New Machine Build- first attempt sandtable

[cyclestart]

I lucked into a magnetic sand table damaged in shipping. As you can see, most of the sand has leaked out due to a fractured base sheet. The inspiration for what comes next comes from here;
http://www.taomc.com/art/kinetic_scu...us_series.html
Take a walk through his site, the man is an ubergeek in the best sense of the word.

The first build will be a crude gantry. No pics as the parts are currently at a machine shop getting fitted with screws.

I'll be writing some stuff in python to sketch what can defined by math. Is there a way to convert free hand sketches to gcode ? Something like mspaint-to-gcode . Preferably open source, cross platform would be a big plus.

edit/ checking out an inkscape solution . Looks very promising.

[Weldtutor]

Originally Posted by cyclestart Is there a way to convert free hand sketches to gcode ? Something like mspaint-to-gcode . Preferably open source,

Perhaps your eureka moment was Inkscape with Switchers Ver12 DXF plug-in.
The resultant DXF can be processed in Sheetcam etc. to give your G-code.

If not see the "Share your files" thread for more information.

A video tutorial for Switcher's plug- in is HERE.

[cyclestart]

Originally Posted by Weldtutor Perhaps your eureka moment was Inkscape with Switchers Ver12 DXF plug-in.

Nope, but I'll check that out for sure. Thanks. What I found converts directly from sketch to gcode
http://wiki.linuxcnc.org/cgi-bin/emc...?InkscapeHowto

Now to find some new hardware. Drawing free hand with a mouse is a bit tough

[cyclestart]

Waiting for parts leaves plenty of time for dreaming

YouTube - Sisyphus III (Bruce Shapiro) (1/2)

YouTube - Sisyphus III (Bruce Shapiro) (1/2)

This can't be as easy as it looks

[cyclestart]

Finally freed up some time. Here's one axis up and running. It's built out of what was at hand, the goal being to spend as little as possible. The acme screws are the only new out of pocket expense so far.

[cyclestart]

I was hoping to have some video up by now but unfortunately this isn't working out as hoped.

Problem one, the machine shop somehow managed to bend the screws. This will need to be fixed.

Problem two is the bigger concern. The 3 pound speaker magnet doesn't provide precise movement. A delay here, a jerk there kind of thing. The machine movement itself works quite well considering the materials used. My background in agriculture shines through

Not throwing in the towel. Also have a different fun idea for this gantry if sandtable reaches stage II.

[cyclestart]

Slow going.
It's hard to work in the basement when the weather is nice, especially up here in Canada.

Playing with a different type of movement. Here's a picture of it drawing a square.
Hey, it's a felt marker on a cardboard box. Use you're imagination.

The jerky ball movement was solved with a heavier ball.

Any thoughts on how to keep the wire on the outboard stepper from twisting in knots ?

cheers

[Tristar500]

I'm currently building version 5 of my sand plotter "Osiris"

This version will be built on polar geometry as was Osiris 1 and 2.

Osiris 3 and 4 were Cartesian (x/Y) machines.

Here's a couple of pics of Osiris 2.

L

[vger]

cyclestart,

I saw a sand table at a local college not long ago and was really interested. I like your polar "2 axis contraption" A vision came to mind of a possible soulution for you. On top of our fridge is a huge turntable I built. Suppose you start with a large lazy susan bearing and mount big circle of MDF on top of it. Mount your linear drive on the MDF and then your sand table above that. Driving the turntable with belts might be best, long timing belt style. Some of them will mesh well when placed face to face, so you could turn one (the smaller of 2) with the teeth facing out and cut (route) a drive disk the right diameter to slip/glue it onto. Then use the larger of the 2 belts around that and the motor, with appropriate cogged drive.

As to the wire twisting problem, slip rings will probably be the only way to go. I suppose you could build someting that would fit under the turning MDF made of PC board etched in rings with several spring loaded carbon brush sliders under that. Use at least 2 contacts per ring to ensure postitive contact.

Just some thoughts.

Steve

[Get lucky]

This is great idea. I had never seen one until now, were would start if you wanted to build a sand table. I have never built a machine but sure i could make all the parts just really not sure how you would tie it all together.

Kyle

[vger]

Kyle,

The machine I saw at the college was an xy machine and was stepper driven. A servo machine would be quieter (this one had to be moved from it's original location because of the noise it made) but a bit more expensive.

The basics? A mechanism to move a fairly strong magnet under a table with a thin layer of sand and a ball bearing on top. Here are a couple of links

http://www.taomc.com/art/kinetic_scu..._i_and_ii.html

Here is a link to one of a different style (and a bit larger)

http://picasaweb.google.com/lh/photo..._kbTS9wZXpXexQ

Enjoy

Steve

[cyclestart]

Sorry for not replying earlier. I took a deliberate vacation from everything cnc related, including this site. The first snow has fallen and I've returned to my toyroom.

A few things learned over the past few days:

Inkscape is nothing like CAD, it has a learning curve all it's own.

Sand can be a frustrating medium. Getting grains of sand to move where intended has a lot in common with herding cats.

Taking a decent photograph is an acquired skill. It's going on my to-do list.

Tristar500,
Thanks for the pics. That first photo is amazing. Sand likes to form ridges, creating those 'clear' areas must have taken a bit of experimentation. I see this is a commercial project for you so I won't badger for the trade secrets.

Steve,
A turntable has crossed my mind but I'm undecided whether the toy would lose some of it's visual magic. If anyone has a video of a rotating sandtable please share. I've spotted you're kind offer of a slipring device in another thread, will send a pm.

Kyle,
Assembling one of these things is pretty straightforward. Gathering up the materials is time consuming. There's no one-stop-shop for these kind of projects.

A couple of photos from recent playtime included.