Wiring up

In our last exciting episode, I found that the new Melzi board works on the extruder port, as does the new motor, and there is some problem between the board and the extruder motor when mounted. Let's see what today brings.

First trying if the old extruder motor actually does work. It would be nice to not have to take stuff apart to get it out. Setting the extruder temperature to 185, but noticed that it started out say 43, which is definitely too high. Shouldn't be a problem for now, though, since I have no filament in there.

Yay! The extruder motor works! Now I'll let the print head cool off while I mount the other things.

Wired up the stops and the bed temp. The X, Y, and Z endstops work. How do I know when I don't have motors wired yet? I turned on communication debugging, made each axis home, then pressed the endstop and saw it triggered in the debug window.

The bed thinks it's at 38 C. That both temperature sensors are off by about the same amount maybe hints at a wrong setting.

Next test the bed heater. When I tried starting it, the power supply stopped. Turning it off for a while then on again made the power supply happy, but something is bad. I don't expect that the bed would draw more power than the extruder heater, but it looks like the fuse is blowing, even when I don't have the extruder heater on. Short circuit is most likely then. On close inspection, there's a loose wire:

Rewired more carefully, now it works.

Wired the motors, X, Y, and Z work beautifully. Since all parts of the Melzi work (except the temperature adjustment part), I mounted it back on the frame. Now try to get some more info on the thermistor problem... Aaargh! Nothing works! Yelp! Oh, it's just the yellow power that popped out when mounting it. I have to say, the Mendel90 doesn't leave much room for all the wiring. If I were to redesign something, it would be putting the Melzi out at the rear edge and the resistors in the corner. Might be too far away for some power supply cables, though.

I got tired of how the power connectors are awkwardly pressed in. Instead, I put a nail on the black wire and a larger wire on the yellow, soldered them well and wrapped them in insulating tape:

After this, Y and Z works fine, but the X motor has a ticking sound when doing nothing and is very rumbly when moving. Apparently, that's what happens when the red wire gets pulled out. Reattached, but boy is that a bother. Upgrade idea: Attach jacks on all wires.

Everything works now except the extruder connection and the temperature. Looking at the connections first. With the extruder motor disengaged, I measured the resistance between the connectors. Between K, B, and G, there is connection, but not between any of those and R. Even when the print board at the extruder is disconnected.

Compared to the other stepper motors. They have connection between R and B and between G and K, but not between those groups. According to the schematics, they are all the same. So something is wrong. Again:( According to an electrical engineer who came by at open house, I should understand what the variable resistors do and how to safely adjust them before powering up. That might have been a good idea.

At this point, my laptop ran out of power and I had no charger with me.

Regarding the temperature measurements, one page mentioned that a 50K thermistor would show up as 40 C. That's what would happen if there's a short-circuit that puts the two thermistors in parallel somehow.

New Melzi, new motor, new hope.

I got a new Melzi and Nema17 from 3dnielsen.dk. The motor didn't budge when hooked up to the old Melzi, so it does seem to be the Melzi (at least).

I carefully marked the existing wires using masking tape and unmounted the old Melzi. Admittedly, it was a rather crappy cheap make, not silk screen or anything.

Wired up E Temp, Power, and E Motor, and tested. Didn't work, of course, without Hot End wired. Added then, then tried again. It responds to input (it has an actual Blinkenlicht), but doesn't heat. Oh, right, haven't uploaded the right firmware. Do that, adjust baud rate, trying again, and now it heats! Ah, toasty!

That's not enough to satisfy the extruder motor, though, it still refuses to budge. Try wiring it straight into the board, and that works! So there is definitely a problem in the wiring. Wonderful. Enough for now, though.

It seems to heat faster, so I have that going for me, which is nice.

Motor delays

Armed with a diode, more croc-wires, and a Ritter Sport marzipan, I'm going to get that motor sorted out once and for all.

First test that the LED does what I want it to, by running it across the Y motor. Ok, so that wasn't a multi-color LED as I hoped, but I can at least see it change intensity when the motor starts and stops.

Wiring:

Black-Red: Lights up a bit, but doesn't change when "extruding".
Green-Red: Lights up a bit, but doesn't change when "extruding".
Black-Blue: Nothing.

After carefully marking the wires the wrong way (RGBK instead of RBGK), I put the extruder wires into the Z axis jack. The light lights up more now when I run the Z motor. Wiring the motor back up, I get - no movement whatsoever.

Finally took some better wires and wired directly from the Z jack to the motor, carefully matching the colors. Motor moves not the least bit, even though the heater is at full. I can only conclude that this motor is no more. It is an ex-motor. It has ceased to be.

Curious: I set the LED back on the extruder wires, but didn't actually wire the extruder. When I do the first extrude after the power cycle, I still hear a "chunk" sound. That can't be the extruder, then, like I thought. Some kind of cross-wiring? It appears the X axis will sometimes move a bit when starting to extrude, to get away from homing. So does Y and Z. But that doesn't give that "chunk" sound.

Powercycled again and looked carefully. The "chunk" is indeed the X-axis moving a tiny bit the first time. So the actual extruder was dead the whole time.

FabLab has no spare compatible stepper motors, nor do I. So I can't get that much further.

Tried wiring up the extruder wires to an incompatible stepper motor. Didn't get any reaction out of it with any combination of wires, but then I don't know if it works or if I'm giving it enough power to work or anything, so that doesn't prove much.

