250 ML Double Station Deflashing Blow moulding Machine

Extrusion Blow Moulding Machine.

Extrusion blow molding machines are used for producing hollow containers from Plastic. Majority of Blow Moulding use HDPE (High Density Polyethylene) resin for producing end products. Poly Propelene PP, Low Density Polyethylene LDPE and engineering plastics such are ABS etc can be blow moulded.

In the abouve video, 100 ml round jar is manufactured from HDPE with auto deflashing. In normal Blow moulding, some runner or flash will be there in the product which should be manually trimmed. In auto deflashing machine, this process is done by machine and reduce the usage of Labour ensuring steady quality and quantity of product.

For further details please visit www.shreeplas.com

KUDAM running on a 10 litre Blow Moulding Machine

Kudam is extrusion blow moulded from HDPE plastic resin. ShreePlas manufactures automatic extrusion blow moulding machine for manufacturing Kudam and Cans and Jar. The video attached shows Kudam running on 10 litre automatic extrusion blow moulding machine from HDPE with green color masterbatch.

3 litre double station double head auto deflashing machine

50 ml Blow moulding machine

How to Choose a Blow Moulding Machine

Buying a blow moulding machine can be a nerve racking experience for the fresh entrepreneurs. There countless specification, capability and price factors to be considered. This blog sets out to help anyone who wants to buy a blow moulding machine but does not know where to start.
Mould Size:
The most important spec is the mould size of the machine. The range of product you want to produce should be matching the model. For this refer the maximum mould size mentioned in the machine specification chart.
Production Capacity:
Estimate your production capacity required like containers per month and cross check with the machine supplier whether this can be met. It is advisable to keep a 25% extra capacity. This relates to the extruder size, plasticizing capacity and possible cycle time of the machine.
Quality of the machine:
Quality of the machine is a relative subject. Normally the cost of the machine will vary proportionally with the quality of the machine. Quality itself is in two sections – machine built quality & product (container) quality. The product quality depends on your end user. The machine built quality affects the maintenance cost and breakdown cost of the plant.
Other Machine Specifications:
The Die-Core (Cup-pin) size of the machine should be enough for the proposed containers intended to manufacture. The mould clamping force also critical with respect to your products. Then for the accumulator head type machines. The accumulator shot capacity is important.
Automation:
The machine automation can be done by a PLC control or by a wired relay logic (this become outdated because of the limitations and bulkiness of control panel). The PLC control has very wide range of options available. This can be from ordinary custom built micro processor controller to industrial grade established control systems like MOOG, B&R etc.
Additional Options:
Automatic Deflashing:
Here the product is automatically deflashed or trimmed in the attachment of the machine. Fully ready container will come out of the machine. If deflashing option is not present, every product (container, bottle etc) have to be trimmed by an operator manually.
Ancillaries:
Selection of ancillaries like air compressor, scrap grinder, cooling system are also required to be selected in accordance with the machine manufacturers recommendations.
Parison control:
A parison control system helps to improve the product quality and reduce the flash waste. This will be useful for large containers.

Trouble Shooting of Blow Moulding Process

Pitted surface appearance

Possible Reasons:

• Air entrapment inside the mould
• Condensation
• Low Blow Rate
• Low Blow Pressure

Possible Solutions:

• Vent the mould to reduce the air entrapment.
• Check mould finishing, polished mould causes air entrapment. Very coarse mould surface results in rough part surface. Sand blasted mould surfaces are usually desirable.
• Check mould for condensation coolant temperature
• Increase the size of air orifice to allow faster blow rate
• Increase blow pressure.

Vertical groves and lines in the part

Possible Reasons:

• Dirty and / or damaged die

Possible Solutions:

• Clean die surface.
• Scratches in die or core, to be removed
• Check for contamination.
• Set the parison straight to eliminate hold up in die.

Irregular markings on the part

Possible Reasons:

• Water condensate or water leakage in the mould

Possible Solutions:

• Run faster cycle.
• Run warmer mould.
• Stop leakage in the mould.

Rough part surfaces and / or poor gloss.

