Home made Drum Sander

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Originally Posted by Mountaincraft

I'm actually considering 3 possible methods, and one of them involved making two shafts with two cams on each with a screw to adjust the rotation of the shafts to lift the table up or down.. Rollers would be mounted to the underside of the table for the cams to push against...

The idea for leveling on that system would be to mount each end of the four shafts through threaded heim rod ends which could be adjusted up/down using nuts on their threads through a mounting plate..





The other method is to use four ACME screws and a bicycle chain underneath.. A smaller dive sprocket would be used for gear reduction, and on the opposite side a spring tensioned idler gear... and yes, set screw mounting of the gears on the screws for leveling of the system..

The reason I'm starting to lean this way is because with the cam method I'd have to install four 1/2" guide bars to lock x/y lateral movement of the table anyways.. and that means drilling the holes and installing shafts right where the screws would go anyways..

The other method I was considering was using a scissor lift type of mechanism, but I'm having a hard time figuring out how I would do 'leveling' of the table with that system...

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Since I do not have access (anymore) to a machine shop for precision built parts, I have become a fan of designing everything to be adjustable! The scissor lift mechanism you mentioned could work. The "Leveling" adjustment I would use for each of the four corners would simply be an eccentric mounting method of the actual table-to-scissor lift mechanism. This could be accomplished with a common drill press. Simply stack 4 round pieces of plate steel, and clamp them together. Drill a center hole through them, then an offset hole (to serve as the actual eccentric). Disc brakes work so well on an automobile because of the clamping action against the brake rotors that they use. So, the locking method to employ here, would be to design the discs to be locked with either a second piece of plate, or a large flat washer using a bolt which would be threaded into the actual frame of the table. A lever could be attached to the outer perimeter edge of the discs (either tapped into the edge, or welded onto it) to allow for ease of adjustments in leveling each of the four corners. Or (since this SHOULD be a one-time only operation) a simple series of holes could be drilled into the perimeter of the discs, into which a small allen wrench, or punch could be inserted and used as the handle to adjust the position of the "eccentric" for leveling. I really miss having access to the machine shop where I used to work. But since the plant closed, I have learned MANY ways of achieving precision designs by simply designing the machines I build with similar adjustment mechanisms. There IS more than ONE way to skin a cat!

Images linked in this thread might not be visible for a day or two.. Switching over from a windows based server to a Linux based one so that I can set up a web based store.. YAY!

So pictures and what not will be back soon..
Thanks,
Mark

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Originally Posted by Mountaincraft

Images linked in this thread might not be visible for a day or two.. Switching over from a windows based server to a Linux based one so that I can set up a web based store.. YAY!

So pictures and what not will be back soon..
Thanks,
Mark

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Cool a store, Linux is a better platform than platform for a server than windows...

Lou:wee:

All right, this thread fixed too...

Okay, a little more progress this week.. Had a couple days where the weather was forgiving enough to play welder.. (we've been getting hammered with the rain and snow)...

I have decided that I need to add a 4" length of tube on each upright to mount the pillow blocks, but decided that after I got the thing in the house.. unfortunately, my HFT 14" cutoff saw brushes are on their last legs and I called them and they don't stock.. So tomorrow I need to order some more.. and I can't finish the base frame until they arrive...

Anyways, I decided, that while not the cheapest route, the easiest and least space consuming route is to go with four 1/2" acme screws.... I just hope that the feed belt assy is not too heavy for them... as I'm probably looking at a 1:1 ratio for the adjustment wheel and the drive screw sprockets..

The thing will have a max capacity of about 9-10 inches... will rarely need that.. and so 100 turns to get to that won't be an issue.. most stuff will be 2" or less....

I ordered the acme nuts and screws.. I'll be using 1/2" pillow blocks on the bottom end of the screws (with the sprockets underneath them), the acme nuts welded to the bottom of the feedbelt assy plate, and on the top I'm going to use the CNC to machine some HPDE bearing blocks..

The adjustment wheel will have a u-joint and sprocket at the end of it's drive shaft. and the position of that sprocket will be adjustable to act as a chain tensioner...

Have been MIA for a couple weeks as I've been building an on-line store and that's an undertaking if you've never done it before.....

Anyways, a couple more pictures...

http://www.mountaincraftworks.com/pi...msander002.jpg


http://www.mountaincraftworks.com/pi...msander003.jpg

Mark looks good..

