SoliForum - 3D Printing Community — Position-dependent curl? Preparation or temperature?

Re: Position-dependent curl? Preparation or temperature?

null@example.com (wardjr) — Sun, 08 Mar 2015 21:07:08 +0000

It is mostly documented here and there but no particular write up. Due to the nature and hazards of a setup like mine I prefer to leave it to those with the expertise to truly understand all that is involved. If you don't understand all aspects involved I would not recommend this mod.
That being said DIYengineer also went with this setup if you search his posts you'll find all the info you need or you can send me a PM.

Re: Position-dependent curl? Preparation or temperature?

null@example.com (w_smith) — Sun, 08 Mar 2015 21:00:36 +0000

So do you have a writeup on your SSR/500W AC Heated Glass Bed? Parts list?

Thanks!

Re: Position-dependent curl? Preparation or temperature?

null@example.com (wardjr) — Sun, 08 Mar 2015 20:57:45 +0000

It is more likely you are at the limitation of the PSU. although the bed heater isn't exactly overpowerfull either.

Re: Position-dependent curl? Preparation or temperature?

null@example.com (w_smith) — Sun, 08 Mar 2015 20:54:03 +0000

I was unable to get my glass bed higher than about 92.7C, is it possible the stock heater just doesn't have enough power, or am I running into some firmware limitation that won't let me set the target bed temperature to 145C? The terminal says the printer accepted the setting, but the temperature never got any higher...

Thanks!

Re: Position-dependent curl? Preparation or temperature?

null@example.com (wardjr) — Sun, 08 Mar 2015 14:43:46 +0000

I can print out to the edge but look at my signature. You can as well it is just certain parts that will lift near the edge. Printing with a brim will help with those tricky ones.

Re: Position-dependent curl? Preparation or temperature?

null@example.com (w_smith) — Sun, 08 Mar 2015 13:32:31 +0000

jagowilson wrote:

wardjr wrote:
You will get very inaccurate readings from an IR thermometer on glass. I can tell you the stock bed heater temps fall off rather quickly out near the edge. So you may just have to work around that or upgrade to a better heater.
+1, the stock heater really won't let you fill the bed like that unfortunately... The temperature gradient is pretty severe. User TickTock (and previously Adrian I think) showed the stock heater has outer temps around 80c when the temp is set to 105. In other words, warp nation. I'm still using the stock heater and my solution is to print only a couple things at a time and try to keep them as close to the center as possible.

So is there a "good" 8x8 bed heater solution? I read http://www.soliforum.com/topic/9004/sd4 … tallation/ but that seemed inconclusive without a complete rebuild using parts of unknown origin...

Or do we just accept that it looks like an 8x8 bed, but it's really a 4x4 bed?

And what's with IR thermometers? Apparently glass has an emissivity of 0.95, which ought to be pretty good. Maybe the hairspray throws it off?

I'm characterizing my bed with a thermocouple this morning...

Re: Position-dependent curl? Preparation or temperature?

null@example.com (jagowilson) — Sat, 07 Mar 2015 18:29:17 +0000

wardjr wrote:

You will get very inaccurate readings from an IR thermometer on glass. I can tell you the stock bed heater temps fall off rather quickly out near the edge. So you may just have to work around that or upgrade to a better heater.

+1, the stock heater really won't let you fill the bed like that unfortunately... The temperature gradient is pretty severe. User TickTock (and previously Adrian I think) showed the stock heater has outer temps around 80c when the temp is set to 105. In other words, warp nation. I'm still using the stock heater and my solution is to print only a couple things at a time and try to keep them as close to the center as possible.

Re: Position-dependent curl? Preparation or temperature?

null@example.com (wardjr) — Sat, 07 Mar 2015 17:54:50 +0000

You will get very inaccurate readings from an IR thermometer on glass. I can tell you the stock bed heater temps fall off rather quickly out near the edge. So you may just have to work around that or upgrade to a better heater.

