Blow Moulding – Bajaj
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Injection Moulding

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Blow Moulded Tank

Film Application

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Blow Moulding Applications

Blow Moulding process is simple & effective way of producing complex, intricate hollow shapes that are light weight and have excellent stiffness to weight ratios. Blow molding is a cost-effective alternative to injection molding, with both production and machinery being cheaper typically. Blow molding works well for products that are one single piece in mass volumes.
The costs in blow molding are lower as compared to injection molding because machinery costs are typically lower as well. In blow moulding process, one-piece construction is done so that there’s no need to connect part halves, which can achieve shapes that injection molding cannot produce

NEED FOR BLOW MOULDING

Blow Moulding process is simple & effective way of producing complex, intricate hollow shapes that are light weight and have excellent stiffness to weight ratios. Various types of Bottles, Jerry cans, Containers, Drums, Carboys & Water tanks are also made through this process.
Blow Moulding process is simple & effective way of producing complex, intricate hollow shapes that are light weight and have excellent stiffness to weight ratios. Various types of Bottles, Jerry cans, Containers, Drums, Carboys & Water tanks are also made through this process.
Blow molding is a cost-effective alternative to injection molding, with both production and machinery being cheaper typically. Blow molding works well for products that are one single piece in mass volumes.
The costs in blow molding are lower as compared to injection molding because machinery costs are typically lower as well.
In blow moulding process, one-piece construction is done so that there’s no need to connect part halves, which can achieve shapes that injection molding cannot produce.

TYPES OF BLOW MOULDING

A) Extrusion blow molding(one stage)

It’s the most commonly used & simple type of process used widely, it can be continuous or intermittent. In continuous extrusion blow molding, a parison will be constantly fed into the mold and each form will be cut off with a blade as it forms. Intermittent extrusion blow molding expels each new plastic from the metal mold when it is cooled and the parison is fed into the mold only after the preceding parison is expelled.
Extrusion blow molds are generally much less expensive than injection blow molds and can be produced in a much shorter period of time. Extrusion blow molding is appropriate for smaller runs. Advantages include cost savings on tooling and shorter production time while disadvantages usually include lesser control of wall thickness and greater amount of scrap material.

B) Injection blow molding (one stage)

In injection blow molding, a blow or core rod is used throughout the process. First a parison is injected into a split mold cavity around the rod. The parison that is formed looks similar to a test tube. The core rod transfers the parison to the blow mold machine where forced air creates the final shape. The rod then transfers and extrudes the finished product from the machine.
This process is generally suitable for smaller containers with large volumes. Here, tighter tolerances can be expected than when extrusion blow moulding is used. Other advantages are the assurance of uniform wall thicknesses, production free from waste & seamless products in the neck and base areas. This enables blow products to resist pressure strains and endows them with high surface finish.

C) Injection stretch blow molding (two stages)

Injection stretch blow molding combines the injection molding and blow molding processes. The plastic material is first molded into a solid preform, to create a threaded bottle neck. Once the preform cools it is fed into a stretch blow mold machine. The preform is then reheated using an infrared heater and blown into a plastic bottle with forced compressed air.
This process is best known for producing PET bottles commonly used for water, juice & beverages. Biaxial stretching of plastic material increases the tensile strength, barrier properties, drop impact, clarity & load bearing for containers produced. This also helps in reducing weight of bottles.

Advantages of Using Bajaj Masterbatch for Blow Moulding

Ability to handle complex part

Fast Production Rate

Enhanced Strength

Increases the tensile strength

High level of producivity

Low Costs

Instead of having pre coloured compounds, usage of our masterbatches facilitates low stock holding as and when required.

Compared to compounds, our masterbatches gives a choice of wide range of colors and other properties besides saving huge cost as the inventory level & space required is very minimal .

Provides “dust free” environment without any health or safety risks in comparision to conventional usage of pigments powders & additives individually.

Optimum dispersion of pigments and additives in our masterbatches facilitates ease of processing. Also, it reduces the cost of purging & flushing .

Elimination of ‘trial and error’ development or formulation work, as this is done already by us ensuring color strength and consistency forever.

Our masterbatches are filler free and they are fairly highly concentrated (in comparison with the target composition), with “let-down ratios” affordable and economical as per the client’s application requirements.

Provides aesthetic appeal with gloss and brightness on the finished product without any surface defects.

As blow moulded bottles, containers, carboys and drums are extensively used in Pharma and Chemical applications, our masterbatches has the ability to maintain the chemical stability of the pigments and other ingredients incorporated in it. This facilitates migration resistant , leaching free and non reactive & ease of using at any conditions.

We use eco friendly pigments which are not harmful to the environment, on request we can provide ROHS (Restriction of Hazardous Substance) compliance.

Ease of consolidation with polymer at any addition levels and has uniform dispersion.

They are suitable for food contact applications as the ingredients used in it are non-toxic , non hazardous and the articles incorporated with our masterbatches are safe for use.

