Planning a build

I have just found this, and feel like I need one of these in my life. I am thinking a dining room table size, large patterns, nice and slow draw.

I want it to run 24x7. But I have a few questions before I get too far into it.

  1. At the size I am looking, I can store batteries, I think I could easily get 12volt at 40amp worth of batteries installed and still be hidden. Now I need to work out how often I would need to charge it, question: without LEDs, what sort of amps do these things use? Battery solution is optional depending on charge requirements.

  2. Generally speaking, when looking at yours, do you like it to go faster or slower?

  3. Has anyone ever tried kinetic sand, if so, what is the impact? How does it compare to bi-carb soda?

  4. The big question. In an ideal world, with money being no object, I want this thing to be near silent. What is the best solution to get one of these as silent as possible?

  5. In the forum builds I see a lot of pulley/belt systems, for some reason, I was expecting more threaded rod or trolleys (sorry, not sure of the technical term). Is the pulley best, or just easiest?


Interesting questions. If you are looking for a ready made, money is no object solution, I would check out the sysiphus tables.

But I’ll assume you want to make it yourself. Keep in mind, from the reports here, there are just about a dozen of these, although there are probably many times more that aren’t public. That still leaves just a few dozen. Most users only build one, so you’ll get speculation to some of these questions.

  1. There are two motors and they are set to very low current. I would guess they are at 250mA on my table. For a large table, or faster speeds, you will need more current. But at 1A, 500mA each it would be 40 hours. If you put 1A each (which is more than I use on my CNC machine), it would be 20 hours.

  2. I am really only running mine when I am testing sandify patterns. So I would like it to be faster. But I imagine when I get it in my living room, I will want it to be about 20 mins per pattern. Maybe a bit slower. On a big big table, you could do separate patterns in separate regions of the table. That would be interesting without waiting for the corners to fill up. @mrehorst has a big build and he remade it to be very fast.

  3. Kinetic sand is rigid in compression and flexible in tension. At least that’s my estimate. I don’t think the marble would be able to pull through it and it would sag on the older parts of the pattern. He need the exact opposite. Easy to plow through, but holds its shape after we go through it.

  4. TMC drivers running in stealthchop drive would reduce the motor noise a bunch. Then avoiding anything that acts like a drum (a big sheet held at the edges, with a magnet and ball scraping it in the middle). Then any metal on metal. I wrapped some of my pipes with heat shrink. I am going to try the same with the other pipes too. The corexy design also needs really tight belts. Maybe even much tighter at very large sizes. High tension belts are noisy too at high speeds. They are quieter than leadscrews though.

  5. Threaded rod is heavy, and hard to make large pieces that are straight. They also trade speed in for torque. We need very little torque to move a 1/2" magnet. If you want inspiration from other machines, look at laser engravers or laser cutters. I think belts are the right drive train but I wonder if low rider style motors and belts make more sense, especially for larger machines. You still need some kind of linear rail. The ZenXY uses 308 bearings on tubes. Other common choices are v slot aluminum extrusion, rods and LM bearings, or mgn rails. They each have their own compromises.

thanks a lot Jeff, that give me a bit to think about.

Initially it scraps the idea of battery and kinetic sand though.

I put in a lot of effort to make my table run quietly and learned a bunch of things along the way. Slower is quieter, especially with steppers, even if you use TMC drivers that can do 256:1 ustepping. Big pulleys are quieter than little ones and last longer, too- forget about using crappy 3D printer pulleys. Go for stacked ball bearings. At low speeds belts are quiet but at high speeds they make zip zip noises. You can get rid of most of that noise by twisting the belts so that the only pulleys touched by the teeth are the drive pulleys, but even just those make noise at high speeds.

I used t-slot aluminum to make the base of the table and use the slots as the Y axis guidance. I found that the belt tension was causing the frame members to bow outward so I added a brace at the center of the table to prevent that.

I have two last noises to eliminate- I now push the magnet against the bottom of the table with a spring, so it adds some noise as it slides along the bottom of the table. In the final version of the table I will make sure there’s an air gap between the magnet and the bottom of the table to eliminate that sound. The worst noise remaining is the caused by the poor fit of the Y axis bearings in the t-slot frame. Whenever the X axis reverses direction the whole axis shifts about 1 mm and it makes a klunking noise. That will soon be fixed by spring loading the Y axis bearings so they rmain in contact with the bottom of the t-slot at all times.

I have a big corexy table (710 x 1650 mm printable area) and like to run it fast. I was using smallish NEMA-23 steppers to drive it and running it at 500 mm/sec with acceleration at 1k or 2k and it was right at the limit of what the motors could handle. Once in a while a pattern would just be too much for it and cause the motors to stall, making a terrible sound and ruining the pattern on the table.

I recently installed NEMA-17 servomotors and they are absolutely the best thing I have done for the table. At 500 mm/sec they run quieter than the steppers, and I can actually run patterns at 1500 mm/sec with acceleration set to 20k when more noise is acceptable. They absolutely never stall, no matter what is in the pattern. Unfortunately they cost about $100 each.

