Finish Problems
| Condition | Description | Probable Cause | How to Correct |
|---|---|---|---|
| Glazing | A glazed surface is simply one where there are too many knife marks per inch. | The desired number of knife marks per-inch is determined by the cutterhead knife speed, the feed rate of the material, and the number of knives involved in the finish cut. | Raise the feed rate of the material. |
| Use less knives in the finish cut. | |||
| Reduce spindle RPM’s. | |||
| Burning | Burn marks on the finished surface of the material. | Will usually occur when feeding is stopped with material in the machine. | Keep material flowing through the machine. |
| When cutterhead knives are dull, some species like hard maple, will tend to burn. | Keep knives sharp. | ||
| The edge of the knife will burn on a vertical plunge in the pattern. | Grind a relief angle on plunge of knife. | ||
| Skipping | Areas on the finished part that did not get cut. | Sometimes a cutterhead prior to the finish spindle removes too much material. | Check the depth of cut on the cutterheads prior to the finishing spindle. |
| Not enough material will be left for the pattern head to make a finish cut. | Stock preparation. Enough material should be present in the rough material to allow at least 1/32″ depth of cut per cutterhead. | ||
| Parallel lines | (Ridges) – Can be seen along the length of the material. | Parallel lines can be caused by irregularities in the cutting edge of the knife due to grit and lumber defects. | Keep knives sharp. |
| Use a pre surfacing cutterhead to remove grit before the finishing cutterhead. | |||
| Heavy Joints on knives cutting soft wood can crush the grain instead of cutting it. | Keep joint on the knife to a minimum. | ||
| Chatter | (Washboard effect) – Will show as a ripple in the finish. | Can be caused by improper setting of chipbreakers or holddowns. | Keep chipbreakers and holddowns tight enough to prevent the material from moving. |
| Unbalanced cutterheads. | Balance knives, gibs and cutterheads. | ||
| Worn spindle bearings. | Replace or repair spindle assembly. | ||
| A one-knife finish at high feed rate. | Joint the cutterheads or slow the feed rate. | ||
| Taper | The finished material is tapered down the width. | Is caused by improper adjustment of guiding surfaces. | Realign the side guides. |
| The finished material is tapered down the thickness. | Is caused by improper alignment of the bed plates and outfeed table. | Realign the bed plates and outfeed table. | |
| The finished part is tapered side to side (or top to bottom). | Can be caused by improper alignment of the bed plates or outfeed table. | Realign the bed plates and outfeed table. | |
| Can be caused by cutterhead knives not being ground parallel to the cutterhead. | Check the alignment of the grinder. | ||
| Can be caused by the jointer not being parallel to the \spindle. | Realign the jointer bar. | ||
| Can be caused by the spindle not being parallel to the bed plates. | Realign the spindle. | ||
| Fuzzy grain | The fibers of the wood project from the finished surface of the material. | Usually caused excessive moisture content. It is most prevalent in basswood, elm, and aspen. | Proper drying of wood will help eliminate this problem. |
| Decrease the feed rate. | |||
| Increase the cutting angle of the knife. | |||
| Can be caused by the wrong cutting angle of the knife for the material being cut. | Increase the cutting angle of the knife. | ||
| Face grind the knives. | |||
| Can be caused by dull knives. | Keep knives sharp. | ||
| Corrugated grain | Occurs mostly in yellow pine or red wood when the summer wood fibers project above softer spring wood fibers. | The feed system or holddown crushes the wood and it springs back after being cut. May be amplified by wet material. | Reduce feed pressure. |
| Keep knives sharp. | |||
| Reduce the feed rate. | |||
| Layered grain | The growth rings curl up, giving the surface a raised grain appearance. | A defect found most often in yellow poplar when annual rings curl up. | Keep knives sharp. |
| Feed material with bark side to the pattern as much as possible. | |||
| Chip Marks | Abrasion marks in wood surface caused by chips being scraped across the finished surface. | Wood chips dragged across the surface by the cutterhead knives. | Decreasing the feed rate. |
| Keep knives sharp. | |||
| Increase the dust removal system. | |||
| Wood chips clinging to feedrolls on through-feed moulders. | Increase the dust removal system. | ||
| Tear-out | Can occur as moderate to severe; where sections of the material have split along the grain. | Can be caused by knives cutting against the grain (such as near knots, etc.). | Align grain directions in glued stock. |