Possible Reasons:

• Rough parison

Possible Solutions:

• Increase die temperature
• Increase mould temperature
• Increase melt temperature
• Increase extruder speed
• Use low molecular weight resin
• Clean die core

Rippling on parison / melt fracture

Possible Reasons:

• Unsuitable die shape
• Extrusion rate too high

Possible Solutions:

• Increase die land
• Increase die diameter
• Reduce extruder speed

Thin areas or holes on the part surface

Possible Reasons:

• Airflow in head is faster
• Parison is not straight
• Moisture in resin
• Contaminated resin in head or die

Possible Solutions:

• Reduce airflow through head
• Set parison
• Pre heat the resin
• Clean the head and die core

Poor wall thickness distribution – longitudinal

Possible Reasons:

• Parison sagging
• Parison control not working

Possible Solutions:

• Change extrusion rate
• Decrease melt temperature.
• Use low M.F.I. resin.
• Check parison control timings.
• Check parison control pressure.
• Check flow control valve setting.

Poor wall thickness distribution- circumferential

Possible Reasons:

• Non symmetrical parison
• Non symmetrical article

Possible Solutions:

• Set parison straight
• Use larger die
• Optimise article weight
• Use larger die

Excessive dimensional shrinkage of article

Possible Reasons:

• Low blow pressure
• Insufficient cooling
• Melt temperature is too high

Possible Solutions:

• Increase blow pressure
• Decrease mould temperature
• Increase cooling time
• Decrease melt temperature.

Warpage

Possible Reasons:

• Insufficient cooling
• Non uniform cooling

Possible Solutions:

• Reduce mould temperature
• Check for efficiency of water flow in mould channels
• Increase cooling time.
• Check efficiency of mould venting.
• Provide more cooling, especially in pinch of area of the mould.

Parison doughnut formation

Possible Reasons:

• Core temperature is low
• Core gone inside the die

Possible Solutions:

• Allow core to reach temperature equilibrium with rest of the system
• Lower the core slightly (to get the weight of the article, reduce the core diameter)

Thinning or stretching at parting line

Possible Reasons:

• Low blow pressure
• Pinch off is too sharp

Possible Solutions:

• Increase blow pressure
• Check efficiency of airline
• Widen pinch of land
• Reduce head and die temperature

Parison tail sticking to the article

Possible Reasons:

• Parison too long

Possible Solutions:

• Shorten Parison length.
• Increase pinch-of land to compression cool the tail

Black specks in parison

Possible Reasons:

• Degraded resin
• Hold ups in the die head

Possible Solutions:

• Thoroughly clean and purge extruder. Avoid prolonged shutdowns with resin held at high temperature
• Improve streamlining of the melt inside

Contamination

Possible Reasons:

• Poor house-keeping

Possible Solutions:

• Keep production area clean

CLAMPING FORCE (TONNAGE)

Clamping Force is one of the main parameter in Blow Moulding. It restricts the size of container can be molded on a particular machine. The clamping force is required to balance the force created inside the container by blowing air. Blow molding machines don’t require very high tonnage like Injection molding machines.
For a standard 3-plate single cylinder direct mould clamping unit, the clamping force is calculated as below:
Clamping force (N) =cylinder Area (mm2) x Pressure (bar) /10
Clamping force (kgf) =cylinder Area (cm2) x Pressure (kg/cm2)
Clamping force (lbf) =cylinder Area (in2) x Pressure (pound/in2)
For example, if a unit has 100 mm dia and applying a pressure of 100 bar, then
Clamping force, N = 50 x 50 x 3.14 x 100 / 10 N
= 78500 N
= 78.5 kN

Clamping force, kgf = 5 x 5 x 3.14 x 101.9716 kgf (1bar=1.019716kg/cm2)
= 8004.77 kgf
= 8 Ton

Clamping force, lbf = (5/2.54) x( 5/2.54) x 3.14 x 1450 lbf (1bar=14.5psi)
= 17643 lbf

If the machine has more than one cylinder, multiply the result by the quantity of cylinders.
Now this helps us to find out the clamping force, but how you decide on what clamping force is required for a certain container? That depends on the blowing pressure and inside area of mold & pinch off length. The thumb rule is
Total Clamping force (kgf) = Surface Area (cm2) x Air Pressure (kg/cm2) /2.5
+ Total Pinch Off Length (cm) x 200

The 2.5 divider in first part is an assumption factor for round drums to find out the force acting in mold clamping direction. The 200 multiplier in second part is based on that 1 Ton clamping force is required for every 5 cm pinch off.