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paulsroom

levelling error?

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I wanted to use the new Breakaway support material and also start dual colour printing - which I have not yet done.  So I have had to change print core 2 from BB to AA.  This seemed like an easy operation and it slotted in okay, but then of course I needed to re-level the print bed for the new arrangement.  Well as you can see from the attached print, this hasn't worked properly.  What's happening is that at some positions on the first layer, it is not sticking to the bed.  As a consequence the nozzle grabs this loose string on its next path and simply destroys the print before it gets going.  This happens with or without the glue stick applied.

I am assuming that I need to re-level again.  I did follow the instructions very carefully, so I can't see what I may do differently.  Does this result suggest an unlevelled bed or or something else? 

I've shown what the print should like as displayed in Cura

 

bird-outline.jpg

cura-bird.jpg

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I do not see lines getting thinner or more transparent. To mine creaky eyes, this looks like the plate was not quite clean in those spots. It does not take much to pollute the surface of the buildplate. I am super anal about my buildplate cleanliness with great care to create as clean a surface as possible. But all it takes is one random touch to make it pick up oils from the hands. A simple gesture such as brushing off a bit of schmutz on the glass can do it.

 

I always clean my glasses with a grease cutting dish soap and then rinse the heck out of it until I can hear the glass squeaking under my fingers. The soap degreases me wee baby hands as well.

 

When the glass goes down on the platform, I only handle the very edges and then do a very thorough wipedown with isopropyl alcohol. I always try to get 99% pure when I can. It is not always in stock locally. But, the more pure, the better.

 

For most adhesion issues, I then brush on a layer of recycled PVA slurry I make from previous prints.

 

But, if I goof, and that does happen, my prints will look just like what you showed in your pic.

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Well before I went through the levelling procedure, I had washed the glass plates in warm soapy water and dried it thoroughly.  First with a cotton cloth and then with a microfibre clth to ensure no strands of cotton remain or areas of grease.  I also only touch the glass at the edges.  But I'm going to clean the glass again before anything else.

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55 minutes ago, paulsroom said:

Well before I went through the levelling procedure, I had washed the glass plates in warm soapy water and dried it thoroughly.  First with a cotton cloth and then with a microfibre clth to ensure no strands of cotton remain or areas of grease.  I also only touch the glass at the edges.  But I'm going to clean the glass again before anything else.

but what are you using to adhere the print to the glass with?

There are a lot of options. Hairspray, @gr5 and @geert_2 know some cool alternatives.

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Well I only use the glue stick that was supplied with the printer.  I'd have thought that hairspray was rather fierce for an adhesion method.

 

57 minutes ago, fbrc8-erin said:

This is a pretty complicated first layer shape (as shapes go). I would slow down your first layer speed by about half and see if that has any impact.

 

Yes I think that it would be an idea to slow it down and I'll probably try that.

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I happy that I have correctly levelled the print bed and that the glass is either very clean or I am applying glue. Just before the print core gets ready to print, it extrudes about a 2mm strand of extraneous filament. This hangs from the nozzle and seems to interfere with the first printed line. As this is usually the skirt or brim line, it doesn't matter, if it is then absorbed into the further lines of this type.

But then I think – I can't easily tell – when the nozzle moves to the model printing outline, it is still extruding this extraneous strand. That means that it doesn't starting printing properly until a short distance past the starting point. So there's a gap in the first printed outline. If it's capable of ignoring this and still building up layers, then this area is actually printed thinner than required. It may not pose a significant problem depending upon the model.

But the starting printed outline can result in a vertical positioning of this extraneous strand and the gap. This is where the problem is because when the nozzle comes around to do the next line, it can easily get caught up in this arrangement and drag the printed layers along with the nozzle. That's when I have to abort the print and start again. My only option, if it works, is to pause the print and snip off any vertical strands. Then resume and hope that the gap doesn't cause a problem now. It's hit or miss.

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