| Decrease the cutting angle of the knife. | |||
| Lumber is too dry. | Set the knives in to the cutterhead. | ||
| Machining glued stock with grain variations. | Set the chipbreakers and inserts as close as possible to the cutterhead. |
Feed Problems – Caused by Machine
| Probable Cause | How to Correct |
|---|---|
| Guides misaligned. | Realign the side guides. |
| Bed plates misaligned. | Realign the bed plates. |
| Feed works worn. | Repair or replace worn parts. |
| Feedrolls worn. | Replace or sharpen feedrolls. |
| Improper feedrolls. | Use the correct feedrolls for the material being run. |
| Hopper worn. | Repair or replace worn parts. |
| Overloads kicked out. | Check amp readings. Replace worn overloads. Repair or replace bad motors. |
| Spindle belts slipping. | Check the tension of the spindle belt. |
| Bed lubricator not working. | Repair, clean or fill bed lubricator. |
| Feedrolls not set at the same height. | All infeed rolls should be the same height from the bed plates. |
| Holddown not parallel to the bed. | Use a dial indicator to set the holddown shoe parallel to the bed plate. |
| Worn spindle bearings. | Repair or replace spindle unit. |
| Low incoming air pressure. | Check air system. Upgrade if necessary. |
| Worn spindle belts. | Replace worn spindle belt. |
| Grooved bed misaligned. | Align the grooved bed plates using the right hand groove. |
| Patterned holddown twisted. | Position the patterned holddown when a finished part is under the holddown. |
| Clogged or inadequate dust system. | Repair or upgrade dust system. |
Feed Problems – Caused by Material
| Probable Cause | How to Correct |
|---|---|
| Wet lumber. | With some exceptions most lumber produces a better finish at 7% to 9% moisture content. |
| Warped twisted or bowed stock. | As much as possible keep the bow (concave side) of the board down and to the right guide. |
| Wax tar or chemical on stock. | Trim ends of material. |
| Un-square stock. | Mostly effects short material. Adjust the chop saw to cut square ends. |
| Stock dimensions vary more than 1/4″. | Variations in material greater than 1/4″ can create jams in the machine. Look into stock preparation. |
| Pitch build-up on guides or bed plates. | When running soft woods it may be necessary to clean the machine more often. Increasing the bed lubrication can help. |
| Soft spot or dry rotted area of the material. | Look into stock preparation. |
| Case hardened Material. | Check the material drying process. |
| Dry lumber. | Moisture contents below 6% become harder to machine. Check the material drying process. |
| Knots or slivers of wood jammed in the machine. | Clean the machine. Look into stock preparation. |
| Length shorter than the self-feed length. | Keep the material butt fed into the machine. Try hopper or conveyor feed systems. |
Problems – Caused by Tooling
| Probable Cause | How to Correct |
|---|---|
| Dull knives. | Dull tooling makes the machine work harder. Keep the knives sharp. |
| Too heavy of a joint on knives. | When the joint on a knife is more than 1/32″ the machine works harder. Never run tooling with more than a 1/16″ joint. |
| Cutterhead on backwards. | Check tooling when installing on the moulder. |
| Cutterhead not on the machine. | If a spindle is not being used and the cutterhead is not turning, be certain the guides or bed plates are even before and after that cutterhead. |
| Wrong cutterhead on machine (cutterhead too narrow). | The knives in the cutterhead must cut across the entire width/thickness of the material. |
| Too few knives in cut. | The fewer knives in a cutterhead the bigger the chip load per knife. When running faster use more knives in the cutterhead. |
| Too large a diameter on the first bottom cutterhead for the diameter of the reference cutter. | If the first bottom cutterhead is too big in diameter, then the cut made by the reference cutter will not be higher than the reference guide. The material will hit the top of the reference guide. |
Snipe Problems – Bottom
| Description | Probable Cause | How to Correct |
|---|---|---|
| A snipe on the bottom of a finished part created by the second bottom spindle and on the leading end of the part. | Cutterhead is set higher than the out feed table. | Check the setting of the cutterhead with the outfeed table with a straightedge. |
| Outfeed table is too far away from the cutterhead. | Loosen the outfeed table and slid towards the cutterhead. Leave about 1/8″ clearance between the swing of the cutterhead and the table. | |
| Lower infeedroll is too high. | Set the lower infeedroll 1/32″ above the infeed table. | |
| Deep snipe from the first bottom cutterhead. | Check the setting of the first bottom cutterhead. | |
