PLA not sticking to glass

It seems like every other day I have a wunderbar moment where everything is sticking to the bed perfectly. I'll be thinking, oh, great! finally I fixed it, the settings are perfect. Then, I'll print maybe 3 or 4 things, everything will be perfect, and then after that nothing will stick anymore. Right now I'm deep into a yin phase--nothing has been sticking to the bed for about 24h. It'll put down a strand, and most of it will be attached to the bed, but any part that isn't totally adhered will get caught by the nozzle on the next loop. Sometimes it'll make it to the second layer, but often it ends up as a big ball of goop on the nozzle. It isn't always like this, maybe like 40% of my prints stick, and 20% are perfect, but it used to be much better, I used to not have much of a problem with sticking to the glass, so I think that maybe my glass is accumulating gunk or something. I just wiped it down with acetone then isopropyl alcohol, so hopefully that'll help.

Does anyone have any tips for getting PLA to stick to the glass, or tips for cleaning the glass aside from razorblades and alcohol? Also I'm laying down the first layer 1mm wide, .35 high, at 220C, 24mm/s.

Just cleaned the bed really well and am going to try to change to .5mm wide and 20mm/s for the first layer. But, even if this works I'm not confident that it'll consistently continue to work, as it never has yet.

I'm finding that corners on the base are especially problematic. Right now I'm printing this [www.thingiverse.com] with a brim of 5cm, and extra PLA accumulates on the corners which seems to be causing problems

To print PLA direct on glass, this is my experience:

1. Don't clean the glass with acetone, isopropanol or any other organic solvent. Instead, wash it in hot soapy water. Then avoid touching the printing surface with your fingers.

2. Prime the surface before each print by wiping it with distilled malt vinegar. Ordinary vinegar is OK too.

3. I use a bed temperature of 65C. The actual temperature on top of the glass is about 55C.

4. Use a low first layer speed, especially if the print has sharp corners.

5. Some PLA filaments just won't adhere to plain glass. For those filaments, I print on a layer of diluted solvent pipe cement instead.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Word, I'll try all this out.

What is a 'low first layer speed'?

And do you know anything about bed insulation or lids so that they can heat up faster and stay hotter?

Does it matter what type of pipe cement? I assume that if I go looking for some the easiest to find will be PVC cement.

Awesome, working way better on this first print. Here are the changes:

> cleaned it with warm soapy water while wearing new disposable latex gloves
> disabled the fan for the hot end on the first layer, which allowed the bed to get up to 70C pretty easily, I've never been able to easily get it past 60C.
> wiped the bed off with distilled white vinegar after the bed was hot, a few minutes before starting the print.
> first layer speed is 15mm/s, but the thing I'm printing is round - no sharp corners to make things difficult.

Add.:

The print finished, the first layer went down perfectly, and it was difficult to separate from the glass with a razor blade after cooling completely.

Edited 1 time(s). Last edit at 03/04/2015 11:32AM by kre8.

A few suggestions:

1. DO NOT disable the hot end fan. It is needed to keep the top end of the nozzle assembly cool.

2. Use a sheet of thick corrugated cardboard or cork to insulate under the bed.

3. If the bed won't go higher than about 60C then something is wrong. Have you measured the voltage across the heated bed terminals? Check that the firmware is set to use bang-bang control and not PID (you only need PID for the heated bed if it is has very powerful heater that causes the temperature to overshoot significantly), otherwise there may be a PWM limit kicking in.

4. Most prints will fall off the glass once it is has cooled to room temperature. For the ones that don't (typically prints with a large base), put the glass + print in the freezer for ten minutes or so. I have several glass beds so that I can start a new print while waiting for the old one to cool and release.

5. Regarding first layer speed, I have slic3r set to print perimeters generally at 30mm/sec, small perimeters at 10mm/sec, all multiplied by 70% for external perimeters, and further multiplied by 50% for the first layer. But these settings are probably more conservative than necessary.

6. Make a note of where you got that filament from! Many PLA filaments will not stick to glass in my experience. I am in the UK and find filament from Galactic Warehouse (aka eBay trader latest-bidder) can be printed direct on glass reliably.

7. The solvent pipe cement I use is Marley KS10, but the actual brand is unlikely to be critical. I used to apply it neat, but now I dilute it with several parts acetone to make it go further and easier to spread. PVA glue stick works quite well too. Othr people use super-hold hairspray, but I haven't tried that.

Edited 2 time(s). Last edit at 03/04/2015 01:02PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Try a thin layer of school glue stick (Elmer's, UHU) on clean glass. Usually works for several prints and cleans off with water.

Cold glass bed with PVA glue, in two thin layers should do the trick. I'm using my printer this way for about 5 months...

I get to 65C in 15mins, 70C in 20mins. I can probably get hotter, I just don't want to wait that long. Does that sound like a regular time to heat up? My friend said it takes him an hour to get his to 70C, although it's in a cold room.

Good idea to have a second sheet of glass, that'd significantly speed up my production.

First layer speed of 15mm/s is working perfect still.

Can I do any damage to the end barrel by letting it overheat? or will it just mess up the PLA inside and jam the hotend?

Quote
kre8
Can I do any damage to the end barrel by letting it overheat? or will it just mess up the PLA inside and jam the hotend?

In a word - yes.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].