Plastic injection molding machine

clamping tonnage 650TON to 1080TON

Plastic chair raw material:
Most of the plastic chair material are useing COPO-PP with MFI 6-30, the higher MFI the plastic chair will be softer, but the plastic filling  will be easier. Many plastic chair producer add 10 to 20% Talcum powder or other kind of calcium carbonate into the COPO-PP to make the plastic chair backrest, armrest and leg harder. In the same time to reduce some production cost due to the heavy competitive market.

Plastic production related auxiliary machineries

• water chiller or cooling tower

• autoloader

• mixer

• crusher

The chain safety device can protect the safety ofoperator and machine.
The material is thick ,strong and durable.
Well-distributed mixing can be done in a shot time, low energy consumption and high efficiency.
Time setting can be controlled easily and preciselyin the range of 0-15 minutes.
Chiller also provided cooling to cool lubrication oil in mian shaft.and transmission medium in hydraulic system of numerically-controlled machine tools, jig boring machines, grinding machines, processing unit,combined machine tools and all kinds of precision machines. Able to provided accurately temperature & effectively, reduce machine tools' deformation and improve processing accuracy.
Save energy & user friendly, no training required;
Strong cooling system without adjust thermostats, able to cool system rapidly;
Simple and easy to operate.

Good design ensures each device easy to service.

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·         Auto Loader

·         DKM - 330 / 360 series adopt single phase carbon brush motor with superior suction power and easy installation. It is particularly suitable for conveying new materials. SAL - 430 / 460 series use a three phase inductive motor with low noise level and long service life. It also has an automatic motor reverse cleaning device.

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·         Hopper Dryer

·         DKM series " Econo " hopper dryers offer an effective and low-cost method for plastic material drying. Hot air is used to dry wet materials that due to moisture absorption during packaging, transportation, and recycling cycles. They can be directly mounted on the moulding machine for quick drying and space saving. For this series, hot air blows evenly from bottom to the top ( both SHD-800 and SHD-1000 have down-blowing air pipe and accessible door for easy material clearance ) of the hopper with capacity ranging from 12 1000 kg.

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·         Crusher

·         DKM - 16 / 20 series low - speed granulators are suitable for by - the - press recycling of sprues they feature easy operation, excellent performance, low noise and dust level. They are in " Euro " style design and compact in size. High quality blades ensure long - life span. The high security grade also conforms with CE safety standard.

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·         Mixer

·         Both mixing pail and vane are made of stainlesssteel, easy to clean and absolutely no pollution.

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·         Water Chiller

·         The water chiller is to provided cooling process to plastic moulds to improve molded products quality & cut down injection cycle time.Hence maximizes plastic molding machines`productivity.

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·         Cooling Tower

·         Remove heat from the water discharged from the condenser so that the water can be discharged to the river or recirculated and reused.

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·         Mold Temperature Controller

·         Adopts PlD thermostat to provide dual(heating & cooling)control,maintains temperature, Precise temperature control within ±1℃；

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·         Air Compressor

·         The compact construction may meet the requirements of stable operation Many sets of compressors may be as- sembled on a steel baseplate with internal piping and line connecting each other, easily to fix. A complete set of sino-pm compressor equipped with efficient motor, Vee-belt drive, beltguard, high pressure switch and (delta-star, on-line) starter.

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·         Air Filter

·         Atmospheric air contains a mass of pollutants including dust, water aerosols, hydrocarbon and other gaseous contaminants by the addition of liquid oil, oil aerosols, oil vapor, (if an oil-lubricated compressor is used) liquid water, water aerosols, water vapor, pipe rust and scale as well as any extra micro-organisms that may be living, growing and multiplying in the compressed air lines. All of these unwanted, contaminants will arrive at the point-of-use of a compressed air system but can be removed by various filters depending on the level of clean compressed air required.

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·         Robot

·         PET Preform Beam Robots is dedicated to 350-1500CC PET Preform, applicable to PET Preform machine among 200-600 tons to get preform out, and also suitable for 1.16 cav. 1.48cav. preform production. Being installed on a fixed plate, take preform out and move to the outside of safe door. It is equipped with cooling system, so the forced air cooling after coming out preform can reduce the inmould cooling time sharply, so as to increase the production cavity.

