Grits

Scratches

2010-05-22T19:55:00.014-04:00

Hey all. I'm back. My new daughter is about 5 months old and sleeping through the night with some regularity now, and my laptop is fixed and I can actually up and download pictures to the web. Surprisingly, that was very hard to fix. I appear to be back in the saddle again after the roller coaster that was the last 6 months.

OK, on topic. Wide belt sanding on wood.

How does this look to you?

Of course everyone wants the best finish scratch they can get, and while many things can affect the aesthetics of the scratch, the scratch pattern is only changed when sanded by a physically different head, such as a drum head or a pad head. The depth of scratch on a steel drum head will be deeper than a soft rubber one, but the pattern will be the same.

Ok. Now that I've lost everybody, including myself....

As I've said before, one of the biggest reasons sanding wood well is so difficult, is something I like to call "subjective quality". What I mean by this is that the surface finish I like may be absolutely terrible to a coworker of mine, and vice versa. "How does this look?", is a question that I avoid when I can while discussing sanding and finishing with customers and clients of mine, not because I don't want to answer it, it is because I can't.

Why, you ask? It seems like a pretty innocuous point. "Do you like this finish?" Simple yes or simple no would do. It's not that I don't have an opinion. Opinions flow from me like......well I don't know, everything I can think of is gross, but trust me, 99% of the time, I have absolutely no problem expressing my opinion to anyone that will listen. Grrrrr....back on topic. Simple question, right?

Not so much. I can only answer this question if I am either a person about to buy this product, whatever it may be, or I am the manager or owner in charge of making these products for myself or to sell to others.

Not Quality, Quantity!

What I strive to do for my customers is to help them achieve the finish they want but even more importantly, I help them maintain that desired finish on every part, every day.

I cannot stress more the importance of the sentence above. It is relatively easy to get one of your cabinet doors, or conference tables, or office desks, or modesty panels perfect. The key is to be able to maintain that finish and color with perfect consistency, regardless of who is running the machines that produce that finish. Consistent quality is the goal.

2 Kinds of Manufacturers in the Wood Industry 1. Manufacturers that Make but don't Finish

One crucial factor of the subjective quality to the finish that is often overlooked on your product should be profitability. Many of the shops and factories I consult with strive valiantly to get the smoothest, glossiest, most perfect finish they can achieve. These perfect finishes, whiles very aesthetically pleasing, may not be the most profitable to the company, especially if you are a company that doesn't put the stain and lacquer on that fantastic finish. A great example of this occurring is in the engineered wood industry, at the the veneered particle board, MDF, or plywood manufacturer. Most of these factories are either buying or making their own veneer faces, pressing them onto the substrate, sanding the panels to a P150, P180 or P220 grit finish, and packaging them for transport to many, many distributors and manufacturers of fine furniture, cabinets, architectural millwork, etc. Here they are routed or cut to proper size and then sanded again prior to finishing. (See my "pre-sanded wood" blog entry.)

While it is understood that the panel manufacturer strives to sell the best quality panel they can, and that part of that process is removing layers of veneer tape, minor handling damage, and many other things, do they really need to sand to such a fine finish? Wouldn't a P80 or P100 finish work just as well as, if not better than the grit sequence normally used? The goal for the panel manufacturing industry shouldn't be the finish quality of the veneer face. These resources would be better utilized concentrating on substrate thickness tolerances, proper substrate densities, proper veneer face adhesion, etc.

I shouldn't pick on the panel plants specifically, because everything I mentioned above is applicable to any manufacturer of any component made from wood that sands their product but doesn't apply the final finish to it themselves. Scratch pattern shouldn't really be all that important to your final product.

I have two quick questions for you:

1. Wouldn't your customers choose to have thicker veneer/wood than a better finish from your industry? (not that your customers ever have to do rework!)

2. How much money could you save on abrasives if you only sanded to P120 instead of P220?

2. Manufacturers that Finish what they Make

I guess I'd like to start out with a quick question. What is the first thing your customer looks at?

Normally the answer to this is either design, or finish.

Design? Can't help you there. I have about as much imagination as does my new daughter, and she drools.

Finish. Here is where I might be able to find a couple pennies here and there. I'll be back next week with the conclusion to this post. (I've determined that if I want to carry on with this, it has to be when the wife is at the store AND the baby is sleeping, or at 3:00 in the morning.)

I think I just heard the garage door.........Hi honey..........of course, I'd LOVE to see your new nail polish........

New Seminar @ MATC

2009-09-30T17:53:00.008-04:00

For all of you Wisconsin, or northern Illinois woodworkers, there is going to be a sanding seminar held on the MATC campus on October 27th. It is free of charge but you must call and reserve a spot due to limited space. Please contact Patrick at PMolzahn@matcmadison.edu

If the response is over what can be handled, we will plan on having another. Here is a run down of the topics:

Sanding Seminar Outline
Madison Area Technical College
Patrick Molzahn
Stiles Machinery
Peter Van Dyke
October 27, 2009

12:30 - 2:30

Sanding – Basic Principles

Why do we sand?
Dimension
Flatten surface
Create desired surface (scratch pattern)
Clean up surface
Edge breaking
Preparation for finishing
First step in finishing not the last step in manufacturing
Preparation between finish coats
Prepare for Polishing for high gloss finishes
P2000 grits and higher

What do we sand?
Raw lumber
Glued up blanks
Panel core
MDF
Partical board
Plywood
Stave core (glued up lumber blocks)
Mineral core
Veneer
Unsanded
Presanded
Tape
Reconstituted veneer (man made – office furniture)
Sketch faces
Exposed wood bands
Mouldings
S4S Lumber
Raised panels
Assemblies
5 piece doors
Face frames
Doors
Windows
Sealer
High gloss finishes

How do we sand?
The cutting tool – 10 minutes
Abrasive types
Backings
Types of coatings
Treatments
Stock removal
Scratch depth
Sanding methods include pro’s & con’s of each)
Everything from Hand Sanding to Robotic Sanding
Sanding defects
Machine demonstrations
Questions

From the looks of it, this will be an all encompassing seminar on many different types of sanding, hopefully to get the finish you need.

