Prints drop at ends after coming off the bed
Hi,
This may be a common issue but I cannot find anything about it on the WWW or this forum. This is not a standard lifting or poor adhesion problem, the print is perfect on the bed. After it cools, and as I am using ABS I let it cool naturally, it comes easy off the bed but has a bend in it as if the stresses in the print is more on the bottom than on the top. Is there anything I can do to get them to be flat. I have tried different fills and some are better than others. Most of my printing are these panels of different sizes and they really could be doing with being as flat as possible. Here are some pics showing what I mean
Pretty much a perfect print. But..
As you can see it bends in the middle.
Thanks for any comments
Jessica
RE: Prints drop at ends after coming off the bed
The effect is similar to that which causes a blade to bend as its cooled when forging. Different stresses pull and warp it. As you say different infill patterns cause different stresses. As ABS is notorious to shrinking I'm not surprised, Ive seen it to a lesser extent in PETG too.
The following is speculation as I haven't tried it myself but perhaps annealing using a similar technique to that used to remove stresses from forged blades may work. Basically put the part on a perfectly flat plate and put it in the oven at just below the glass transition temp of the material so that it softens ever so slightly will allow it to flatten out and relieve any internal stress. You would have to be pretty careful with the temperatures though and experiment with temp versus time.
RE: Prints drop at ends after coming off the bed
There are a few tricks I've learned for printing ABS which do seem to help.
First is to make sure the machine is thoroughly warmed up and stabilized before launching the print. I'll preheat for at least 10-15 minutes before doing the first ABS print after a change from another filament or from a cold start.
Then (but it may not help you with those thinner prints) is to use the draft shield option, with 2-3 skirt loops for a taller or larger print. This really helps out with consistency for ABS prints.
I'll also wait for the print to cool to almost room temperature before attempting to remove it. ABS is far more dimensionally stable when cool, plus I learned the hard way with my first large ABS print on the then-unfamiliar Prusa flat PEI sheet.
I've had very good luck with printing small and thin objects in ABS, such as fire escapes, trim and railings for model railroad buildings.
RE: Prints drop at ends after coming off the bed
Try printing with a big brim attached to model 6 or 8 lines.(more sticking to bed).
Use glue stick so model can not warp, and that the model even wen it cooled down, will not release.(or different glue).
ABS could have a lot off moister, try a different roll or different company or try to dry the filament.
Keep wind away from model.
If it does not help, try to print hotter, 10-20 degrees.
RE: Prints drop at ends after coming off the bed
Hi All,
Thanks for your suggestion. I have improved it quite a lot by allowing the bed and inside air temps to stabilise before removing it. I am now getting some very good prints
Jessica