Hvorfor opstår der båndrids?
Fra Wood-Mizer, Europe
To increase sawmill blade life, there are eight significant reasons for premature sawmill blade rupture to look out for when operating a sawmill.
How many hours does a bandsaw blade have, or how many cubic meters can it cut before needing to sharpen or replace? The answer to the question "How long does a sawmill blade last?" depends on the blade quality and many more factors. In this article, you can learn what you need to pay attention to when working on a band sawmill to avoid premature blade breaks and increase blade life.
Sawmill blade manufacturers do not indicate the exact number of hours or cubic meters the blade should cut. The fact is that there are too many factors affecting the blade condition, which are not under the manufacturers' control. For example, Wood-Mizer is in charge of the sawmill blades manufacturing process and ensures that it produces the blades from quality steel alloys. Wood-Mizer operates state-of-the-art equipment for profile making, hardening, sharpening, setting, and welding blades.
In addition to quality, bandsaw blade life also depends on the following factors:
- The sawmill blade maintenance: how you sharpen the blade and set teeth.
- The sawmill: what sawmill you operate, how it’s adjusted, and if the blade is correctly aligned on the mill.
- The wood: are the logs clean? Are there metal inclusions in the logs? Does the sawmill have a debarker?
- The feed speed: the moment the saw blade enters the wood is especially important.
Let's take a closer look at the causes of premature bandsaw blade failure.
Reason 1. The blade has been in operation for too long.
When operating a band sawmill, a general rule is to replace the bandsaw blade with a sharpened one on average every 1,5 hours of cutting. In the case of cutting dirty wood, this time will be shorter.
Et rids i svejsesømmen tyder på en dårlig søm, af den grund tilbyder Wood-Mizer GmbH en livslang garanti på denne søm.
Går båndet i stykker et andet sted, er der en anden grund til dette.
Rækkefølgen af de hyppigste årsager:
1. Båndet er for lang tid på saven:
Efter 2-3 rummeter bør det tages af og slibes, og savtænderne bør udlægges. Teorien om, at båndet så skal hvile, før det tages i brug igen, er efter vores mening en myte.
2. Fejl ifm. slibning og udlægning:
Her er den typiske fejl, hvis tandgrunden ikke er slebet rigtigt ud. Her bliver ikke kun „tænderne kortere“, også mikroridser i tandgrunden, der ikke slibes ud, bliver dybere under yderligere brug, indtil båndet går i stykker (båndrids). Øgede båndrids kan også opstå, hvis udlæggepunktet er fastlagt for lavt.
Reason 5. Check the position of the blade on the blade wheels.
Adjusting the idle pulley is usually straightforward, and it is described in detail in the user manual. A more complex operation is adjusting the blade wheel on the drive side. Make sure that after adjusting both blade wheels, the sawblade extends from the wheels equally (average 3-4 mm between the sawblade gullet and the blade wheel rim). If you have questions about blade wheel adjustment, please consult a technician at your Wood-Mizer service center.
Reason 6. The bandsaw blade is dull.
How do you know when a bandsaw blade is dull? If the blade is dull, the tension constantly drops during operation and makes the sawblade wave in the wood. You cannot solve the problem simply by increasing the blade tension above the recommended value indicated on the sticker on the saw head. It may help but only for a while. For the sawblade to be always correctly sharpened, you need to check regularly the condition of the CBN grinding wheel, replace the oil in the sharpener, and in case of a dirty grinding wheel, cleanse it with a solvent.
Why is the bandsaw blade blunt?
The blade has been running continuously for more than 1,5 hours.
The logs are covered with bark and dirt. Sometimes it is enough to cut only 15-20 cm of such a log to make the blade dull. When sawing dirty logs, you need to manually clean the bark before sawing or use a debarker – an option on most Wood-Mizer sawmills. A debarker is a circular blade that removes a thin strip of bark directly in the place where the sawmill blade enters the wood.
The blade can also encounter metal objects in the wood, including nails, bullets from wartime, etc. In this case, you should replace the blade for further sharpening and check the blade guide rollers' alignment.