Get your prints to stick - Check your skirt!

One of the most simple, yet frustratingly difficult things to get figured out when you are learning about 3D Printing is how to get and keep your prints stuck to the bed. People have all kinds of tricks.  Bare clean glass, borosilicate glass, plate glass, PEI, buildTak, aluminum plate, circuit board perf material,  Painters Tape, Kapton Tape, Glue stick, hair spray, PVC film, higher temperature, lower temperature, etc.  The list goes on.  There is science behind this and there are reasons why some materials work better than others.  There are also factors associated with the environment you are operating in and your technique that are difficult to control.  As things often are on the internet, everyone thinks their method is the absolute best and that all of the others don't work.  Don't worry about them too much.  If you've got a build surface that works well for you, stick with it (pun intended).  If you're curious, we typically use either painter's tape or glue stick/PVA on glass for most materials with a bed temp of 50-70C or Room Temp if I'm using a printer without a heated bed.  On the rare occasion when we run ABS, we use hairspray on Kapton at 100C.  We've played with bare acrylic and PEI but haven't been too impressed. However, of all of these build surfaces, none of them will work if you don't get that first layer right. Over on the Robo3D forum, we've got two amusing terms that have become part of the vernacular. 'Check your Skirt' and 'Throw your nuts'.  The second term is pretty specific to the design of the first version of that machine, but the first is particularly useful for anyone new to printing who is trying to figure out how to get that first layer to stick. Here's the idea. Get your bed cleaned / primed and leveled to the best of your ability. For all prints, run a skirt that is at least a few nozzle widths wide. Run the print speed relatively low during the skirt printing so that you can clearly see what is happening. If possible with your machine, you can adjust your bed level / tram and nozzle gap during the skirt printing to achieve the desired criteria. If you get a nice clean skirt that meets the criteria I am going to describe, then let the print continue.  If not, stop the print and restart. Here's the criteria.  Your skirt should look pretty similar to the one in this picture:

This picture shows a good first layer. The multiple skirt lines have cleanly merged together and appear to be a single line. Note the changes in height towards the center are due to the operator adjusting extrusion ratio as a demonstration. Photo courtesy of Jeff Janes

Here's a little more explanation if you like the details.  Note that some of the details here (specifically the wagon track) vary with nozzle geometry, but it's good general guidance.    

We highly recommend giving this method a shot if you're struggling with getting your prints to stick and/or getting a good first layer.  This is an excellent quick and dirty, but very effective method.  Advanced users going for high z-axis precision may prefer to us a more technically sophisticated method of setting nozzle gap with precision shims or a dial indicator. Full credit for the 'check your skirt' idea and the pictures used go to Jeff Janes.  Check out some of his models here:  Tesseract