| A snipe on the bottom of a finished part created by the second bottom spindle and on the trailing end of the part. | Cutterhead is set lower than the outfeed table. | Check the setting of the cutterhead with the outfeed table with a straightedge. |
| Bed plate under top spindle is too far away from the bottom cutterhead. | Loosen the bed plate and slid towards the cutterhead. Leave about 1/8″ clearance between the swing of the cutterhead and the bed plate. | |
| Lower outfeed roll is too high. | Set the lower outfeed roll 1/32″ above the outfeed table. | |
| Long stock is unsupported after leaving the moulder. | Place a table or conveyor under the stock to support it while it is leaving the machine. | |
| A snipe on the bottom of a finished part created by the second bottom spindle and on either or both ends of the part. | Bowed stock fed into the machine with the bowed side down. | Increase the depth of cut on the first bottom spindle. |
| Increase the pressure on feedrolls and holddown to flatten the part. | ||
| Outfeed table is un-level with the rest of the bed plates. | Check the shims under the outfeed table for equal thickness. Check for dirt or slivers of stock under the table. | |
| Deep snipe from the first bottom cutterhead. | Check the setting of the first bottom cutterhead. | |
| The holddown is not parallel with the bed plates. | Use a dial indicator to adjust the holddown shoe. | |
| Thin stock. | When running thin stock it is necessary to set the chipbreaker and holddown shoes as close to the cutterhead as possible without hitting the knives. Thin stock finishes better if the ends are kept butted up. | |
| Snipe from the top cutterhead can leave the part loose. | Fix the snipe on the top first. | |
| Holddown shoe is too short. | Slide the end of the holddown shoe over the leading end of the outfeed table. Use a longer shoe. | |
| Unsupported pattern on the outfeed table. The pattern rotates to one or both sides. | Place a support on the outfeed table to prevent the part from moving. | |
| Employee lifting stock to pull it out of the machine. | Solve the feed problem. Place a table at the outfeed end of the machine |
Snipe Problems – Top
| Description | Probable Cause | How to Correct |
|---|---|---|
| A snipe on the top of a finished part created by the top spindle and on the leading end of the part. | Too little chipbreaker pressure. | Increase the chipbreaker pressure. |
| Chipbreaker too far away from the cutterhead. | Slide the chipbreaker toe towards the cutterhead. Be certain the toe does not hit the knife. | |
| Sliver lifting stock. | Clean out the machine. | |
| A snipe on the top of a finished part created by the top spindle and on the trailing end of the part. | Not enough holddown pressure. | Increase the holddown pressure or lock the holddown in place. |
| Holddown too far away from the cutterhead. | Slide the holddown towards the cutterhead. Be certain the cutterhead knives do not contact the holddown shoe. | |
| Excessive stock removal with top head. | Increase the depth of cut with the first bottom cutterhead and/or the first top cutterhead. | |
| Lower infeed roll too high. | Set the lower infeed roll 1/32″ above the infeed table. | |
| Chipbreaker too low. | Set the yield of the chipbreaker at 1/8″ to the thinnest stock. | |
| Bottom cutterhead is set lower than the outfeed table. | Check the setting of the cutterhead with the outfeed table with a straightedge. | |
| A snipe on the top of a finished part created by the top spindle and on either or both ends of the part. | The holddown is not parallel with the bed plates. | Use a dial indicator to adjust the holddown shoe. |
| Stock may be bowed. | Run the stock into the moulder with the bowed face down. | |
| Unsupported pattern on the outfeed table. The pattern rotates to one or both sides. | Place a support on the outfeed table to prevent the part from moving. | |
| Pattern is unsupported by the holddown. The pattern rotates to one or both sides. | Create a special holddown for the part that holds the part down on both sides. Can be a counter-profile holddown. | |
| Long stock is unsupported after leaving the moulder. | Place a table or conveyor under the stock to support it while it is leaving the machine. | |
| Deep snipe from the first bottom cutterhead. | Check the setting of the first bottom cutterhead. | |
| Thin stock. | When running thin stock it is necessary to set the chipbreaker and holddown shoes as close to the cutterhead as possible without hitting the knives. Thin stock finishes better if the ends are kept butted up. | |
| Intermittent feedroll too high or too much pressure (only on machines with two top spindles). | Reduce roll pressure. Set the lower roll at 1/32″ above the bed plate. |
