Troubleshooting pinched first few layers

I’m trying to dial in a Taz 6. I’m having trouble getting decent 1cm cubes printed. The first few mm of the cube are pinched in like its wearing a girdle. Then it straightens up ok.

I’m just using the Quick print setting for High Detail HIPS plus an expert-settings tweak not to over extrude (I’ve bumped by diameter to 3mm and my flow to 95%) My top and bottom layers are 1.08mm and my initial layer thickness is .425. Neither of those would seem to be as high up as the 3mm or so I’m seeing of rounded corners.

Any ideas what might be causing this?

I have seen something similar on my prints in the past but not as extreme. I am not familiar with HIPS printing properties but if it is known for warping and you have to print it at a higher heat like above 220c, then maybe its like ABS and is sensitive to temperature while printing.

Since it only happens at the base maybe the print bed is too hot or not enough cooling till you get around higher layers. Have you tried messing with bed and cooling temperatures?

Did you find a solution?

I’m seeing the same problem: