Part 1 of Article (visible defects on work piece)
Download the PDF guide with both parts, to keep as a reference near your sander.
Wide belt sanding is anything but simple, so when you’re experiencing problems it can be complicated to isolate and identify the source of the issue. Whether you’re seeing visual defects on the work piece, or problems inside the machine or with your belts, that can definitely be frustrating, especially when your wide belt sander is a key part of the manufacturing process.
Our wide belt technicians see several common issues, from chatter and other surface faults, to burned belts and too much dust, and they help our customers to get their sander back up and running and improving the overall process and results.
Overall, three common themes arise for the sources of the most common issues – 1. machine maintenance issues, 2. incorrect sanding procedures/techniques/settings, 3. problems with the belt.
This in-depth article, goes into the machine maintenance issues that will most likely be the source of your issues.
For visual defects on the work piece, check Part 1 of this two part series.
From dust and static to shattered belts, a guide to maintaining your wide belt sander and abrasives.
5. Too Much Dust & Static Electricity
If the inside of your sander has a lot of dust, such as in the photo above, or you’re experiencing finishing issues like lines on the work piece; premature wear of the belt; or burning, you may have high static electricity, low airflow (CFM) in your machine, or a faulty dust extraction system, all leading to dust build-up.
Because the action of sanding is based in friction, or the constant rubbing together of two surfaces, the natural results are heat and static. In the case of sanding, the activity produces dust and debris from the cutting action. In a high static environment, the dust will stick to various surfaces inside the machine and collect over time, leading to various problems. You can use a static meter to check the static discharge. If the reading is more than +/- .01, the sander will need grounding.
GROUND YOUR SANDER
One solution to static issues is to ground the sander by literally using a metal screw and rod from the conveyor bed into concrete floor and several feet into the ground below. If the sander is not on the ground floor, look for options to connect to metal support beams that are in the concrete/foundation. If in doubt, consult with an expert before making changes. For more information about how to properly ground the sander, click here.
CHECK YOUR CLIMATE
Did you ever notice in the winter, you’re more likely to experience a static “shock”? That’s because the winter has low humidity, which is an environment more conducive to static electricity. If you have excessive static problems, review your climate, the temperature and humidity levels in your shop and locale, as you may need to amend the climate controls in your shop.
DUST EXTRACTION SYSTEM
It is critical that your air flow and dust extraction system function correctly in removing debris from the machine, as stray particles on the
work piece, abrasives or laser eye, will likely cause the other problems in this guide, such as lines, loaded belts, broken belts, and
tracking issues. First, inspect the elements of the system and check to make sure the system is not clogged.
LOW SUCTION / AIR FLOW
If dust is collecting in your machine, you may have problems with the suction/air flow from the dust extraction system. Use an air flow meter and calculator to check the CFM (cubic feet per minute) for your dust extraction system, and make sure that it is operating to the manufacturer’s specification. If the reading is off from the recommended rating, there may be a problem with the system itself, so contact your manufacturer for repair assistance.
6. Burned Belt & Too Much Loading
Replacing belts often due to loading can become very costly, very quickly. Whether your belts are over-loading, burning or leaving black lines on the work piece, believe it or not, there may be some technical and process aspects to optimize that will improve the life of your belts and cut down on your replacement intervals.
You may be trying to remove too much in one pass. Each grit is designed to remove a certain amount. We recommend not skipping more than one grit in a sequence. When in doubt, refer to the following to check that you are in the correct grit range for your application:
1) abrasive planing (24-40 grit),
2) heavy stock removal (50-80 grit),
3) cutting/surfacing (100-150 grit) and
4) finishing (180-320).
Work Piece Material
What material are you sanding, and what type of belt are you using? If you’re sanding a very soft wood, such as pine, there will generally be more loading as these woods have a higher resin content. Check to make sure you are using the right type of belt (cloth, paper, etc) for your application. If you’re unsure, contact your UNEEDA rep to determine if you might be better served with a different product.
Sanding location on belt
If you continually sand in one place on the belt, this can lead to loading and belt burning. Make sure to vary your entry point on the machine to better utilize the full width of the wide belt.
Resin buildup on work piece
You may have glue or resin built up on the work piece itself, leading to additional residue getting caught up on the belt, as a result of the heat produced from the sanding action (friction).
Belt too worn
The belt may simply be used up and it may be time to replace the belt.
