Waxing Machines

Waxing machines are used for coating purposes in the packaging sector. Waxed paper, for example, is a popular packaging material. Optima has been involved in a number of waxing machine upgrades. One particular project was very demanding due to the machine’s unreliability and high fault rates. The fundamental purpose of the machine remained unchanged. Our proposal addressed the problems experienced through poor sequencing of the control system, and the tension control issues in both the main wax roll area and the rewind area.

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The waxing machine’s working principles are shortly described below (please, refer to the diagram):


The unwind is a brake controlled unwind with a feedback medium and controller. It is a turretting unwind. It comprises a reversing contactor pair with an overload unit.

Waxing Roll

The waxing roll is a driven roll (master speed controller) with a manually applied nip roll. It is driven by a single phase, variable speed DC drive. The motor-gearbox is a Shunt wound DC motor coupled with a right angled worm and wheel gearbox.

Super Chill Roll

The super chill roll is a driven roll, controlled in open loop torque mode. It is driven by a single phase, variable speed DC drive. The motor gearbox is a shunt wound DC motor coupled to a right angled worm and wheel gearbox. The operator adjusts the tension (torque) on the motor by a ten turn potentiometer with a vernier dial.

Main Chill Roll

The main chill roll set is a driven roll operating in speed control. It is driven by a single phase variable speed DC drive. The motor gearbox is a shunt wound DC drive coupled to a right angled gearbox. The exact type could not be easily determined. The chill rolls allow the waxed paper to slip over their surface.


The rewind is a manual turretting, torque controlled stand with manual splicing operation. The rewind spindles are controlled by single phase DC drives with automatic diameter compensation and taper control. The diameter compensation and taper functions are controlled by a single analogue system. The compensation system is changed over from spindle to spindle when a splice is performed.

The differences between the existing scheme and the proposed by Optima system are as follows:

Sequential relay logic replaced by the PLC

This provides the flexibility to allow timed and controlled sequencing of the control system elements to allow a controlled start up.

Three Phase Drives on the Rewind section

Three phase drives provide improved form factor for the drive/motor combination. This allows full tension range to be achieved without overheating the motors. The diameter/taper control unit is replaced by individual drive resident winder configurations (more sophistication and better control achieved).

A load cell is used to indicate the tension in the web prior to the rewind spindles.

From start up, the tension can be applied using a ‘soft start’ technique, so eliminating the web break problems at initial thread up stage.

Emergency Stop System

The emergency stop system is replaced with a compliant system to meet the requirements determined by your risk assessment.

Torque control of the Super Chill Roll

The tension in the waxing section is controlled by a shunt wound DC motor operating in torque control. The drive train comprises a 3000 rpm motor and right angled worm and wheel type gearbox. Worm boxes are not efficient and have relatively high mechanical losses. Losses for which the torque required to overcome them are significant when associated with the torque required to tension the web. This is evident to the operators who have less than 1% of a ten turn potentiometer and dial with which to control the section’s tension.

The torque control for this section is modified by monitoring the torque requirement of the machine during commissioning and setting this value on a potentiometer inside the control cubicle. A potentiometer mounted on the control cubicle has an additional torque trim of ± 10% over the full range of the potentiometer. This with the addition of a motor current meter allows the operators to set the motor torque more consistently.


Would you like to know more about other control system projects we have completed on waxing machines? Please, leave us a short message here and we will send you additional information within 24 hours!

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Recent Posts

Safety Scanner Issues and EN999

Optima were recently asked to advise on a safety guarding application for one of our customers. 

There had been a number of false trips of the laser scanner causing the machine to stop. As a result of this, a plastic chain ‘barrier’ had been fitted as a temporary measure with instructions to operators to not breach the barrier whilst the machine was running. 

The customer naturally wanted this rectifying as soon as possible, so Optima performed a short-notice service visit to site.

On the site visit, our engineer noted that the scanner was showing a code which indicated that the front screen required cleaning.

Once the screen was cleaned thoroughly the scanner did not show any faults or errors and was in normal run mode.

However, we performed further checks on the original software to ensure that the scanner configuration still met the requirements of the safety guarding application. 

The diagrams to the left show the Warning Field configuration (Yellow) and the Protective Field (Red). Both of these were confirmed to be operational. 

The warning field causes the klaxon to operate and the protective field caused an emergency stop of the machine.

We did, however find a few concerns that needed to be addressed.

1. None of the scanner safety circuit had been documented on any drawings.

2. Non-compliance with EN999 ‘Safety of machinery – the positioning of protective equipment in respect of approach speeds of parts of the human body’ includes a formula to be used to calculate the distance from a hazard that a safety zone must be triggered. Based on the stopping times of the machine, the scanner was placed too close to the machine to be effective in an emergency.

We are working closedly with our customer to assist them with this application and help them achieve a safe and effective solution to this.

If you need any support with safety applications or other upgrades, please get in touch.

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