Bottom layers caving in

Hi guys,

I'm having a problem where the bottom layer of my prints start off smaller than they are supposed to be, causing the bottom to be caved in. This happens consistently up to around 3mm height, then the dimensions return normal. How can I fix this?


I've tried various prints fiddling between the following range of settings, but they didn't have much effect:
Material: PLA
Print temperature: 190 - 200C
Heat bed: 50-60 degrees C
Extruder dia: 0.4mm
Print speed: 20 - 45mm/s
Layer height: 0.15 - 0.2mm
Raft/support: Yes

Cheers,
Ben

Try to print a brim instead of a raft.
Or raise the temp for the first layers to 210°C.
-Olaf

... could be your heat bed temperature is too high for PLA - with ABS a similar effect with shrinking bottom layers is common with higher temps and known as 'elefant foot' ...

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Viktor
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