3D printer progress

If you thought I had given up you were almost right.

I got the gantry on rails and a cable drive system to convert the
paper feed into movement of this gantry all sorted baring a slightly
stiffer spring for the cable tension. I disconnected the cable drive
from the gantry expecting the worst and powered up. Then I realized I
had not put the spanner in the paper-in opto to tell the printer it
had not picked up paper. The head went crazy crashing from left to
right and I got a paper jam error. And from then on all I would get
was a paper jam error.

Unfortunately for me something like this happened when I was testing
the partially assembled printer, it just would not unjam. I now
realize that it was because I had the printer at an angle and the
light weight paper detector arm was not blocking the opto as it
should. But because I didn't twig at the time my imagination started
to run wild.

I tried absolutely everything before finding real problem fueled by a
feeling that there might be something I had missed; I removed the
seals from the bearings on what was the paper feed roller and is now
the cable drive roller to degrease and oil them fearing the little
motor had too much to do. I took apart the linear encoder to ensure
it was completely clean, I even tried merry dances with the paper pick
up sensor to try and kid it that all was well again.

In the end I bought another printer and it wasn't even in the bargain
bin, in fact its the lowest end all-in-one HP do but the internals are
the same as the D1360. I had the insides of one printer controlling
the insides of the other, I swapped print head boards and encoder
strips and I steadily removed the extra bits from the new printer to
rule out any weird load detection schemes (as the print head has to
struggle to dock and to engage with the cleaning apparatus).

In the end the only thing different between the working and non
working setup was the servo motor, the erratic movements of the print
head were not because it expected the cushioning effect at the ends of
travel or because the printer was in the bargain bin... NO.

It was because when I lengthened the wires to the gantry motor I
reversed them at the splice and for good measure slid the ferrite bead
over the splice so I didn't notice!

I can now print a test page although the cable drive is now not in
place so really its a test stripe :)

More straight forward news: I got my giant syringe pumps to turn into
build and supply chambers at the weekend, I've lopped them off short
and they look like the will work a treat.

I also did a few experiments with corn starch and all were positive,
basically the corn flour goes up and down with the piston with no
problems jamming on the sides. In fact the sides of the build
cylinder along with the corn flour act as a sort of bearing, in fact
you can push a vertically walled column of flour up out of the tube
and it stands quite freely, the stuff is so amazingly fine I'd forgotton.

One final thing, the older zcorp printers did not have counter roller
powder spreaders so there is some hope for just a squeegee to be going
along with.

And finally, the HP does much less random paper feed stuff than the
epsons but it still does quite a bit, if anyone is considering having
a go you will need to make the machine quite long, especially if you
want a larger build area. I should have some actual numbers for the
required dither zone later in the week.

Graham