Thoughts on Z axis endstop, power control and tip cleaning.

Hey all.
Just wanted to start a little discussion on the various topics above.
First i want to start with the Z end stop.
Any body ever think of putting on the extruder?
i was pondering the idea yesterday.
But that was in bed and now this morning, watching a print, i dont think anything but the extruder should stickin down.
There goes that idea, but lets leave it open cause its an interesting concept.

How do you guy control power?
Right now i have a switch that turns off the 12v pc supply when im done printing or as an emergency stop.
I just want to make sure that is an ok way of doing it..
and how you guys do it.
Im on a USB cord so if i cut power im still connected to arduino.
thats one main reason im asking is cause i know there is some gcode being executed while the motors are off.
and that the drivers are sensitive.
I usually disconnect from the printer when i do hit the switch and start from scratch though.
So i feel its a viable solution, with the ultimate goal of having a relay control power so i can start a large print at night and let it go till its done and shuts off power to everything.
Ideas?

What is your procedure for cleaning your tips?
from light cleaning to heavy maintenance?
I use a pair of diagonal cutters to try and scrape any left over plastic on the nozzle and around the tip.
First when things are still cold and again at temp.
Prime with a few mm of extrusion to make sure the nozzle is full and warm.
and just click print.
Now i have only been at this for a 5 days or something, so i havent needed any heavy maintenance.
but i was reading about acetone baths?
when would one of these be needed?
50ft, 100ft of PLA?
a change of color?
Monthly?
Obviously if there is a lack of quality.

Thats all for now.
I look forward to your thoughts.
-E

> Any body ever think of putting on the extruder?
> i was pondering the idea yesterday.
> But that was in bed and now this morning, watching
> a print, i dont think anything but the extruder
> should stickin down.

yep. also, too many moving cables already.


> How do you guy control power?

power switch on the power supply, either the main one, or one that grounds the power on signal cable.

> there is some gcode being executed while the
> motors are off.
> and that the drivers are sensitive.

to what?

the drivers are sensitive to motors getting disconnected when powering them. No power, no problem.

> I usually disconnect from the printer when i do
> hit the switch and start from scratch though.

according to the degree of disaster reached, you may need a fresh restart of pronsole / pronterface too.

>
> What is your procedure for cleaning your tips?

what cleaning?

> from light cleaning to heavy maintenance?

no seriously: have got a very classic nozzle,

[reprap.org]

"cone angle" looks to me slightly more acute than a bit tip angle, however.

not really any maintenance needs. residual plastic stuck to the nozzle hasn't bee a problem. Occasionally you may need to pick up a blob away with anything other than your fingertips. No scrubbing here.

> Prime with a few mm of extrusion to make sure the
> nozzle is full and warm.

"extrude 10 30"

alternatively or additionally, use skeinforge's skirt

> but i was reading about acetone baths?

???

hey thanks for the clarification.
I pretty much assumed what you had clarified.
Just wanted to cover all bases.
Thanks
-E

with the mendelparts new v9 hot end and extruder (or the Carriage extruder), you could mount the hot end so that it was spring loaded, so that if the z collides, it pushes the hot end up. if you also mounted a flag on the top of the hot end, and an opto or switch above it, you can tune it so that when the z collides, it pushes the flag into the switch.

the major problem is that Z0 will then be ever so slightly below the bed surface, but you can adjust this in skeinforge Bottom.
That's fine for printing, but any user-initiated x/y moves before printing will drag the hot end tip on the bed.

Good point.
i like the no collision thing but that can be mitigated with a max endstop.
But sounds like the way Z0 is handled there is a collision problem.
Hmm more thoughts to ponder.
-E

From time to time you'll bump on gcode that unexpectedly sends your hot end straight into the heated build surface.

Good practice is to get into the habit of oogling the first few lines of the gcode that is going to be sent to the machine for actual Z positions, before hitting print.

With the print bed on springs (needed anyway to level them), eventual collisions carry few consequences.
Also I tend to not bolt down the extruder blocks, just pressure fit them. This way, if the disaster is a major one, they thend to pop up.

another benefit of mounting the z endstop above the hot end is that it would make bed mapping very easy: i.e. you wouldn't need another sensor and pins to do so. There's even a bed mapper application.

it'd be really nice to get some feedback from the machine about how much i need to move each corner of the bed. full-bed prints are always a little scary for that first layer.

Exactly what i was thinking there Buback.
Have feed back about were the system is on the z plane with respect to the bed would be crucial.
Im gonna have a crack and that bed mapping app.
I didnt know about it.
Imagine a laser that could give the feedback.
No parts to get in the way and precise.
just a thought

> Imagine a laser that could give the feedback.

As for position feedback, there is also a working magnetic linear encoder solution, seems very accurate

[store.makerbot.com]

[wiki.makerbot.com]

You can get that chip in sample quantities from Austria Microsystems too

Never read of anyone actually using it though.

And code is yet to be developed.