High-Quality Glass Bottles Manufacturing Tolerances

Glass products are used frequently in POS and promotional items. Therefore, if you’ve decided to use glass as a material for your next project, it is important to understand the manufacturing process of promotional glass bottles. Having a good understanding of what factors affect the quality during manufacturing is essential. This ensures your product is made to the highest standard.

When manufacturing promotional glass bottles 3 main materials are used. Silica Sand, Soda Ash and Limestone. To reduce the energy needed during production, cullet (recycled glass) is also added to the raw materials.

Maintaining Quality During Promotional Glass Bottle Production

Manufacturing promotional glass bottles can be done using two methods Blow & Blow or Press & Blow. Both of these methods require stringent quality checks. This is to certify high-quality products are manufactured. Moreover, it ensures any defective items do not enter the market.

Producing High Quality Glass Products - Promotional Glass Bottles Manufacturing Tolerances

Furthermore, two processes are used to check the quality of products. Firstly, items are checked for defects. There are 3 categories of defects when manufacturing glass products namely, Major, Minor and Critical. Minor defects are generally aesthetic, whereas major and critical defects can be potentially dangerous. Secondly, tolerances are checked. This ensures bottles are constant in height, shape and glass thickness.

Identifying Defects in the Production of Promotional Glass Bottles

Below is a list of Major and Critical defects that can occur during the production of promotional glass bottles

Critical Defects

Stuck Plug. A piece of glass, usually very sharp, projecting inwards just inside the neck bore.
Overpress. Is a defect where a small ridge of glass has been formed on the sealing surface of the finish.
Split. An open crack starts at the top of the finish and extends downward.
Check. A small, shallow surface crack, usually at the bore of the container.
Freaks. Odd shapes and conditions render the container completely unusable. Bent or cocked necks are a common defect of this type.
Poor Distribution. Thin shoulder, slug neck, choke neck, and bottom are terms used to describe the uneven distribution of glass.
Soft Blister. A thin blister is usually found on or near the sealing surface. However, it can show up anywhere on the glass container.
Choked Bore. Excess glass has been distributed to the inside of the finish or opening.
Cracks. Partial fractures are usually found in the heel area.
Pinhole. Any opening causing leakage. It occurs most often in bottles with pointed corners.
Filament. A hair-like string inside the bottle.
Spike. Spikes are glass inside the bottle.
Bird Swing. Glass thread joins the two walls of the container.

Producing High Quality Glass Products - Promotional Glass Container Manufacturing Tolerances

Major Defects

Chipped Finish. Pieces broke out of the top edge in the manufacturing process.
Stone. Small inclusion of any non-glass material.
Rocker Bottom. A sunken centre portion on in base of the container.
Flanged Bottom. A rim of glass around the bottom at the parting line.

Tolerances During Glass Manufacture

Tolerances are the allowed differences between individual glass products. In order to ensure production is consistent tolerances are set during manufacturing. Glass tolerances can be applied to most products. However, if the glass product has to fit inside a container e.g. aftershave and perfume bottles then the tolerances may need to be reduced.

Producing High Quality Glass Products - Promotional Glass Bottle Manufacturing Tolerances

Reducing Defects During Manufacturing

Producing consistent glass bottles is easily achievable during mass production. However, from time to time defects can occur. Most of the time these defects are minor. Despite this, defects can sometimes cause minor size differences in bottles. Below are the two most common types of defects, how they are caused and what can be done to prevent them.

1. Uneven or bad distribution of bottle body

Definition:

Uneven wall thickness.

Causes:

Feeder – Uneven glass temperature.

Machine Setup and Operation – Uneven cooling of blank moulds, Incorrect drum setting, Excessive blank cooling, Settle blow time too long, Counter blow time too short, Machine speed too low, Incorrect timing of gob delivery.

Mould Equipment – Blank design unsuitable, incorrect plunger design.

Remedies:

Adjust glass temperature, Apply cooling air evenly on the blank moulds, Adjust drum setting, Adjust blank cooling, Reduce settle blow, Increase counter blow time, Increase machine speed, Check loading position, Adjust the blank design, and Adjust plunger design.

Producing High Quality Glass Products - Promotional Drinks Glass Manufacturing Tolerances

2. Out of shape ware

Definition:

The container is tilted to one side due to the bottom not being level.

Causes:

Feeder – Glass too hot.

Machine Setup and Operation – Insufficient final blow time and/or pressure, Incorrect application of cooling wind – mould too hot, Machine speed too high, Blow mould cycle too short, Unsuitable ware pusher design, Container not hanging in the takeout long enough.

Mould Equipment – Change the blow mould, Correct the Blank design.

Conveyor – Incorrect cooling over the dead plate, Pushout moving bottle onto the conveyor too soon.

Remedies:

Adjust feeder temperature, Increase final blow time and/or pressure, Adjust mould cooling wind, Adjust machine speed, Increase blow mould cycle, Improve ware pushers design, Reduce time in takeout position, Increase run time, Change the blow mould, Correct blank design, Adjust cooling over the dead plate, Delay bottle moving onto the conveyor, Check movement of container on the conveyor.

Quality Control During Manufacturing

Quality control reduces defects in production. Following the steps below results in the reduction of errors.

Test bottles at regular intervals during production.
If any bottle in the round fails to test, four additional bottles need testing.
If a failure occurs among the four bottles tested then all bottles should be rejected until the fault has been rectified.
When all four bottles pass testing production can continue.
After an initial failure has been verified, all pallets loaded with bottles produced from the last unsatisfactory test are detained.
Once nonconforming bottles are removed detained pallets are released.

Need Help Producing High-Quality Glass Bottles?

Custom glass products require expert knowledge to ensure a high-quality product. ODM are experts in designing and manufacturing high-quality, promotional glass products.

If you need assistance with your next project contact us. Our team have experience in designing and manufacturing high-quality promotional products and display tailored to your brand’s marketing needs.

Contact ODM Today!