need help calibrating

Hello reprapforumusers,

I need help calibrating myprinter.
I just finished building it a few days ago and now am trying to calibrate it.
I already got my nozzle at the right height and leveld the bed and set the right fillament size and my tempetures are 100c for heatbed and 230c for nozzle.
I am printing abs.
Now my problem is when i had all this done i just printed a little wall in a L shape but there are little blobs(or tiny holes) in it( ).
So i need help solving that and i need help for further calibrations of my printer.
So i am wondering if someone can help me on my way to calibrate my printer and solving the blobs in my part?


Thanks in advance

The blobs in my opinion are caused by gasses being emitted from the filament as it prints, sometimes you'll hear little pops sometimes even see vapour leaving the nozzle if you extrude in free air. The gasses are either water absorbed into the filament (so seal your filament into a bag with silica gel or put it into the oven if you have one that will keep the temperature below glass transition (105 for ABS or thereabouts to dry it out) or are being caused by additives in the filament (I notice you are using black - often in my experience the filament with the most additives, and also the smelliest when printing) being vaporised by the temperatures in the hot end.

Try experimenting with your temperatures, you'll get less blobs and strings with lower temperatures but the filament is harder to push through so it tests your extruder, both motor and hobbed bolt/drive gear/pinch wheel. Also lower temperatures mean less strong layer bonding, and might limit your printing speed if you are using a big nozzle (0.5mm or above - presuming a 40w heater in the hot end) as it just wont melt fast enough not to go stringy especially on infill where speed is high. In the extruder make sure the pinch wheel/idler is tight, you want it as tight as it can go without crushing the filament into an oval, adjust your E-motor current to ensure if there is a jam the motor clicks/stalls rather than the filament slips on the drive gear. This clogs your drive gear and is harder to detect than a clicking motor. The motor driver/stepstick will shut off if the motor reaches an overloaded condition as heat builds up in it.

You might have to chose between strong and blobby (apply sandpaper afterwards, less easy with black it spoils the finish), or weaker and less blobby if you can't find the optimum between too hot and too cold, unless its just the filament quality or moisture absorption causing it. Sorry to throw so much stuff at you but solving these problems is a lot of the fun.

You're getting some warping as this is a long thin part (the worst type for lift), and I presume you are not using a heated build chamber, which for larger ABS parts is required aim for around 45 deg C? Use a brim of say 5mm around the part, maybe increase bed temp to 110-115 degC, put a cardboard box around/over your printer and move it to a warm place, use gluestick/hairspray or a printing surface like printbite/PEI to prevent this.

Edited 1 time(s). Last edit at 07/14/2016 08:39AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Okay,

Thanks for the tips!

In order to prevent water vapor bubbles, place your filament in a desiccator. This can easily be made by putting your filament in an airtight container and adding dry packs such as the ones found on Amazon (https://www.amazon.com/Dry-Packs-Silica-Desiccant-40gm/dp/B006L882NM/ref=sr_1_9?ie=UTF8&qid=1468610787&sr=8-9&keywords=silica+gel). This will suck the water off your filament because water has a higher affinity and avidity for the silica than your filament. Nylon filament may take longer to desiccate and may require several regenerations of the silica gel.

In addition to the problems you sited, it looks like you also have z-wobble. These are the evenly spaced horizontal lines. Usually a weak frame is to blame. What is your frame made of? Almost all threaded rods have some warpage. As your threaded rod turns it pushes and pulls on your z-axis smooth rod causing a weak frame to contort to accommodate the z-axis movement. As the z-axis moves back an forth along the x-axis and Y-axis planes the nozzle moves back an forth. This displacement of the nozzle shows as regularly spaced lines called z-wobble. By using a stronger frame, you get less movement of the smooth rod and less displacement of the nozzle.

Edited 4 time(s). Last edit at 07/15/2016 03:31PM by Lymphomaniac1.

I think another cause of this z wobble is the flex couplers used at the base of z threaded rods/leadscrews. They do flex, especially if doing z-lifts with retracts as the direction changes.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Longer, thinner parts like that will want to pull up and curl like that too when you print ABS. When the top layers cool they shrink and pull pulling it off the bed. A warped part won't be so good for calibrating. I'd print a different calibration object, like DigitalDentist's Calibration Cube

ABS likes a heated bed, I'd set it at 105c-110c

Is your printer enclosed? ABS also likes an enclosed chamber at around 50c
How's your print bed setup? Like is it a PCB heater, or aluminum with a heater stuck to it. Is there anything on top like bare glass or Kapton?

Getting that first layer right will help out greatly too.
Looks like yours isn't squished down as much as it should. That first layer should be squished down fairly well.