Snipe Problems – Left Side
| Description | Probable Cause | How to Correct |
|---|---|---|
| A snipe on the left side of a finished part created by the left side spindle and on the leading end of the part. | Not enough pressure on the LSH chipbreaker. | Increase the pressure on the left side chipbreaker. |
| LSH guide too far away from the cutterhead. | Adjust the left side guide towards the cutterhead. Be certain the knives do not hit the guide. | |
| Un-square ends of stock (usually only on short stock). | Adjust the chop saw to cut the ends square. | |
| Holdover rolls not holding stock against the right side guides. | Adjust the infeed holdover rolls. | |
| Left side guide outside the cutting circle. | Check the setting of the left side guide to the left side cutterhead with a straightedge. | |
| Right side cutterhead not set to the right side guide. | Check the setting of the right cutterhead to the right side guide with a straightedge. | |
| Bottom feedroll on the top roll shaft. | Serrations pull stock away from the right side guide. Replace rolls. | |
| A snipe on the left side of a finished part created by the left side spindle and on the trailing end of the part. | Left side guide not holding the stock tight. | Check the setting of the left side guide to the left side cutterhead with a straightedge. |
| Left side guide not parallel to the RS guide. | Realign the left side guide. | |
| Right side guide not parallel to the referencing guide. | Realign the side guides. | |
| Chipbreaker too far away from cutterhead knives. | Adjust the chipbreaker closer to the left side cutterhead. Do not permit the chipbreaker to hit the knives. | |
| Chipbreaker un-square with bed. | Check the chipbreaker for sliver, wear or damage. Repair or replace. | |
| Infeed guide not parallel with right side guide. | Realign the side guides. | |
| A snipe on the left side of a finished part created by the left side spindle and on either or both end of the part. | Bowed stock. | Feed stock into the machine with the bowed edge against the infeed guide. |
| A snipe from the right side can cause a snipe on the left side. | Fix the snipe on the right side first. | |
| Both side of the stock are not held down by the feedrolls (usually only with wide material). | Space feedrolls out across the width of the material. | |
| Slivers in the moulder. | Clean the machine. | |
| Narrow stock. | When running narrow stock set the guides and chipbreakers as close to the cutterheads as possible with out hitting the knives. | |
| Chipbreaker hitting the feedroll when running narrow material. | Remove a feedroll across from the chipbreaker. |
Snipe Problems – Right Side
| Description | Probable Cause | How to Correct |
|---|---|---|
| A snipe on the right side of a finished part created by the right side spindle and on the leading end of the part. | The right side cutterhead is behind the right side guide. | Check the setting of the right side cutterhead with a straight edge. |
| Right side guide too far from cutterhead. | Adjust the right side guide towards the cutterhead. Do not permit the guide to hit the knives. | |
| Infeed guide not parallel. | Realign the side guides. | |
| A snipe on the right side of a finished part created by the right side spindle and on the trailing end of the part. | Right side cutterhead is outside the right side guide. | Check the setting of the right side cutterhead with a straight edge. |
| A snipe on the right side of a finished part created by the right side spindle and on either or both end of the part. | Un-square ends of stock (usually only on short stock). | Adjust the chop saw to cut the ends square. |
| Right side guide not parallel with infeed guide. | Realign the side guides. | |
| Left side guide not holding the stock tight. | Set the left side guide to the material. | |
| Referencing cutter not set to guide. | Check the setting of the reference cutter to the reference guide with a straight edge. | |
| Infeed guide out of parallel to the referencing guide. | Realign the side guides. | |
| Holdover roll is across from the right side cutterhead and not the referencing guide or infeed guide extension. | Use the longer reference guide. Adjust the infeed guide extension. Adjust the holdover roll. | |
| Bowed stock. | Feed stock into the machine with the bowed edge against the infeed guide. | |
| Both side of the stock are not held down by the feedrolls (usually only with wide material). | Space feedrolls out across the width of the material. | |
| Lower feedroll on the upper roll shaft. | Serrations pull stock away from the right side guide. Replace rolls. | |
| Slivers in the moulder. | Clean the moulder. |