Consistent, invisible glue joints are the whole point of tapeless veneer splicing — and when something goes wrong, the defect usually shows up immediately and costs material. Most splicer issues come down to one of a handful of root causes: pressure bar and heater bar adjustment, feed chain wear, jointer condition, glue application, or moisture and heat management. This guide walks through the eleven most common defects we see in the field, with a diagnostic table for each symptom.For preventive maintenance procedures on your splicer, see our tapeless veneer splicer maintenance guide.
Overlapping
Overlapping — where the edge of one piece of veneer rides on top of the other instead of butting cleanly — is almost always a symptom that the veneer isn’t being held flat through the feed zone. The fix path typically starts at the pressure bar and heater bar adjustments, then moves to the matching rolls and holddown springs if the problem persists. If the overlap only occurs at one or both ends of the sheet, the issue is almost certainly with the jointer rather than the splicer itself.
| The edge of one piece of veneer is on top of the other. The veneer is not being held flat. | The pressure bar may be too high. | Check the float gauge. Lower the pressure bar. |
| The front suspension bolt is too tight. This lifts the infeed end of the upper heater bar. | Loosen the suspension bolt. | |
| Upper heater bar is too high. | Reset the upper heater bar. | |
| The front end of the heater strip is not against the lower heater bar. | Place a slight bend in the heater strip 4″ from the infeed end. | |
| The heater strip will not “float” up and down at the infeed end. | Check the lower heater bar for level. The feed chains are pulling on the heater strip. | |
| The pressure setting is too light.Check for pressure marks, the shine, on the veneer. | Increase the pressure setting. | |
| The veneer overlaps before entering the feed chains. | The holddown springs on the matching roll are not holding the veneer flat. | Lower the holddown assembly. |
| Replace the holddown split springs. | ||
| The matching rolls pull the veneer into the machine at angles. | Readjust the cant on the matching rolls. | |
| Reduce the pressure on the matching rolls. | ||
| The edge of the veneer curls up against the infeed guide. | Readjust the cant on the matching rolls. | |
| If the veneer is curled at the edge set the holddown block as close to the matching roll and as low as is possible. | ||
| The jointed edges of the veneer are not square. | Check the jointer blade for sharpness. Only use the veneer edge from the flat side of the Guillotine. | |
| The veneer overlaps on one or both ends only. | The edges of the veneer are not straight or parallel. | Check the jointer. |
Mismatching
Mismatching happens when the ends of two spliced veneer sheets come out offset from each other. The cause depends on where in the machine the mismatch occurs — at the infeed, under the matching rolls, at the start of the feed chains, or under the pressure bar. Operator feeding technique is a frequent culprit at the infeed (always align edges and use one hand to feed both sheets), while downstream mismatches almost always trace back to worn rolls, chain tracking issues, or pressure bar height.
| The ends of the spliced veneers are offset. | Improper feeding. The veneer is fed into the machine unevenly. | Align edges and use only one hand to feed both sheets of veneer. |
| Mismatches under the matching rolls. | Too much or too little spring pressure on the matching rolls | |
| Large lower idle roll not turning with feed chains. Replace bushing. | ||
| Matching rolls and/or lower feed rolls worn. Replace parts. | ||
| Burr on the infeed guide or table catching the veneer. Repair. | ||
| Mismatching at the beginning of feed chains. | Heater strip not “floating” up and down. Check adjustments of lower heater bar. Reset machine. | |
| Pressure bar is too low. Check the float gauge. | ||
| The suspension bolt is too loose. Tighten the suspension bolt. | ||
| Upper heater bar is too low. Readjust the heater bar . | ||
| Mismatches while under the pressure bar. | Check the adjustment of the lower heater bar, the upper heater bar, and the pressure shoes. | |
| Pressure bar is too low or high. Check the float gauge. |
Burning of Veneer
Dark brown scorch lines along the glue line — most often on the bottom face from the lower heater bar — indicate excessive heat that’s both burning the veneer and crystallizing the glue. Correcting this is straightforward: lower the temperature setting (consult your temperature/thickness chart) and increase the feed rate so the veneer spends less time in contact with the heater bars.
| Dark brown scorch lines on either side of the glue line. Usually dominant on the bottom side from the lower heater bar. | Excessive heat from either the upper or lower heater bar. Also crystallizes the glue. | Lower the temperature setting. See temperature/thickness chart. |
| Increase the feed rate. |
Burnishing of Veneer
Burnishing shows up as a crushed, shiny surface along the glue line. It’s almost always a pressure problem — too much force on the veneer as it passes under the pressure bar. Back off the pressure setting and verify against your float gauge.
| Crushed and shiny surface along the glue line. | Too much pressure. | Check the pressure setting. |
Crimping of Veneer
Crimping within 1″ of either side of the glue line typically indicates worn inside edges on the feed chains. Chain replacement is the permanent fix, though reducing pressure can minimize the defect in the short term while replacement parts are being sourced.
