Tube Polisher....

[JimDawson]

.... or why spend $8K on a machine when you can build one for $25K. In the true Hobby Machinist tradition, why buy one when you can build it, and spend more doing it?

As part of our Stable Camper product, we have to cut and polish 1.5'' aluminum tubes ranging in length from about 30'' to 80''. After we work our machining and assembly magic on them, they need to be polished before they go to powder coat. We normally make runs of about 500 tubes at a time, and hand polishing them in the lathe with Scotch Brite pads is a PITA and normally takes about 2.5 to 3 days for a run. Way too much time, effort, and a mess of fine aluminum powder all over everything. We looked at farming this out, but couldn't get lead times that were within reason.

So the obvious solution is to acquire a tube polisher, many designs are available but the most reasonable solution for our needs seems to be the rotating sanding belt type.

But this is about a $8K machine, if the prices have not gone up since we last checked a year or so ago.

We can build this for about $3K in materials, and a lot of design time and chip making labor. So as of right now I have about 2 weeks of design and drafting time in @ $120/hr, or about $9600 so far and I'm not close to finished yet. I've also purchased about $800 in parts so far. The good news is that when I'm working for myself, I can pay me in cheese burgers. I figure about 2 weeks of chip making and fabrication once I get the designs completed. Since I finally learned (and am still learning) 3D modeling I find it saves me a lot of shop time and I make fewer design mistakes. I can catch the mistakes on ''paper'' before I turn perfectly good material into scrap. It's really easy to make changes with a few mouse clicks.

The main wheel will turn at about 300 RPM and with the 18:1 drive on the pinions, the belts will run at about 5000 FPM, right in the optimum range for aluminum polishing. I ordered a 2HP single phase motor to run it, but I may have to go with a 3 phase motor and a VFD to get variable speed. We'll just have to try it and see how it works out at a single speed. The commercial machines seem to have a variable speed on both the wheel and belts using some sort of coaxial drive system and 2 motors, I hope my single motor design does not come back to bite me.

The one thing that the commercially available polishers seem to be missing is a dust collection system. Mine will have a downflow suction system connected to a Harbor Freight 2HP dust collector. https://www.harborfreight.com/2-hp-industrial-5-micron-dust-collector-97869.html The sheetmetal guards will be designed to direct the air flow where it's needed to remove the dust, and hopefully keep most of it out of the works.

That aluminum dust is nasty as well as being explosive. Also, this machine will be forklift portable and will only be used outside, never in my shop.

On with the show.... The unfinished assembly drawings. Uses standard 2 x 42 sanding belts. I'm trying to use as many off-the-shelf parts as I can, saves a lot of time. The main wheel will be 20'' diameter x 1'' thick aluminum. The Poly-V belt grooves will be machined into the OD, using the ''J'' profile.

Front side



The back side



And a detail cutaway.


The belt wheel kit is from Amazon https://www.amazon.com/VEVOR-Comple...elt+sander+wheels+2x48&qid=1651692894&sr=8-12




The flywheel is small block chevy, it serves as the main support for the works as well as providing the drive for the sanding belts. The pinion gears are standard chevy starter gears.

Amazon.com: JEGS Flywheel | For 1971-1980 Small Block Chevy 400 | External Balance | 168 Tooth | Fits 2-Piece Rear Main Seal | Non-SFI | 14.125” Diameter : Automotive

Buy JEGS Flywheel | For 1971-1980 Small Block Chevy 400 | External Balance | 168 Tooth | Fits 2-Piece Rear Main Seal | Non-SFI | 14.125” Diameter: Transmissions & Parts - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

The feed rollers are 3'' boat trailer bow bumpers, and will be somewhat modified to fit. https://www.amazon.com/dp/B0913BCWTS?psc=1&ref=ppx_yo2ov_dt_b_product_details

I have one of these and they seem pretty substantial.


More later.......

 

[C-Bag]

Very interesting design. I was figuring it would be the type I see where a single belt wraps way around the tube that they use for polishing SS hand rails, but with two belts facing on opposite sides you can’t really do that. Is this your take on the $8k design?

 

[Papa Charlie]

Nice design, a couple of thoughts:

1) I would reduce the flywheels RPM by half if it were me. That is a lot of speed and if not perfectly balance will be quite the walker.
2) As you are using a resistance between the two belts, have you thought about having them open to feed the pipe in otherwise you may be destroying belts if fed in while turning. Not so much an issue if you do it off.
3) Lastly, is there any chance that you may add other size tubes at some point down the road? If so you may want to consider making the gap adjustable. Even if it is for pressure adjustment on the tube.
4) You may want to consider the the woven sanding belts, depending on the condition of the pipe they give a much nicer finish.

Hope you don't mind me throwing my $0.02 worth.

 

[mmcmdl]

Tube polisher ? My mind was in the gutter as always ! We used to clean up our conveyor rollers on the big lathes . We made up a belt sander which mounted on the tool post and engaged the feed . Saved countless hours . Always found your projects enjoyable Jim . Keep us posted on the progress .

