Hi all, I’ll start off by saying thanks for the ZenXY design, sandify and bard dring’s board. I’m about complete assembly of a smaller table before trying something a bit more ambitious. I essentially bought an old end-table with the glass top already and modified it to hold the mechanism, and using some 1/4” hard board for the underside. The hardboard isn’t perfect but I think close-ish.
For the most part it is working splendidly and my wife is now obsessed with it after being ambivalent when I first tried to explain it to her.
Issues:
Occasionally the magnet will ‘drop’ the ball. I’m unsure if this is a result of too much baking soda, not sufficiently strong magnet, or inconsistencies in the baking soda and/or magnet distance, or some combination thereof, or possibly caused by #2.
The ball moves somewhat jittery where it will seem to fall behind by a few mm and then catch up to the magnet. The magnet moves nice and smooth. I’ve tried feed rates betweenb 500 and 2000 and the jittery movement remains.
As I type this and looking at the picture I see some ‘artifact’ in the upper area almost like a rectangle, though the previous few drawings have all been wipers alternating between 45 and -45 degree angles..
Is the sand/soda thicker where the ball drops or is the board farther away? Magnetic force falls off with distance, so you want the stuff as thin as possible. The ones I’ve seen in action go somewhat slow relative to a printer, but maybe a bit faster than a cnc… 1000-1500 mm/min maybe? Perhaps @jeffeb3 could comment on speeds and thicknesses. His was the only one i’ve seen in person. The one i have is not yet completed.
Yeah I think it may be a combination of the soda being a bit thicker there and the magnet being a bit further away in that region. I’m going to think out the soda there and if that doesn’t sort it I see some shimming in my future.
The rectangle artifact is more visible in the picture than in person so I may just live with it for now.
I’ll see also if thinning out the soda more across the board helps with the jitter. I’m thinking about going with a smaller ball to get more detail on the relatively small table as patterns with text are not great so far, so I assume smaller ball means I’ll need shallower sand.
I built a larger one and ran it shortly for testing. Your soda looks too thick to me from my limited knowledge. Also you want the magnet as close to the bottom as you can get it without it rubbing.
Thinner medium will also provide better detail, even with the same size ball. I have about 2-3mm of baking soda on the surface of my first (The ZenXY v2 beta build) and it provides excellent detail. I have about 6mm on my other one, and it’s still good, but noticeably less detail. The deeper medium requires less combing. The thinner one shows where frequent drawing gets inconsistent depth sooner.
for the magnet distance, strength drops off as per distance squared. I am OK with a little bit of rubbing on my tables, so long as it isn’t noisy. The ball going through the baking soda makes a little noise, and even with the TMC2209 drivers the motors aren’t perfectly silent. I can’t hear rubbing, but since I know that the top surface of the magnet isn’t chrome reflective any more (Looks kind of coppery colour) I know that the magnet rubs a little, in at least some points. I can’t hear it, so I’m OK with that. Most of the noise from my TMC2209 table comes from the ball crunching through the baking soda. I can hear the motors more on my DRV2588 driven table. Both have the chrome polished off of the top surface of the magnet.
The build on the drawing board now (As soon as I get a couple of pancake steppers, in transit now) will be using countertop laminate as a floor. This stuff is super thin, about 1mm thick but still quite stiff. I think it will work out well. My other builds used 2mm hardboard as a base, and the hardboard is less stiff, though probably stronger. I wanted to try just using posterboard, and stretching it over a frame, but I came across the laminate stuff cheap, and plan to run with it.
I’ve manually raked the medium to about 2.5mm avg depth and running a fresh job now to see how that goes. The magnet touches the bottom in most places but does pull away a bit in the area most prone to the ball getting stuck so I think I’ll have to shim that out. I’ll explore other options for the bottom or potentially stronger magnets. I do have a piece of aluminum sheet in the garage that might work though I suspect that might be a little noisy. Same with some acrylic sheet I can just imagine a stray piece of grit gets between the magnet and sheet the screech that would make.
Random tangential thought.. I wonder if anyone has made a zenxy ouijja board driven by voice commands for hands-free spookiness
The ball should be rolling in the soda, not sliding through it. Imagine it as a bike tire. Anything over half the diameter of the ball is going to be like hitting a 12" curb.
Glass is the best surface for the bottom, IMHO. It is much more rigid and flat than hardboard.
Is your baking soda smooth yet? It takes a little time for the marble to pulverize all of the little clumps. Maybe 5-10 full wipes. I’ve mostly seen the jittery when there is sand and not baking soda. Or the magnet is too far away. If it’s too close, it tends to slide and not roll.
Smooth-ish I’d say, it was quite lumpy (i’m using the expired stuff from the fridge) but I now only see smaller clumps. I’ll run some more wipes to smash them up. I do also seem to favour 1000mm/min speed, as it seems a happy medium for noise level. Maybe slightly slower. I really only tried 500 and 2000 as a means to rule speed out as the culprit. I’m actually designing up a graduated adjustable rake right now to see if I can find the perfect depth, but really need to get that bottom as flat and planar as possible before I can expect consistent results I think.
The glass that came with the table is a brownish tint and I’d initially intended to use that as the bottom but I couldn’t find a decent price on appropriately sized tempered glass for the top, and made some sacrifices in the name of getting it finished but now I’m reconsidering..
Thanks all for the advice so far , I’ll update once I have a chance to re-jigger the bottom, hopefully over the weekend.
Most glass tabletops are tempered glass. The glass shelves from Ikea that I use for my Zen table tops are also tempered glass, conveniently in a size that works for me. My tables are designed around the glass that I can easily (and cheaply ) get, so I start there. I’m not so much worried about someone chanelling Chris Farley, as I am about someone dropping an Amazon box on the table, and it happens to contain something heavy. It’s going to happen. For that, I want a strong, and relatively safe option for the table top at least.
For the bottom, it might not be as important where you have control of who is around it. For something that is “public facing” safety is probably even more important.
With my 3D printer, at the start, I used to use dollar store picture frame glass. It’s thin, flat, and an 8.5x11" piece of glass fits very nicely on a 220mm bed. If (when) it breaks, it’s cheap and easy to replace. As a bonus, band-aids are also cheap at the dollar store. I was pretty careful with the 3D printer, but that last point was still a point. I probably am going to fiddle with the bottom of my Zen table less than I did with the printer build plate, but the mess when I dump a whole box of baking soda on the carpet isn’t something that I look forward to. (But hey, at least the carpet will smell fresh for a while.)
The downside to tempered glass is that it’s a little thick. Most that I have or have seen is at least 4mm thick, and I’d really like it to be 2mm or less. This is relatively easy to find with regular glass, and not difficult at all to find with hardboard. So there’s that.
Maybe the best solution is a tempered glass top, regular glass bottom, but with an under tray of some sort to catch glass/baking soda/machine pieces?Doesn’t let you show off the machine quite as well, though maybe with the scalloped sides like the demo unit that @jeffeb3 did for RMRRF that doesn’t matter as much?
) get, so I start there. I’m not so much worried about someone chanelling Chris Farley, as I am about someone dropping an Amazon box on the table, and it happens to contain something heavy. It’s going to happen. For that, I want a strong, and relatively safe option for the table top at least.
I was pretty careful with the 3D printer, but that last point was still a point. I probably am going to fiddle with the bottom of my Zen table less than I did with the printer build plate, but the mess when I dump a whole box of baking soda on the carpet isn’t something that I look forward to. (But hey, at least the carpet will smell fresh for a while.)