Powder Coating

2009-09-18T00:57:00.004-04:00

Powder coating MDF is certainly not considered a "new" technology, but it is certainly still an emerging technology.

I stopped at a company today to provide possible automatic surface preparation solutions for a company that has, in my humble opinion, nearly perfected this technology. There product has the best finish I have seen yet. They also had a full range of finishes from textured to high gloss.

If this is something you've been looking for on any of your design projects large or small, this company is somebody that should definitely be looked at.

The company's name is BTD Wood Powder Coating Inc. in Brainerd, MN. A good point of contact there is Mr. Achim Burgardt.

This is only just a little unsolicited information because I was so impressed. Extremely well done.

The sky is definitely the limit on this process. I can't wait to see what comes next.

"Pre-sanded Wood"

2009-09-03T21:40:00.000-04:00

This post will concentrate on the sanding of wood.

HMM...."I don't need a multiple head sander. I bring all my product in pre-sanded."

Head Scratch..."We just touch these up by hand. They all come in pre-sanded."

Call 911..."Our company sands our veneered particle board sheets to 220 grit before we ship them. Our customers pay a premium for the convenience of not sanding them again. The parts they make from my sheets are ready to go straight to finishing."

Although I am paraphrasing these statements, they are entirely too common. The three examples above are kind of a poor, poorer, and poorest comments I hear almost daily.

I'll explain them all in a little greater detail in a bit, but first I would like to cover a few things that often get overlooked.

Why do we sand anything? What is my goal pertaining to the surfaces of my workpieces?

When I ask the first question, 9 out of 10 people will give me part of the right answer. "Too make the surface smooth."

Correct........kind of.

Actually, we need to sand the surfaces of the wood for another reason, just as important. We can demonstrate this with a simple procedure some of you may have heard of. It is commonly referred to as The Water Drop Test.

Source: Douglas J Gardner "The Relevance of Surface Properties & Wood Finishes to the Wood Science & Technology Research Community“

The above picture shows the differences in wettability on a piece of yellow birch. The two arrows are pointing to the inactive and activated surfaces. The test has three drops of water placed on the surface at the same time. The drops above were photographed after 30 seconds. The drop on the left has kept its large contact angle with the unsanded wood surface. The surface under the middle drop was sanded with 2 passes of 220 grit sandpaper, you can see that the wettability is much improved. The last drop has almost completely soaked into the surface. The wettability is even more improved on this surface due to 5 passes of 220 grit sandpaper.

The best write-up I've seen written is published in the book "The Encyclopedia of Wood" - by the U.S. Department of Agriculture. Chapter 9 is the relevant portion of the book.

In a nutshell, when you sand the surface of the wood, not only are you making the surface smooth, but are also reactivating it. Extractives from within the wood cause a poor wettability seen by the left hand drop. These "extractives" mainly come to the surface of the wood from either heat, such as when the part is in a press, but also with time. This is why we have 2 very important thumbrules in the sanding world. The first is that all wood should be sanded no greater than 24 hours before it is finished and sealed. The second is that when sanding veneer, it should be the goal of the operator to remove about 1/2 the thickness of the veneer. Some woods are more alkaline, while some are more acidic. This is also affected by sanding the surface. Whether it be adhesive or stain or polyurethane, sanding the surface allows the bond to be formed not only mechanically but also chemically.

So, the problem with the first statement is that normally the grit I need to use to uncover a raw, active wood surface is not the final scratch pattern I want. If I do use my finishing grit on one head with one pass, I will either prematurely load the belt, or I won't take enough stock off and my surface will be blotchy. Below are three pictures at the cellular level of wood. One is normal, and 2 are shown crushed by using a dull or loaded sanding belt.

How well do you think the wood from that third picture finishes? Not good.

Ok, what does all this mean to my business? One example is easily shown on the water drop picture above. With the daily increase we see in water based stains and coatings, it seems that I would have to only use a fraction of the coating on the activated surface leaving much less to wipe off. Obviously, the less I have to wipe, the more thats in my bucket. That will save a suprising amount of money in a short amount of time. By allowing your stain to wick out evenly, will make for a much more uniform color not only within one part but also part to part. Also, if I don't finish and seal the workpieces I produce, why sand to the ultimate finish grit? Your customers need to sand everything again anyway. Yes, please remove defects and for sure any and all veneer tape, but a 150 grit is usually more than acceptable. You instantly cut your abrasive budget in half. That's huge and that is the problem with the 3rd statement.

Nothing can sand as delicately as my hand, but it's pressure on the board is all over the place depending on what I'm thinking about.....vacation, speeding ticket, etc. The machine gives you consistency, which is the problem with the 2nd statement. Every part may look great but that grain matched display case looks nothing like the desk, which in turn looks nothing like the cabinet doors even though they were made from wood from the same tree.