I used a Duet WiFi controller so I don’t have to have any control panel on the printer. I connect to it with my laptop and upload pattern files, etc. The firmware allows you to create sequences of patterns by calling individual pattern files from within a macro. You can set it up to run a macro on power-up which means you don’t have to connect with a laptop to run the table. You can add a touchscreen to the Duet if you want local control without having to network the table.

Michael Dubno, one of the sand table pioneers, has released pattern generating software that runs on RPi so you can network the table and control it using your phone or Alexa. If you’re into RPi it’s great stuff- you can get it here:

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this is great information, thanks. I think i will go with this plan.

I dont have a 3D printer (unless I can convince the wife i need it toget my zen on). What sort of pulley thing am I needing to buy, does such a off the shelf pulley exist?

Been going through your videos…
How do you get the belt the exact length you need?
Also, do you use stoppers or can you go without?

Is there any merit in this style of design over the belts. If you use rubber wheels then I assume it would have less noise? ( i cant include links, but if you google this on openbuilds - “modular-diy-cnc-machine.6140” )

All the pulley mounts are custom designed and printed for my sand table, and have gone through about 6 versions, and will probably go through a couple more before I’m done. There’s no reason you couldn’t make those parts from metal if you have access to a mill. The pulleys are also 3D printed and use stacked F625 bearings that are normally used in electric motors. Compared to 3D printer pulleys, they have bigger balls (size matters!) and should last a lot longer. They definitely run quieter. 3D printer pulleys with tiny bearings failed in about a year of occasional use in my table.

The belts are tensioned by pulling the motors in the t-slot until the belts are tight, then tightening the motor mounting bolts. In a corexy mechanism the belt tension is used to set the X and Y axes square to each other (though they should start that way before the belts get installed). Installing the first belt will pull the axes out of square, and installing the second belt will pull them back into square.

I have used microswitch endstops but now use optical endstops because they are silent. The Duet board’s motor drivers (if you use them) can theoretically detect motor stalls, so you can home that way, but it will probably be a little noisy when the magnet carriage and Y axis start banging into the physical ends of the axes. The servomotors have their own built-in drivers, so when connecting to the Duet board all you’re doing is taking the step/direction/enable signals from the Duet. You might be able to use the alarm output from the servomotor drivers to tell the Duet when the physical end of the axis is hit, but the motors are very strong and it is going to be noisy. You probably wouldn’t want to do that with the servomotors- if you manage to stall them mechanically they will probably cause the power supply(s) to shut down -if you’re lucky. If you’re not lucky they’ll break something mechanical in the process. A lot of people seem to want to build 3D printers without endstop switches for some reason. Most who try the endstopless homing go back to using endstop switches of one sort or another. They are easy to wire, very cheap, very reliable, and in a 3D printer where it matters, very precise.

I have scoured the web for every bit of info I can find on the servomotors and have been unable to come up with anything in English about tuning these specific motors. The English language manual and tuning software are all but useless. It looks like a couple guys in Germany may have figured them out, and I’ll be sending them some email about it, but the good news is that they work fine and quietly with the factory settings so there’s probably no need to tune them for a sand table.

That mechanism you linked will work, but it uses belts- they’re just hard to see. The problem with that type of design is that you have to run a cable to the motor that drives the magnet carriage, and that is on a moving part of the mechanism. That means a long drag chain has to be installed, and it usually means much lower reliability because the cables in the drag chain end up flexing too much and eventually break. The corexy mechanism is ideal for a sand table because both motors are stationary.
Wheeled carriages are always an option for the mechanism in a corexy machine, but they take up a lot of space. I don’t know if they’re quieter than bushings (like I use) when run fast, but at low speeds they are quiet. I don’t think rubber wheels would be a good idea- I think they’ll develop flat spots when the table sits unused and they’ll start making noise when you run the table.

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thanks again for all this great information Mark.

2 questions please.

  1. How do you get the belt the right length, i imagine yours are 8 meters long or so. Where do you buy such a belt?
  2. The pulley as a complete assembly, I assume they can be purchased that work with aluminum extrusion. But I am not sure what to search for, any tips please?



The first thing I learned from reading is don’t try to use cables. Belts are worth every penny.

Your table will cost more than the cheap 3d printer you might use to help build it once you’re through with it.

My table has the belts as loose as possible. Less drag from the bearings that way, runs a little faster and a little quieter - 160mm/s. Nevertheless the necessary precision for a sand table is maintained. It is running octoprint and Marlin

It is very easy to get the belts the right length. Add up the rough length plus a bit more. Thread, tension, and snip off the excess.

Like a ceiling fan, there’s no reason to run the table when you are not in the room.


  1. I bought two 5m long belts, attached one end to the magnet carriage, looped the belt through all the pulleys and motor and back to the magnet carriage. Then I cut the belt, attached the free end to the magnet carriage, and then repeated the process for the second belt. In my table’s design, the belts are tensioned by pulling on the motor mounts until the belt is tight, and then tightening their mounting bolts.

  2. the pulley mounts and pulleys are not available as off-the-shelf assemblies. I designed them specifically for the table. Each pulley consists of two F625 bearings with 3x M5 washers and a 5mm steel pin for the axle. One of the M5 washers goes between the two bearings. I use a printed tube to hold two printed flanges in place on each pulley.