This is a very difficult article to write without making some folks angry and some absolutely irate.
Machinery salesmen have a vested interest in selling the machines they have on the floor instead of the machine the customer needs. What is worse is that those same people often do not really understand the essence of sanding and how to optimize it for the customer. They need you to be happy enough to make the final payment and then they are pretty out of the equation.
Customers buying sanding machines are very rarely sanding experts. I have personally witnessed a plant manager at a very large company raving about how wonderful his very expensive wide belt machine was, while I was watching his operator pushing parts through with a stick.
Why do I get streaks? Where does orange peel originate? Why do I have top or bottom heavy spray patterns? Find solutions for these and more spray finishing challenges.
That manager blamed the operator for every single difficulty with the day to day operation of the machine, even though there were huge design flaws in the machine that were actually responsible. The operator doesn’t know he shouldn’t have to use a long stick to push parts through, so he doesn’t argue about it too much. The manager doesn’t know the design flaws contribute to constant quality problems. Meanwhile the company plans to buy another machine with the same flaws and issues.
Several years ago I worked on a tiny little SCM Sandya 2 head for a customer in Central Indiana. This is a very respectable little machine with a steel drum and a combination head in the second position. They were running 100 and 150 cloth belts on close to 1,000 parts of various sizes per day. They sanded cabinet doors, frames, and all the associated parts. They used up those two belts every day. Honestly, not too bad for such a small machine. I have a soft spot for these little buggers.
The owner of the company asked me to help him pick out a larger used machine. He wanted to shop around the various websites and find 3-head machines that looked like they would serve his purposes. My response was to tell him he should really look at a new machine from a particular company that sold a great quality machine with very particular traits.
The machine should have dead shafts, air exclusion (pop the heads up/down with the flip of a switch), and it should have a steel drum, 60 shore drum, combi-head with a 36 shore drum, and bladder platen. I told him this machine would run 80-120-180 extremely well and his belt life would be unbelievable.
He said no way could he afford to buy a new machine. He decides to just run the used machines by me for approval…. Week after week he calls to tell me about different machines and asking me my opinion.
Him- “I found a completely rebuilt ___________! New drums and everything!”
Me- “What color is it?”
Him- “What? You can reject a machine because of the color of the paint!”
Me- “Is it a 75 shore drum, 55 shore drum, platen with a relieving table?”
Me- “The 75 shore drum isn’t hard enough. The 55 shore drum is too hard. The relieving table machine hold-down shoes are a huge pain. The beds don’t hold calibration. Live shafts are not as rigid as dead. The eccentrics lock up with corrosion and lose timing.
What he did not understand is that the configuration of the machine in question was only a mild improvement over his two head. It could only run 100, 150, and 180 really well and still keep up with his stock removal requirements of .020” per side. You should not skip a grit going into a platen from a drum.
So-called raised grain is due to excessive pressure during machining, compressed softer cells, and then spring-back.
Miss match in the frame construction would max out the sequence in various spots. The belt life would be around 2 times longer than the 2-head. The scratch pattern would be okay but nothing extraordinary. I have worked on hundreds of these machines so I know them like the back of my well scared hands. Not to mention the difficulty in calibration and maintaining accuracy.
We did this for weeks with machines from various companies and configurations. One day he called and I rejected another machine again for the last time. He got angry with me and said, “You won’t let me buy any machine but the one you told me to in the first place!” “I just want you to be happy” I told him.
He called the guy I knew at the machine company and told him to call me to find out what he needed. The machine company guy calls me laughing because the customer was extremely annoyed…. I told him to run steel, 60 shore, 36 shore, bladder platen, 80/120/180 paper belts, and exactly how much to take off each head. The 120 had to remove .008” to get rid of the 80 grit scratch and the drum on the combi-head needed to remove .004”. The platen was to remove .001”. The machine had to be ordered so it took a few months to come in.
After the machine ran a month the customer calls me on the phone.
Him- “When do I change the belts?”
Me- “Are you on the same set?”
Me- “Do you see any problems with the scratch? Polishing? Lines?”
Him- “No. It’s perfect.”
Me- “Keep running.”
He calls me a month later.
Him- “I just changed the belts.”
Him- “Because, you can’t run 3 belts for two months. It’s impossible.”
Me- “You just did.”
Him- “I know. It still looked great but it’s impossible!”
His first set of belts ran for approximately 40 working days. That is right around 40,000 pieces through the machine. Yes. You read that right. No. I’m not kidding.
I told him to change the belts every month to maintain consistency and not have to worry about polishing. No need to push things to that extreme to make back his money.
He might have been paying around $40 for the cloth 36”x 60” belts. He was paying around $50 for the larger paper wide belts. $40 x 40 belts a month is $1600. $50 x 3 is $150 for the 53”x 103” belts in the new machine. Thirteen times less belts and 9% of the abrasive cost.
Do you think that paid for the machine payment?
The rebuilt used machine might have taken the belt usage down to $800 a month or better, but the configuration was the limiting factor. It could not produce the quality of scratch over time that the new machine could. This “X” factor cannot be easily calculated but represents far more savings than mere sandpaper.
The reason one configuration was better than another is the subject of some of my other articles. I could write books on this subject. I tell this story a lot in my travels because it’s a great illustration of how much money you can leave on the table if you make poor choices. I feel so helpless seeing so many customers snatching defeat out of the jaws of victory!
I recently told a customer that if their main line machine had a 4th head the difference in configuration would have saved so much money in abrasives it would pay for the machine they had every couple of years for the life of the machine. When I finally put numbers to my words it worked out to around $5,500 a month savings with a proper grit sequence for that customer.
Please educate yourself before you sign on the dotted line. I can’t bear to see another customer suffering a crappy machine and losing money in the process. Base your decisions on real costs and savings rather than the lowest prices and what is sitting on the show room floor. Give your operator a proper tool for the job they must do each day. I will happily come and help them understand it better and protect your investment for years to come.
Please don’t consider this article as a recommendation to buy a specific brand or configuration of machine. Try to view it as a warning against just buying something to fix an issue without fully understanding the avenue to success. There are always specific reasons I recommend what I do. Not every customer needs the same cookie cutter machine.
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