Ok, ok.....I'll get off my soapbox now.

Thanks for reading, please let me know if there are any comments or questions.

Lastly, I want to give a special thank you to Buetfering GmbH for supplying the photos in this post.

Oops

2009-07-27T18:07:00.000-04:00

Went to a customer last week that had made a very big oops. Generally speaking, wide belt sanders are pretty hard to mechanically damage. When things do go wrong, and damage occurs, there is usually a conglomeration of events that had to happen in a specific order to cause the negative end result.

One big exception to this is height adjustment. While it is always safe to open the machine, care must be taken when closing. Especially after some kind of evolution has taken place such as maintenance, cleaning, or testing. A great habit to form is to check the inside of the machine before closing it, especially if the feed belt is not running.

Some machines have a sensing roller or rollers in the front of the machine that prevent the machine from automatically closing to the preset height unless the feed belt travels a certain distance to ensure that there is no part in the machine. When a part, or tool is placed into the machine like when calibration is checked these sensing rollers are taken out of the equation. The machine will close to whatever value is in the controller as soon as the machine is switched on.

This will crush the tool or part and push the sanding head up. Damage can range from a chunk taken out of a rubber roll, to wrecking the graphite layer of a platen, to bending of a segmented pad. Worst case scenario is that the head frame itself and the frame it is bolted to get bent and/or cracked.

This is what unfortunately happened to my customer last week. Very expensive lesson.

Brush Sanding

2009-07-19T23:47:00.000-04:00

Hello,

Hope everyone's week went well. I had a very interesting week dealing with 2 brush sanding applications. Both companies had just recently bought a brush sanders.

They both brought me in to get the machines to work for their application. This application turned out to be the same one. They are both making cabinet doors from MDF, brush sanding them, and then pressing them.

One company actually wants to use the same brush sander to sand the MDF, "denib" the glue after it is applied, and then remove the glue overspray from the back of the door. The other owns a Gottschild machine for removing the glue and doesn't need or doesn't want to denib the glue.

The problem both are having is that they thought they couldn't get the tool marks out from their router. One was a KOMO, and one an Onsrud. Coincidentally, they both use a brand of MDF from Flakeboard out of Canada called Superior Plus.

What I saw from the product though was not tool marks, but rather core tear out from the tooling. There is no way a brush sander can remove these marks without obliterating the corners and edges. See picture:

This is a tooling issue, not a sanding issue. Our next step here is to bring in a router tooling expert to work with me on getting perfect product to their membrane presses. The most important thing to remember about a brush sander is that it is for scratch pattern, not stock removal.

Please check out the video from my friends at Flex Trim on my Facebook page. The link is on the right.

Please let me know if there is anything I can help you with.

Have a great week.

Miscellaneous Links

2009-07-12T23:14:00.000-04:00

Here are a few articles I wrote, some I'm quoted in and a webinar I did all on Brush Sanding. Just trying to get them all in one spot.

Here is a general brush sanding article from ISW Online: http://tinyurl.com/mtvpy5

Here is a webinar that I authored and gave last year. I will be giving another on Brush Sanding after the Las Vegas show. Sometime in the beginning of August. Please let me know if you are interested in attending.

Please look for the article 06/08. Thanks.

http://tinyurl.com/n96j4k

5 Piece Doors - Part 1

2009-07-02T12:30:00.000-04:00

Hello everyone. Thanks for visiting today. I'm posting a short pamphlet on finishing 5-piece doors today. I have this in PDF format if anyone wants it emailed to them. I made them JPG's here for ease of downloading and viewing.

Please let me know what you think about these on the comments below or feel free to Twitter me @SandingMan. Happy 4th of July everyone.

This is continued on the next post.

5 Piece Doors - Part 2

2009-07-02T12:14:00.000-04:00

Again, please let me know if you have any comments.

Dressing your machine's conveyor belt

2009-06-24T12:50:00.000-04:00

I posted the document in jpeg format for easy saving. Just click on the picture for a larger view. Please let me know if something is unclear.

Thanks.

Select Veneer

2009-06-20T23:32:00.000-04:00

Found a good look at a great company from a nice video of one of my most talented favorite customers/friends - Frank Kilibarda. Unbelievable veneer quality.

http://www.sawdustsoup.com/profiles/blogs/manufacturing-efficiency-and

Discussion on chatter marks and critical maintenance.

2009-06-18T16:55:00.000-04:00

Thanks to ISWOnline for posting this valuable information from many different perspectives. If anyone has any questions on the article, please feel free to ask!

http://tinyurl.com/l52zgc

Very cool place to hang out for woodworkers

2009-06-18T13:15:00.000-04:00

Welcome to the dynamic business networking tool designed just for the woodworking industry!

http://www.sawdustsoup.com/

Check it out....they have their own blog, forums, photo albums, etc. all in one spot. Lots of valuable information there.

NeoCon 09 Impressions

2009-06-17T21:58:00.000-04:00

Overall, I think that NeoCon '09 was probably considered a success by most attendees. Almost everyone I spoke to said that of course attendance seemed to be way off but that was expected. What wasn't expected was that most of the vendor's seemed exceptionally pleased with the quality of the customers. Almost unanimously, vendors told me that the potential customers that went to the show were the decision makers. There were few students, and even fewer customers that came just "to kick the tires". From what I could discern, sales seemed to be on par with a normal, non-recession year. Of course this is a relief to those of us in capital equipment sales because the majority of these vendors are some of my most important customers.