Lou

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Originally Posted by LouF

Mark looks good..

Lou

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For his age anyways! :D

Ordered the brushes for the cut off saw this morning, as well as the bearing blocks to support the bottom end of the acme screws...

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Originally Posted by Mountaincraft

For his age anyways! :D

Ordered the brushes for the cut off saw this morning, as well as the bearing blocks to support the bottom end of the acme screws...

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Mark,
It took me awhile to find the file, but this is one I designed some time back. Take a look at the attached TableHeight.PDF you may find it of interest, as it sounds like you are building something very similar.

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Originally Posted by Mountaincraft

For his age anyways! :D

Ordered the brushes for the cut off saw this morning, as well as the bearing blocks to support the bottom end of the acme screws...

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That he Do...(wedge)


Lou

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Originally Posted by adprinter

Mark,
It took me awhile to find the file, but this is one I designed some time back. Take a look at the attached TableHeight.PDF you may find it of interest, as it sounds like you are building something very similar.

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Hey thanks for that.. I like your tensioner, and will keep that in mind if I have problems... I might need to do something like that anyways to allow for slightly larger gears on the lift screws...

Here is what I am shooting for right now.. The adjustment gear shaft will have a u-joint just above the tensioner gear that will allow the adjustment wheel to be angled slightly outside of the structure...

You used a stepper? How did you control it?

http://www.mountaincraftworks.com/pi...m-overview.jpg

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Originally Posted by Mountaincraft

You used a stepper? How did you control it?

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I used the original controller board from my first build CNC Router table(Mechatronics- cheap ebay purchase). But after upgrading to a Gecko G540, I disconnected everything I had set up on this table. It was really just an experimental build, to see if I could automate table height adjustments. The system actually did work, but after more upgrades (and more weight added) I redesigned my table to be adjusted basically only once, to true everything up to "Level". And since I had to redesign, and rebuild the whole machine to accommodate a 4th axis, the driver was better implemented for the 4th.

The only issue I see with your design, will be "tuning" the individual corners of your table. The same benefits received with a toothed belt, or roller chain controlling all four screws simultaneously is also an enemy for individual corner adjustments. You will have to basically build the whole thing, and tension the chain, BEFORE you attach the gears to the screw shafts.

Instead of welding the nuts to the plate, you might want to consider welding them instead to individual pieces of plate. Then tap a couple of holes on either side of the plates (into your bottom plate), and use bolts with flat washers to clamp these individual plates down to your bottom plate. This will allow for individual corner height adjustments to be possible, once your chain begins to wear and stretch (which will happen).

When the chain gets slack between any two screws, the simultaneous adjustment is lost! (And the affected corners will become unlevel). This was the reason I designed the tensioner mechanism to be such, that it simultaneously tightened the belt. But even this, was a problem. (Since I had tapped the bottom plate, instead of using the four individual plates/clamped down method described above). With the gears pinned to the screw shafts, the only option was to drill out the threads in the bottom plate, and install the four individual plates (and tap the threads for the lead screws into these plates).

Just something to consider.....

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Originally Posted by Mountaincraft

Here is what I am shooting for right now.. The adjustment gear shaft will have a u-joint just above the tensioner gear that will allow the adjustment wheel to be angled slightly outside of the structure...

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Mark, After looking at your photos.....
Just another thought about table height adjustment mechanism, although it would require 4 clamp mechanisms to lock it in place. (Think disc brakes against the sides of the racks). A single crank handle (or motor) could be used the adjust it. Sorry for the "quick and dirty" drawing, but I think you get the gist of it- using four sections of gear rack, with guide bearings on the opposite sides. Could even be installed INSIDE of the vertical tubes of your frame.

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Originally Posted by adprinter

The only issue I see with your design, will be "tuning" the individual corners of your table. The same benefits received with a toothed belt, or roller chain controlling all four screws simultaneously is also an enemy for individual corner adjustments. You will have to basically build the whole thing, and tension the chain, BEFORE you attach the gears to the screw shafts.

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My thinking is that the set screws on the gears will allow me to turn individual screws in relation to the gears and adjust height that way...

