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Vibratory bowl finishing - ebonite and acrylics/resins

NewtonPens

Plastic
Joined
Jan 6, 2016
I have a bowl tumbler and am trying to figure out the best media/polishing compound combo to get a nice high gloss finish on my parts.
I hand sand everything first b/c machining marks, but that plus the hours buffing is really taking a toll on my shoulder and arm.

Any suggestions?
IS it even possible or a pipe dream? I ran a batch of barrels the other day for about 24 hours with some water and polishing compound in the green pyramids, and they came out perfectly matte, which looks awesome.
All the little sanding marks I left behind are gone and this saved me a ton of time buffing, but I still had to buff.

Thanks
Shawn

So here's the batch after 24 hours in the bowl.
PXL_20220811_191039621.jpg

Here are a couple of those buffed up and washed. Very happy with the finish. Pic doesn't really show it well enough.
PXL_20220812_153655582.jpg

My 2nd hand burr king.

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The stuff inside. Too much water? No idea...

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The stuff I mixed with the water. Too coarse of a compound?

PXL_20220812_153630102.jpg
 

sfriedberg

Diamond
Joined
Oct 14, 2010
Location
Oregon, USA
Vibratory finishing is a bit of an art and a lot of trial and error to get the best results. If you were finishing metal parts, I would say "no standing water at all, just damp media" and "no need for an additional polishing compound, the grit is in the media". But I have no experience vib finishing resin parts.
Let me suggest, though, that you plan on two passes. One with your current media, no additional compound and a lot less water to take the machine marks off. This should get you (less expensively) to where you are now. Then a second pass with either smooth porcelean/ceramic media (tiny balls) or a very low abrasive organic medium (ground walnut shells or corn cobs) plus your polishing compound. Start with small quantities of compound, experiment and take notes to see what is most cost- and time-effective.
 

latheman78

Hot Rolled
Joined
May 28, 2022
Location
Southern Ca Mtns.
Too much water. What size is that tumbler? Too much water you don't get enough action, vibe tumbling as said is trial and error. Have you tried walnut shells and polish? Tumbling often is a multi step process. I think your bowl also needs more media, how is it all moving when on? It needs to churn.
 

Tom Lg

Cast Iron
Joined
May 1, 2006
Location
Laguna Beach CA USA
The photo shows a rubber band holding the top on the bowl. My experience has shown me that you will get better "churn" in the bowl if you secure the lid with another wingnut, and it's got to be tight "just right", not just holding the lid on. Don't ask me how/why it all works, because it's magic. You need the "right" media/parts/water ratio, certainly. You want the contents to move up the side of the bowl and "go over the falls" as well as moving around the circumference of the bowl.
 

NewtonPens

Plastic
Joined
Jan 6, 2016
Thanks! I'll look at ceramic media. With walnut, I didn't know you could add to it. I thought it was dry and done.
I have some walnut, and messed with it last year when I got this thing (it's been sitting put up for most of the last year), but didn't seem to do much.
But I bought this all used, the walnut media might have been used as well. Not sure.
 

latheman78

Hot Rolled
Joined
May 28, 2022
Location
Southern Ca Mtns.
A vibe bowl tumbler should have the parts running up the bowl sides then falling down and getting under towed in the center or there isn't enough action.
 
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latheman78

Hot Rolled
Joined
May 28, 2022
Location
Southern Ca Mtns.
Thanks! I'll look at ceramic media. With walnut, I didn't know you could add to it. I thought it was dry and done.
I have some walnut, and messed with it last year when I got this thing (it's been sitting put up for most of the last year), but didn't seem to do much.
But I bought this all used, the walnut media might have been used as well. Not sure.
You can get usable walnut shells at Harbor Freight for like $30 for 25#. If you throw dirty parts in them they will pull the dirtiness off the surface, absorbing like a sponge. Then if you add polish it will be absorbed in the walnut shells and polish the parts. You did not list the size of your vibe bowl yet or I missed it. That info will help with the recipe you need to use.
 

henrya

Stainless
Joined
Jun 25, 2008
Location
TN
Regarding walnut shelIs, I would run it dry except for the little bit of polishing compound you add to the bowl. The other thing is to get the size and amount of media particles right for the particular part load.

As noted above, you want the parts and media circulating through the bowl. Not parts just laying in the bottom.
 

NewtonPens

Plastic
Joined
Jan 6, 2016
It's a 5 pound bowl. At least it's the same size as the 5 pound one at harbor freight.

regarding parts to media ratios - so as I add parts I might need to take media out?
 

henrya

Stainless
Joined
Jun 25, 2008
Location
TN
You want your parts to be suspended in and moving with the media. More parts probably needs more media but its set by the size of the bowl and the power of the motor. Too full will work less well and work lots slower, while a minimum number of parts and media won’t be good throughput.
 

NewtonPens

Plastic
Joined
Jan 6, 2016
That makes sense. I'll run things in batches then. Even if it takes longer it's worth it to not wear my shoulder out any more than it already is.