| The veneer is crimped within 1″ of either side of the glue line. | The inside edges of the feed chains are worn. | Replace the feed chains. |
| Reduce the pressure. |
Marking of Stock
If you’re seeing indentations left by the serrations in the lower feed chains, the issue is either pressure setting or splicer adjustment. Start by reducing the pressure setting — if the marks persist, check the alignment of the lower heater bar, upper heater bar, and pressure shoes.
| Indentations left by the serrations in the lower feed chains. | Improper pressure setting. | Reduce the pressure setting. |
| Incorrect adjustment of the splicer. | Check the adjustment of the lower heater bar, upper heater bar, and the pressure shoes. |
Grooving Along the Glue Line
Gouges or indents running parallel to the glue line — on either the top or bottom face — almost always point to crystallized glue buildup on the upper heater strip or lower heater bar. Excessive glue application is the root cause. Clean the affected surfaces using only soft materials like wood, brass, or bronze; running a heavy piece of veneer crossways through the splicer will often clean them effectively. If nicks or burrs are present, repair or replace the strip or bar.
| Gouges or indents in the veneer next and parallel to the glue line. Can be either top or bottom face. | Build up of crystallized glue on either the upper heater strip or lower heater bar. | Excessive glue on the veneer is the source of the problem. Clean the upper strip and lower bar. If scraping is necessary use only soft materials such as wood, brass, or bronze. Running a heavy piece of veneer crossways through the splicer will usually clean them. |
| Nicks or burrs on the upper strip or lower heater bar. | Repair or replace. |
Incomplete Glue Joint
When the leading end of a veneer sheet splices cleanly but the trailing end opens up, the edges of the veneer aren’t parallel. This is a jointer problem, not a splicer problem — check the jointer before making any adjustments to the splicer itself.
| The leading end of the veneer is spliced but the trailing end is open. | The edges of the veneer are not parallel. | Check the jointer. |
Poor Jointing
If you’re seeing sections of the glue line that splice properly alongside sections that open, or slight openings along the joint, the issue is either inconsistent glue spread (some sections received too little or none) or torn veneer slivers along the jointed edge. The first is a glue application method issue; the second is a jointer issue.
| The sections of the veneer are spliced but sections open. Slight openings found along the glue line. | Inconsistent or insufficient glue spread. Sections of the veneer received too little glue or none. | Check the method of applying glue to the veneer. |
| Small slivers of the veneer were torn out along the edge. | Check the jointer. |
Excessive Glue Spread
Excess glue shows up in two ways: visible buildup on the veneer surface, or tear-out along the glue line caused by crystallized glue on the heater strip or bar. Both point back to the glue application method — reducing spread at the source resolves the issue and prevents the downstream buildup that causes grooving and crimping.
| A build up of glue on the surface of the veneer. | Too heavy of a glue spread on the veneer. | Check the method of applying glue. |
| Tear out of the veneer along the glue line. | Build up of crystallized glue on either the upper heater strip or lower heater bar. | Check the method of applying glue. |
Crimping
This second form of crimping — where the leading edge of the glue line gets pushed back along the joint — is distinct from the feed chain crimping covered earlier. Here, the cause is either crystallized glue buildup on the heater bars (again, a glue application issue) or a lower heater bar that’s set too high.
| The leading edge of the glue line is pushed back along the glue line. | Build up of crystallized glue on either the upper heater strip or lower heater bar. | Check the method of applying glue. |
| Lower heater bar is high. | Readjust the lower and upper heater bars. |
Blue Staining
Blue staining appears as metallic-looking stain marks on either side of the glue line, caused by condensation and moisture reacting with the veneer. It’s most common on high-humidity days and shows up most often in coarse-grained oak. If veneer is already stained, a 10% oxalic acid solution will remove the ink. Prevention is about moisture management: dry the veneer to a proper moisture content, store it in a humidity-controlled area, allow glue to dry completely before splicing, and consider equipment modifications like compressed air jets on the pressure chains, a hot air gun in the center of the pressure bar, or chrome-plated chains for operations running in consistently humid environments.
| Metallic stain marks on either side of the glue line caused by condensation and moisture. More common on high humidity days. Generally exist in coarse grained oak. On veneer already stained, the ink can be removed by applying a 10% oxalic solution to the stain. | Moisture content of veneer is too high. | Dry veneer to lower moisture content. Store in humidity controlled area. |
| Glue is wet when veneer is spliced. | Allow the glue to dry completely before splicing. | |
| Humidity in area is high. | Reduce the temperature setting as much as possible and increase the feed rate. | |
| Install a compressed air jet blowing on each pressure chain in the pressure bar. | ||
| Install a hot air gun in the center hole in top of the pressure bar. | ||
| Install chrome plated chains. |
Related Maintenance and Reference Guides
Troubleshooting is most effective when paired with regular preventive maintenance. For additional support on your tapeless veneer splicer, review these related resources:
Still Can’t Resolve the Issue?
If you’ve worked through the probable causes above and your splicer still isn’t producing clean, consistent joints, our factory service team can help. Mereen-Johnson technicians have the original manufacturing records and decades of field experience on every machine we’ve built, which means we can diagnose issues other service providers can’t.
Contact Mereen-Johnson service or call (612) 529-7791 to speak with a factory technician about your tapeless veneer splicer.