CNC Painter Development Update

[vacpress]

Here is a quick outline for a proposed "hardware" simulator for cnc. it is going to facilitate the software development of the raster image print drivers. i am looking for comment on whats missing. this program is going to recieve step\dir pulses from the software being written to drive the thing. with luck, that software will end up living in a microprocessor, and only a front end driver will be on the PC..



this link will take you to an interactive 3D model of the painter. you need the "edrawings" viewer software.

http://www.vacuumstudios.com/painter.htm <---500k so it takes a while to load. also, there are 3 parts that are unexplicably floating by one of the wheels. i would right click em and hide them.

comments appreciated... espeically criticism

[Bloy2004]

Nice presentation, Vac!

[vacpress]

Why thanks Bloy,

Heres a few more pics of current development. The gantry moves pretty nicely on the toothed belt and ball bearings. With everything clamped together for fitting, there still dosent seem to be much backlash. This is a good sign, because the distance from the ganty to the ground might limit this prototypes usefullnes as a pen plotter device... we shall see in a few days.

I found that limit switches were easy to hold on with large document clips. Nice and adjustable untill i find the right positioning.

[vacpress]

This picture shows how i mounted the motor to a piece of large angle aluminum, and then used the motor mounting bolts sticking through to hold the ball bearings. The gnatry does a nice job of tracking this way. I have to goto school, but when i get back i look forward to the first motorized testing, as i try and figure out the best place to position the motor. Im sorta guessing with the toothed belt centered to distribute the force is going to be best.

[vacpress]

MUAHAHA More Building

[vacpress]

This is a side of the machine. next up is wiring and testing the assembly. i allready know it needs more metal. it is sorta flimsy. i didnt have enough acrylic to make the sides as bulk as i wanted, either. the next machine(!) will be much bigger, and probably be made of mostly this wierd steel channel i found at home depot for $13 per 10 foot piece. basically long steel C chanel. cheap

[vacpress]

This is another shot from the side. top down. simple motor to stepper direct drive.. a next machine will have at least 4:1 reduction on the drive train. i think .02in/step is WAY to big. probably 1:6 to 1:10 reduction will be appropriate. i am hoping to find some surplus gearhead steppers, to avoid more machining on this guy.. tomorrow i will probably build a spring loaded marker holder.

[vacpress]

The whole thing, so far. still needs lots of work.. at least i saw the gantry move tonite. even with a crappy unipolar driver at 10v and no clamping diodes got the belt drive axis going very fast. with a xylotex and 24v on it, i am sure it will be able to hit 200-250ipm ?

it was doing at least 50 to 80 tonight..

[vacpress]

One last image. this one is from the bottom. i used 1" wide L-brackets to connect the rails to the sides. the rails are NOT very ridgid, they are made of 1x.25" aluminum bar with .5" 1/16wall aluminum C-channel riveted to it. i am going to add a considerable amount of metal to this to make it more ridgid and heavier, so its more stable. i am worried i might have to decelerate the gantry, and i am not sure if thats possible with the software available.

[tachus42]

By decelerate the gantry you mean starting and stopping gently to avoid to much wobble?. This sequence could be part of the "move down command' and you will end up with a bit of a margin.
I got around to reading the pixation site and as I suspected they are using a very 'unsquare' resolution to give the effect of continuous tone output. They give the X resolution at 1500 dpi and Y at 5 or 10 each application of color must only cover the canvas 2/3% needing 150 overlapping pixels to get a saturated color. You will probably want to do the same thing.

240 ipm will give you 20 square feet per hour at 5dpi if you haven't worked it out. So your resolution proably is not going to be very high and if you are lucky lack of accurracy or rigidity might not be as big a problem as you think.

[teilhardo]

Nice job Vac,
is that your kitchen your using as your shop?

[cutfinger]

You are using a 10.5 inch dia wheel driven directly by a stepper motor microstepping X8 right?
Now Pi x 10.5 /1600 is .0206 inch/step, right?
When you change the speed of a stepper you are only changing the the length of the pause between the steps so whether you input G00 or G01 F1 that .0206 step will fly at the same speed, is that OK?
I'm sure it's all going to bounce around and that gantry looks rather light!