In automated packaging lines, marking the bottom surface of a product is often a difficult step. Manual flipping and labeling is not only inefficient but also prone to weak adhesion and surface wrinkling. As equipment has improved, bottom labeling has gradually become the mainstream approach. In actual production, however, many companies still struggle with wrinkled labels or bubbles on the bottom surface. Drawing on the technical features of the WZ-129 bottom labeling machine, this article outlines how to troubleshoot and resolve these common issues.

Causes of bottom labeling defects

Bottom labeling defects typically stem from the condition in which the workpiece is conveyed, the label material, and the pressing mechanism. When the workpiece shifts slightly or vibrates on the conveyor belt, the label is subjected to uneven force the moment it contacts the bottom surface, which easily causes wrinkles. In addition, if the peel angle between the label liner and the face material is unsuitable, or the pressure of the foam pressing roller is unevenly distributed, air cannot escape in time and stubborn bubbles form. Packaging boxes and plastic cups with slightly curved or textured surfaces are particularly demanding in terms of the labeling head descent angle and pressing force.

How the WZ-129 solves these problems

To address these pain points, Wanzhi Automation developed the WZ-129 bottom labeling machine with targeted improvements. The labeling head is mounted in a lowered position, so the bottom surface is labeled while products travel forward, avoiding the positioning errors caused by flipping workpieces. To prevent bubbles and wrinkles, the machine has a separate touch-screen control panel where operators can accurately adjust the label feed length and pressing pressure to keep labels flat and firmly attached. The conveyor belt is fitted with dedicated guide and positioning structures that keep products centered as they pass through the labeling zone. In terms of core specifications, labeling accuracy is stable at ±1 mm and throughput ranges widely from 20 to 80 PCS/min, meeting high-precision requirements while accommodating different batch rhythms. Workpieces up to 300 mm wide are all handled by the same configuration.

Practical tips and applications

For day-to-day operation and equipment selection, the Wanzhi Automation technical team offers the following recommendations:

  • Check the conveyor belt for wear and verify the position of the guide plates regularly to keep products moving smoothly.
  • For plastic workpieces that tend to build up static, add an anti-static ion air gun to reduce the poor adhesion caused by dust.
  • If the line needs to integrate traceability information, an optional coding or inkjet module can be added to combine labeling and coding in one pass.

The machine is widely used for food containers, household product cans, paper gift boxes, and wooden panels, running automated continuous operation throughout and greatly improving packaging line efficiency.

FAQ

Q1: Bubbles keep appearing during bottom labeling. How can I fix this quickly?

A: First check that the label material is suitably flexible; overly stiff labels tend to spring back and trap air. Next, increase the pressing pressure slightly on the WZ-129 touch screen and adjust the tilt angle of the labeling head so the label is applied gradually from one end to the other, pushing air out as it goes. Also make sure the bottom surface of the workpiece is clean and free of dust.

Q2: The label position keeps drifting beyond tolerance. What should I do?

A: Label drift is usually caused by products not being centered on the conveyor. Check and adjust the positioning structures on both sides of the WZ-129 conveyor belt so products do not sway left or right as they move. Also check whether the labeling head mounting screws have loosened, then recalibrate the label feed position; this keeps the error within ±1 mm.

Q3: Is changeover complicated when switching between workpieces of different sizes?

A: The WZ-129 bottom labeling machine supports visual parameter adjustment and program storage. For products of different sizes, simply recall the stored program on the touch screen and fine-tune the guide plate width mechanically. The machine handles widths up to 300 mm, so switching between standard sizes is quick and easy.

Q4: Can the bottom labeling machine print the production date directly on the label?

A: Yes. The machine supports an integrated traceability approach: depending on line requirements, a thermal transfer coder or inline inkjet coder can be integrated to print the production date, batch number, or barcode at the same time as labeling, with no separate coding step.

Written by Wanzhi Automation