Sota heat bed problem

[geoffs]

I have a piece of corrugated cardboard between the aluminium Y carriage and the heatbed, seems to make some difference. I've ordered some crimp terminals I can rivet to the MK2 board so in the meantime, I'll keep playing with the Lava board.

I found some self adhesive 12V LED strips so added one to the bottom of the X carriage. I have an RRD fan extender thingy that can be used to drive it, Having it on while printing seems the most useful so I need to work out what I need to enable/modify to get it to work. At th4e moment it's just hooked directly to 12V - bright!

[fulg]

I have LEDs also on the X axis (using the excellent mounting system from flurin), I wired them to a pin on my controller to turn them on or off via GCode, but it turns out that in practice I always want them on whenever the printer is powered on, so I never turn them off.

Good luck with the Lava board, hopefully it is just a thermistor table issue. My understanding is that the Lava board has a 10k SMD thermistor already mounted (similar to what I use).

It is unfortunate that this board "died" without documentation...

Cheers,
Ben.

[geoffs]

It is unfortunate that this board "died" without documentation...

Yeah, most if not all of the references I can find about it are on this forum and most are complaints

[geoffs]

Well some success tonight.
In trying to get the LED lights working via the RRD fan extender, I had a problem using the M42 gcode to control the pin value. Fixed this by installing a new version of Marlin.
I also went back to the 10K thermistor and it seemed to be tracking the actual temperature of the bed quite well, a little high but consistent.
A few test cubes came out quite well so I thought I'd print some new feet for the printer - no success at all!
First layer starts to stick quite well (hairspray on glass) but then there's a quick change of direction which causes the print to lift at that point.
At least it's a different problem to the heatbed one

[geoffs]

More success with the Lava bed.
If I run a few cycles to get the bed up to temperature before I attempt a print, I can get the reported temperature within about 5 degrees of that measured with my infra-red thermometer. Good enough for a test..
I started a print of a new Y axis foot for the OrdBot and it was printing perfectly for about 1 hour (of about 2.5 hours) when I got a THERMAL RUNAWAY error and it stopped. No evidence of overheating visible on the print, no actual temperature log to refer to though. A few tests afterwards shows that the hotend thermistor is
working OK.

I'm going to say that the heat bed problem is, if not solved, then working acceptably provided I preheat a few times..
Time to troubleshoot the new problem ...

Regards
Geoff

[fulg]

First layer starts to stick quite well (hairspray on glass) but then there's a quick change of direction which causes the print to lift at that point.
At least it's a different problem to the heatbed one

I had this problem at first when I started printing, and it was caused by improper first layer adhesion. I used to baby-sit the printer through the first layer, because if it managed to stick then the print would usually complete successfully. Round holes inside printed parts were the worst, I could never get them to stick properly, the nozzle was dragging away freshly extruded plastic when traveling elsewhere on the bed. Thankfully those days are gone... PLA prints are almost always fire-and-forget now.

In my case there were several possible causes:
- non-level bed (check your v-wheels!)
- non-level X axis (if you touched the Z-rods at all or turned the Z steppers by hand, you need to level the bed again)
- improper hotend mount (if it flexes, you will have a hard time keeping the nozzle at a precise spot from print to print)
- first layer printed too fast (I use 15% of the print speed, and I usually print PLA at 150mm/s -- but you're better off too slow than too fast)
- first layer not being squished enough (it helps to have a Z adjustment screw on the limit switch, I used this before adding auto-leveling: https://www.thingiverse.com/thing:26534)
- first layer not hot enough (I used to print my PLA at 185 but 215 yields much better results for me)
- heated bed not hot enough (60C + hairspray is perfect for me, I rarely get warping from large PLA parts)
- dirty/oily print surface (clean with rubbing alcohol once you have too much buildup of hairspray, don't touch the buildplate with your fingers!)
- cooling fan should not be turned on for the first layer (if you have one)

Hopefully these can help you. It took me several months once the printer was working before I was able to print reliably with it, so don't despair. I was quite a bit jealous of my friend with a PrintrBot Metal, he was up and running 30 minutes after unpacking it... It took me 6 months of troubleshooting to reach the same quality as him. On the other hand I know my printer very well, and can deal with most problems that come up

BTW if you can, get some Nylon filament, it is extremely useful to use as a cleaning filament. Very useful when changing colors, or just to remove stray/burnt particles from your nozzle!

Cheers,
Ben.

[geoffs]

Thanks for the pointers Ben,
The roll of PLA I'm currently using was in a vacuum sealed bag with desiccant until the other week, it had been sitting on the shelf for 2 years prior to that so a new roll might be a good idea.
I've ordered some ACME screwrods to replace the standard threaded rod currently in use, I'll need to make some nut holders for them.
Bed levelling I think is OK. The glass surface is level and as far as I can tell, the PCB is in contact with the glass at all point - no air gaps. Auto-levelling might be a good thing to look at too.
Hot end seems pretty solid, no flex. Nozzle (0.4mm) is clean and plastic seems to extrude nicely.
I did slow the first layer down but dropping a bit more is probably a good idea, no point being quick if it doesn't work! Skirt goes down slowly but if I print a raft, it seems a lot faster so I need to check if I can control that (marlin f/w, slic3r and octoprint on a Pi)
Using a piece of paper as the guide for z-axis homing, assume that's still accepted procedure?
Temperature range I've been using has been from 190 - 215 with varying success. I think that 210 is about right but with the first layer issue I'm having, it's hard to know how later layers look as I rarely have any!
Bed temperature seems to be sorted out, 60C is what I've been using.
No cooling fan as yet, a couple of those turbine style fans are on order with the ACME rods

I've had a bit of a break from the 3d stuff for a couple of days, lack of progress gets frustrating. I've been playing with the X-Carve instead - but I'm at the point where I need to print a couple of plastic parts for a dust shoe so it's back to the 3d printer tonight.

Regards
Geoff

[geoffs]

As I'm still having trouble getting the temperatures just right, I decided to print something on tape. PLA at 210C.
3.5 hours with no issues at all (note to self, check the current time when you start a 3+ hour job - it's after 2:00AM ...)
Sitting here watching it print for the last few hours, I noticed that the fan used to cool the j-head hotend, blows a lot of air down onto the build surface. Need to do something about that.

It's a cover for the power supply

[fulg]

That's awesome. I wouldn't worry too much about the fan causing backdrafts on the plate, these will not cause issues for PLA. Happy printing!

Cheers,
Ben.

[geoffs]

Looked good, didn't lift but ...

When I had a close look at the bottom, first layer, there was a problem.
The diagonal strands put down were stuck to the perimeter but not too each other - it's like a multi strings instrument!
The first layer is not 'squishy' enough. Bed is level and Z home adjusted (paper thickness). Nozzle size is 0.4mm, first layer height is set to 0.35.
Filament measures 1.68mm which I've plugged into slic3r.
I'm going to double check the extruder step settings as it looks as if it's under extruding.
Image here http://i.imgur.com/WKQ9Ht3.jpg

Part wasn't a write off though, I mixed up some epoxy and gave it an even coating. When It's dry tomorrow, a quick sand and a coat of paint.