In conclusion, I have an extruder stepper motor that is almost certainly dead, wiring for it that is possibly faulty, and still no prints. *sigh*

Ramping up slowly. Very slowly

With the fighting season winding down, printing season starts up. Last, I was stuck at the extruder motor being unwilling to move, even at proper temperature. +Tim Hatch gave some ideas for fixing that in the last post:

Check motor current - checked black wire first, it shows about 10-20 mA whether running or not. Green and blue show nothing.
Can the extruder move without any filament - heated up and pulled out filament all the way. Still doesn't move.
Compare with a spare motor - don't have any here.
Swap drivers with X - tried swapping pins in pins.h, but that didn't take, oddly.

Noticably, the motor gave a brief "clank" when first set to move. That could be problems inside the motor, or maybe that one of the connections is faulty, so the motor moves a quarter rotation, then stops. This is repeatable after the power has been off.

Enough for tonight (got out here rather late and poorly prepared). Next time, bring extra motor and extra clippy cables - everything has moved here in FabLab. They also got a huge laser cutter, that'll be fun once it's up and running!

A Dance of Filaments

Next step is getting the extruder tuned. I grabbed a piece of filament from the scrap box, and went "What is this, actually?" Some googling found several methods of testing, most of which weren't practical: Burning a bit and sniffing it - no open fire in FabLab. Dunk in acetone - don't have any. Test in the extruder - not good when the extruder isn't tested yet. Break it quickly - it whitens a bit and breaks, but I wouldn't call it "snapping". Rubbing it against clothing and smelling it - no noticable smell (hints at PLA). Heating with a properly controlled soldering iron - seems to not melt a lot @200. Dipping in warm water does make it bend easily, that strongly indicates PLA.

From the last test I'm going with it being PLA. And indeed, some properly marked rolls of PLA behave the same way.

With the glass plate one, Z level is 1.6 and it's perfectly flat. Turns out I'd missed the bit about clipping on the glass plate. I have the clips, and they just barely fit in the opening, if I place them just right. Adjusting the firmware to have a Z home of 201,7. Then re-measured and subtracted another 0,2 mm to allow for expansion, and set the Z screw pointers.

Annoying thing about the clips is that one is right where the extruder comes down if I just home and then down.

Strange hiccup while heating up the extruder, the temp reading stayed the same for a while then jumped. That's potentially dangerous, but it did end up at the right temperature.

Alas, actual extrusion failed. A small amount of the previous black filament drippled out, but I was unable to force the new orange on in by hand, and the extruder motor refused to turn in either direction more than a brief second at the start.

Took out the hobbed bolt to see if it was ok, looks fine to me. Loosened the idler on the side, fastened it, no difference.

Took out the idler and looked inside. Aha! A stump of old filament from mid-bolt down. Heating up the hot-end, I was able to pull this out. Didn't help on getting more in.

On a lark, I looked at what happeend when the idler was in but the hobbed bolt was out. Turns out my filament wasn't even making it through to the hobbed bolt. When in doubt, more violence! Pressing harder moved the idler aside. Knowing now how much to press I was able to do this with the hobbed bolt in, and have it grab. I then hand-cranked until I started feeling resistance, then turned on the heater and handcranked out black goo till it turned white.

Still no luck running the extruder motor, though. Tried measuring the inputs, but that's not so easy with a stepper motor's varying input. Looked like the right-hand input was at least different than the others when measuring alternating current across them, so maybe there's something up with that one.

Enough for tonight, alas. Tomorrow a more physical battle awaits (if anybody but me are crazy enough to go fight in this heat:)

Little lost connection

Got a new D-Sub connector to replace the suspect one, finally. Got two, actually, just in case, and indeed I broke one during installation. New one is on and seems to work.

Took the opportunity to cut some 1mm plastic for holding up the ribbon. Much better, but I'm only attaching it on the X-axis so far (which was the worst) since the other ones would require major disassembly.

Putting the D-Sub back on didn't make the hotend work. After some futile debugging of the connector (the firmware aborts when the thermistor is disconnected), I finally did the simple thing and measured across the male D-Sub and the wires. Voila, no connection on pins 3, 10, and 11. That would explain it.

Turns out one of the pins one the circuit board wasn't soldered well enough. Fixing that helped, now there's hole all the way through and it heats nicely, all the way to 230 degrees.

Calibrating the bed. Put in extra washers on the right side, which, once I re-read the instructions, turned out to be the wrong way to calibrate those. Front-back is fine, but the middle sags a little.

Re-adjusted the Z-height, but still want to do it like the instructions say. Not tonight, though. Also need to calibrate the extruder.

Picking up where I left off - or what?

Moving has taken almost all my time this year, but the dust is now starting to settle (figuratively and literally - I should call that cleaning service) and I can get back to my printer and get on with calibration and testing. 

After a moment's confusion about negative temperature warnings, I remembered to switch the firmware back to a standard 100K thermistor setting.

Following the testing part of the manual meticulously now. I have 250K baud rather than 115200, not entirely sure why. Limit switches work. Added some oil to the Z lead screws, but I don't see any lithium grease for the extruder gears. Motors move nicely, and oh so much faster and reliably than on the old machine.

Even with the cardboard under it, the bed still sags somewhat in the middle, even though the corners are within a washer's height from each other. I may have to stick with smaller pieces at first and calibrate for the middle.

I'm slightly concerned about how the ribbon cables sag and get tangled occasionally. I should get some stiffer plastic to hold up the ribbons instead.

Bed heats nicely, but the extruder heater does nothing. Measuring on the applicable screws, the HOTEND+ does not connect. Or HOTEND-. I'm getting inconsistent readings. Getting too late. Maybe the mount in the D-connector is off. It looks a little funny:

TODO

• Get lithium grease (Lithiumseife) or acceptable alternative.
• Get better cable strip