Brim line partialy loose after a couple of lines (PLA)

[paburk 0]

Hello!

 

I got my first printer a couple of days ago and since then I'm printing my FreeCAD models with great enthusiasm.

 

When I started to use brims as support, I noticed a strange problem which I'm not able to solve yet.

 

The PLA brim gets printed nicely and sticks to the layer well. After a couple of brim lines, the line sticks still well to the bed, but then suddenly it comes loose on a section of maybe 5 to 10mm (depending on the part size). When the head passes the loose section again, the new line presses everything back on the bed. But just after 2 to 3 seconds it comes loose again on this section.

 

I tried to re level the bed many times and also experimented with slightly higher bed temperature and also played with the speed. Nothing improves it, it just get worse.

 

For me it seems as if the PLA tends to expand when it is cooled down and then there is not enough room for the material and it expands to the Z axis.

 

Maybe this is a common problem and someone could help me with a tip in this regard?

 

Best Regards

Patrik

 

 

 

 

 

 

Edited February 22 by paburk

[Brulti 167]

Did you make sure that the bed is properly cleaned? I'm currently printing many small parts with PLA and using brim, and there's no adhesion problem as long as the bed is properly cleaned.

[paburk 0]

Hi Brulti, thank you. It seems so - It looks optical clean and I also cleaned it with Isopropyl alcohol.

 

Can I ask you how you calibrate your table? Do you use the Ultimaker calibration card (0.15mm) or do you use a 0.1mm paper? I still suspect that the calibration is off.

[gr5 1,256]

I either use my eye or the calibration card.  But then more importantly when it's printing the brim or skirt I adjust the 3 screws to get the right look to the brim.  I talk about this technique in this video with photo samples of "too squished" and "not squished enough" in the "squish" section but all sections of the video are very important to understand.

 

 

[paburk 0]

Many thanks for this video!

 

I re-cleanded the glass plate again with isopropyl alcohol, wiped the alcohol and printed.

 

The brim came loose on all borders very quickly. I then wiped the plate with water and soft paper. And from then on the brim sticks perfectly for the last 6 prints.

[geert_2 331]

For PLA, try wiping the glass with salt water and paper. For me this gives very good bonding when the glass is hot (ca. 60°C), but no bonding at all when cooled down to room temp.

 

Also, make sure the first layer is squeezed well into the glass: the bottom surface should be flat and shiny, like this. This PLA-surface reflects almost like a mirror (the bottom pic shows the cover and fan blades of a fan behind the model, the top pic shows the model itself. It is the same model, but I couldn't get both in-focus at the same time).

 

 

[paburk 0]

We have quite a lot calcium carbonate in our tap water. I assume this makes a very well bonding. I will for sure also check out salt water. It seems that minerals in the water make the solution (haha) and alcohol makes a too clean surface.

[Brulti 167]

On 2/22/2019 at 5:58 PM, paburk said:

Can I ask you how you calibrate your table? Do you use the Ultimaker calibration card (0.15mm) or do you use a 0.1mm paper? I still suspect that the calibration is off.

 

I was using the calibration card, but I often had to adjust it as @gr5 advises. Now, I'm using a metallic calibration plate. I never intended to buy it, it was a misclick when buying stuff on the site, and I didn't check once I was done. But, I found it to be quite more precise than the calibration card, and I did not had to adjust the screws so far after using this to calibrate my bed.

 

Also, for cleaning the glass bed, I would advise to sue the yellow window cleaner from Karcher,

That's what I'm using and it works wonder, even to dissolve remnants from PVA after a print or glue from a stick.