Zebra Plate

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minusbacon
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Re: Zebra Plate

Post by minusbacon » Wed Sep 30, 2015 3:43 pm

I was thinking about starting a new topic but I figured since my issues have to do with the zebra plate I'll post it here. I apologize for the length of this, but I'm going to explain in detail exactly what I did last night...

Monday night I heated the plate to 70c, removed it from the bed, placed it on a flat surface with heavy books on it (larger than the plate), and let it sit overnight.

All four corners have been clipped-- two in back, two in front.

I heated the nozzle and plate to 250/70 figuring that would be the max temp I'll possibly print at and based on Jules (or maybe someone else's recommendation) to heat the nozzle and bed to PETG temps for z-stop calibration and bed leveling. Calibrated the Z-stop using the center of the bed. Used a .15mm feeler gauge and adjusted it until I felt some resistance and could easily slide it between the nozzle and the bed. Moved the nozzle to the right and left sides (from center) but when I got to half the distance of center to either edge the nozzle was touching the bed. Couldn't fit the feeler gauge at all. Decided to try leveling the front and back, which I did. Feeler gauge on both felt just like it did in the center of the bed. Tried the left and right sides again but it was the same as before.

Let zebra cool a bit. Removed it and gently bent it the opposite way on the X axis only. Placed it back on bed and replaced the clips in all four corners on the front and back.

Reheated plate to 250/70. Calibrated z-stop. This time leveling on the x axis was much better. I was able to level the bed on the X axis but the feeler gauge was noticeably tighter than it was in the center. No big deal, at least I'm making progress. Then I level the front and back so they're even with the feeler gauge. I go back through to check the gap on the center, left, right, front, and back. Now the feeler gauge is WAY too tight in the center. It fits but it's VERY snug.

I'm gave up for the night at this point. Now I have to adjust the z-stop in the center of the bed, which is just going to throw off all the leveling points. Again. I know I'm not going to get it perfect, BUT I can't even find a happy medium. A point where I get at least SOME contact with the feeler gauge at all points.

The zebra plate seems very inconsistent in flatness. Even if I bend it, it eventually goes back to it's old form especially when heated. I can only imagine how much the z-stop and leveling will be thrown off when the plate is removed and twisted a bit to remove a print.

I don't know what else to do here. I know fine tuning is done with offsets and other settings in Simplify3D, but I know the z-stop and bed level have to be set right in order to get good prints. I spent four hours last night trying to get the hardware calibrated and I've gotten nowhere. Please tell me what I'm doing wrong. Anything else I can do to get this right or make it easier? I'm doing everything as described in Jules and other's write ups. I admit, I'm meticulous when it comes to stuff like this-- I like things as perfect as I can get them. But tonight I wasn't going for perfect, I'm just trying to get as close to even as recommended but I'm nowhere near close.

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Tim
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Re: Zebra Plate

Post by Tim » Wed Sep 30, 2015 8:52 pm

minusbacon wrote:I don't know what else to do here. I know fine tuning is done with offsets and other settings in Simplify3D, but I know the z-stop and bed level have to be set right in order to get good prints.
This is only true to an extent; there's a tradeoff between "set right" and "good prints"; possibly you're just setting an unusally strict standard for flatness and leveling that is not obtainable with the Zebra plate. In particular, if you're printing something that isn't taking up the whole plate, then only worry about the flatness in the area that's being printed. If you're printing something that does take up the whole plate, then maybe you should go back to glass and hairspray, or whatever was your favorite method, for that print.

I got the Zebra plate as part of playing around with the Z-probe, and since the whole point of the Z-probe is that it compensates for lack of flatness, I wasn't concerned with it; in fact, the more warped my Zebra plate is, the easier it is for me to see if the surface level compensation is working right. Ultimately, I think 3D printer designs will end up gravitating toward this combination of a lightweight, flexible bed plate plus a Z-probe for compensating the lack of flatness you get with a flexible bed plate. I think this will end up as the standard because glass is too fragile and requires prep work, and MIC6 is expensive and heavy. If you're really picky about absolute flatness, the MIC6 plate is the best (and probably only decent) solution. The Zebra plate is really convenient, but you have to be willing to put up with a bit of imperfection.

minusbacon
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Re: Zebra Plate

Post by minusbacon » Thu Oct 01, 2015 2:51 am

I'm not necessarily concerned about flatness, I'm concerned about not being able to find that happy medium where I can at least get the feeler gauge to fit between the nozzle and the bed on all sides. I don't care if they're all not perfect, I just don't want there to be an area where the nozzle is rubbing against the plate when it's printing.