The booths and showrooms were stunning as usual, even if they were a little less extravagant than years past.

Trends

Here are some of the trends in design that I noticed in most of the booths and showrooms.

Reconstituted Veneer (Recon) - Nearly all of the largest furniture manufacturers had at least 1 or more office unit, desk, or conference table done with recon. While recon is fairly common in some sectors of the woodworking industry, and even some sectors of the office furniture industry, this was the first time that I've seen this used so widely. I don't know if this is just a new design trend, or they are subliminally sending a message to the wood industry about prices, it looks like we will be seeing more recon for the near future. People like TreeFrog should be very happy with that. Sanding and finishing recon is unlike sanding some cherry veneer. It is quite hard actually, due to the amount of glue. The important thing to accomplish when sanding it is to ensure the veneer is flat. You will have to use a cross-belt (preferred) or a soft, large diameter rubber drum to get this done correctly. If not, it becomes extremely hard to sand the sealer coat evenly without burning through the high spots.

Bamboo - It seemed as if this was everywhere. This has been popular as flooring, of course, for years, but I saw it used as wall coverings, the decoration in pressed acrylic or resin walls, veneer for desks and conference tables, and even the chairs. This material is a very good choice for many applications due to its hardness and resistance to wear. When calibrating bamboo for thickness, I usually drop down a grit from where I would normally start my sequence because of this hardness. Although not as oily, the wood this grass is most like is teak.

High Gloss - Like bamboo, this application is always at the show, but usually you see it mainly on solid surface, stone, and painted wood (MDF) surfaces. This year most of the vendors had at least one collection done to a mirror finish. This is pretty standard fare in Europe, but it seems to be migrating west. All of the vendors had exceptional high gloss finishes, but I have to note that The Mayline Group had a collection, manufactured and imported from China, that was so perfect, it took them awhile to convince me it was really veneer and not laminate. The reflections on the surface of the desk were not the least bit distorted. When sanding high gloss, the best option, if available, are cross-belts. They are long which helps dispel heat, they always use a "chevron" or felt strip internal belt which again helps to dispel heat, while keeping the scratch very, very short. This hides most sanding belt defects, and prevents the snake lines that occur when using an normal wide belt pad head. They are also much less expensive that a wide belt of the same grit. Believe me, it is very easy to damage a 9 micron grit belt.

Lastly, I just wanted to say thank you to all who took the time to talk with me at the show. I know how important and valuable your time is. Of special note: Nucraft Furniture, OFS Brands, Haworth Inc., Hon, Gunlocke, Paoli, Steelcase, Herman Miller, Indiana Furniture, Leggett & Platt, Bernhardt, Kimball, The Mayline Group, Knoll, Armstrong, Green Choice Flooring, Legacy, Terrazzo & Marble Supply, 3 Form, Coaster Office, Real Wood Floors, Lumber Liquidators, Schneller, Gianni Inc., Kittinger, Capri Cork, and Avian. If I forgot anyone, sorry, I guess I owe you dinner, your choice of venue.

P.S. Please remember this is only a small humble view of an incredibly large show. Please feel free to correct anything I may have wrong. Also, my opinions, not my employers. Thanks.

NeoCon 09

2009-06-15T18:03:00.000-04:00

Getting up at 4:00 tomorrow morning to go to the NeoCon show. Can't wait to see some of the new trends and materials the office furniture industry is gravitating towards. I heard that calling this show "green" would be an understatement. I'll let you know.

Amazing Furniture

2009-06-12T22:31:00.000-04:00

Take a look at this site. This guy has everything anyone would ever need.

Welcome to Villa Reale! ... http://link.gs/0qzx

High Gloss

2009-06-10T20:58:00.000-04:00

This is a video of a very small company in Germany that manufactures brilliant automatic high gloss machines. The parts need to be sanded to a very fine grit and then inserted into the machine for polishing. This machine was made with wood in mind, but has been successfuly used on plastics, solid surface, some stone/concrete.

The company's name is Bauerrichter, and is privately owned.

Please let me know what you think in the comments section or on Twitter @SandingMan.

Heesemann's New Automatic Orbital

2009-06-09T19:48:00.000-04:00

Here is a picture of Heesemann's new automatic orbital head from the Ligna show. What follows is a functional description of the process this head uses to remove cross-grain scratches without leaving swirls. (I get somewhat technical and dry.....sorry.) Let me know if you have any questions.

Functional Description of the Principles of the Heesemann OSR-Units

OSR = Orbital Scratch Removal. Drawing 1 shows the basic principle of a simple orbital sander. A pressure beam equipped with abrasive paper is supported by two eccentric bearings on a fixed frame. The eccentric bearings bring the frame into an orbital motion (picture 1). Individual sanding grains on the abrasive paper move on a circular path with the radius of the eccentric bearings. When a workpiece passes the abrasive belt moving in that way, protruding sanding grains will mark individual areas. These sanding lines are similar to the ones shown in picture 2. Even though there are no visible sanding lines only in longitudinal direction, as after wide belt sanding, these sanding marks are clearly visible. They are often called "swirls". Existing orbital sanders try to wipe out these "swirls" by an additional motion overlapping the rotating-swiveling pressure beam. The most common way to achieve a favorable effect is to overlap a second rotary motion. This figure is more complicated; therefore, we show here a motion transverse to the feed direction. This is shown in picture 3. You can see that the swirls on the workpiece surface are overlapping and are somewhat cancelled out. Basically, what the OSR-system has tried to do is to avoid the development of swirls altogether. The sanding paper is pressed down from the inside by a lamella system (photograph 1). It is motor driven back and forth transverse to the feed direction at varying speeds depending upon application. Pictures 4 to 6 schematically describe that constantly new areas of the oscillating abrasive paper are pressed down. This avoids the development of the characteristic marks (swirls) so that they do not have to be wiped out. The result is a high-quality surface without annoying sanding lines. An additional advantage is that a bearing system of high-quality and lasting liability can be used because of the simple orbital motion.