ONE STOP SOLUTION FOR BLOW MOULDING PROBLEMS / DEFECTS

Problems / DefectsPossible CausesSuggested Remedies
Rough crystalline surfaceOverheating of co-polymer1.Lower the temperature and enhance cooling to certain extent. Reduce Melt temperature below 200°C
2.Slow down extruder speed.
Great number of large gelsOverheating of co-polymer in blow moulding machine or grinder1.To dismantle head , screw & thoroughly clean.
2.Purging is needed
Contamination from highly incompatible resins, etc1.Some times polymer resins consists of foreign particles
2.Contamination by decomposed particles
1.Inspect bags, hopper loader, grinder and all other parts wherein polymer is used.
2.Clean die and extruder to evacuate degraded material.
3.Cool the extruder before shut down.
Pin marks, bubbles or streaks in part1.MoistureDry resin at 60-70°C for an hour approx.
Cloudy or hazy part1.Contamination
2.Melt temperature too high / low
3.Mould temperature too low
1.Dry resin at 60-70°C for an hour approx.
2.Adjust Melt temp between180-200°C(approx)
3.Adjust Mold temp between 25-35°C
Part dull in appearance1.Mould is not polished properly.
2.Mold finish is untidy
3.Improper Mould temperature
1.Do polishing
2.Clean thoroughly and polish with Simichrome
3.Adjust Mould temperature between 25-35°C
Poor wall thickness distribution from top to bottom1.Parison necking down
2.Larger part periphery at top
1.Parison programming to be done
2.Increase extrusion speed
3.Lower Melt temp
4.Invert mould if possible.
Poor wall thickness circumferentiallyNon symetric part shape1..Shape the die to increase parison thickness in thin area.
2.Pre blow parison.
3.Use larger parison diameter.
Parison rupture or part “Blow out”1.Too large a blow up ratio.
2.Mould separation
3.Pinch-off too sharp
1.Use larger die tooling.
2.Increase clamp pressure / decrease blow pressure
3.Provide wider pinch-off land.
Die linesUntidy or damaged die1.Clean die land surfaces
2.Nicks or scratches in die or mandrel may have to be removed.
3.Check for foreign material
4.Streamline flow to eliminate die buildup
Problems/DefectsPossible CausesSuggested Remedies
Parison “Doughnut” formation1.Mandrel temperature not adequate
2.Mandrel is at too high position.
3.Die face is untidy
1.Allow mandrel to reach equilibrium with rest of system.
2.Lower Mandrel position slightly
3.Clean the die thoroughly
Parison length variations1.Cooling to extruder feed zone not turned on
2.Insufficient back pressure.
3.Extruder operating erratically.
4.Extruder slipping.
1.Turn on air / water cooling to feed zone.
2.Increase Back pressure
3.Repair extruder and ensure smooth running.
4.Same as above.
Low part weightWall thickness of parison is too thinIncrease annular opening to make wall thickness to increase slightly. Make parision programming faster.
Part weight too heavy1.Wall thickness of parison is too high1.Decrease annular opening to make wall thickness to decrease.
Part not fully inflatedBlow air pressure inadequate1.Increase blow air pressure
2.Check for blocked air lines if any.
Blow needle not puncturing parison1.Insertion rate too slow
2.Needle stroke too short.
3.Needle is blunt
1.Increase pressure to needle cylinder.
2.Lengthen stroke if possible. Install cylinder with longer stroke.
3.Sharpen needle to ensure good puncture.
Parison collapses inside mouldBlow air incorrectly timed outStart blow air earlier in cycle.
Thinning or stretching at parting line1.Low blow pressure
2.Air entrapment inside
1.Increase blow pressure.
2.Improve mould venting.
Poor wel at pinch off1.Mould temperature high
2.Mould closing speed is fast
3.Pinch off land too sharp
1.Adjust Mold temp between 25-35°C
2.Increase Mould “Cushion” or decrease mould closing speed.
3.Widen pinch land , Dam up inch-off relief to thicken pinch weld.
Warpage1.Insufficient cooling
2.Non-uniform cooling
3.Cooling differential in thick & thin areas
1.Provide good water flow in moulded channels
2.Increase cooling time.
3.Improve wall distribution of cooling channel.

Product Solutions for Blow Moulding

Blow Moulding Applications for
Color Masterbatch

PLAST COLOUR produced with high pigment loading to provide light fastness, migration resistance, dispersion, thermal stability , food contact compliance & colour consistency for every supplied lot. We can offer wide range of Colours from our existing product range or customize based on pantone shades given by clients

Blow Moulding Applications for
White Masterbatches

PLAST SUPER 131,181 (70% TiO2 content), PLAST SUPER 157, 132 (50% TiO2 content). These products are having superior dispersion, opacity, gloss, ease of processing and food packaging compliant. Also, they do impart heat resistance & UV protection to the end product to certain extent.

Blow Moulding Applications for
Black Masterbatch

PLAST BLACK with Carbon content – 40% & 50% made from high quality carbon black, filler free with excellent jetness & dispersion

Blow Moulding Applications for
Transparent Masterbatch

PLAST FILL, PLAST CLEAR & PLAST HIGH MIX to increase output, economical advantage by reducing material cost and energy cost saving .
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