Why Can't I Achieve the Dyne Levels I Once Could?
If you were able to get a particular dyne level at a given watt density and now you can’t, something obviously changed – either the material or the corona treating system.
Our experience is that this is the most common cause of treatment level problems. For extruders, any change in the Resin Blend such as the type or quantity of additives (slip or anti-block) or for converters, the age of the substrate may cause a change in the “treatability” of the material and make it harder to treat. It may require more power to achieve the same dyne level.
To help determine if your material is the problem, we would recommend that you:
- If you are not running the power supply at full output, turn the output up to see if you can get the dyne level you need. If you are running at full output slow the line down. Cutting the line speed in half is the equivalent of doubling your output power. Determine what watt density is required to get your dyne level.
- Try a different batch (preferably a batch that you know has worked in the past) – if you can treat it successfully using the same watt density , the substrate has changed – contact your supplier.
- If another corona treater is available, try treating the problem batch on a different treater using the same watt density – again, if you can treat it successfully, the substrate has changed – contact your supplier.
Corona Treating System
Our experience is that the most common cause of treatment level problems is a change in the material. As far as the corona treating system is concerned, there are very few things that can cause this symptom.
To help determine if your corona treater is the problem, we would recommend that you:
- Check the ground brush(es) Each treater roll should have a ground brush to bypass the bearings as a ground path. If the brush is failing, it is possible to develop a corona in the bearing, which is robbing power from where you want it, on the surface of the material.
- Insure that the treater roll is clean. Any build-up on the roll may lift the web from the surface of the roll and cause backside treat. This also robs power from where you want it.
- Check the High voltage wiring from the high voltage transformer to the electrode for loose connections or for an area of the wire that comes too close to ground. If the high voltage wire comes too close to ground, you may be developing a corona from the wire to ground. This also will rob power from where you want it.
- Ensure that the output wattmeter is functional. More than likely, if the meter is functional and hasn’t been tampered with, it should be calibrated correctly.