Maintenance Class Timeline

2009-06-09T00:29:00.000-04:00

Here is an agenda for one of the typical classes I teach. They can be on site or at my facility. I also hold classes on general operation of wide belt, profile, and brush sanders which are not brand specific in addition to classes based on application.

One note about the maintenance class is that I only do this at my facility because we actually tear down components of the machine in addition to putting real mechanical and electrical faults in the sander. I think it would be bad if I broke the machine at your facility and not be able to fix the problem.

Comments?

SA550 “Heesemann Belt Sander Maintenance”

DAY 1

8:00 - 8:30 Orientation & Welcome

8:30 – 9:30 Wide Belt Sander Nomenclature

Major Machine Parts
- Contact Roller
- Combi-head
- Segmented Pad
- Pressure Rollers/Shoes
- Graphite/Felt Pad
- Wide Belt/Cross Belt
- Planer Head
- Orbital Head
- Controller
- Electrical Cabinet

Sequence of Machine Operation

Sanding Applications
- Solid Wood
- Veneer
- Sealer

9:30 – 10:00 Abrasive Belt Technology
Wide Belt Abrasive Technology
Types of Abrasives
Grit Designation
Backing Material & Splices
Storage & Handling

10:00 - 10:15 Break

10:15 - 11:30 Sander Set-Up & Operations (Hands-on)
- Mounting Sanding Belts
- Machine Adjustments
- Pre-Settings
- Thickness Settings
- Sanding Belt Speed
- Feed Speeds
- Selection of Activated Heads

11:30 - 12:15 Lunch

12:15 - 3:15 Conveyor Belt Maintenance
Daily Maintenance

Dressing
- With Contact Roller
Ø Precautions
Ø Dress Board Dimensions and Placement
Ø Grit Selection
Ø Procedure
- Without Contact Roller
Ø Precautions
Ø Dress Roller alignment and installation
Ø Grit Selection
Ø Procedure

Bed Removal for Belt Replacement
- Removal Procedure
- Replacement Procedure

3:15 – 3:30 Afternoon Break

3:30 – 4:00 Poly V-Belt Tensioning & Replacement
- Troubleshooting and Replacement
- Installation Procedure

4:00 – 4:30 Wide Belt Sander Safety
Guarding
Belt Condition
Dust Collection
Sparking

DAY 2

8:00 - 8:30 Review & Questions

8:30 – 9:30 Contact Roller Maintenance
Daily Maintenance
Operation and Setup
Dressing

9:30 – 9:45 Morning Break

9:45 – 10:45 Contact Roller Maintenance (cont’d)
Alignment Procedure

10:45 – 11:30 Segmented Pad Maintenance
Daily Maintenance
Operation and Setup
Platen
Repair
Replacement

11:30 - 12:15 Lunch

12:15 – 1:00 Segmented Pad Maintenance (cont’d)
Alignment Procedure
Diagnostics

1:00 – 3:00 Sanding Defects & Troubleshooting

Identification
- Dubbing
- Rounded Edges
- Sand Through
- Snake Lines
- Shadows
- Zig-zag Lines
- Chatter Marks
- Splice Marks
- Polishing
- Dull and Worn Belts
- Burn Marks
- Stock
- Controller & Machine Adjustments
- Sanding Belts
- Others

Corrective Actions

3:00 – 3:15 Afternoon Break

3:15 – 4:30 Controller Vibrations
Machine parameters
Controller screen
Diagnostics
Basic Operations

DAY 3

8:00 - 8:30 Review & Questions

8:30 - 10:30 Machine Controller (hands-on)
Basic Operations
Fault Diagnosis
Machine parameters and their effect

10:30 – 10:45 Morning Break

10:45 – 11:30 Reading Heesemann Schematics
Symbols
Manual Schematic Drawings

11:30 – 12:15 Lunch

12:15 – 3:00 Electrical Troubleshooting (hands-on)
Component Locations
Electrical Cabinet Layout
Real Fault Troubleshooting

3:00 – 3:10 Afternoon Break

3:10 – 4:15 Specific Maintenance
Ordering Parts
Cleaning Machine
Using External Computer

4:15 – 4:45 Conclusion, Exam & Course Evaluation

Some common finishing defects from sanding, daily care, and operations

2009-06-08T20:42:00.000-04:00

I wrote this a few years ago for the sanding technicians. I, of course, had help from many different sources. Love it or Hate it, let me know what you think. I can expand on any of them if desired!

Thanks and have a good night.