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Originally Posted by adprinter

Instead of welding the nuts to the plate, you might want to consider welding them instead to individual pieces of plate. Then tap a couple of holes on either side of the plates (into your bottom plate), and use bolts with flat washers to clamp these individual plates down to your bottom plate. This will allow for individual corner height adjustments to be possible, once your chain begins to wear and stretch (which will happen).

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The pillow blocks on the bottom come with slotted mounting holes so adjustment is possible there, and the HPDE bushing/holders at the top I plan to make with slots as well... So I should be able to make adjustments there as well.. Instead of adjusting the 'nuts' I will be able to adjust the screws... That being said, I plan to only use two spot welds per nut, so that if for any reason I decide I need to break them free, it will be quick work with a peanut grinder...

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Originally Posted by adprinter

When the chain gets slack between any two screws, the simultaneous adjustment is lost! (And the affected corners will become unlevel). This was the reason I designed the tensioner mechanism to be such, that it simultaneously tightened the belt. But even this, was a problem. (Since I had tapped the bottom plate, instead of using the four individual plates/clamped down method described above). With the gears pinned to the screw shafts, the only option was to drill out the threads in the bottom plate, and install the four individual plates (and tap the threads for the lead screws into these plates).

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I'm also planning to mount the sanding head assembly to the frame using two 1/2" adjustment screws on each side.. So not only will I be able to adjust feed belt level, I will be able to adjust the drum in relation to that feed belt...

The possible issues I see in my system that are still unknowns, are will there be a problem using set screws to secure the gears to ACME screw threads? If so, I may have to use shaft extenders (which 'might' cost me a couple inches of table height).. and also, will this system lift the heavy feedbelt assembly easily enough (ie gear ratios, stress on the gear to screw connection, etc..)

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Originally Posted by adprinter

Mark, After looking at your photos.....
Just another thought about table height adjustment mechanism, although it would require 4 clamp mechanisms to lock it in place. (Think disc brakes against the sides of the racks). A single crank handle (or motor) could be used the adjust it. Sorry for the "quick and dirty" drawing, but I think you get the gist of it- using four sections of gear rack, with guide bearings on the opposite sides. Could even be installed INSIDE of the vertical tubes of your frame.

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Couple problems I see with that, the crank handle would hit the feed belt assembly, and I've already ordered the acme screws, nuts, bearing blocks, and one of the gears... This thing is already getting expensive enough that I'm starting to second guess whether I should have just saved up and bought Grizzly's 24" drum sander for $1K... Such is the plight of the DIY (wannabe engineer)... LOL

Although, mine will have some nice features that I haven't seen on 'any' sander of this type... like the ability to surface sand from the top, an edge sanding fence with adjustable miter using T-Tracks, quick change sanding drums, extended feed tables, etc..

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Originally Posted by adprinter

Instead of welding the nuts to the plate, you might want to consider welding them instead to individual pieces of plate. Then tap a couple of holes on either side of the plates (into your bottom plate), and use bolts with flat washers to clamp these individual plates down to your bottom plate. This will allow for individual corner height adjustments to be possible, once your chain begins to wear and stretch (which will happen).

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Thinking about this some more, I can see how the nuts might need to move along with the bearing blocks top and bottom.. I have to think about this some more... I'm thinking that perhaps welding a couple of parallel small bars on the underside of the feedbelt plate to prevent the nut from turning might be the hot ticket.. The feedbelt assy is heavy enough to keep the nut up against the steel plate... If I oversized the hole (which I planned to do anyways) then the ACME nut could just 'float' inbetween the two bars and adjust itself along with any bearing block adjustments.. This would reduce any potential for binding due to misalignment...

It would also allow for 'very easy' adjustment of individual screws, by simply lifting the feedbelt assembly up and turning the nut 60 degrees... that's .016" per 60 degree turn... Combined with the adjustability of the drum itself, I would think that would be good enough... But if not, I could always loosen the setscrew on the gear at the bottom and rotate the ACME screw slightly.... worst case, add shim washers between the nut and the feed belt plate...

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Originally Posted by Mountaincraft

Thinking about this some more, I can see how the nuts might need to move along with the bearing blocks top and bottom.. I have to think about this some more... I'm thinking that perhaps welding a couple of parallel small bars on the underside of the feedbelt plate to prevent the nut from turning might be the hot ticket.. The feedbelt assy is heavy enough to keep the nut up against the steel plate... If I oversized the hole (which I planned to do anyways) then the ACME nut could just 'float' inbetween the two bars and adjust itself along with any bearing block adjustments.. This would reduce any potential for binding due to misalignment...

