First few mm are messy with heated bed

[nick-foley 5]

When printing small-to-medium sized prints, I've noticed that the bottom few mm always look a little messy when using a heated bed. I was printing parts of Robert's extruder yesterday and had a pretty clear example of this... identical settings but one with the heated bed (left), one without (right):

(Roughly 205 nozzle 80 bed temp, though my bed is significantly lower in actual temp than reported temp. Ignore the upper part of the print for the left print, I was futzing around with the filament which caused some uneven extrusion.)

Any tricks to avoid this?

 

[Dim3nsioneer 557]

I wonder if covering the unused area with something thermally isolating might help.

I think the effect is caused by rising hot air from the bed slowing down the cooling of the deposited material.

What fan speed did you use? (And why does your temperature sensor show higher temperature? :blink: )

 

[jonnybischof 60]

If you're printing PLA, then 80°C bed temperature is probably simply too hot. Have you tried lowering the bed temperature?

/edit: Just read that your actual temperature is lower... But maybe it's still too high? Sometimes PLA sticks well even at only 40°C bed temperature...

I've noticed that sometimes, when you lower the bed temperature but increase nozzle temperature for the first layer, you will still get it to stick nicely. Sometimes you can also drop the bed temperature right after the first layer is complete. But that depends on the material of the heated bed.

This was quite tricky with my Basalt bed, but with my new PEI plate I can do pretty much anything and it still sticks like crazy

 

[IRobertI 520]

Make your fan(s) come on earlier. I like to start mine up at 1mm at the latest.

 

[nick-foley 5]

Fans are on from the first layer of the print. Using a crossflow fan so there is certainly a large amount of airflow.

Will try with lower bed temps I guess. May also just get a PEI platform as well... been wanting one for a while.

 

[gr5 2,173]

Yes - lower bed temp.

This is a problem I've talked about quite a bit now. It's because for smaller parts they don't have enough time to cool and so the "base" layer that you are printing onto is still too soft and the upper layer pulls it and "warps" it. Printing slower might help for the bottom 5mm or so to give it more time to cool. Above 5 or 10mm it's not a problem as the air is cooler. Fan will help also.

60C is probably good enough for you. I found that for getting parts to stick to the bed 40C to 80C seems to be all about the same but somewhere around 30 to 35C there is a sudden transition where parts don't stick as well because the plastic doesn't flow as well to make good contact.

 

[IRobertI 520]

I need to stop skimming posts... I completely missed the 80C bed last time. Lowering that temp will help a lot. Sorry about that.

 

[eldrick 65]

PLA works nicely on a 65C bed, which keeps the plastic soft, but I usually drop the temp to 55 after the first layer or two to make it a bit firmer.

For small pieces such as those, you can probably print them on a room-temp glass bed.

 

[deflaminis 0]

I've had quite a few problems with melting parts and the default settings for temp with PLA. For me, 50-55 degrees is perfect. 65-70 seems to always give me trouble.

 

[jonnybischof 60]

One more thing:

It's probably better to print the first layer with the fan OFF. Even if it's a crossflow fan. I never got anything to stick on my Basalt plate with the fan on. Proably why Cura doesn't turn the fan on on the first layer as well...

 

[medicalmodeller 5]

I am new to Ultimaker2 and 3D printing, so please go easy

I am printing out models of bones. The raft does not stick overly well to the baseplate. I only have a thin layer of glue on the heated plate. In the expert settings in Cura it is set for the fan to be off until 0.5mm. Would it better to have the fan off a longer? You guys are talking about the base plate temperature. Can that be set in the gcode or can it only be set on the U2? Do I have to set it for each model or once changed does it remain? If I have to change the setting on the U2 is this easily found in the menu???

Thanks

MM

 

[Blizz 53]

For me 45ºC for the bed when printing PLA works perfect for the first layer.

I up it to 55 a 60ºC after starting either the 2nd or 3rd layer (basically at the point I start my side fans).

75º (what the default was when I bought the printer) was simply too high so 80 will probably be as well.

I am printing brims lately for parts with a smaller base, they come of easy enough with little visible "damage" and it helps a lot.

 

[Blizz 53]

@MedicalModeler: You can set them both in the code and on the printer (while printing in the Tune menu).

In the gcode will probably be for advanced users only.

If you are using Cura you can switch to advanced mode and use the "Tweak at Z" plugin. Just double click it to add an instance to the list below. Set the height at which you want to change things (either in mm or layers) and configure what you need. You can add multiple instances of the plugin if you would like to change stuff at different heights.

 

[gr5 2,173]

There are many ways to set the temperature. The two best ways are:

1) Once you hit PRINT and choose a model go into the TUNE menu and you can view and adjust the nozzle and bed temperatures. You must exit TUNE for the print to start but then you can optionally go back in there if you want to do more adjusting.

2) If your MATERIAL is chosen as PLA normally you can modify this setting and change 4 settings for PLA including temperature and then you can save this back to the PLA slot.

There are at least 3 other ways to change temp (one listed above) but I don't recommend those for beginner. Learn these 2 methods first.

 

[Blizz 53]

gr5 my UM2 happily continues printing while I'm messing in the TUNE menu, as a side note. If I'm modifying the speed it even changes while I'm turning the knob

 

[gr5 2,173]

Once it starts printing, if you enter the tune menu it's too late. You have to enter it while it is waiting for the bed or nozzle to warm up. Usually after the homing procedure but before it primes the extruder. If you enter during that time period it will not start printing until you exit tune menu.

However once it does the nozzle prime, entering tune menu will not pause the print.