Wide Belt Sanders:
Operation, Troubleshooting and Maintenance

Daily Care

Good House keeping should be a priority, as should ensuring that the correct tension is used. When the belt is running it is important to use the right tension. Equally at night, don’t forget to release the tension on the abrasive belt. Correct storage of abrasive belts can save a lot of problems, as belts are vulnerable to variations in relative humidity. Do not allow new belts to become cold and damp, always have 2 days supply of belts near to your machines. This allows the belts to normalize to the atmospheric conditions before being put onto the machine. Everyone should build a good widebelt storage rack for hanging you sanding belts. You can build it with simple pipes not less than 50 mm in diameter attached to the wall. You should space your pipes at least 6 to 8 inches apart. Hanging your belts relieves stress in the seams, makes them more supple, and easier to install on the machine. The belt rack can even be hung high on the wall to save floor space. Don’t allow the belts to hang in damp conditions. This will cause damp patches to form at the bottom of the belt, then when the belt is put on the machine it will be out of valance and cause vibration and will not track, or take a long time to settle creating other problems.

Pneumatics

A sander’s air system is designed to run dry, meaning without the presence of oil and/or water. Never mount a pneumatic oiler in line with the sander. Always keep the water trap drained. If you have any problems with water in your air lines, it needs to be addressed with the highest priority. If water gets into your air system the repair could easily cost you thousands of dollars.

Cleaning the Machine

Blow out the inside of the machine every day. Close the belt access doors and open the cover on the opposite side of the machine and clean around the infrared eyes and tracking mechanism. Some owners make a long (3 ft) blow gun nozzle by threading a piece of 1/8” pipe onto a regular blowgun. This allows access to dust and residue deeper inside the machine. It is also important to clean the very bottom of the machine at least weekly focusing on the height adjustment and spindles to keep them free of debris.

Conveyor cover

Cover the conveyor belt when you are not using the machine. Ultra violet rays from the fluorescent light deteriorate the natural rubber making it harder and very slippery. Most wood workers make covers out of wood but the nicest I have seen is canvas with a Velcro strip on the machine for easy removal.

Operations

Sanding Applications

Solid Wood
- The softer the wood, the harder the platen that needs to be used. (i.e. pine use 0.68 density or harder) Otherwise differences between early and late wood can be felt as waves in the wood. The harder felt evens out these differences.

Veneer and Veneer Sanding

Webster’s Definition : A thin sheet of a material. A layer of valuable or beautiful material for overlaying an inferior one. A thin layer of wood to be glued to a cheaper wood.

Veneer, in the woodworking industry, is applied to the surface of the following most common core type material. These cores are:

- MDF (Medium Density Fiberboard)
- Particleboard
- Veneer Plywood

The core material is generally calibrated prior to veneer being applied to first create a rough surface for glue penetration and second to remove the thick and thin nature of the core.

During the “lay-up” process, a thin layer of glue is applied to the surface of the core. The veneer is then placed on that surface in preparation for pressing. Pressing is generally done via a cold or hot press operation.

Veneer tape is applied to the surface of veneer to hold the veneer faces together during the press cycle. This is done to prevent any negative separation at the joints of the veneer.

Veneer Core Variation

The most stable core material is MDF, whereas, plywood core is the most unstable. The numerous layers of a plywood core contribute to the highest amount of thick and thin variations after the lay-up process.

Press Variation

Hot pressing is also a large factor in creating variation. When the veneer and its core are heated during the hot press cycle, the wood core will “swell” and change thickness. When allowed to cool to room temperature, thin and thick variations occur. Plywood core is the most unstable due to the multi-number of layers within the core. MDF is again the most stable. The advantage of cold press operations is to minimize these core variations.

In Summary

To list in the order of degrees of variation (thick and thin), from the least amount of variation to the highest amount, the following would be good to use as a rule of thumb:
- MDF cold pressed
- Particleboard cold pressed
- MDF hot pressed
- Particleboard hot pressed
- Plywood cold pressed
- Plywood hot pressed

Veneer Tape

The number of layers of veneer tape applied at one specific location and the type of veneer tape used, add to the degree of difficulty presented to the next sanding operation. Veneer tape has generally been seen in the industry of three different types, which are:
- Perforated / white in color
- Perforated / brown in color
- Solid / brown in color

The thinnest and easiest to sand would be that of the white perforated type. The most difficult to sand would be the solid brown type.

Given the use of the solid brown veneer tape and multi-layers applied on top of one, and other pressed via a hot press, creates the hardest sanding scenario. The multi-layers of tape are embossed into the thin layer of the veneer face.

Veneer Sanding of Taped Veneer Product

- Cannot remove all tape and/or very rough surface (tear out) with one pass without a crossbelt?
- Higher end companies need a crossbelt with two wide belts (optimal).
- All high quality needs a crossbelt if in a finishing line or if stand-alone and doing solid wood or veneer, first pass should be against grain on wide belt.

A crossbelt sanding head is generally used when three or more layers of veneer tape are present. The crossbelt is very effective removing the veneer tape that runs left to right across a given panel. The crossbelt is in full contact with the left to right tape and has the longest “dwell” time. A widebelt has a very short “dwell” time on tape running left to right. On the other hand, a widebelt does have a long “dwell” time on tape running infeed to outfeed. For the best results on multilayers of tape, a crossbelt followed by a widebelt is recommended. Generally, abrasive grits of 120 on the crossbelt and 150 on the widebelt are used. This is then followed by abrasive grits of 180 and 220 for a final polish.

