N00B Issue

Hello everyone. My name is Brian and I am a newbie. Just got my "almost new" i3 PRusa Friday, took it completely apart and rebuilt it using the video so I know what does what where, no problems there. (I used EVERYTHING that is referred to in the instructions as for software and drivers) and the machine prints some OK Cubes, etc. Did the gorilla too, came out OK by my standards, however I have one other problem as yet:

Sometimes, the object I am printing comes off of the table midway thru and it gets ruined. I am not sure why. I looked at the code for the gorilla and noted that about 1/3 way thru, it changed both the bed temp and the extruder temp on me, effectively lowering the temps to the point where they were unworkable. My machine came with 1/2 reel of some plastic and I do not know if it is ABS or PLA. I bought some ABS and PLA and loaded up a reel of black ABS and let her go. No problems with the print until I tried the obligatory Yoda bust and got up to about the nose when it popped off the table and I got a ball of squiggles. I have not looked into the Yoda code yet as it is huge and I was tired.

I was using the recommended temp settings of 230Extrude and 110Bed. I am using the 1/8 glass plate and all of the stock hardware as supplied by the manufacturer. If anyone has any thoughts I would gladly appreciate the input. GREAT FORUM! Been on here a few minutes and already learned a lot.

Thanks in advance,

B

Are you not applying any fixative to the glass first? e.g. hairspray, ABS juice, or whatever?

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Waitaki 3D Printer

I've not long ago finished building the Mendel90 (not from a kit), and am happily printing directly to the glass...no juice/spray/PVA/tape...nada. I just make sure it is clean with a scraper blade, and a good wipe down with isopropyl alcohol. Since the build, I have not had the need to unclip the glass from the bed.

I also manually turn the bed on well before starting the print so that the glass has time to heat to the same temp as the PCB. The thermistor will say target temp has been reached, when in fact the glass (top side) is still reasonably cool. That's just a fact of life of the thermistor measuring the PCB temp, not the glass temp.

Initially I had parts let go because (as already mentioned) the slic3r settings would fire up the fan, and turn off the bed temp partway through. This has a rapid cooling effect on the glass and I could actually hear the print start to let go as the glass contracted. I don't use the fan now, and leave the bed temp on during the whole print. Since then I have not had one let go.

What would be cool is if there was a way to set slic3r to only do the z lift on the first solid layers. This is where I hit problems with zits causing the next layer to jump steps. Once I get that first layer down, it's all good and will do the rest of the print unattended. Since enabling z lift (only lifting 0.2mm) not had a problem with getting the first layer down, but also prints are not as clean as I was getting before. I'm picking it is because the lift is taking away the wipe action achieved when not lifting on fast moves.

BTW...Mendel90 (sturdy with acrylic for the panels), 0.3mm J-Head Mk5 and 1.75mm PLA @ 0.25mm layer thickness, Marlin on RAMPS 1.4.

Yes, I agree that just a spotlessly clean glass is all that is needed for PLA but Bkwapisz seemed to be using ABS.

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Waitaki 3D Printer