I bought a second 5 pound tumbler from harbor freight (it's gotten warm from running all afternoon).
The burr king is full(er) of the green pyramids and just a tiny bit of water and car polishing paste.
The HF bowl is full of the walnut stuff I got when I bought the burr king. Slowly been adding a finer polishing compound over the course of the afternoon so the walnut absorbs it. And boy it has. The little pieces have at least doubled in size. Seems to be doing a good job though.

I'll post pics in the morning with what happens.
 

latheman78

Hot Rolled
Joined
May 28, 2022
Location
Southern Ca Mtns.
I caught you too late. I had a Thumler UV-18 die, and found they are basically out of stock everywhere including the motor I needed to fix it. The motor is a special due to double rpms of similar sized ones. I reluctantly bought the large Harbor Freight model. I am opposed to buying made in China unless I have no other choice. Anyway that thing is huge compared to it's weight rating. It has a top and lower drain, it holds 4 gallons, even though rated at 15 pounds or so. So I figure poor design, but it seemed to run fine with 40 some odd pounds in it. Since the motor is just free spinning with a counterweight on the shaft over loading won't
hurt the motor it would just damper the vibration at worst.

Since you have light parts I would definitely buy one of those large HF models it was a bargain at $179. Nice having a lower and top drain. It is the size of a Thumler UV-45. To get best action load the bowl with no more than 1/3 parts and fill in media till it is about an inch from the top. As for motors getting hot that is what shortens their life, but most can run hotter than you think and be fine. My solution is just sitting a cheap box fan next to the tumbler, trapped non moving air can heat up quick, those fans on the motor shafts don't move much air.
 

NewtonPens

Plastic
Joined
Jan 6, 2016
1/3 PARTS? I thought it was 1/3 media. X)

as for heat - well - I got the warranty on the HF tumbler, so if it dies no real loss. I barely have room for these two little guys let alone a box fan. My shop space is really tight.

Here are pics of about 18 hours in polishing paste walnut stuff. Shiny for sure, but not where I want it. Would probably look better if I washed the polish residue off before photos...
I have a box of little gray stones that are real smooth. I guess it's ceramic? Would those do a better job with polishing paste or should I just keep it up with the walnut stuff?

-thanks so much for the help!

PXL_20220813_162139529.jpg

PXL_20220813_162156067.jpg

PXL_20220813_162206022.jpg

PXL_20220813_162218159.jpg
 

latheman78

Hot Rolled
Joined
May 28, 2022
Location
Southern Ca Mtns.
Where did you get those walnut shells, they look like grape nut cereal. I use the HF ones and they never swell. They look clean for being used with polish. First as previously said use walnut shells dry. The best polishes I have used with walnut are either like jewelers rogue or a paste in a tube. I will admit the only plastic I have tumbled is acetal of which one type is known by the trade name Delrin. If those walnut shells in the picture have been used with polish they look too clean. You are not getting enough action.
 

latheman78

Hot Rolled
Joined
May 28, 2022
Location
Southern Ca Mtns.
Another thing, I think I see machining chatter in the last photo on the flat. That means you need two stage tumbling, polishing won't rid the parts of that unless left in forever. The picture also shows a bowl not full enough. 1/3 parts , 2/3 media that is just a starting point and then you adjust as you learn.

As far as you buying the warranty you obviously aren't a 60 mile round trip on windy roads from HF like I am. Add that to the fact you have clean, uncut, unscarred hands with clean finger nails I think you are a metro sexual city slicker. Not sure I should be helping your kind. Anyway, until you get that bowl properly full your results will be meaningless.
I wish you would have started this thread a month ago. I did all kinds of tumbling experimentation trying to make a carbon steel part look liked polished carbide. Customer said they were the best he has ever seen, yet wants them better. I have nothing currently to tumble or I could sent you videos of what a vibe bowl running needs to look like to get proper results.
 

NewtonPens

Plastic
Joined
Jan 6, 2016
The grapenuts came with the burr king I bought used. The box was labelled walnut shells. I don't have any idea what they might actually be, but if I can get better results with something else I will try it.

The chatter mark you're seeing are fingerprints. And if I can cram more parts in there that's good. I'm new at this so have no idea.
City Slicker??? I guess Hot Springs, AR is city. A small city. I make fountain pens so don't do much at all with metals, so no sharp stuff to cut my fingers on. I have scars from cutting veg in the kitchen when I was being careless. That counts, right??

Thanks for the help latheman.
 

latheman78

Hot Rolled
Joined
May 28, 2022
Location
Southern Ca Mtns.
I am just screwing around calling you a city slicker. This website is strange and I am a newbie, some areas seem to be over moderated like no other I have seen, while long term members claim this place used to be everything goes. I am concerned about you claiming
lack of space, saying you can't put a box fan next to a tumbler. Does your wife or girlfriend insist on parking her vehicle in the garage? Is the closet full of all her shoes and different colored purses? I am new here but close to applying for social security, I need a lot of sit down breaks, so here I am.
 








 
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