If one or two layers of veneer tape are used, a two-head or three-head sander is recommended. The first sanding head is used to remove the veneer tape and the following sanding heads are used to polish. Abrasive grits of 120 or 150 are used to remove the tape. Abrasive grits of 180 and/or 220 are used to polish the product.

Veneer Cut Down

Veneer cut down is terminology used in the industry referring to the sanding of a veneer surface. It has been stated that most veneer sanding requires the removal of one-half the thickness of the veneer to achieve proper cut down. This amount of stock removal should remove any and all defects in the veneer used regardless of the core used.

Sealer and Sealer Sanding

Webster definition of sealer is: “Any device to prevent the passage or return of gas, liquid or air into a product.”
Sealer used in the woodworking industry can come in various forms. They may be: a primer paint coat, lacquer, sealer, UV fill, or water-based sealer. All of these sealers are used to seal the wood and prevent outside elements from penetrating the surface. In most all cases, the seal coat is applied prior to a final topcoat. Sealer is also used to “freeze” the wood fibers to become a stronger structure. The key element prior to a seal coat being applied, is preparation of the wood surface. Sanding to a very smooth surface (180 grit or higher) and denibbing via brush machines or orbital sanding, are very important factors. Denibbing will remove loose and/or broken wood fibers prior to the seal coat being applied. In the modern world of water base sealers, it is even more important that the wood surface be prepared properly. By the nature of “water base” sealers, grain raise can become a problem. In most cases, customers converting to water base sealers are sanding to a finer grit.

Seal Sanding

Seal sanding or a form of seal sanding has been used since the early 1960’s. On most print and/or laminating lines, UV fill is applied to the surface (180 or 220 grit finish sanded) of particleboard or MDF. The product is then sent through an oven for drying and curing. After the oven, a finishing sander is used. This process creates a very smooth solid surface for printing and/or a thin laminate to be applied. The requirements for a seal sander (flat stock) are:
- A segmented pad with the smallest segments possible.
- Variable edge pressure.
- An electronically controlled “rise” and “fall” time.
- A very fine abrasive grit (280, 320, 400, 600, ….etc.)
- A very slow running speed of the abrasive belt (1.5 – 4.5 meters per second), controlled by a frequency inverter.
- Abrasive air-blast blow-off systems to clean the fine grit abrasive belts while in production.
- A fast running speed of the conveyor belt (10 to 15 meters per minute), controlled by a frequency inverter.
- A vacuum bed conveyor feed system is recommended when product to be processed is “slippery” on the bottom surface or the material is coated on both sides.

Generally, after a product has been seal sanded via a widebelt, the material is run through a grit impregnated bristle brush to sand very small areas that were not sanded by the widebelt. All areas must be sanded to prevent what is called “orange peel”. Orange peel would be a given area that did not receive ample amounts of seal sanding. This area will turn to a dark look or orange look as to the remaining properly sanded areas. Thus, the name “orange peel”.
On non-flat products such as cabinet doors, a brush machine equipped with grit impregnated bristle brushes are used.

Operations (cont.)

Sanding Belt Choices

- Stock Removal – 60, 80, and 100 grit
- Finishing – 120, 150, 180, 220…etc.
- Wide Belt multiple head machines can skip 1 grit size between belts or heads. (i.e. 80 to 120 to 180)
- Cross Belt multiple head machine sequence is as such: 80 grit crossbelt to 80 grit wide belt to 120 grit wide belt, or 120 grit cross belt to 120 grit wide belt to 180 grit wide belt.
From Wide belt to cross belt, 3 grit sizes can be skipped (i.e. 80 grit wide belt to 150 grit crossbelt).

Things that can and do affect quality.

1. Feed speed.
2. Abrasive belt speed.
3. Grit size.
4. Pressure – Surface and Edge.
5. Wood species.
6. Number of Heads.

It is always better to send a work piece through 1 or 2 degrees off from parallel to rollers.
- Control has a better or easier time seeing the work piece
- It also ensures segments are hitting the entire work piece due to falling and rising time cover all four edges.

Ensure Belt tensioning is set to the proper level.
- If you are having a problem with belt flare out on sanding surface but increasing rise time rounds the corners, try raising belt tension pressure.
4 to 5 bars is the nominal operating range.

Sanding Defects

1. Chatter Marks
If the marks are uniformly spread across the board, the rollers being out of balance can cause the problem, or the bearings may be worn. The rollers may have become “oval” or the pad, where fitted, may have become stuck. Another cause can be vibration caused by poor machine mounting or loose foundation plates. The spacing between the chatter marks will indicate whether it is the contact roller or a defective abrasive belt. To determine whether the belt is causing the marks, one of two things can be done.
1) Measure the distance between the chatter marks, mark the belt with a wax or graphite stick and pass a trial piece though the machine. The wax or graphite mark will chow up on the trial piece, to indicate if the distance between marks is the same. If the belt is suspected as the cause, try fitting another belt, preferably from a different supplier in case one batch was faulty, If this fails to cure the problem, then look for another cause i.e. the machine bearings. Listen with a stethoscope, or a screwdriver, placed on the bearing head and place your ear to the screwdriver handle to listen for bearing rattle, or place a coin on the bearing head to see the vibration. Also feel the bearing head with the hand for heat build-up during running.
2) Splice Marks are similar to chatter marks but are caused by a poor belt splice. There is a difference between the frequency of marks caused by a splice and chatter marks from a roller. To see if the marks are from the drum or the splice, sand two workpieces, 1 at a fast conveyor speed, and the other at a slow conveyor speed. Compare the marks, if the marks are similar it is chatter from the drum. If the spacing of the marks is different, the abrasive belt splice causes them.