Too high sanding load to compensate for machine problems
If you are trying to compensate for issues with the machine, such as a damaged contact roller/pad, poor alignment between sanding unit and feed system, damaged or worn feed system (feed belt or rolls), or faulty extraction system, this can cause problems with your belts, and cause burning. Instead, check these areas for problems and address them.
Quality Variation in Work Pieces
Check for inconsistencies in the quality of your work pieces – both before and after sanding. If the wood is poorly dried, they have glue penetrations, or the edge milling was insufficient, these things can lead to burnt belts or loading.
Improper storage of abrasive material
Storing belts improperly can lead to many issues. If belts are stored on the floor, they will absorb moisture and become out of round, leading to many issues. Belts should always be hung, preferably on a round rod, to maintain their shape.
7. Belt Breaking
If you’ve got a damaged belt, whether from frayed edges, broken joints, tears or snapping, something is amiss. The following areas provide a starting point for determining the cause of the breakage. Some are deeper problems also covered in this guide, such as over loading, storage and tracking issues. See those areas for further information.
One common issue that can lead to broken belts is tracking. If the belt is not tracking properly in the machine, it can cause tears in the material.
Damaged from loading/unloading machine, packing/shipping, storage
Pay careful attention when unpacking your belts from shipping or storage. Make sure they have hung prior to inserting them into the machine and always verify the quality of the belt prior to loading. When loading or unloading, pay careful attention to correct placement and not catching the belt anywhere it shouldn’t be.
Your belt may break as a result of too much loading. If this is the case, you may have one of the following problems: too high removal rate of a removal rate, large thickness variations of work pieces, or foreign particles in the sanding machine or on the work surface. Check to make sure you are using the proper grit sequence for your application and that your work pieces are the same thickness and clear of dirt or other residue.
Wrong backing for application
Choosing the right backing for your belts is key to avoiding sanding problems, and broken belts. While paper belts may lead to a better finish, if your application requires a more durable or flexible abrasive, cloth may be a better fit – so as to avoid breakage, tears and creases. If you’re unsure about which backing is best for your applications, check with our sales or tech teams to get personalized recommendations.
If your belt is old or well used, the structural integrity may have weakened over time, and the most common place for it to break would be in the joint. On a rare occasion, a belt joint may be faulty in manufacturing, leading them to pop or separate under pressure. Lastly, certain types of joints are reversible – i.e. they can run in both directions on the machine. Verify whether your belt joint type is uni – or bi directional.
8. Belt Tracking off The Machine
If your belt is not tracking properly on the machine, that means it the belt may actually be coming off of the rollers, or is otherwise mis-aligned while in action. As you might imagine, this can cause all sorts of issues, some of which have been mentioned previously – like belt breaking. See below for possible problem areas.
Check to see that your tension pressure is set correctly, based on the following standards: for paper – 45-55 psi, cloth – 55-65 psi and polyester – 65-85 psi.
The laser eye might be covered in dust. Check if this is the case and clean it. Check to ensure proper functioning of the eye.
In some cases, the belt may have been cut improperly. Check to make sure the belt is of acceptable quality.
You may be trying to remove too much in one pass, which could cause the belt to become dislodged.
Improper storage of abrasive material
Belts should be hung – not stored on concrete floor, as they absorb moisture and become out of round. This can lead to the belt not functioning properly in the machine, including improper tracking.
Rollers not parallel or unevenly worn
If your rollers have worn down unevenly or are not parallel, for whatever reason, this can cause the belt to track improperly. If the rollers are not parallel, using a digital indicator, such as the ones our wide belt technicians use during client visits, will help to reset the machine with precision. If the rollers have worn unevenly or flat, on the other hand, Parallel is something we correct with indicators. If the rollers aren’t flat (worn unevenly), they need to be removed, flattened or recoated then reinstalled. Always make sure to keep your machine well maintained and replace parts that are worn out.
With all the moving parts and variables associated with wide belt sanding, any number of things can easily go wrong. If anything is certain, the most important areas to focus your energies to avoid future issues are maintaining your machine properly, following wide belt sanding best practices for technique and proper product selections for your application, and maintaining quality control for your belts – such as changing them at appropriate intervals and checking the overall quality of the belt before inserting it into the machine.
If you need help with your wide belt sanding process, and you’re a Uneeda Customer, get in touch to set up an appointment with our technicians. Uneeda has two full time wide belt technicians that make site visits to our customers to help address these issues and get you set up for success and achieving the best finish for the most effective and efficient price and process possible.