Monday, 29 August 2016

3D printer tips and tricks

One of the constants of designing and building kit or custom 3D printers is the continuous 
exploration of ideas and changes to make things work more effectively or more robust and reliable. I started my 3D printing journey last september with a basic Kossel kit printer, and I've been reworking and refining parts of it ever since. I've compiled some of the better and current modifications below, along with some tricks that I've found that make working with the printers easier.


Micro Kossel Extruder
Mini Kossel Extruder
     First up on my tour of modifications is the extruder module, probably one of the most critical parts of a 3D printer. There are literally hundreds of different designs available online, both DIY and commercial, but the one I'm using is the Prusa/Makerbot MK8, which is available online as an aluminum kit. I've modified mine with a stainless steel MK8 drive gear and a M6 pneumatic fitting that I've drilled out with a 5/32 inch bit to allow the 4mm bowden tube to reach the drive gear, it makes loading the filament much easier and allows for the use of flexible filaments as well. The other change I've made is to add a M5x10mm bolt(found at the local hardware store) to the spring to allow for higher compression, this helps grip the filament better and makes handling some of the cheaper brands easer.


Masking tape, BuildTak, UHU glue and a palette knife on my Mini Kossel build plate
     Next is bed adhesion techniques. I've only worked with PLA, so most of this probably doesn't apply to the more unusual filaments. For printing without a heat-bed, I've used masking tape, plain and with glue stick on top, works fairly well but degrades quickly and doesn't work for parts with small footprints. Best unheated surface I've used to date is 'Buildtak', a branded PEI film sheet material, it comes in 3-packs in a variety different sizes, and according to the literature, most types of filament will adhere to it without any difficulty. For heated beds, I'm currently using lightly applied UHU glue stick on 3mm glass at 45 Celsius for PLA, provides good adhesion and lets go easily if you put the glass and print in the freezer for about 10 minutes to let things cool, just remember to wash the glass every 10 prints or so, otherwise the glue will eventually build up to the point that the print gets nearly permanently stuck on the build plate. If a print does get stuck, clamping the glass firmly to a solid anchor and applying a 5-inch putty knife to the bottom of the print with a hammer can usually fix the problem.

     Last up are a couple of Delta specific tips, a simple way to measure delta rod arm length and a simple add on that drastically reduces the noise generated by the printer. 



Measuring delta rod arms for exact length step 1
Measuring Rod arms step 2
     I recently had to rebuild the rod arms on my Mini Kossel, turns out that carbon fiber tubing will strip out over time if threaded ends are used. Regardless, I had to make a quick jig to get the lengths mostly the same, and I had a bunch of Lego bricks laying around, so I drilled a couple of holes for some M3 screws, and built the jig using one arm dry assembled to set the approximate length. After the jig was finished, I used some five-minute epoxy to lightly coat the threaded parts of the rod ends and used the jig to get them to approximately 
the correct length. After everything had dried, I rejigged each rod and used a spare Lego brick and my 6" calipers to measure the exact length of each arm. The spare Lego brick acts as a marking block, providing a point of reference for the calipers, since the arms are roughly 8.5" long. 


Vibration damping feet
     And lastly, I found these useful little vibration damping feet while browsing Thingiverse. They're quick to print and easy to install, and the difference was immediately noticeable when starting my next print after installing them on the Micro Kossel, it's now very quiet and bumping the table doesn't disturb things at all.
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