The Spice Must flow

I built a coreXY sand table for the Milwaukee MakerFaire in September. The table is about 2 m x 1 m and has “printable” area of 735 x 1570 mm, lit with red and blue LEDs along the long sides.

 

The mechanism is made using 3D printed parts in a classic stacked-belt corexy configuration. It uses a SmoothieBoard 3D printer controller to play files from an SD card. Some details and photos here. I run this table with a 1/2" ball at 500 mm/sec with acceleration set to either 1000 or 2000 (can’t remember the last value I tested). It has NEMA-23 motors because that’s what I had on hand.

I have recently rewired it to make it neater and it’s a big improvement, but I want to do more to make it quieter and more convenient to send files to it and to select files to play:

  1. use NEMA-17 motors for reduced noise and vibration
  2. rebuild the sand box with thinner bottom to allow a gap between the magnet and the table bottom to reduce noise
  3. new controller with 256:1 ustepping drivers to reduce noise and vibration
  4. Ultimately I plan to build or buy a glass top table or just the glass top and then rebuild the whole thing to make it more like furniture.
I am looking for suggestions for a new controller. I'm thinking a Duet WiFi board would do the job, but it's a little pricey. A sand table needs just a small subset of gcode interpretation and 3D printer hardware, so I think there should be a smaller, ultimately cheaper solution out there. Any suggestions?

I have an esp32 grbl board that had three axis and you can put trinamic tmc2130s (not spi, but in standalone mode). It’s working pretty well but I think a pi would be smarter for wifi. This wifi and sd card work, but it’s a bit particular. Octoprint or cnc.js or something would probably be better.

The einsy retro is another good choice, it’s also a bit pricey but would take out a lot of hastle. That, plus a pi would be a great fit.

I would also be tempted by the el cheapo 2/3 channel cnc boards that run grbl from China. That and some standalone tmc drivers would work well.

I’ve redesigned the mechanism in The Spice Must Flow and changed the controller. It now runs pretty quietly at 500 mm/sec.

Changes include installing a Duet WiFi controller with drivers configured for 256:1 ustepping, 1:5 motor speed step up using pulleys and loop belts, and twisting belts to put smooth side of belts on the pulleys. It’s a stacked belt corexy mechanism that uses the slots in the t-slot frame for the Y axis guides and a square aluminum tube for the X axis.

The 1:5 step up in motor speed is needed to keep the table moving fast while the motors turn relatively slowly so they’ll be quiet. At 500 mm/sec, the motors are only turning 1.25 revs/sec.

[attachment file=115275]

There’s a Fusion360 file of the entire table here: https://a360.co/2M6vWPs

Video of operation here:

https://vimeo.com/361955435

https://vimeo.com/361952669

https://vimeo.com/361953455

More here: https://drmrehorst.blogspot.com/2019/09/more-sand-table-updates-making-it-run.html

This thread gives me a phishing warning in Chrome, I guess because of the google groups link (the first image in this thread, which is linked on your blog as well)

I don’t know what’s going on with that. I think it’s the blog link, but the red warning screen mentions google groups. I get that red warning page when I access some of my blog pages.

The first image has a URL of googlegroups, so any page on your blog that has an image from google groups will give the warning.

Why on earth would google’s chrome browser flag all of google’s blogger/groups links as dangerous? I’ve reported it to google at least 5 times, but it keeps throwing up the red page of doom.

I dunno, but now it has extended the “dangerous” flag to all of v1engineering.com for me, which is quite annoying.

I think I fixed the problem. I don’t know why I linked that image from google groups, or why google would flag it and any site with it as dangerous, but I replaced it with another copy that should let the topic open without a red screen of doom. I did the same on my blog page and the red screen went away.

I think I fixed the problem. I don’t know why I linked that image from google groups, or why google would flag it and any site with it as dangerous, but I replaced it with another copy that should let the topic open without a red screen of doom. I did the same on my blog page and the red screen went away.