Preventing Splitting in Spliced Veneer Seams

A little advice on gluing success with spliced veneer seams. June 11, 2014

Question (WOODWEB Member) :
I am working on an A3 troubleshooting project in which the objective is to have no open veneer splicing seam defects and eliminate the need to use veneer tape. We use a hot press to then laminate the veneer to a particle board core. The veneer tape, as you know, must be sanded prior to final finish. We want to eliminate this need by splicing various wood veneers without the need to tape or stitch any defects. Does anyone have any advice?

Forum Responses
(Veneer Forum)
From contributor C:
I can think of three things. Some people actually zig-zag, then fold the joints open and put a very thin glue-line on the edges, then flatten them. Second, use the lowest temp you can on your press (heat equals shrink which equals open joints). Small shops in Europe use zig-zag machines but press at low temps. The best thing, however, is to get a good Diehl splicer of some similar machine that actually splices with glue on the edges.

From contributor R:
I'm not sure I understand the problem. Are your seams opening up after you splice them? Are you looking for a cost effective splicer? If you have a splicer there are some things you can do to eliminate seam problems and keep the tape to a minimum. Forget about getting a Diehl if you’re looking for a splicer.

From the original questioner:
My situation is such that the seams split or open up on occasion. We run a wide variety of multiple leaf widths and lengths. We run maple, walnut, oak, cherry, etc. Initially seams will splice together, but as multiple leaves are added we begin to see some of the previous seams break open on the ends.

Here is a breakdown of our process. We use a double blade jointer to cut all of our veneer leaves. We check for cut quality every day. We then process all of our veneer leaf bundles through an edge glue machine (Kuper) and then through a fanner. A glue thickness check is done 3-times a shift. A Wet gauge wheel is used and we keep our glue thickness between 3.5 and 4 mils. The bundles are stacked on staging tables and are allowed to dry for approximately one-two hours. We then splice the leaves together, in various lengths and widths, with multiple seams. A Kuper Splicemaster unit is used for this operation.

Out settings for the unit are two bars for pressure, 200-220 degrees Fahrenheit for both the upper and lower heater bars. We feed the leaves through the splicer at approximately four-five seconds per seam. All of this is converted from metric and Celsius parameters. From all this, we still see 30-45% of our sheets have splits or open seams on the end of our multiple leaf sheets. We use veneer tape to repair the seams and then process them through a hot press operation.

From contributor V:
When your veneers are stored on the carts after having the glue applied are the ends of bundles hanging over the edge of the carts? If yes, then the veneer that is hanging over is drying out more than the veneer that is on the cart. This will cause the veneer to shrink so you are asking the splicer to splice veneers which are not the same dimensions from end to end. What type of splicer glue are you using? How long does the pre glued veneer sit around before splicing?

From the original questioner:
The veneer glue is a Splyset 300. It has been used for years. Further, the edge glued veneer bundle is left to dry for one hour and then processed through our linear splicers. As the edge glued veneer bundles dry, the bundles are fanned out like a deck of cards allowing the glue to dry and preventing the bundles from sticking together.