Not ready for the real world

The diy 3d printers are not ready for the real world. My RepRapPro has a nasty habit of loosing connectivity with my PC. Halfway through a 4 hour print THIS SUCKS!

Turns out it’s not a problem specific to my printer supplier. It’s the open source electronics which control the printer. They appear to be sensitive to anyone switching on or off another device nearby. THIS SUCKS.

I’ve ordered a small UPS which should clean up the power to the unit and will make a metal box to house the currently open-air control board. Fingers crossed.

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Back from Hols, back to printing

I’m now almost at the point where I can walk away from a print run and have some confidence that it will complete OK.  Almost.

I do a paper pinch test on the three points on the bed which correspond to the three mount points. A z-home should pinch the paper to the bed while still being loose enough to draw the paper out by hand. This seems pretty stable now but I get the occasional problem with the z-axis sticking. Even fettling the z-axis holes (on the x-motor mounts) as per the build guide they are still too tight. This causes problems when z-homing because the small springs in the x-mounts compress slightly rather than the axis moving downwards. The axis then jumps a few mm downwards, leading to incorrect z-home. This is only an issue when moving the hot end downwards. So as long as it works at the start of the print then the rest is OK.

The plan is to print a spare new x-axis mount  (https://github.com/reprappro/Mendel/blob/master/Print-mendel/Individual-STLs/x-end-motor-1off.stl)  with slightly wider z-axis holes.

The other issue I have is that the hot-end does not fit vertically.  It tilts slightly backwards which I think is causing it to collide slightly with already deposited layers. It’s only a slight effect but with small tower structures it tends to knock them off the build platform. if they dont have enough raft/skirt.  Needs further investigation.

 

 

Oh why do I have to go to work!

There’s this thing at home, sat there idle, that needs love and attention and maybe a slap. My RepRapPro Mono Mendel! And instead of tweaking, printing, adjusting, printing, de-clogging, adjusting, printing … I have to work.  What could be more important the riding the bleeding edge of home fabrication ?!

The sticky fan got me again last night.  The fan that sits on the hot end attempting to keep the filament from melting until it gets to the very end of the hot-end. It’s wired in parallel with the power supply to the printer. It should be on all the time. The build instructions say this is loud print. But my fan is crap. About 1 in 5 it fails to spin up when the printer is turned on. I should check every time but sometimes a hard reset is called for and it’s easy to forget. Three minutes into a print and … nothing. Sigh. Dismantle hot-end (again), snip out plugged plastic, re-assemble, reset everything.

I bit the bullet and dug out a box of old fans. There’s a real doozy in there which is twice the depth of the supplied fan. It almost hovers when you power it up 😉   I need to fit that but it required longer screws than I have. So I picked an old ‘pabst’ fan and stuck that on, So far, so good.

Why is stuff not coming out of my hot end ?

One of the joys of building your own 3D printer (our’s is a RepRapPro Mono Medel) is that when it buggers up (and it will) you know exactly how to fix it.

The most common issue is getting the print to stick to the plate/bed. The first layer is critical. There’s plenty of advise out there but I find that having Kapton tape on the glass bed works 100% of the time as long as I give it a quick wipe with a drop of window cleaner before each print.

The other big issue is when stuff stops coming out of your hot-end. This is not good, especially half way through a 6 hour print. There are two places the filament can get stuck; the hot-end or the extruder.

My hot-end sticking was caused by the main cooling fan not spinning up. It  should always spin up. It’s connected in parallel with the main control board to the PSU. If the printer is on then, in theory, so is the fan. Once or twice though I power on the printer and the fan sticks. A poke with a finger gets it going. But now I always check the fan spins up at the start of a printing session.  If it’s not running heat from the hot-end travels back up the assembly and softens the filament in places it should not be soft. In my case it deformed into a ‘plug’ that I could only remove by letting the hot-end cool and dismantling it. 10 minute job but I was lucky in spotting the problem quickly. A cooling failure can really stuff up your hot-end with molten plastic.

Last night, half way through a long print, I spotted that no plastic was bring extruded. Argh! Start to take the hot end apart again only to find it free and easy. Hmm. Checking the extruder showed the filament to be stuck fast. The filament was so mangled in the extruder block that the ‘big gear’ lifted straight out (this is usually held in place by the filament). A bit of careful picking, prodding and pulling got the mangled filament out along with a tiny bit of grit.  It looks like the grit was drawn in with the filament, stuffing things up. This type of failure appears to be well know, there are plenty of filament cleaning devices on thingverse (one of which I’ve not printed and installed).

It would be nice to be able to kick a print off and go do something else but at the moment I don’t have the confidence in my machine to do that. I babysit every print.

What I need to do is add some self-monitoring to the machine so that it stops if the main cooling fan is not spinning or the filament is not being extruded as expected.

Rob