What Features Are Important to Review When Evaluating Heat Sealers?

One of the main features to review when evaluating heat sealers is process control capability for temperature, seal dwell time/speed and pressure as well as the ability to interface with the heat sealer for data acquisition, operator identification and recipe control.

Capabilities for controlling process parameters such as temperature, pressure and time

When evaluating heat sealers, it is critical to review each machine’s capabilities for controlling process parameters such as temperature, pressure and dwell time. For packaging medical devices, temperature is one of the most critical process parameters to control, but it can also be the most challenging. Constant heat sealers heat to a specific setpoint, which then must be maintained within the validated window. Impulse heat sealers heat up and cool down for each seal, and the entire cycle must occur within the validated window.

The amount of pressure applied to the seal must also be carefully controlled. If too little pressure is applied, there is not intimate contact of materials in the interface layer and the seal will be spotty or too narrow or weak. If too much pressure is applied, the adhesive in the interface layer may squeeze out or the packaging materials could be thinned.

One of the best ways to ensure a repeatable pressure process is to use seal bars that apply direct force versus a cantilever design. It is also beneficial to have a protected air reservoir such as an air accumulator tank within the regulated side of the pneumatic system of the heat sealer. This ensures that the sealing process is not subject to other equipment that might be cycling in the plant between the machine and the air compressor. Having a protected air reservoir inside the heat sealer helps guarantee that the sealing process is protected and the risk of other equipment cycling at the same time is mitigated.

Capabilities for HMI, the interface with the heat sealer, and data storage

It is also essential to review each heat sealer’s capabilities for communicating with operators when functions fall outside of the validation window. Alarms help operators ensure that they are not putting incorrectly or improperly sealed product into the good disposition area. CeraTek tray sealers have a light tower, and the HMI is mounted on the swing arm. That way, regardless of where the operator is standing, they can always see the messaging that is on the HMI.

The light tower also includes a green light that, if illuminated, notifies the operator that at least from a time, temperature, and pressure process standpoint, the seal cycle was completed without encountering any alarms. Of course, that doesn’t necessarily mean that there is a good seal. The lid could have been put on upside down, the product may not be fully seated into the tray, etc.  Errors like these can be mitigated with cameras and sensors that can detect that a lid is oriented correctly, that the tray is fully seated into the tool, and that the product is fully inserted into the tray.

What other features are important to review when evaluating a tray sealer?

It is critical that the tray sealer deliver consistent heat across the entire usable seal area. CeraTek uses a blanket style heater that is wired in series so that one line comes into the heater, makes a closed-circuit pattern throughout the entire heater, and then exits out of the heater. The custom heater pattern ensures a very even temperature profile across the entire usable seal area. Other tray sealer manufacturers use cartridge style heaters. These heaters use rods that run parallel through the heated dye so that, theoretically, the heat will migrate from the rod to the areas in between the rods.

However, what actually happens is that there are hotter areas underneath the rods and cooler areas between them. That means there could be one tray flange underneath the rods that could be getting good heat exposure and another tray flange that is in-between the rods that could be at a lower temperature exposure and so not able to create a good hermetic seal.

Cartridge style heaters also introduce a risk that a failed heater rod could go undetected during a run. This cannot happen with CeraTek’s blanket style heaters because they are wired in series, and if one zone fails, then the entire heater fails. CeraTek has been selling heat sealers since 1996 and has never sold a replacement heater due to a failure in the field. Our heat sealers are known for their reliability and durability, which are especially critical for medical device manufacturers.

For tray sealers, it is also important to review platen orientation and which platen moves in a tray sealer. CeraTek tray sealers have a stationary top platen. During the sealing process, this platen heats up and the tool is moved up to it. That enables extremely precise parallelism between the top heated die plate and the bottom tool area. In fact, CeraTek’s four post guided press maintains parallelism within five thousandths of an inch for the life of the machine. This extremely precise parallelism makes it possible to deliver an even amount of pressure across the entire tool area.