing materials for WIT materials in Europe. Schulman.
The two main candidates for early commercial use were Nylon 66 and PP.
Also tested are PC/ABS, HIPS, tb, B & L and co-polyester TPEs.
For example, DuPont\'s Zytel EFE73 reported promising witty results92 30% glass-
Make 1-filled nylon 66in. -diam.
BMW cooling pipe \"this part is currently using gns-
\"Help in 60 seconds, but we tested the same material in the same mold with WIT in 35 seconds,\" Bender said . \".
DuPont has also studied other thermoplastic plastics such as its Hytrel polyester TPE.
\"We think that WIT can be used in our product line, including both B & L and pbx.
Bender added, \"We have been working with WIT technology for a year and a half.
I hope to see the business development of the automobile industry next year.
\"Some industry insiders question whether WIT will lead to rapid quenching of crystalline resin, thus changing the crystal structure and thus the performance of the parts.
The information obtained so far from the material supplier does not indicate any significant impact on the microstructure of the material.
On the other hand, there will be more macro effects.
A. Stier says crystal materials can be A problem with WIT because they form skin so quickly when they cool down. Schulman.
He said that it should be tailored for materials with slower crystalline speeds to obtain a smoother inner surface and fewer external Hesitation Marks.
Six business intelligence applications have been running their nylon, ABS and PP materials since 1998, and eight other projects are in progress.
According to Claus bend, DuPont found that the rapid quenching of crystalline nylon can lead to the shrinkage gap inside the wall of the part, which may damage the structural performance, the process Director of DuPont Swiss engineering polymer technology center.
DuPont and Engel tried to inject warmer water to solve the problem, but the use of water up to 140 degrees Fahrenheit had no effect on nylon, said Bude.
This result seems to suggest that the modification of materials for slower crystals may be a better solution.
Need to know more?
Alliance gas systems
Chesterfield, Michigan. (810)948-5000 www. waterassist.
German Port Ludwig BASF621)60-0 www. basf.
Injection molding technology of German battonfield, maynetz Germany 49 (2354)72-0 www. bmf. battenfeld.
Com sets Cinpres Gas injection company.
Ann Arbor, Michigan. (734)663-7700 www. gasinjection.
41 22-DuPont Engineering polymer, Geneva, Switzerland, Europe717 6779 www. plastics. dupont.
Lnc website, Canada. , Guelph, Ont. (519)836-0220 www. engelmachinery.
Martdingen masinburg, Germany (49)7644)78-0 www. ferromatik.
IKV, Aachen, Germany 49 (241)80 93 806 www. ikv-aachen.
German Simme Masisi 49 (7261)94 54 0 www. maximator-sued.
Rodia engineering plastics 49 76 42 92 31 45 Rodia engineering plastics 49 (761)5 15 88-0 www. rhodia-ep. com A.
German kempan Shulman Co. , Ltd. (49)22 73)56 11 35 www. aschulman.
Coventry Warwick Manufacturing GroupK.
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