DIY Belt Sander

[WayneC]

I'm on a quest to build a wide belt sander for my woodshop. I make wood parts with a CNC router, and the sanding afterwards is a huge bottleneck. I want to make a wide belt sander that has an oscilating belt assembly and a belt tracking mechanism.

So I'm looking for examples, drawings, pics, etc of the appropriate mechanism to create the oscilation of the belt assembly. It can be mechanical, pnuematic, electical, steppered, whatever.

Also, I need to be able to keep the belt correctly tracking during operation, so I want to build in a tracking mechanism that senses when the belt gets out of alignment, and possibly corrects.

I use Geckos and steppers on my CNC. Can I use this same technology somehow to build the tracking mechasim, or is there a simpler way? I can use a computer and a Gcode script to monitor and control, or some other controller.

I've seen DIY projects for drum sanders. I'm just trying to move some of the same motion control technology from my CNC to work in other shop machines.

Any advice is welcome, except possibly 'just go buy one'. Wide belt sanders start at $3K and go up. If I can build one for half of that, I'd be thrilled. I'm also very intersted in learning how to use what I've learned about CNC control in other applications.

Thanks in advance for your help.

[ger21]

I'll have to look tomorrow to see how the top roller is mounted, the one that moves. One side uses an air cylinder which moves a cam, which has a pin in it to rock the roller back and forth. An optical sensor actuates the cylinder when the belt passes in front of it. So basically it's adjusted so the belt moves toward the sensor, and when the sensor activates the cylinder, it causes the belt to move in the other direction. Nothing complicated, just a sensor which switches a cylinder on and off. It's probably a double acting cylinder.

You'll need a pretty large motor I think. The one on ours is probably around 10 HP.

[vger]

Sounds like an interesting project. I was planning a drum sander and pulled a roller off a large heavy duty treadmill (about 24" wide) to use as the drum. To my shagrin, the roller was ever so slightly crowned and would not work for my application. I figure the slight crown helped keep the belt centered. A thought occured to me on your belt tracking.... Suppose you used just a simple DC motor (geared down) to drive the adjusting screw on one side. With sensors or switches detecting the track of the belt you could just cause the motor to run the correct direction as long as the sensor was actuated. As soon as the belt was off the sensor, the motor would stop correcting. As to the oscillating function, I would be tempted to use a crankshaft actuator to accomplish the oscillation. One of my customers uses a cranshaft oscillator to move a 1200 lb assembly back and forth about 6 inches at a 1 Hz rate. The assembly is in a very very harsh environment (splatered molten silica sand) and works pretty well.

Steve

[WayneC]

Thanks so much! Any way to get some pics? I'd love to see the air cylinder and cam/actuator. Also, if you can get any pics of how the belt tension adjusts- I assume its air cylinder on the top roller.

Also, how does the feed belt look? Is it a DC motor with a pot? Anything special there?

I have seen some pics of WB sanders on websites, but I'd like to see more detail. Also I'd love to see one oscillate, so I can see what range of motion is used in pro machines.

Finally, will I need a control circuit for the belt tracking? Or just a simple cylinder valve open/close switch for the belt tracking adjustment? I'm not sure how to get this to work.

Thanks so much for your help. If you can get pictures, fantastic. If not, I'll find someone who's willling to let me poke around and watch one.

Agree on motor size. I'm thinking to design one for a 5hp motor, and then try to upgrade later. 5hp is about all I'll be able to afford to start. Also, the mechancials of the machine become an issue with more HP. Since I can't really cast a frame for the rollers or base, my machine will have some limits related to materials. I may use some beefy plate steel for the rollers, but it may not be as strong as some of the cast pieces I've seen.

I guess I really need to find a machine to look at closely.

Thanks again!

W

[ger21]

Ours is like this, but about 20 years old. Although it doesn't look much different.

I think the top roller is mounted to a cradle that rides on a single large air cylinder in the center, which allows it to pivot on the shaft of the cylinder. The oscillation amount varies, depending on the belt. There's an adjustment for the oscillation, to make sure the belt travels towards the eye (sensor). The adjustment controls the speed of the oscillation. There's really no circuit involved. Adjust the belt so it moves towards the eye. When it breaks the eye, the eye triggers the cylinder which reverses the travel direction. When it clears the eye, the cylinder reverses and the belt starts going the other way again. I'll have to take another look to make sure that's right, as it seems like there's more travel than my description would allow.

The feedbelt is a large 3 phase motor with a 90° gearbox. Belt speed has a manual control, which I believe changes the width of a V belt pulley. The feedbelt is mounted to 4 acme screws which are motorized to raise or lower the table. There's also a hand wheel to raise and lower for finer adjustment.

[WayneC]

Thanks so much Gerry. I think I have a decent idea now. I was expecting the oscillation to be a separate thing from the belt tracking, but what you describe can have the same sensors for the belt tracking doing the end-of-travel sensing for the oscillation. That sure sounds simpler than the cluster-buck I had in mind. Pays to ask.

I need to take a closer look at that air cylinder setup, but I get the jist of it I think. I was thinking to use four acme screws and a bike chain and gears to adjust height, and devise some way to lock in place.

I also need to take a look at the feed belt and figure out what sort of material I'll need for that.

This is a winter project, right behind a couple much simpler upgrades on my CNC.

Fun stuff. Thanks so much for your help!

Wayne

[ger21]

Forgot the link.
http://www.ramcosanders.com/m_catalog15_07.asp

[ger21]

For the feed belt, see www.mcmaster.com pages 1230, 1232 and 1233. Ours looks like it uses the hammer in alligator lacing.

[Regnar]

I dont have exactly what your looking for but you might want to check out www.stockroomsupply.com They have a nice drum sander that handles up to 30 inches wide. You could mount a feed wheel to it so all you have to do is push it in and walk away. Just giving another option. Check out the videos. They only show the 18" model but I remember seeing the 30" in action and was impressed. They used it in a cabinet shop and the owner was happy with cost and production.

[bgolash]

Hi

You might take a look at the machine I built. It is a combination wide belt sander and 20 inch planer. It was a fun project but very time consuming. Here`s a link that describes the build process.
http://www.woodsolutions.com/planer-sander.htm

Barry

[WayneC]

Barry, that's a fantastic machine! Sorry for taking so long to respond, but I sorta dropped the project for awhile. I still need a sander, and I still think a wide belt sander is a better option for me than a drum sander. I'm thinking to buy an entry level machine rather than take time to build one.

Your machine is inspiring, though. Part of what I want to do is learn some PLC control and automation technology. I got a start in this working with my CNC, but I'd like to use that same technology to build other shop machines.

I'm inspired by your project. I'm thinking...

Wayne

[CalG]

If you are in a hurry to have something to ease your sanding woes while you work on your machine project.

Think about a stroke sander.

The capacity can be quite large, and using narrow but long belts, the cost of abrasives may be less than a similar capacity wide belt sander.

Sadly, stroke sanders are not "automagic" , just fast.

CalG