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Tim
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Re: Zebra Plate

Post by Tim » Thu Oct 01, 2015 1:20 pm

minusbacon wrote:I'm not necessarily concerned about flatness, I'm concerned about not being able to find that happy medium where I can at least get the feeler gauge to fit between the nozzle and the bed on all sides. I don't care if they're all not perfect, I just don't want there to be an area where the nozzle is rubbing against the plate when it's printing.
I haven't had any particular problems with the Zebra being so non-flat that it isn't within the usual tolerance I need for a print to stick reliably, but then I haven't been using the Zebra for very long, and the number of prints I've made on it number in the dozens, not hundreds. I also have been continuing to use my former method of getting parts off of the bed with a razor blade, so I don't purposefully flex the plate unless a print is being very stubborn about coming off (which has happened only once).

minusbacon
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Re: Zebra Plate

Post by minusbacon » Thu Oct 01, 2015 3:36 pm

Tim wrote:
minusbacon wrote:I'm not necessarily concerned about flatness, I'm concerned about not being able to find that happy medium where I can at least get the feeler gauge to fit between the nozzle and the bed on all sides. I don't care if they're all not perfect, I just don't want there to be an area where the nozzle is rubbing against the plate when it's printing.
I haven't had any particular problems with the Zebra being so non-flat that it isn't within the usual tolerance I need for a print to stick reliably, but then I haven't been using the Zebra for very long, and the number of prints I've made on it number in the dozens, not hundreds. I also have been continuing to use my former method of getting parts off of the bed with a razor blade, so I don't purposefully flex the plate unless a print is being very stubborn about coming off (which has happened only once).
I've had mine about a week now and I've also only printed about 12-20 prints on it since. I've been using the same method as you-- if I can't gently twist off the print after the bed cools I tap it gently with a flexible putty knife and it pops off. I had a print on Sunday that I lightly twisted (the print, not the plate) and it popped off. When I tried printing something after that, I noticed the skirt and first layer were incredibly flat/smooshed, much more than normal. That's when this whole resetting the z-stop and leveling the bed nightmare started for me.

Last night I leveled it the best I possibly could. Z-stop was good, front and back level was good, left and right sides were still tight with the feeler gauge but I balanced that out as much as I could. Printed a calibration cube to calibrate Z offset and extrusion multiplier. When I measured all four sides of the cube vertically so I could set the Z offset, each side was way off. Measurements were something like 1.97mm, 1.95mm, 2.01mm, and 2.05mm. Before the issues on Sunday, I NEVER had measurements like this. They were always within 0.01mm of each other in the same direction. I don't even know how to set the Z offset with those measurements.

I double checked my zebra plate flatness by spinning it on a flat surface. Both sides spun equally, so it seems flat.

When you guys went from the glass plate to the zebra, did you recalibrate your z-stop only or did you re-level the bed as well? I'm thinking about going back to the glass plate, resetting z-stop, re-leveling, and printing a few things to make sure everything is working well. Once I'm able to calibrate the z offset and extrusion multiplier like I used to, then I'll switch back to the zebra plate and recalibrate the z-offset and leave the bed level ALONE.

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ednisley
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Re: Zebra Plate

Post by ednisley » Thu Oct 01, 2015 4:26 pm

minusbacon wrote:I'm not necessarily concerned about flatness
You desperately care about flatness, because (IMO) that's the root of all the problems you've described in various threads.

rant ON

The initial nozzle-to-platform space that produces the first layer determines pretty nearly everything about the success of the printing session. For a 0.20 mm layer thickness, the filament won't reliably stick to the platform when the gap exceeds 0.30 mm and won't extrude properly below 0.10 mm. In order to get good results, I've found the tolerance must be ±0.05 mm around the nominal 0.20 mm.

If your Zebra plate is warped / non-flat / wedge-shaped to the extent that the nozzle has the proper clearance here and negative clearance there, then it's just not ever going to work. You can screw around with it all you like, but the extruder just can't deposit plastic the way it must without a uniform gap to the platform (or previous layer).

The original MakerGear borosilicate plate is about as good as you can get for flatness (unless you got a defective plate, which is possible), but plastic doesn't stick well to bare glass (at least in the long run). Aluminum plate can be slightly flatter, but adds an absurd amount of weight and (may) still require various adhesives.

IMO, the tight tolerances rule out any bendy surface, because there's no way to uniformly eliminate the air gap between the sheet and the heater: clamps around the edges tend to bow it upward in the middle. Folks around here definitely get good results from Zebra plates, but it seems to require a bit of fiddling; none of that guarantees you will instantly get good (or even passable) results.

rant OFF

If you want, we can work through the (admittedly tedious) process I used to verify the platform alignment and initial gap before going to the direct platform sensing switch; it's better handled by email than here on the forum. Basically, there's a lot of careful measurement and gentle adjustment, followed by plenty of thinwall boxes, with the end result that the M2 Just Works: turn it on and it prints with no drama.

