Bed Treatment for PLA  

Re: Bed Treatment for PLA

Hi Brian

Generally I use blue tape for printing PLA, except for the occasions where I need a smooth bottom.

With glue stick, you should simply re-apply a thin layer of glue on the printed area after removing the print to replace the glue stuck to the print. If you have problems with the part not sticking, then there are a few issues you need to look at:

1. Bed levelling - check and double check the distance between nozzle and glass
2. Glass warped - turn it over to see if the other side is flatter
3. Bed temperature - increase bed temp by 5 or 10 degrees
4. First layer height - must be 0,25mm or greater

To force a good first layer, you can make the nozzle/glass gap slightly less than 0.23mm. Print the first layer slower.

When using blue tape, the temperature should be lower than when using glue. Blue tape loses its stick at higher temperatures.

Peter

Re: Bed Treatment for PLA

Good day,
My first print was the PRUSA Logo. It went just fine, no issues at all.

When I tried to print the frog as my second print it comes off the bed.

Still in PLA, still using the default settings. I tried twice to put some glue stick on the bed and try again... both times the frog prints the first 2 or 3 layers and then the main body pops up. I tried the castle, but it popped loose right away on the outline.

I let it cool off overnight, coated it cold this afternoon, and tried again this evening with the vase file. One side is fine, but the front side is having issues with the "frills".There was a little bit of an issue in the center with one or two lines. I let it go and it seems to be okay.

I watched a bunch of videos that mentioned blue tape and hair spray..... but I can't find any step by step instructions that explain the right process for glue sticks.

Should I be cleaning the glass between runs? Do I need to re-apply glue between each run? hot? cold? how thick? can it be too thick?

What is really going on with the glue and PLA? why does it work?

I have several years of screenprinting, laser engraving, and machining experience. I find that understanding what is supposed to be happening helps me achieve better results.

All PJR's stuff is great advice.

I use glue on glass for PLA And have no issues. So people like the blue tape, in the end its whatever works for you. 🙂

Most likely your issue with adhesion is due to your bed level and height. Auto-home your print head through the menu, then using a buisness card (or similar piece of paper) make sure that the printhead is close enough to the bed were you start to feel drag between the nozzle and the card. Do this in all 4 corners and the the center adjusting to get a level bed.

When the first layer is applying you should see the bead of filament smooshing outward ever so slightly (showing you have good adhesion ) If you see a light or spotty line it means you have the head too close.

As for application. You want to apply the glue to a cold glass. I apply in one direction, let dry, then apply in the other, let dry, and you should be good to go. Never apply to a hot bed. You shouldn't need heavy coats.

As far as cleaning goes, I clean my glass with soap and water maybe every 10-15 prints . Ill use the same putty knife i use to remove prints to scrap off a little excess glue between prints, so it doesnt build up to much. I've had great success with this so far.

Re: Bed Treatment for PLA

I concluded that it was the model of the tree frog. 🙁

I shut the printer down and went to bed. In the morning I washed it and re-applied and printed the vase with no issues. I've gone on to do almost 20 prints of a small part I designed with few issues.

I did buy Simplify3D so I would have control over the gCode. I noticed that for the most part it does a very good job of printing.

I need to figure out what the stripe/wipe code is though.... the Prusa logo prints along the left side and appears to wipe the print head before jumping to the center. I've looked at a few files and have not figured out what code does this so I can put it in my Simplify3d pre-print routine. Any thoughts?

Re: Bed Treatment for PLA

Brian

Wipe is to prevent stringing during a move; the head moves back a few millimetres over a line it has just printed to wipe any excess filament.

No idea what stripe is though; I don't fee inclined to pay for software, when I can get good results for free.

Peter

Re: Bed Treatment for PLA

Great info guys.

My background is CNC machining, I can tram a full sized 2.5 ton bridgeport mill, I'm sure I can level a bed on a 3d printer. Tramming is where you use a dial indicator mounted on the spindle to ensure the Z axis is perfectly aligned to your table in the X-Y axis. This is using a accuracy of ten-thousands.... or .000x inches.

What I am referring to is the start sequence in some of the prints that were packaged with the printer. I called it a wipe. Basically the printer prints a "stripe" down the left side of the bed before going on to print the g-code file. This ensures that the nozzle is primed.

I have noticed that sometimes the printer doesn't print for the first 10 to 15 seconds. I have gotten into the habit of pre-heating the printer and leaving it for 10 to 15 minutes. This allows the glass to come to thermal equilibrium.

I've also pre-heated the printer on HIPS to bring the bed up to 100 degrees before switching to PLA for the actual print. The thinking is that this makes the plastic more pliable for the first layer and helps it stick.

I have not tried blue tape.... I don't like trying to line it up. If I go down the tape route I'll find some pallet tape around the width of the glass and be done with it. Pallet tape is what screen printers use on their pallets. It's very wide masking tape that can take heat and still come off.

Re: Bed Treatment for PLA

Brian

I think you mean 10-thousandths on an inch...

You don't need a bed temperature of 100 degrees for PLA. I print fine on glass at 45 degrees (my slicer default setting), 50 for most object s and occasionally (when I remember) 55 degrees for larger items.

When you leave the nozzle hot for so long the material will ooze and empty the chamber, so what you have described is quite normal. However, you also have to be careful that you don't leave the nozzle hot without printing for too long as you could burn the plastic and block the nozzle or worse, damage the PTFE tubing.

You will normally print with a skirt which is the main priming loop; the line you mention is only generated in certain slicers by default and is part of the start gcode which can be changed by the user.

Regarding tape, stick with the blue stuff, it's proven to work. And lining it up is not an issue. When the bed is heated, the glass expands and there will be gaps between the tape, so installing it perfectly is quite pointless.

For me, using a set of feeler gauges is ideal for getting the calibration precise, although I work with modified firmware which allows me to actually zero the Z axis. After homing, I lift the Z axis by .02mm and use the feelers in the corners and centre. Once calibrated I can do maybe 20 prints before I have to do it again.

Peter