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changedsoul

Help with getting correct first layer

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A Picture is worth a thousand words. I just dont know what this is telling me. I am still new to 3d printing, and I dont speak this pictures language.

I am trying to get a good first layer, but I always see this when creating a brim or skirt with more than a few lines. The first few lay down good, then the rest start to bubble and peal uo from the table like in the pic.

Can someone help me diagnose this? I have calibrated my table as best I can, I have calibrated the extruder. Temp is yet to be dialed in, but its close to normal for PLA, around 190, Bed is at 65. Printing on glass, cleaned with alcohol.

I always see this garbage, and it bugs me. Once I get past this first layer, it prints relatively good.

image1.thumb.JPG.9a80bc4dd019e6abdd0f947471564358.JPG

image1.thumb.JPG.9a80bc4dd019e6abdd0f947471564358.JPG

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I Noticed my nozzle tip was slightly off level. I must have damaged it when hacking on it a while back. I got a nice new flat one and its printing like a dream. First layer is flawless! I had no idea such a small defect could cause so many problems. Wish I had a pic to show, I tossed it already, but it wasn't that far off.

If you brought the tip to Z0, and looked at the gap between the tip and table, you could see about a .003 gap. Sure is not much, but it made a big problem.

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Ok, Im back at it. I thought I had it, but something else came up, and I realized I didnt have it.

Im having trouble understanding just what should be happening on a first layer and I am hoping someone here can help clear it up, and maybe steer me in the right direction to nail this first layer.

In Cura, I have set .25mm layer height, .25mm layer First layer height, and wall thickness at .4mm.

So what I did was laid down a single line on the table and stopped the print.

If I am understanding this correctly, this single line should be .25mm thick(in Z height), and .4mm thick spread out on the table....correct?

Since I have to wait for a response, I am going to assume it is correct. What I really have though is .25mm thick(in Z Height), and 1.245mm thick spread out on the table.

I have checked my extruder. I fed out 6" of filament, and I was only off .4% over 6", so I know its not perfect, but its pretty close. I dont think I am over extruding by a bad steps/mm setting.

What else am I missing?

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Is there a reason you changed the default initial layer height of 0.3mm? Top/Bottom Line Width should also be set at 0.4mm, so you might want to check that.

I believe the reason the default initial layer is so thick is to make it less sensitive to bed leveling. A thicker initial layer can absorb a varying gap between the bed and nozzle a bit better.

Also check the feed rate on your printer and make sure it's set to 100%, not something higher. But otherwise I think you are correct in your assumption about what to expect from that single line laid down on the printer bed.

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What printer are you using, with what firmware?

If What does the printer do right before printing this first line? Did it prime?

If you print the biggest object that your buildplate can fit, the brim will be big as well. That enables you to see if the line width normalizes within say, 20 seconds, or that it keeps being too wide. In the first case, it is a startup issue, in the latter case there is some error in the extrusion rate.

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What does it do when you print a square plate of let's say 30mm x 30mm x 1mm, 100% infill? Without brim. Does the infill come out well, or also weird?

And in your photo, is that overextrusion (too much material), or is it the material curling up due to poor bonding to the glass, and thus giving a different reflection? This is hard to see in the photo, but it should be clear if you remove the print and inspect its bottom.

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What printer are you using, with what firmware?

Its a custom build running marlin.

The printer does prime before it prints.

Looking into this issue more, I find I have something very wrong and I dont know what it is. I began thinking it was a first layer issue, because I was only focusing on that.

Keep in mind this printer has been printing well for a while, so something just happened and I cant figure it out.

 

What does it do when you print a square plate of let's say 30mm x 30mm x 1mm, 100% infill?

I printed a cube with zero infill, single wall to test the wall thickness. This too was WAY over sized. I had to decrease the flow rate to 33% just to get an expected flow rate. Thats obviously not normal. I have double checked my steps/mm, and it is almost spot on, I tell it to extrude 120mm, and 120mm gets feed, so I know the steps/mm are correct.

I just cant figure this out.

 

And in your photo, is that overextrusion (too much material), or is it the material curling up due to poor bonding to the glass,

That problem is gone. I thought it came back and thats why I posted again here, but what is going on now I think is a new issue, more severe.

I thought maybe Cura got some parameter stuck, so I installed the beta 2.6beta and it does it with that too.

I am using a .4mm Nozzle, and 1.75mm filament. The values are set in the printer setup. The steps/mm are set in firmware and it does extrude what I tell it. The wall thicknesses are supposed to be .4mm, but are coming out 1.1mm abouts. Something is severely over extruding.

Could it be a software bug? Some setting somewhere behind the scenes that is stuck at a large value causing over extrusion?

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Well, it was a software bug. I dont know what it was, or how to reproduce it, but when I installed 2.6beta, it took my previous profiles from the other install of cura 2.5. I giess what ever was messed up in 2.5 carried over into 2.6beta. I dont know where 2.5 files are stored, but 2.6 places them in appdata. So I removed all other curas, deleted the cura folder in appdata and started 2.6beta allowing it to create a fresh profile.

Ran the same test cube and all is fine.

How bizarre.

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.....Ran the same test cube and all is fine.

How bizarre.

Not really. Anything can corrupt a computer file in a way that is unusable in some glitchy way, but can still be opened and appear fine. I have seen this a gazillion times throughout my career.

Since you basically started from scratch (cleaned out old files etc), I would assume that it was a tiny corruption in the file and not in the program itself.

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To finish off this topic, that first picture I posted i belive was indeed because my nozzle was to close. I measured the thickness after the brim finished, so I was getting an erroneous reading by measuring over all the bunched up material.

By laying down one single line, I found I was actually layding down a layer closer to .006" and not .0116", so after I adjusted it, that issue went away.

This had nothing to do with this last "OVER" extrusion problem I had though.

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