Why is my print not as detailed and sunken in on the bottom few layers?

[Raymond2123 0]

On the first few layers of my prints above the raft, the print is always less detailed and smaller than the rest of the print. Why would this be? This is extrememly frustrating when I am trying to make a part that needs to fit into something perfectly. Any help would be greatly appreciated.

[gr5 897]

Photos please.

Raft isn't needed on modern printers. What kind of printer is it?

I assume you are using PLA as it's the best for most uses. I assume you mean the outer corners are "inward" from where they should be? PLA acts like a liquid rubber band before it hardens and it's under tension because it cools in milliseconds and so shrinks while still molten. It's kind of like snot or other mucus.

So as it wraps around the edge it pulls inward.

This effect is worse just above a heated bed. You can lower the temp of the bed to 60C and the part will still stick like hell. But even at room temp you will have some issues.

Vertical holes in a part will also have this problem for the same reason - too small. Can you supply more details? Basically the fix is usually to just adjust the CAD model once you have very consistent printing results. It sounds crazy but it works very well - measure the error and adjust the size by that amount in cad and you end up with a perfect printed model.

[gr5 897]

About raft: it was used before PLA was popular on printers that tried to print ABS on a cold heated bed - on blue painters tape. The warping forces of ABS are tremendous and would pull the part up or rip up the tape. The fix was to use a raft which was flexible and could bend a bit - just enough to relieve the tension and keep the part down and not "warp" off the print bed.

Now we have many newer technologies and no one needs raft anymore. These technologies include PVA glues, heated beds, PLA (half the warp), brim and other surfaces like build tak.