Plastic injection molding is the primary process for manufacturing plastic parts. Plastic is known to be a very versatile and economical material that is used in many applications. Although the tooling is expensive, the cost per part is very low. Complex geometries are possible and limited only to mold manufacturability. Your computer monitor, mouse and keyboard are injection molded plastics.
Injection molding involves taking plastic in the form of pellets or granules and heating this material until a melt is obtained. Then the melt is forced into a split-die chamber/mold where it is allowed to "cool" into the desired shape. The mold is then opened and the part is ejected, at which time the cycle is repeated.
Design Considerations
Part design should include draft features (angled surfaces) to facilitate removal from the mold. Depending surface length draft angles down to half a degree are reasonable. Typical draft angles should be about 1 too 2 degrees for part surfaces not exceeding 5 inches. Dimensional tolerance specification will govern the part cost and manufacturability. If you have a small region of the part that needs higher tolerances, say the location of a critical feature used for alignment. DO NOT specify tight tolerance, instead design and plan for post molding processes such as machining using "assembly intent" fixturing.
Wall Thickness
Wall thickness for thin parts such as a soda bottle or ball point pen ink inserts are quite possible and economical. Thick wall sections are possible as well. Uneven wall thickness present challenges to the plastic molder manufacturer. Designing your part with uniform walls and cross section will simplify manufacturing and costing. At wall intersection or "tees" sinking will occur. Thick walls cool slower and greater shrinking will occur. Thin walls cool faster as thus, less shrinkage.
Radii and Corners
Maintain uniform wall thickness at corners. External and internal radius should share the same center point . External radii = internal radii + wall thickness. The minimum radii should not be less than 1/4 minimum wall thickness. Design for radii to be 1/2 to 3/4 of the nominal wall thickness. When significant stress is present, design in larger radius as larger radius distributes stress uniformly.
Ribs
Ribs should be 1/2 to 2/3 of the nominal wall thickness and less than 3 times thickness in height. Taper of 1 deg. is typical. Note: excess thickness promotes shrinkage. Excess rib height combined with taper will produce thin sections requiring extra fill time at the mold .
Bosses

·         Diameter = (Outside Diameter) \ (Inside Diameter) = 2 to 3

·         Thickness = 1/2 to 2/3 nominal wall thickness

·         Gusset Height = 2/3 Height

·         Height = Fastener minimum requirements

·         Taper = 1 deg. all around

·         Diameter Ratio should be minimum ratio of 2., this will reduce risk of failure.

Weld (Part) lines

location should be considered by design and the molder. Weld lines are formed at the mating of the flow fronts of the plastic during molding. The weld line area is more susceptible to cracks and stress failure.

Single Phase Transformer

PROCEDURE:

   The transformer was examined, and given a special attention to the construction, rated voltage, kVA, frequency, etc. The rated currents for each side were calculated. Then the

1. Terminal identification test

2. Polarity test

3. Open circuit test

4. Short circuit test

                           are made on the transformer as follow the instructions which are given in the handout sheet.

DISCUSSION                                                                 

Transformer is an electrical device consisting of one coil of wire placed in close aproximity to one or more other coils, used to couple two or more alternating-current (AC) circuits together by employing the induction between the coils. It has two windings, which are connected through a magnetic core.

The coil connected to the power source is called the primary coil, and the other coil is known as secondary. A transformer in which the secondary voltage is higher than the primary is called a step-up transformer. If the secondary voltage is less than the primary, the device is known as a step-down transformer. The product of current and voltage is constant in each set of coils, so that in a step-up transformer, the voltage increase in the secondary is accompanied with a corresponding decrease in the current.

Efficient power transmission requires a step-up transformer at the power-generating station to raise voltages, with a corresponding decrease in current. Line power losses are proportional to the square of the current times the resistance of the power line, so that very high voltages and low currents are used for long-distance transmission lines to reduce losses. At the receiving end, step-down transformers reduce the voltage, and increase the current, to the residential or industrial voltage levels, usually 230V.

Power Transformers

Power Transformers are large devices which are used in electric power systems, and small units in electronic devices. Industrial and residential power transformers that operate at the line frequency, may be single phase or three-phase, and are designed to handle high voltages and currents.

