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Holz Her Sprint "wish boning" on 2mm PVC5/24
We have had this problem on both our old sprint 1310 and now on our 1320.
By wish boning I mean where the edge tape pulls away from the board for the first and last inch to inch and a half of the board. This shows up mainly on white.
We have had to set the pressure rollers to 3mm to basically eliminate the use of the 2 smaller rollers.
On our the 1310 it was the main large roller and we tied it back a bit with a bungee cord. :-)
I am told the reason they are not back normally is they gain to much momentum when kicking in that they kick the board out.
Anyone else having this type of issue?
We had this issue on a Holzher 1320, 3mm PVC tape was pulling away from the workpiece at the leading and trailing edge.
In the end, the way we fixed it was to use what we call a sacrificial piece in front of and immediately behind the workpiece as it goes through the machine. Then we pry them off after. It results in excess tape on each end, which we have to trim manually, but it seems to get rid of the pull away issue.
Our shop invested recently in a more heavy duty edge bander that is supposed to be able to handle 3mm PVC better. We shall see...
We run A LOT of 3mm edged doors (PL on Melamine) and I found that if you tighten the tolerances up on the tape feed, then set the front and rear overhang from the guillotine cutter to about 4 mm, then the problem mostly disapears. The pressure roller was hitting the excess tape , and trying to press on it while it was unsupported, causing it to release a bit just inboard of the workpiece, before the glue could set. Also, make sure the nylon guide roller adjacent to the feed turntable was in its most distant position (farthest from the applicator). This helped release *some* of the memory from being rolled, before the tape gets to the work.
Try dialing your glue temp down a few degrees to allow it to cool/cure a little more before hitting the secondary rollers. We sold our old Sprint a while back but I know it (and our new EB, not a HolzHer) did odd things as the spring temperatures warmed up, and we'd have to drop our glue temps back 5-10 degrees.
You could probably guess how the hot glue could cause the glued-side of the 3mm band to heat up and want to expand.
Also, make sure your rollers are not causing friction. I don't remember if our old Sprint had secondary rollers that free-spin, or if they were geared with the main roller. Either way, make sure that there's otherwise no friction between the rollers and edgeband.
Our tech just increased the temp to get good flow. We are currently using Wurth (Kliebert) "natural" just ordered some clear. I remember it sticking a whole lot better.
The secondary rollers spin free but are spring loaded inward of the board.
Our Holz Her struggles with thicker banding. The problem is, as you've observed the pressure rollers push where they shouldn't. Trying to cut the banding closer with the guillotine has other issues, like the banding sometimes not covering the leading edge. Our IDM bander has air cylinders on each of the 4 idler rolls that engage and disengage them so they only press when needed. A much better solution. But a much more expensive bander.
Problem almost completely eliminated by switching to clear glue. It holds much better.