Hello and welcome back.
If you follow the channel, you know that I just got an HP 7475, courtesy of my generous
viewers.
And to my surprise, it just worked perfectly.
That is, until it failed a couple days later.
Yay, in this quick update video, we finally get to see the inside, and also show how to
repair what I suspect is a common failure.
So for those who wanted to see the inside of this, I was trying to make plots with it,
to plot schematics.
And it stopped working just when I was about perfect.
And what happened is that it stopped rotating the carousel.
It was all plotting monochrome.
And what happens, is - apparently I’m not the only one with that - is that the Geneva
wheel over here, which turns the thing one by one, kind of shattered.
And the way it works, if I have it grab pen one…
Here you go.
It turns it until it hits the stop.
There is one of the wheels that has a stop.
And then it gets to the other one - and then it knows it’s at zero.
And that’s pen 6, right?
And that’s pen 1.
And that little wheel shatters, for everybody.
There is a little nib, had fallen off, and then I tried to fix it by putting a rivet,
and that worked for a while.
But then the wheel completely shattered.
This appears to be a common failure.
The wheel is made of a special soft plastic, I suppose for better shock absorption in the
mechanism, which just relies on bumping into a stop to provide the pen one registration.
And that plastic material just crumbles away with age.
There was even a drawing on the interwebs.
I could have spent a laborious day to machine it on my manual mill, but this part really
screams CNC or 3D printing, both of which I don’t have.
But Mike is a champion 3D printer.
Mike, explain what you have done here.
[Mike] So Marc send me some dimensioned drawings for the part, and so I printed some replacement
for it.
[Marc] And you have two - not only one, but two printers, right?
[Mike] Yeah, printed on two different types of printers, so the black one is from my decade
old FDM printer, and then this one is from my fancy new SLA printer.
[Marc] Yeah, I’m tempted to do the SLA.
So that’s a Formlabs printer, or equivalent?
[Mike] Equivalent.
It’s a much cheaper version.
[Marc] OK, because the Formlabs is Form-idably expensive.
[Mike] Yeah, no, this is like a $300 printer.
[Marc] Really?
Oh, wow!
And you surprised me by the resolution of the parts you printed on it.
So I was like maybe I should buy one.
Because I use this old-fashioned thing.
Actually, I could machine one, but this is one where it would take me longer to do it
than to print it, because it’s all compound angles.
So this one comes like this out of the machine?
[Mike] Yep.
[Marc] And this one, you have to - I saw Adam Savage, he has a giant Formlabs.
To get the parts clean, you have to wash them in isopropanol, then you have to cure them.
[Mike] So to get those to print well, I also printed it at like a 15 degree angles with
a whole bunch of supports coming down.
Then I had to clip it all off and sand the bottom flat.
[Marc] So there is still some work involved doing those.
[Mike] Yep.
This is the calibration print from the factory.
The printer I am using is a Phrozen Sonic Mini 4k.
It says Phrozen on the front, but this is the level of quality you can get out of the
thing.
[Marc] For a $300 printer.
[Mike] Yeah, it doesn’t look 3D printed at all.
[Marc] No, it’s amazing!
And then you just have lots of isopropanol, and you just rinse it off?
[Mike] Yep.
[Marc] Do you need a UV curing setup?
[Mike] Yep.
[Marc] Do they sell it too, or you have to make that yourself?
[Mike] I got that from another company.
[Marc] OK, so you need actually a main machine and then a little post-processing thing.
[Mike] Yeah.
[Marc] So in the meantime, your part seems to fit perfectly.
I just had to file a little bit so the center fit.
It’s a tight fit.
Let’s try it.
OK, so let’s try to see how it’s going to reset.
And one…
OK, it seems to be fine with it.
So now we can put that in.
It gets it.
Gets it.
Wow!
I’m impressed, I’m impressed.
OK let’s try the plot!
So all I am doing is sending an HPGL file, and this was done in KiCAD and then refined
in Inkscape, and then spat back out as an HPGL.
So if I do open…
Here we go.
So a few free programs still support HPGL, notably KiCAD.
I find it useful to then edit the KiCad output in Inkscape, to make colors for example by
putting lines in different layers.
And then Inkscape happily will spit it back out in HPGL.
You can also do Adobe Illustrator, import it in Inkscape and then spit it back out as
HPGL from Inkscape.
And then you just send the file to the plotter and away it goes.
That’s the fun part.
So as long as it’s straight, it goes fast.
And then when it has to do round things, it just sticks its big tongue out.
[Ken] So it looks like it could be optimized a bit to not draw things from one side to
the other.
[Marc] Yeah, I think that’s not too bad, that’s directly out of KiCad, and I blew
it up, I scaled it in Inkscape.
[Ken] It seems mostly optimized.
[Marc] Actually, it’s imported into Inkscape, after it’s ben spat out from KiCAD, and
then re-exported.
So God knows, it might have changed the order of the strokes.
But this is way better than some I have done, the other programs that are just completely
random.
It would start half a stroke and go to the other end of the page, does another half stroke,
and comes back, finishes the stroke.
This mostly makes sense.
But the detail on the paper, if you get the right paper, it works really well.
So anyhow, it’s just going to be boring after that.
You need to have lots of time.
OK, at this point we left and let the plotter do its thing.
You are welcome to do the same and jump to the end.
I recommend you do that to see the details it puts when it does the fine print on the
labels on the plot, it’s really impressive.
All right, see you in the next video.
Full schematics.
Plotted in color.
And with pretty good resolution.
But boy, you must be patient with that thing, it works, but it is slow as molasses.
And it can do the same for PCB designs, so that’s the design of my ECL gate that I
made to repair my HP pulser.
Same thing, very pretty, but takes for ever.
Alright, thanks for watching!