There is no question that there is a high degree of variability in the hardness of the bases of a print. I’ve had prints where the base popped off with almost no effort at all. I’ve had prints where I had to chip the bases off and then chisel the remains away from the build plate. I’ve always just assumed there’s some variation in the build plate’s Z “zero reference” or coplanarity with the resin tank, and some bases get over-compressed when printing, and those are the ones that need to be hammered off the build plate.
I’ve been printing Tough 2000 since I got my F3 last year. The prints have all come off the build plate with hardly any effort at all. This weekend, I switched to Durable. The first prints I made came out just fine, but I could not get them all off the build plate without a significant effort. (and I was glad I had my dangerous knife or there’d have been no chance of removing some of the prints).
Printer’s the same, build plate is the same, resin tank and resin type changed = radically different results.
It’s also worth noting I am not a newbie to Formlabs. My first was a Form1+ I bought when the printer was first released. My second was a Form2. The Form3 is my third. All three generations of printers have exhibited this “issue” to some degree at some point in their lives… it’s not as simple as not having the right “technique” to remove a part. What works for you may not work at all for someone else. Because: variability.