In mould lubrication, detail shows up in the cycle

In hollow glass production, mould lubrication is not an ancillary operation. It affects regular release, cavity cleanliness, mould service life and cycle stability. When the rhythm is continuous, even a small variation in the amount of lubricant, in distribution or in the contact point can produce visible effects: residues, marks, irregular release, need for manual intervention or differences between parts that should be identical.

The technical tube brush enters this phase with a very precise function. It must carry the lubricant to the right point, reach internal or shaped surfaces, work at high temperatures and maintain repeatable behaviour. It is not enough for it to be flexible or resistant. It needs a geometry suited to the mould, a fibre consistent with the type of application and a structure capable of withstanding continuous work without deforming too quickly.

Why hollow glass is a difficult application

Hollow glass presents different problems from many other industrial processes. The mould has internal geometries, transition zones, edges, radii and depths that cannot always be reached with simple contact. The surface to be lubricated is not flat, and the component works in a hot, stressed environment with tight cycle times. In addition, lubrication must be effective enough to protect the cycle, but not so abundant as to create build-up or contamination.

The difficulty increases when the work is automated. In a manual operation, the operator can correct pressure, angle and contact time. In a continuous line, by contrast, the tube brush must almost always do the same thing in the same way. If the component is too rigid, it does not follow the cavity well; if it is too yielding, it loses precision; if it wears unevenly, it progressively changes the quantity of lubricant distributed.

Different geometries, different results

Bottles, flacons, jars and other hollow glass items do not all create the same problem. Mould depth, radii, contact zones, points where the lubricant must arrive and areas where excess can disturb the cycle all change. A tube brush that works correctly on a simple geometry may not be suitable for a deeper mould or one with more articulated internal profiles. Selection should therefore start from the real cavity, not from a generic measurement.

The insertion position also changes behaviour. If the tube brush enters with a linear movement, the required flexibility is different from insertion with rotation or with a slightly inclined path. Entry and exit speed also matter: movement that is too fast can reduce release time; movement that is too slow can create build-up. The balance between tube brush shape and machine movement is therefore an essential part of the choice.

When working on continuous cycles, the difference between an acceptable component and a truly suitable one often emerges in stability. The tube brush must maintain the same response as mould temperature changes, as the cotton loads with lubricant and as the core undergoes repeated stresses. If the contact point changes after a few cycles, lubrication stops being a controlled variable and starts depending again on external corrections.

Cotton, metal core and controlled flexibility

In mould lubrication processes for hollow glass, cotton is used because it offers a way of retaining and releasing lubricant that differs from many synthetic fibres. It does not work only as a contact material: it becomes part of the product transfer onto the mould surface. Fibre quality, compactness, arrangement and resistance to the thermal cycle therefore all matter.

The metal core, in turn, must provide support and shape memory. A structure that is too weak can deform and change trajectory; one that is too rigid may not adapt to internal geometries. The tube brush has to find a balance between access, flexibility and control. In industrial tube brushes intended for glass processing, this combination of cotton, core and shape is what allows the component to work repeatably inside a real mould, not only on a drawing.

The relationship between tube brush and automation

When lubrication is integrated into an automated sequence, the tube brush cannot be considered an isolated element. It must be compatible with arms, guides, fixing points, entry and exit times, cycle speed and the planned path. If the component needs an excessively precise position in order to work, every small variation in the machine can become an application defect.

Movement therefore has to be assessed. Does the tube brush enter on axis or at an angle? Must it reach the bottom of the cavity or work on a side area? Is it compressed, rotated, inserted and withdrawn in sequence? The answer changes diameter, length, flexibility, cotton density and final shape. The correct choice reduces dependence on frequent adjustments and makes the relationship between lubrication and cycle more stable.

Wear, cleaning and control of the result

A tube brush working continuously should not be assessed only when new. The fibre wears, absorbs residues, changes compactness and can modify the way it releases lubricant. The core can also deform if the component works in a forced position. It is therefore useful to define simple control criteria: fibre appearance, regularity of release, possible marks in the mould, variations on the finished part and average replacement times.

Cleaning must be compatible with the process. If the tube brush retains too much degraded product, it can become a source of irregularity instead of a stabilising tool. If it is replaced too often, operating cost increases and continuity is lost. The best choice is not necessarily the most resistant in absolute terms, but the one that maintains predictable behaviour for the longest time in the real cycle.

Practical criteria before selection

Before defining the tube brush, it is useful to collect a few simple but decisive pieces of information: mould geometry, area to be lubricated, cycle frequency, type of lubricant, available space for movement, expected component life and replacement method. These data help avoid a choice based only on diameter and length, which is rarely enough in a hollow glass application.

The test should observe both the mould and the finished part. Lubrication that appears regular on the internal surface can still produce unwanted effects on release or finish. The best check combines tube brush behaviour, mould cleanliness, cycle continuity and quality of the produced part. Only from this combination is it possible to understand whether the component is truly supporting the process.

Traceability of changes can also help. Recording average life, reason for replacement and condition of the removed tube brush makes it possible to distinguish normal wear from an incorrect choice of shape or material.

When the tube brush supports moulding quality

In hollow glass, the value of the technical tube brush is measured in repeatability. It must distribute lubricant where needed, avoid damaging the mould, adapt to the geometry and work at a rhythm consistent with the machine. A minimal difference in contact may seem negligible, but on continuous cycles it becomes an accumulation of defects, adjustments and stoppages.

For this reason, selection should not be reduced to diameter and length. Mould shape, temperature, movement, lubricant type, frequency of use and replacement criteria must all be considered. When these elements are aligned, the tube brush is not just any consumable: it is one of the components that allow the process to remain stable while production continues.