Why is Print Adhesion almost good, but still not right?

Question

It feels like my print is almost there, I spent a long time fine tuning the calibration with a fantastic set of G-code files from Chuck Hellebuyck.

I am using an Ender 3, on which I have modified the heatbed to carry a glass sheet, otherwise factory standard. The prints are done on the bare glass. When I printed a window some 14 feet (~4.5 meters) away was open to the cold New York winter. The cooling fan on the Ender 3 is mounted on the right side of the hotend and uses a simple declector, it can be seen in picture 2.

However, my print is not perfect yet. I'm using 1.75  mm PLA at a temperature of 200 °C for the 0.4 mm nozzle and a bed temperature of 60 °C. Out of the 4 corners, 3 printed perfectly, the back-left one did lift.

What do I need to do to fix the bed adhesion issue?

Answer 1

Based on the pictures, this looks like the bed wasn't clean enough, thus why it didn't adhere correctly in some spots. The lifted corner is the worst, but I can see a couple more spots where the PLA didn't stick well enough, though the brim prevented it to completely lift off the bed.

I would advise you to not print with the window open, even if it's only slightly ajar. Weather conditions and temperature will affect the quality of the print, even if it's only a small variation in temperature. I've had enough failed prints due to a shift in temperature to know that, even though PLA isn't affected as much than ABS by temperature changes through a print.

You might also try to increase the bed temperature a bit, up to 70°C or 80°C. I've looked at the recommended temperature for PLA with my UM3E and it says 80°C for the glass bed.

You should always make sure that the glass bed is clean: ie no dust on it and no grease. Yes, touching it with your fingers will leave a thin greasy residue in the form of fingerprints, and even one fingerprint can prevent good adhesion and result in the problem you had.

There are various products to clean glass beds, I've personally found out that the cheap yellow-colored window cleaner from Karcher works wonder. Do not use the standard blue colored window cleaner products: the blue one has a chemical in it that is made with the express intent to prevent anything to adhere to the glass, which is obviously not what we want. The yellow-colored cleaner doesn't have that chemical, and it cleans without depositing an anti-adhesion film on the glass.

If a thorough cleaning isn't sufficient, you can look into various adhesive products. While there is quite a lot of adhesive solutions marketed as being specifically for 3D printing, with insane prices most of the time, I've found that a simple UHU glue stick works wonders. I usually do not need glue when printing PLA, but I use it for Nylon, ABS and other filament that absolutely require it and it's a breeze to work with, and it cleans easily with soap and warm water.

Answer 2

This is a standard adhesion problem with glass beds:

Glass beds are super level, but they transfer heat less good than metal and BuildTak. This also means that not every spot always has the exact same temperature, which can come from a lot of things, for example, a draft from the open window jitting that corner and causing lifting.

There are some super easy and cheap solutions:

• Painters Tape adds a little bite to the surface, but you need to level to its top.
• a thin PVA (Gluestick, wood glue, hairspray, or specifically designed sprays for 3D printing) bonds the first layers much better to the glass
• for ABS, ABS-in-acetone-slurry is a known bed adhesive
• measure the top of the bed temperature - you will find out that the increased thermal capacity of the bed+glass sheet means that your set bed temperature is not reached on the bed surface. Adjust as needed!
• prevent any and all draft (close windows and doors)

Answer 3

Despite all advice to the contrary, I've had no luck with glue or masking tape. I print directly onto a glass bed.

The glass is much thicker than the surface that was originally on the heat plate, because of this heat takes longer to reach the surface of the glass and the temperature probe on the plate is even more inaccurate than it was originally.

Using a laser thermometer, I found that pre-heating the plate before the build starts solves the problem as this give the temperature time to even out.

Clamp the glass firmly to the heat plate with as many plastic clamps as you can fit (metal ones are too heavy those post office crocodile clips might work). This will give it a better thermal connection.

If that do any work, increase the bed heat to 60° and/or nozzle to 210°.

Also, clean the glass with washing up liquid and then window cleaner and only hold it with a clean tissue after.

Answer 4

I work with a glass surface on my machine and use a drop of superglue to attach the corners after the first layer is complete. The biggest contributors to not sticking are :

1. Bed not level.
2. Temperature of filament not hot enough.
3. First layer print speed is too fast.
4. Heated Bed not hot enough to compensate for cold room. Try enclosing print area.
5. Head is snagging on print edges (no retraction when moving) and ripping print loose.
6. Print bed surface is not clean. Use acetone or ammonia for cleaning glass. Alcohol leaves an oily residue.

If you are printing on painters tape, make sure the bed is very clean when you put the tape down. Then make sure you rub the tape down well so it doesn't pull off of the print bed surface during printing. Then clean the tape surface to get the oil from your hands off of the tape.

I use Glass Build Plate Wizard spray for delicate prints and a heated bed. It releases after the print plate cools down. That eliminates the need to chip the print loose. It releases itself after a few minutes.