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Tim
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Re: Zebra Plate

Post by Tim » Thu Oct 01, 2015 4:46 pm

minusbacon wrote:When you guys went from the glass plate to the zebra, did you recalibrate your z-stop only or did you re-level the bed as well?
Oddly, I find that people seem to be fearful of a complete re-leveling. Personally, I always found the bolt on the side difficult to get to and adjust, and I just always do a full re-leveling whenever I find that the height adjustment is off. It rarely takes me more than a minute or two to adjust, which is negligible compared to printing time. But the short answer is yes, I re-leveled the bed after putting on the Zebra plate.
ednisley wrote:The original MakerGear borosilicate plate is about as good as you can get for flatness (unless you got a defective plate, which is possible), but plastic doesn't stick well to bare glass (at least in the long run).
I've always wondered why that should be, but it seems to be a universal effect: print a dozen prints or so on bare glass, and they stop sticking. Presumably new glass is cleaner than glass that has been printed on for a while, and there must be some kind of residue building up that's really hard to get off. Matt Sharkey swears by printing on bare glass, so I'd like to know what he does to clean the glass, because whatever he's doing to clean off the glass must be getting it back to a near-pristine state. Could it be the hardness of the water you clean the glass with? Would a rub-down with vinegar instead of alcohol work better?

swbluto
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Re: Zebra Plate

Post by swbluto » Thu Oct 01, 2015 5:45 pm

Tim wrote:
minusbacon wrote:When you guys went from the glass plate to the zebra, did you recalibrate your z-stop only or did you re-level the bed as well?
Oddly, I find that people seem to be fearful of a complete re-leveling. Personally, I always found the bolt on the side difficult to get to and adjust, and I just always do a full re-leveling whenever I find that the height adjustment is off. It rarely takes me more than a minute or two to adjust, which is negligible compared to printing time. But the short answer is yes, I re-leveled the bed after putting on the Zebra plate.
ednisley wrote:The original MakerGear borosilicate plate is about as good as you can get for flatness (unless you got a defective plate, which is possible), but plastic doesn't stick well to bare glass (at least in the long run).
I've always wondered why that should be, but it seems to be a universal effect: print a dozen prints or so on bare glass, and they stop sticking. Presumably new glass is cleaner than glass that has been printed on for a while, and there must be some kind of residue building up that's really hard to get off. Matt Sharkey swears by printing on bare glass, so I'd like to know what he does to clean the glass, because whatever he's doing to clean off the glass must be getting it back to a near-pristine state. Could it be the hardness of the water you clean the glass with? Would a rub-down with vinegar instead of alcohol work better?
Here's what I do. Part finishes printing w/ the bed at 110, I push down the plate with one hand and pull the object off with the other with tremendous force. Dampen a cotton ball with 70% isopropyl alcohol and wipe down the plate in repeated QUICK one-direction wipes along the entire width of the plate (Quick wipes to avoid burning). Then I take a damp potato sack cloth and, with pressure, clean it with tiny circles to remove the alchohol residue (Alcohol residue will destroy adhesion). I then dry it with a dry potato sack cloth in one direction to remove any existing moisture (Not that there should be any at this point with the >100c plate.) and create a uniform sheen to the surface so that it provides a nice, glassy spot free bottom layer. I've printed over 100 times on a glass plate with this method and it works perfectly every time. Also allows one to get back to printing within <3 minutes.

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Jules
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Re: Zebra Plate

Post by Jules » Thu Oct 01, 2015 6:44 pm

swbluto wrote: Here's what I do. Part finishes printing w/ the bed at 110, I push down the plate with one hand and pull the object off with the other with tremendous force. ......
:lol: And that doesn't deform the print? (i'm impressed, i think) I probably lack the upper body strength to use that method though. Some of those things won't come off with a blowtorch. :lol:

swbluto
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Re: Zebra Plate

Post by swbluto » Thu Oct 01, 2015 6:56 pm

Jules wrote:
swbluto wrote: Here's what I do. Part finishes printing w/ the bed at 110, I push down the plate with one hand and pull the object off with the other with tremendous force. ......
:lol: And that doesn't deform the print? (i'm impressed, i think) I probably lack the upper body strength to use that method though. Some of those things won't come off with a blowtorch. :lol:
Lol, it depends on the print's design. If it has too much area touching the bottom, it's nigh well impossible to pull off. If it's rigid design will little area on the bottom, easy to pull off immediately. If it's a 'flimsy design'(You know it when you see it), then I usually wait until it cools to 90degrees before forcefully yanking it off to minimize deforming.

'Tis true, I can do 56 pushups. Thank god for navy training! lol.

Also, my prints are ABS on pure glass, so it's probably a bit easier than other combinations.

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