Getting my 3D Prints to stick to the bed is probably one of my biggest challenges. It's mostly with small parts - and I've mostly had issues when trying to print many copies of the same part all at once. But recently, there was a specific part which was giving me issues where a little experiment uncovered something surprising.
The Problem
The part I was printing is a link for a bracelet - so it is only about 25mm square and has 4 protrusions starting at the base layer which are the receptacles for pins which hold each link of the bracelet to the next. Those protrusions - or two of them in particular - were peeling up from the bed after the first few layers of printing, and causing the printer extruder head to force it out of the way as it printed successive layers. This caused some mis-shaping - but luckily the model would eventually self-correct and continue printing to the end without forcing the whole object to come loose from the bed. You can see the start of the problem pretty clearly in the video embedded here - the protrusions on the right side are fine, but not on the left - notice how they are higher than the current print layer.
The ultimate impact of the peeling was that the protruding parts where the peeling occurred were mis-shaped and not smooth at all in the final object. The print head eventually re-melted and flatted the problem sections, but not in the way which the part was supposed to be printed. You can see this in the images here too.
Here's a close up of the final print - those protrusions which had the problems (now shown on the right) were consistently mis-shaped.
Original Position - the left protrusions were the ones experiencing peeling
For you technical 3D Printers - this is the bottom layer from CURA - in the original rotation position
Discovery of an Idea
I was using a live video service - Periscope, on twitter (@periscopeco) - to show people this particular print, and someone commented that perhaps it was the position of the object's receptacle parts that was making this worse. I figured it was worth a simple experiment - since I had tried a few other fixes that didn't help.
Experiment - Rotate the Object
Without changing the model or the slicing parameters at all, I rotated the part 90 degrees clockwise so that the receptacle which had the worst effect was now not the first part of the print layer. I could tell right away that this small adjustment did have an impact, as the first few layers of printing were clean and flat, and there was no peeling off the bed. In the prior experiment, I had slowed the printing of the bottom layer to 15mm/sec (in advanced settings in CURA) - but that adjustment alone did not help - but I left it like that and did the rotation.
After 90 degree rotation, the receptacles are now printing smoothly and are shaped as expected in the model design.
NEW ROTATION POSITION, with the problem parts now pointing away from me on the print bed.
And again for the technical folks, the bottom layer shows hardly any pattern change - just the rotated position.
Results
In the end, the object printed much better, without peeling, with a simple 90 degree rotation! I was quite surprised - but pleased of course. Now I am analyzing the layers to see what may have changed in the slicing - so that I can get to the bottom of what the rotation changed in the printing commands, as I have a hard time believing that the rotation itself actually matters. But - TRY STUFF! When you have a problem, try lots of potential changes to the printing parameters and even the positioning on the bed. You never know what you might discover.
NOTE: Post Updated (5 weeks later):I've found parameters to make CURA slicing very consistently successful - mostly thanks to the folks at LulzBot who sell great filament and provide great filament profile/config files for CURA - but also after a bunch of experimentation. I've been using CURA exclusively now and while I tweak speed and top/bottom layers on different models for different needs, I have not had a fail like the one pictured in this post since writing the original post... but leaving the post here for historical purposes. Original post follows:
I discovered that Lulzbot seems to suggest CURA as their prefered Slicing app for generating gcode files for 3DPrinting (gcode is the language that many #3dPrinters understand). I was initially using Slic3r because that's what the Lulzbot TAZ4 manual pointed me towards. Since I'm just starting to understand the basic controls I have in Slic3r, getting a taste of CURA was a great experience - to see how it exposed and set different parameter versus the way Slic3r did.
CURA model on the left, SLIC3R on the right.
At first, I thought I had discovered gold - since one of my models generated GCode much (much!) faster than Slic3r and then the generated gcode printed extremely fast. My second try also showed improvement - printing the CURA gcode in almost half the time on a small model - and the quality was quite good.
Then I tried a new and very different model. Still very simple - some geometric shapes extruding up off a rounded courder rectangle. Sure - it happened to be the Google Classroom logo - but it's a simple one. This is where CURA not only fails me so far, but perplexes me. The top layer is practically not completed - and there is actually a shape missing. Check out the image here comparing the CURA print to the Slic3r print. See the missing shape? (it's a chalkboard eraser, by the way). The SLIC3R model is by no means perfect - I have some work to do figuring out why the top layer has gaps - but it's still much better than what CURA produced.
I still have lots (LOTS) of experimenting to do - but for now, I can see that I might have to start digging into the gcode to see what's going wrong.
While trying to model and print a simple plastic joint - a way to connect 3D Printed parts - I discovered I had a lot more to learn about basic #3DPrinting. Specifically, keeping my model stuck to the bed became a real problem during this project.
The model was taller than it was an wide or long (about a 3:1 ratio) - and I couldn't print it with the big side down on the bed because of the joint I was trying to print, which like a mortise and tenon (mortise on one side, tenon on the other) and would have had a long overhang. So printed on it's side, there would be no overhangs. Seemed perfect. I've done a taller project like this in the past, but that overall model was quite large, so still a large surface to adhere to the bed, whereas this one has quite a small surface on the bed (the whole bas is only 7mm x 40mm).
Mid-way in the print - 3 times in a row - at two different scales (I tried bigger to see if that helped - it didn't), the model would come off the bed and stick to the hot end (the extruder). The result was a half-made model with a big glob of PLA as it went for a ride with the extruder for the remainder of the print.
Other things to try in the future:
Perhaps the 0.15mm layer height was too small, and the extruder was too close to the previously printed layer (sticking to it and dragging it loose).
Perhaps a "brim" at the bottom of the model would help adhesion.
A hotter bed temperature may help
Coating the bed with a glue mixture (I read about this on support forums).
So far - I've had great success simply printing a smaller part - but that won't work for every design. If you have ideas or similar experiences, let me know.