2. Tramlines (Snaking longitudinal strip marks)
Nearly all tramlines will be caused by damage to the abrasive belt from the workpieces being sanded. Minerals or grit within the material are responsible and once the belt has been damaged it is then of little use. Tramlines appear as elevated lines on the surface of the sanded workpiece. Some of the cause is removed by having sufficient extraction, which will keep any loose particles of grit away from the surface of the workpiece. Sanding the area of the fault with a used piece of abrasive of the same grit can sometimes save the belts. The abrasive belt is the only component moving back and forth on the machine; therefore the belt, not the machine, causes snakes. These can sometime be reduced in magnitude by decreasing air pressure on a segmented pad or air bladder and/or decreasing both conveyor speed and sanding belt head speed. Further causes can be irregular or jerky oscillation movements, which can cause the belt to crease. Checks should be made on the belt tension and that the oscillation movement is as even as possible.

3. Coarse Markings
This is often caused by the incorrect selection of grit size, i.e. too coarse. Where only one roller/pad is available the choices of grit size is critical. The answer is either change to a smaller grit size or use a machine with two heads, one with a pad, allowing for one coarse grit and one finer grit to be used in a single pass. It is good policy never to jump more than one grade between heads. With any bigger jumps than this, the follow-up belt will not remove marks from the first belt.

4. Straight longitudinal strip marks
These can be caused either by the machine or the belt. They can be positive or negative – heavily sanded or unsanded. Regarding the machine this fault is usually caused by neglect of the sanding pad or a build up of deposits on the platens or contact roller, and can be rectified with a new covering to the sanding pad and cleaning the platen and contact roller. If the problem still persists, the abrasive belt will have to be checked and signs of deposit build up on the back of the belt should be checked. If present this should be lightly sanded to remove and further checks made to the graphite pad.

5. Round Edges
Sanding with a very soft contact roller or pad usually causes this problem. On an air pad machine you can increase the pressure in the pad to make it stiffer/less flexible and carefully set the depth of the pad. On segmented pad machines you can select –1 to –4 pad segments on the edges. For delicate work, variable edge pressure is a must for precise control of the pressure on workpiece edge segments.

6. Shadows
These are unsanded areas on the workpiece. They are caused by badly cupped or warped workpiece, too little hold down pressure, too light sanding pressure, too much pressure in an air pad. Be sure to check calibration and pressure ranges for the machine model.
7. Dubbing
This is the rounding over or heavy sanding the front and/or rear edges of a workpiece.
1) Contact Roller – Typically caused by having the contact roller down too far below the pressure rollers, or not having the pressure rollers calibrated properly. Some dubbing can occur when the machine is set too narrow for the piece to be sanded. The piece is pressed down into the conveyor and springs up into the contact roller at the ends.
2) Pad – Older machines with a fixed pad will dub the front and back and there is little you can do. On Butfering machines with the air pad or segmented pad there is a fall and rise timer so the pad sands perfectly on the front and back edges.

8. Shiny Heat Marks
Shiny head marks, which have been reported on veneered panel work, again result from the same problems as the chatter marks and usually can be rectified by following the same procedures for elimination. In severe cases, burn marks are left. Using too fine a grit for too heavy a cut causes burning. Heat builds up as the belt gets clogged with dust. Try a coarser belt or a lighter cut or a combination of the two.

9. Bumpy finished board
This can be caused by the incorrect selection of roller hardness or wrong feed table setting (floating or fixed). Often machines are specified to perform one function when new, and then when demand changes, i.e. from machining solid pine to machining veneers and /or sealer in line, the same machine may still be used. However the requirements can vary tremendously, the chore hardness for one operation is totally different from the other. Also the type of grit and bond strength of the abrasive will change considerably.
10. Grooves
Another common problem is caused by the material being fed into the machine with dirt or foreign bodies on it, this being picked up either from the operators careless handling or whilst in storage. Grooves are like dotted or dashed lines running the length of the workpiece. Grooves can be positive or negative, by a defect or damage to the abrasive belt. Sanding a staple could cause a groove; the missing abrasive will leave raised dashes in the workpiece. Excess glue on the boards is another common cause. A negative groove is caused by a defect in the manufacture of the belt where there are some heavy spots of grit on the belt.

Heesemann's new brush sander

2009-06-06T01:00:00.000-04:00

This is Heesemann's new brush sander. It was introduced in Atlanta '08, but further refined and shown again at Ligna '09. The difference in this brush machine to other disc and drum style machines is their first head. They are using the discs as a mini-carousel.

I'll post Butfering's brush sanding machine next.

Cryokinetics Belt Cleaning System

2009-06-05T08:58:00.000-04:00

This is a Cryokinetics system mounted to a widebelt calibration sander. We've seen a 50-60% savings on abrasive belt consumption during normal production.

They also have a stand alone cabinet that belts can be placed in to be cleaned and a separate hand held gun to use on glue residue and overspray as examples.

New Blog

2009-06-04T13:18:00.000-04:00

Seems like the new thing to do in conjunction with all this social networking to tie them all together. The twitter site is going strong, I'll be launching the facebook site next week. Stay tuned for all my new updates!