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My PLA print won’t stick!

Ah PLA prints not sticking. If there’s one issue with 3D printing that causes the most frustration, this is probably it!

troubleshoot PLA prints not sticking
PLA prints not sticking looks like a tangled mess

You spend all the time and trouble to create something stunning in CAD or scour download sites for the perfect model. Only to have it peel off the bed halfway through or fail to adhere on the first pass. 

Either way it’s irritating and time consuming, not to mention the filament you’re using up! 

No doubt about it, if you can’t get that first layer down clean and stuck to the bed, you’re not going to get a print.

Got a print that won’t work? Fear not, help is at hand

The trick to getting a print to stick is first to choose the best method for the plastic you’re using.  I’ll cover PLA here and ABS in a separate article.

PLA prints not sticking : a guide

Now, I’m going to assume you have a heated bed on your printer.

If not, you will be missing a key ingredient.  My advice would be to add bed heating to your machine ASAP because you’re missing out on being able to control a key component of the process.

PLA has a lower melting point than ABS so it’s probably a good idea to set up a separate profile for it in your slicing software. 

I primarily use KISSlicer on my Leapfrog Creatr but Slic3r and the other available programs all have the same basic controls to generate the g-code. 

I’ll list the process in order to get you in the right ballpark to stick a PLA print.

Bed Preparation

A lot of the cases of PLA prints not sticking comes down to preparation. There are several methods to prep your printing bed for PLA. 

One is the use of Kapton tapeAnother is blue painter’s masking tape (the 3M one is the best).  

However my preferred method is to use hair spray (or if you’re a Brit, hair lacquer.)   I have heard of numerous brands being used so they must all have pretty much the same constituent chemicals. 

When you’re spraying the stuff on, give it a good soak.  Don’t just puff a bit on (like you were doing your hair!).  Wait for it to evaporate and hit it again. 

Keep going until you can see a real buildup of spray on the surface.  I prefer to put the spray onto a warm bed as it evaporates more quickly. 

To save yourself breathing in a heap of spray, just work on the area where the machine is going to print your object.  

If your PLA print won’t stick, just lay on some more spray after each attempt and soon it’ll build up enough to stick.

using hairspray to avoid PLA print not sticking
Using hairspray to avoid PLA print not sticking during preparation.

 

Take note of ideal bed temperature

To avoid PLA prints not sticking and other issues with 3D printing work, you need to find the ideal bed temperature. However, there is no magic recipe. The bed temperature is going to be a matter of experimentation. 

I imagine every printer reads a bit hot or a bit cold even if it’s using a standard 100K thermistor

I’ve found the bed temperature to be fairly critical by a few degrees on my machine.  Too cold and the print wont adhere.  Too hot and the plastic softens too much and is likely to get peeled off the bed by any stray bit of plastic stuck to the extruder nozzle. 

I’ve settled on 67° C for mine.  So experiment around this temperature, your machine could be a few degrees this way or that but it’s a good starting point.

Getting the extruder temperature right 

This is another area that will require some experimentation.  Below is a screen capture of my KISSlicer settings.

 

KISSlicer settings - click to enlarge
Click to Enlarge

The main things you should be looking at are the main and first layer settings. 

Once again, there can be a big difference in the result if the extruder temperatures are out. 

As you will note, my first layer temperature is hotter than the main temperature.  This is to get the best adhesion possible to the print bed and help avoid that issue of PLA prints not sticking.

Subsequently, I want the temperature to drop a little so that the PLA isn’t too runny.  PLA has some odd characteristics, the main one being that it will almost turn to liquid if you push the temperature too high. 

At this point it’s likely to clog the extruder as well.  It’s weird but that’s what happens on my machine. 

Another thing to look out for is stringing.  PLA is worse for this than ABS and frustratingly, the ambient air temperature can cause it to string when it didn’t previously. 

The print at the top of the page printed out well with no stringing yesterday when it was cooler but today, when its warmer and a little humid … strings!

It really is a case of experimenting and noting down whatever you find out to ensure you have the right mix.

Cleanup pointers

At some point you may want to clean off the hair spray so that you can use goop to stick ABS prints.  The best (and cheapest) solvent for hair spray is regular methylated spirits (denatured alcohol).

OK, that’s the basics for PLA and advising on how to troubleshoot when PLA prints won’t stick. 

I won’t go into any other printer settings here other than to recommend you to slow the printer down if you can’t get that first layer down clean.

 

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