Re: Position-dependent curl? Preparation or temperature?

null@example.com (w_smith) — Sat, 07 Mar 2015 17:38:59 +0000

In this video you can see the part peel up just before I cancelled it. The latest print with liberal application of hairspray stuck better initially, but is still peeling up.

Re: Position-dependent curl? Preparation or temperature?

null@example.com (w_smith) — Sat, 07 Mar 2015 17:35:22 +0000

OK, so it's almost certainly that my bed temperature dropped a lot when I put the glass on it, when this print finishes (or fails, sigh) I'm going to calibrate it properly with a thermocouple and my IR thermometer.

I stuck the thermocouple between the heater and the aluminum bed plate and it was reading right around 100C, which is where it was set.

My IR thermometer says the glass is 82-83 on the edges and 86-89 in the center, so I'm probably cool by 10-15 degrees, would that be enough to make nearly every part peel up?

OctoPi/Octoprint has a temperature offset, does anyone know if I want to set it higher (desired offset is higher) or lower (measured temperature is lower than actual)? Of course I can/will fiddle with it and try to get an even temperature across the bed.

Bleah!

Re: Position-dependent curl? Preparation or temperature?

null@example.com (wardjr) — Sat, 07 Mar 2015 14:31:49 +0000

If your printing ABS you should have your bed in the 100-110 range.

Re: Position-dependent curl? Preparation or temperature?

null@example.com (w_smith) — Sat, 07 Mar 2015 11:19:39 +0000

This is very strange, if I print _one_ part it (usually) doesn't curl, but if I print multiple parts some of them always curl.

Do I need to calibrate my bed temperature now that I've got a sheet of glass on it? When I set it to 60C for drying the hairspray it wasn't too hot to touch, and I've always calibrated 50C as too hot to touch....

Could this problem be caused by too low a bed temperature?

Thanks!

Re: Position-dependent curl? Preparation or temperature?

null@example.com (w_smith) — Tue, 03 Mar 2015 12:45:31 +0000

Oh, man, why didn't you guys tell me about glass and hairspray earlier? 8*) I stopped by a glass store, got a (free!) 8x8 piece of 1/4" glass, found some Aquanet Extra Super Hold at the grocery store, (removed the Kapton from my bed), and produced a part that actually stuck to the bed! And popped right off when cool this morning.

"It's times like this I wish I had listened to what my mother told me!"
"Why, what did she say?"
"I don't know, I wasn't listening!"

Now to print the parts I need to fix my printer, then do a full calibration and setup, then print the full set of Lawsy carriages so I can convert to the E3D head, then recalibrate, and then reprint all the plastic parts of my printer! Oh, then I can use it for printing stuff. 8*}

Anyway, thanks again for the assistance!

Re: Position-dependent curl? Preparation or temperature?

null@example.com (wardjr) — Sun, 01 Mar 2015 17:09:24 +0000

You don't need that much hairspray just a fine mist. If it bothers you remove the glass when you spray it. Also use the hairspray liberally on the bottom of the glass then place it on your bed. Heat/cool a few times and it will stick yet still be removable. I promise you will wish you had done this sooner and you don't need to reapply every time you print.

Position-dependent curl? Preparation or temperature?

null@example.com (w_smith) — Sun, 01 Mar 2015 16:23:11 +0000

So I just printed off the bed stabilizer (see other thread) and some of the parts are fine while others didn't stick as well. They worked OK, but I'd like to solve the problem before I try to print something important, like new carriages...

I cleaned the bed with acetone and lightly scuffed it up with a sanding sponge, so it ought to be consistent.

How do I know if the temperature across the bed is reasonably close (and how much variation is too much?) I've got a thermocouple I could use to characterize the bed, but I'd have to open the door (or the top) which would probably throw my measurements off.

I've read all the threads on hairspray, and could give that a try (and a glass bed) but I'm nervous about spraying something sticky around the inside of my printer in case the buildup gums something up in the future.

Thanks for any hints!