2
$\begingroup$

For some recent prints I have been using rafts as generated by Cura to aid in bed adhesion; which helps, but is not as reliable as I'd like it to.

However, it seems to me that the raft generation could be so much better; if I explain what I have in mind, maybe you can explain to me why it is a silly idea; or save me from reinventing the wheel, if some other slicer already implements similar functionality.

What seems silly to me about Cura rafts is that the bottom-most adhesive layer consists of continuous straight lines. This is literally the worst geometry, in terms of being able to relieve its internal cooling strains. Peeling always starts at the extremities of those long first lines, where the accumulated strain overcomes the adhesion, as you would expect.

What seems to me much more optimal is to have many non-connected small 'suction cups' as a first layer; little circles or maybe literal point-like dots. And cover a solid percentage of the surface with those unconnected cups. Like a fine honeycomb pattern. And then use subsequent layers to connect these cups with wavy lines of decreasing spacing, to build a somewhat continuous platform, while still providing a form of natural strain relief within those lines. If you take enough layers with a sufficiently compliant structure, you should be able to master arbitrary spans, with arbitrary shrinkage.

Has this been tried already? Am I missing something? Or should I start writing my own G-code generator and figure out why it might be a silly idea myself? Speaking of which; are there any python libraries to aid in generating G-code from a somewhat higher level format?1


1 Forget about that last question; gcody seems to fit my criteria for not reinventing too many wheels.

$\endgroup$
  • 5
    $\begingroup$ Welcome to 3D Printing! What else have you done to ensure proper bed adhesion? What preps are you doing? How do you level your bed? What kind of filament are you using (PLA, ABS, etc)? What temps are you using on your bed and nozzle? The only time I use any type of brim is if the base of the print is too small to have good adhesion. I use a skirt quite often to prime the nozzle. I've never used a raft. I'm sure there must be reasons to, but I've never needed one ... which brings me back to ... what's happening that you need a raft in the first place? $\endgroup$ – Pᴀᴜʟsᴛᴇʀ2 Oct 1 '19 at 20:53
  • 1
    $\begingroup$ Thanks for the input, but I am not looking to fix a particular print here, but rather to discuss rafts more in general. Will fix my introduction to reflect that; it might give the wrong impression. $\endgroup$ – Eelco Hoogendoorn Oct 1 '19 at 21:10
  • 1
    $\begingroup$ As you should know as an experienced SE user, this is not the place for discussions. Please join us in 3D Printing Chat for discussions. $\endgroup$ – 0scar Oct 1 '19 at 21:15
  • 1
    $\begingroup$ If you have trouble in getting straight lines to stick, you don't have raft problems, you have bed adhesion problems :) Maybe focus on that first as the Cura rafts work perfectly for me and others (but I usually try to avoid them!). Those straight first layer lines are extra wide lines, these "should" stick relatively easily. I've even got rafts to work with POM, which is not easy to stick to the build plate. Please note that many people have problems is printing concentric circles (non sticking circular perimeters are posted here multiple times), they detach quite easily. $\endgroup$ – 0scar Oct 2 '19 at 13:57
  • 2
    $\begingroup$ Perhaps this question should be changed to just ask why it is common for a raft to have the bottom layer consist of parallel lines. Does this offer any advantages/disadvantages over other patterns. $\endgroup$ – Perplexed Dipole Oct 2 '19 at 14:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.