Help: First Layer

[mattkreeft 0]

Hello fellow printers,

 

Over the last 3 weeks I've been struggling trying to get the "perfect" first layer on my Ultimaker 3. The bed is absolutely level, but it's warped. The outer sides are bending downwards slightly.I've fixed that with some tape on the ends of the heated build plate, and stick the glassplate on top. Whatever I try, levelling on the go with all kinds of spiral and 20x20 calibration squares. They all come out pretty succesfully, until I start printing a bigger surface.

 

I keep getting the same results with or without the built-in active bed-levelling.

 

Print settings first layer:

• 210°C Initial Printing Temperature
• 60°C Build plate
• 25mm/s Initial layer speed

 

See images below for the results I keep getting. Any advice?

https://i.imgur.com/wUOcR8e.jpg

https://i.imgur.com/xHwyOh1.jpg

[gr5 2,229]

It's very common for tempered glass to be higher in the center.  It has to do with how tempered glass is made.  Because of the way things are leveled this usually means you get low spots in the rear two corners.

 

1) the amount of force needed to bend the glass flat is tiny.  So you could probably put some sticky tape in the middle under the glass to pull it down - something that can handle 110C.  Then put shims around the outer edge particularly in the rear two corners.  Shims could be washers for example.  Or sheets of paper.

 

Or you could bend the rear two corners of the aluminum bed up.  I did this on my printer only to later realize I could have easily broken the heater traces as they are right under that.

 

2) Or you can contact your reseller and try to get flatter glass.  I would measure your glass very carefully with a metal straight edge and tell them how bad it is.  Otherwise they could send you 5 glass beds that are all worse than what you have now.

 

3) But I don't understand what the big deal is.  Your bottom layer looks fantastic. Yes, part of it looks different but I assume you will have at least one more layer and so that "differentness" will go away after a few layers.

 

Is your part warping off the bed?  If so then there are other simpler fixes I can talk about.

 

[GregValiant 1,351]

37 minutes ago, gr5 said:

3) But I don't understand what the big deal is.  Your bottom layer looks fantastic. 

 

+1 on that.  A bit of imperfection (a TINY bit) on an area that will only see the light-of-day for about 5 minutes isn't an issue.

[geert_2 558]

Layer-thickness also plays a role: generally I found that on my UM2 a first layer of 0.1mm is too thin and gets uneven. A first layer of 0.3mm is too thick and has less contact area and is not so flat at the bottom. A first layer of 0.2mm works best: this gives a nice flat and glossy bottom. The top of that layer tends to overextrude a bit due to it being printed at lower speed and without fan, thus with a lower viscosity and higher flow (less resistance in the nozzle). And I have calibrated my nozzle a bit too close to the bed. But as said above, that first layer is followed by others, so these effects are smoothed out after a couple more layers.

 

The bottom of the bottom-layer is more important than its top, in my opinion.

 

This is what the bottom usually looks like (above = camera-focus on model, below = camera-focus on reflection in the bottom layer; I couldn't get both in-focus at the same time):

 

Another one:

 

Small item printed very slow:

 

[jaylab 0]

I have been getting prints like your first photo so now I will pay particular attention to getting my 1st layer correct.

I was thinking if I increased the number of bottom layers that this might solve the problem you depict in your 1st photo, but my results are still poor with a layer thickness of 0,3mm. Thanks for the tip on going to 0,2mm!

 

-Jay-