Power transformers must be efficient and should dissipate as little power as possible in the form of heat during the transformation process. Efficiencies are normally above 99 percent and are obtained by using special steel alloys to couple the induced magnetic fields between the primary and secondary windings. The dissipation of even 0.5 percent of the power transmitted in a large transformer generates large amounts of heat, which requires special cooling provisions. Typical power transformers are installed in sealed containers that have oil or another substance circulating through the coils to transfer the heat to external radiatorlike surfaces, where it can be discharged to the surrounding atmosphere.

 

Transformer in Electronics

In electronic equipment, transformers with capacities in the order of 1 kw are largely used ahead of a rectifier, which in turn supplies direct current (DC) to the equipment. Such electronic power transformers are usually made of stacks of steel alloy sheets, called laminations, on which copper wire coils are wound. Transformers in the 1- to 100-W power level are used principally as step-down transformers to couple electronic circuits to loudspeakers in radios, television sets, and high-fidelity equipment. These are known as audio transformers and they use only a small fraction of their power rating to deliver program material in the audible ranges, with minimum distortion. The transformers are judged on their ability to reproduce sound-wave frequencies (from 20 Hz to 25 kHz) with minimal distortion over the full sound power level.

At power levels of 1 milliwatt or less, transformers are primarily used to couple ultrahigh-frequency (UHF), very-high frequency (VHF), radio-frequency (RF), and intermediate-frequency (IF) signals, and to increase their voltage. These high-frequency transformers usually operate in a tuned or resonant circuit, in which tuning is used to remove unwanted electrical noise at frequencies outside the desired transmission range.

 

Parallel Operation of Transformers

The following conditions must exist for transformers to operate satisfactorily in parallel:

·   Connection diagrams must be identical. Paralleling transformers with different connection diagrams is similar to short circuiting their secondary windings.

·   Voltage ratios must be the same. If voltage ratios are not the same, circulating currents will flow in the secondary with no or little load and the division of load will be improper.

·   Percent impedance, including primary and secondary leads to each transformer, should be nearly equal. If the impedance's are equal and the turns ratios are identical, the paralleled transformers will divide the load currents (properly) in proportion to their kVA ratings. If the percent impedance's are different, the transformer with the lower percent impedance will take more than its proper share of the load.

Example: Operation with unequal turns ratios:

Two transformers with similar characteristics (both rated 7,200-240 Volts, 3% Z, equal X/R ratios but with different kVA ratings) are to be operated in parallel to serve a 75 kVA load. One unit is rated 25 kVA and the other is rated 50 kVA.

By mistake, the 25 kVA unit has its primary tap set 5% low (6840 V tap) which would give an open-circuit voltage of 252.6 V instead of the desired 240 V. 

When paralleled and energized from a 7,200 V primary, the circulating current is 117 percent of rated current for the 25 kVA unit before any load current is drawn. The open-circuit voltage from the combination is 244.2 V.

Solution:

Difference between O-C voltages = 12.6 V (= 5.25%)
Loop impedance (25 kVA base) = 4.50%
Circulating current (use per-unit values) = 1.17 per unit
(by Ohm's Law) = 117%
Impedance voltage divider ratio = 1.5%/4.5% = 1/3
Terminal voltage rise above 240 V = (1/3) x (12.6 V) = 4.2 V
"No load" terminal voltage = 240 V + 4.2 V = 244.2 Volts

Errors in the Experiment

There may be several reasons which cause errors in the experiment. 

·   Resistance of the connecting wires.

·  Reading errors in volt meter and ammeter.

·  Errors in measuring instruments as they are not ideal.

Also during the experiment as we expect to get some readings at the rated voltage of the transformer it was not possible. The maximum voltage we could take by the supply was 220 V as the voltage is dropped due to other connected equipments which take high currents. Therefore the calculations are done using 220V. Also in the experiment measuring instruments had to be selected with appropriate scales to minimize the possible errors.

REFERENCES

·  Encarta Encyclopedia Deluxe version 2002

·   Electrical Machinery        -    Chalres Kingsley

A.E. Fitzgerald

Stephen D.Umans

·   Electric Machines           -      I J Nagarath & D P Kothari

                             -      Eight reprint 1993

·   www.citycollegiate.com

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