It would also allow for 'very easy' adjustment of individual screws, by simply lifting the feedbelt assembly up and turning the nut 60 degrees... that's .016" per 60 degree turn... Combined with the adjustability of the drum itself, I would think that would be good enough... But if not, I could always loosen the setscrew on the gear at the bottom and rotate the ACME screw slightly.... worst case, add shim washers between the nut and the feed belt plate...

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Mark, you will find that the gears will need to be permanently PINNED to the screw shafts, by drilling a hole through the gear collar and the screw shaft. As a load bearing lifting mechanism, set screws (even Larger allen BOLTS) will slip. Unless you tap the internal bore of the gears (to match the threads of the lead screws), and even doing this will require a Flat to be ground onto the thread of the lead screw to provide a surface for the set screw to clamp against.

It is the Nut, and the top end of the lead screws which will provide the mechanical lifting force. And for repeated use (height adjustments of the table), I would recommend thrust bearings be used on the top end of the lead screws. A bushing will work for this, but you will be surprised at how quickly it wallows out with use. Even a cheap thrust washer will help to prevent this wear from happening. (Makes things turn a lot smoother when adjusting the table height too!).

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Originally Posted by adprinter

Mark, you will find that the gears will need to be permanently PINNED to the screw shafts, by drilling a hole through the gear collar and the screw shaft. As a load bearing lifting mechanism, set screws (even Larger allen BOLTS) will slip. Unless you tap the internal bore of the gears (to match the threads of the lead screws), and even doing this will require a Flat to be ground onto the thread of the lead screw to provide a surface for the set screw to clamp against.

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Well then, if that's the case then my 'only' alternative is to use a short piece of 1/2" round bar stock to mount the gears to, and extend it through the pillow block on the bottom, and use a solid rod coupling to connect it to the 1/2" ACME screw... I 'have' to be able to adjust the rotational position of the screw itself in relation to the gear...

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Originally Posted by adprinter

It is the Nut, and the top end of the lead screws which will provide the mechanical lifting force. And for repeated use (height adjustments of the table), I would recommend thrust bearings be used on the top end of the lead screws. A bushing will work for this, but you will be surprised at how quickly it wallows out with use. Even a cheap thrust washer will help to prevent this wear from happening. (Makes things turn a lot smoother when adjusting the table height too!).

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This makes no sense to me... There will be no nuts or anything at the top of the rods.. just an HDPE block with a 1/2" hole in it....

I 'could' buy split collars to put above and below the block, but why? There is no load bearing force there... It's 'only purpose is to hold the Screw vertical.. If it weren't for the need to hold the table still against the lateral force of the sanding drum, I would not need anything at all at the top.. no block, no nothing..

Either you're not understanding me, or I'm not understanding you... LOL

Here is what I have in my mind... I would probably put a thrust washer in between the pillow block bearing and the solid rod coupling...

http://www.mountaincraftworks.com/pi...crew-stack.jpg

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Originally Posted by Mountaincraft

Either you're not understanding me, or I'm not understanding you... LOL

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Mark,
Please see the attached PDF. I guess that I am not understanding you, because the lifting force will be supplied by the lead screws rotating inside of the Nut. With the Nut held stationary, (at the bottom end) the lift will be exerted against the top end of the lead screws. This was the reason I had to drill out the threaded holes in my stationary plate, and mount the four independent plates (with nuts welded onto them). For leveling the four corners of the table.
The mechanical lifting force happens between the top ends of the lead screws, and the nuts. Hope the PDF helps to clear things up. It is important to note, that the Table moves, while the Stationary plate remains stationary. It is basically a table WITHIN a table. (Male legs on the moving table, Female legs on the Stationary table).

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Originally Posted by Mountaincraft

Here is what I have in my mind... I would probably put a thrust washer in between the pillow block bearing and the solid rod coupling...

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Mark,
I posted before seeing this drawing (after modifying my original drawing). I can see now, what you are talking about. I apologize for not being able to visualize what you were designing. I did not realize that you would be going ABOVE the table's surface. In my design, everything happens BELOW the table's surface. Six of one, half-dozen of the other- I suppose.