Hello everyone.  Planning on starting this blog up again.  Economy is back up and so am I.  Check out a new website on Sanding and Finishing.  Let me know what you think.  Thanks!

http://www.fdmcdigital.com/KnowledgeCenter/SandingandFinishing/tabid/538/Default.aspx

Scratches

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

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

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"

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

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

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.