 

[Aukai]

The SBC external balanced flywheel, has an added weight that might cause vibration. If it is removable okay. The SBC internal balanced flywheel might be better. You can also find aluminum FWs too for less mass. Not sure if this is static mount....

 

[JimDawson]

Very interesting design. I was figuring it would be the type I see where a single belt wraps way around the tube that they use for polishing SS hand rails, but with two belts facing on opposite sides you can’t really do that. Is this your take on the $8k design?

I looked at about every style of tube polishing system I could find. This is the only style that does not either require some hand work or require the tube to rotate. Rotating the tube requires another layer of complexity and I was trying to avoid that.

Nice design, a couple of thoughts:

1) I would reduce the flywheels RPM by half if it were me. That is a lot of speed and if not perfectly balance will be quite the walker.
2) As you are using a resistance between the two belts, have you thought about having them open to feed the pipe in otherwise you may be destroying belts if fed in while turning. Not so much an issue if you do it off.
3) Lastly, is there any chance that you may add other size tubes at some point down the road? If so you may want to consider making the gap adjustable. Even if it is for pressure adjustment on the tube.
4) You may want to consider the the woven sanding belts, depending on the condition of the pipe they give a much nicer finish.

Hope you don't mind me throwing my $0.02 worth.

Suggestions are always welcome.

1) I may need to do that, we'll see how it works out. The main problem is the belt speed is determined by the gear ratio so any adjustment in the wheel RPM is going to affect the belt speed.

2) That would be a problem on squared off tube, but the good news is that we have a cone end already installed in the tube at this point in the operation so it should have a smooth entry. The commercial machines have a slow down feature for tube entry. Just slowing it down takes the centrifugal pressure off of the tensioning rollers and allows a bit more belt give.

Picture this without the ball end installed. About 3/4'' dia on the small end so the belts won't touch on entry.


3) It is adjustable from about 3/8'' to 3'' dia.

4) Absolutely. Woven belts have already been spec'd and we will be trying them.

Tube polisher ? My mind was in the gutter as always ! We used to clean up our conveyor rollers on the big lathes . We made up a belt sander which mounted on the tool post and engaged the feed . Saved countless hours . Always found your projects enjoyable Jim . Keep us posted on the progress .

Get your mind out of the gutter. Thank you for the kind words.

The SBC external balanced flywheel, has an added weight that might cause vibration. If it is removable okay. The SBC internal balanced flywheel might be better. You can also find aluminum FWs too for less mass. Not sure if this is static mount....

That would be a problem if the flywheel turned in this operation. But it is bolted solid to the frame. It is actually the support for the rest of the hardware. The aluminum disk is the part that turns.

 

[mickri]

Did you look into using a rifle barrel spinner? https://ads.midwayusa.com/product/1...3792&msclkid=c2149c26dffc10367b0bfeb03d20d839

 

[JimDawson]

Did you look into using a rifle barrel spinner? https://ads.midwayusa.com/product/1006978176?pid=543792&cm_mmc=pf_ci_bing-_-Gunsmithing+-+Tools,+Jigs+&+Fixtures-_-PTG-_-543792&msclkid=c2149c26dffc10367b0bfeb03d20d839

We are doing around 500 units in a run, with lengths between 30'' and 80'' long. That barrel spinner would require a lot of hand held work. We actually considered a long bed lathe(ish) machine and a handheld or carriage mounted belt sander, but rejected that idea as too much hand work and too slow. The goal is to speed up the process while reducing the amount of handling we have to do.

If this machine works OK, we'll most likely add a magazine type auto feeder, and maybe come up with an auto stacker system or maybe an industrial robot to stack from the outfeed. We have been considering an industrial robot to load and unload some of the labor intensive parts in both the mill and the lathe. Just to give you an idea of the volume we are producing, we buy about 10,000 lbs / month of stainless steel and aluminum.

The ultimate goal is to shove raw material in one end of the shop, and have finished product come out the other, all while we sit on the beach and sip drinks with little umbrellas in them.

 

[extropic]

Another great project Jim.

Here's my $.02.

At this point, my only concern is how narrowly set the bearings are for the belt drive shafts.
Those shafts are going to be doing a lot of work. Instead of a simple "straw hat" looking bearing housing/retainer on the pinion side. I'm thinking of an extended tubular housing (think stove pipe hat), slotted to clear the bull gear, which carries another outboard (other side of the bull gear) bearing to support a longer pinion shaft.

3D modeling is the only way to go (if one can). It's the thing I miss most from my career.

Anxiously waiting progress reports.

 

[JimDawson]

Another great project Jim.

Here's my $.02.

At this point, my only concern is how narrowly set the bearings are for the belt drive shafts.
Those shafts are going to be doing a lot of work. Instead of a simple "straw hat" looking bearing housing/retainer on the pinion side. I'm thinking of an extended tubular housing (think stove pipe hat), slotted to clear the bull gear, which carries another outboard (other side of the bull gear) bearing to support a longer pinion shaft.

3D modeling is the only way to go (if one can). It's the thing I miss most from my career.

Anxiously waiting progress reports.

Not a bad idea

Something like this? Not quite finished but you get the idea.