[tachus42]

Are you talking about air brushes used for cake decoration? Or some sort of pump to dispence dough or icing?
The idea of the Peristaltic Pump (found out the correct name) was as a alternative to the wire in the wire jet. The wire probably can meter out smaller amounts of paint but the pump should be easy to build, is pontentially less messy and clog free. - I'm just throwing it out as a Idea.

5 microlitres times a paint coverage of 7.5m^2 per litre (300 square feet per galon) is 37.5 mm^2 or a dot about 7mm diameter. About 3 or 4 dpi thats, a little low but it's damm close to what is required gearing down the stepper, using smaller tube or diluting the paint or similar techniques would make it feasible.

One possible advantage would be you might be able use the same jet for all four colors with 4 tubes going into one venturi.

[sdfine]

The cartridges used for printing on cakes is the same as any other inkjet ink cartridge. The manuafcturers use clean cartridges and fill them with extremely fine food colorings. Even though the food colorings are very fine the cartridges are still prone to clogging.

[sdfine]

I wonder if the Peristaltic Pump can be used for pumping precise amounts of air (like the Wirejet) instead of using it to pump the ink.

[vacpress]

i just got home with 8' of 1x1x1/16 CRS steel square tube... hopefully this adds the stability this thing needs.

sven- those comments are totally on topic. in another thread, tachus & I discussed a similar idea- that we are not really mixing ink or paint, we are using halftone patterns and "pixels", i think, to create the color density, gradation, etc. the trick is going to be "tuning" the thing, once we get a basic software figured out. if the software knows how to at least do an off\on for each pixel, or pixel area, we can figure a way to make the colors right... i hope.. and if not - then it will jsut be a big quirky plotter.

tachus- the venturi and peristaltic pump is a good idea- and one i thought of also, but i am sorta leaning towards some sort of blade\wire\hoop\disc\etc that is run in a circle through the trough of paint - much like pixation.. i bet "wire metering" or whatever it would be called is used for other uses than the wirejet.

sdfine- i dont think the peristaltic pump can pump precise amounts of air, i dont know why though heres a link: http://www.animatedsoftware.com/pumpglos/peristal.htm
one good posibble thing about the peristaltic, it looks like it could move pretty viscous fluids...

cake painting machine are an interesting thing to bring up - it reminds me of the industrialized inkjet heads i was looking at before i really decided to build this thing. there are problems with inkjets though that the pixation machine overcomes... the inkjet heads seem to need a very accurate delivery

i am gonna spend 5 or 6 hours on the machine today. ill post some pics!

[teilhardo]

Good luck with the steel Vac
At your rate it looks like you might be able to finish the mechanics of it today. Then onto designing the print head...

[vacpress]

teil- yeah. the printhead in my 3d drawings is not a final design at all.. for 1, i only have 1 paint gun..

i think i want to spend a day with the thing doing vector stuff using standard CNC software and a Pen or marker. I can get the thing "dialed-in" that way.

i need new wheels though... my wheels are too light, and too large. i need 6", hard rubber wheels, with heavy metal hubs...

[publitime]

vacpress




I think i will be simple to convert a photo to G CODE.
I tryes something last night.
The program i used is simular with a program for laserwork.
All you have to do is import a photo into the program.
The program will translate the photo to g code.
Thene the laserbeam will burn the photo into wood are an other material.
With the laser you will get a black and white picture .
So to make a black and white picture it will be easy.
I have just to put a spraygun in place of the laser and ready.
To do the same with multiple colors it can not be that hard.

[tachus42]

re Peristaltic pump - i see great minds think alike ha ha
The problem comes down to how to meter out very small amounts of a viscous fluid continuously with a large variation in flow rate without sticking it though any sort of small hole - there aren't two many options other than the 'fluid film' option which is probably the best i can't really think of any others apart from the pump.
I didn't read the pixelation patents but i did notice on one of the pictures of the wire jet the was a area to the side of the print with bands of paint where "the excess paint is cleaned off" does this mean the wire is rewound? air pressure is increased and the wire cycled to remove "cling ons" or perhaps another air jet to clean paint off that is dripping down off something?

Getting the color output right was the reason that i thought ghostscript was a good idea, it has all the mechanisims built in. If you get paints that are close to cmyk the biggest issue will be getting the transfer curve for each color right but there are some simple ways to do this with special test prints.

[publitime]

tachus
right the wire on the wirejet must be rewound after each printed line.
But in one of the pattents you can olso see a construction with a closed wire.
That wire is weld with a laser.
In this construction you don`t have to rewound the wire.
For remoeving paint they are useing scrappers.
Isn`t it possible to RIP the picture with a RIP software like the one we use on a large format printer and thene translate that file to G CODE.
Good RIP`s are flexisign and postershop .

[tachus42]

Ghostscript is a RIP and free! It's every bit a good as the commercial ones, in fact many commercial RIPs are licensed versions of GhostScript.

Rewinding the wire after each line Ouch. That makes things more complicated than they need to be. Now you have 2 spools times 4 that need driving. Can anybody think of a source for premade wire loops without noticeable joins?

[sdfine]

While thinking about cake decorating... for future discusssion...

How about an overhanging gantry machine that decorates cakes, a cake plotter. Vacpress, You were talking about 3D designs. Here's the perfect medium, cake icing. It wouldn't be photo quality but could lay down decorations and line-art.

[sdfine]

Publitime,

Maybe I'm missing something but GCode doesn't seem necessary. The problem is not the path of the head. It's how to control each pixel. The path of the head would be the same for every print job.

As far as a RIP is concerned, my problem is understanding what's the output of the RIP and how to use that information to control the machine. Does anyone have any idea what the output of a RIP is and how to use the information? If I knew how to access the output of the RIP I would be able to write a control program to interface with it.

Sdfine

[sdfine]

Has anyone looked at Pixation's simpler BladeJet technology. I know it uses a fine jeweler's saw blade to transfer the paint in front of the air jet. In one patent he references a Paasche airbrush that moves a reciprocating needle from the paint to the air jet. Does anyone have any more info on this?

[vacpress]

i havent really read all the pixation patents, beause i find them unplesant to look at.. i think they just run their wire in a loop, past some scrapers. the scrapers make sure the paint is even on the wire. the bladejet must refer to the technology that allows the machine to paint on the ground, as opposed to the wirejet on the wall..

i get the impression that a blob of paint probably forms on the wiper, which would help to keep the wire evenly coated. i also think that the large spring-arrangement they use to tension their wire could be removed if a simple "hoop" was used" like 1 2" metal hoop. this would essentially be the same thing - there could be some small wipers that keep it from getting messy, and it would only need 1 small stepper and simple, cheap driver.

airbrush parts could prove handy. i have seen cheap asian nozzles going for $2 each.. so a small manifold to hld 4 airbrush nozzles and adjust their angles positioned behind a very thin metal loop that runs through the paint could work. the nozzles just need to be adjusted to make the most desireable dot of paint.

sdfine- if you goto the ghostsript page, you will find that it can utput lots of files. i think there is a "sun binary format" or something like that. tachus mentioned it earlier in the thread. the sun format is just an x,y location, and a color value.

[ajv2803959]

Hi, I am insterested in this thread some time ago. I think the first time I see the pixation machines was in an subject in yahoo group
DYI CNC.

I have tested some things.
1) Ghoscript aproach. I think is the best so is the most compliacted
you need a bunch of noozles in order to get C M Y K, similar to inkjet printers.
Commercial Noozles are 0.3 mm in diameter, in inkjet printers we are speaking in micrometers. This is frist problem. With 0.3 mm noozles dithering dont work.

2) There is an aproach more economical.
In Adobe Photoshop 8.0 you can convert a true color image to 8 color without loss a lot of quality. In function of image with six or 4 color you get good results. For example for cake boxes I think 6 color is enought.
PHOTOSHOP is aplicating dithering algorithms in order to get magically the conversion.
Next step is save the new image to open format png 8 bits or 256 colors.
Open png and save as bmp 256.
Now you have a bitmap with 6 or 8 or 16 colors what ever you want until 256, and ecah byte is a color pixel.

Example
Suppose you want paint a wall of 1mx1m with 6 colors you must save a bmp with 1000mm of widht for 2000 mm of long with an dpi of 25,4mm/0,5 mm diameter of nozzle

You can execute gcode in order to print 1000mmx2000mm of color1. Now you clean noozle and tube and put color 2, and execute the gcode again.
You can use gcode tool_change in order to clean nozzle, tube load the new paint and intro.
Really you are painting lines of 0,5mm of thickness in color 1,2,3...

I think this approach work, for example in order to paint walls. Have you tried convert textures files in 2 or 3 colors, results are very good.

I hope this help

[InventIt]

Just to throw an idea out there...

Have you guys ever seen the Blow Pens kids play with. Blow air in one end and a mist of dye comes out the other end. Kinda like a human powered air brush. How about a system along those lines. Maybe you could use an system of felt tip markers and insert them into a stream of air for a specified time depending on density of color needed. Just thinking out loud.

[publitime]

ajv2803959

Seems like this will work but can you give some more information by each step.
take also a look at http://www.imagetogcode.com/
Maybe this will be intressting

[InventIt]

Blowing air across the tip of a felt tip pen seems to draw the ink out and spray it onto a target. Of course I was using 130PSI so the pattern is a little on the large side. Just a thought.

[vacpress]

pehaps a sharpie could be used with alarger resevoir of ink above it. the air could come from a very tiny nozzle.. maybe it could be shot through a template to make a smaller dot? thats an idea.

my roommate sugested that just for plotting black vector art. an interesting idea. would have to do some tests.

i gotta get some nozzles now...

[sdfine]

I think you missed my explanation of the BladeJet. It uses a very thin jeweler's saw blade to move the paint from the reservoir to the air stream. It sounds like a simpler print head design than the BladeJet.