How to get good overhangs or cutouts in your 3D prints

[kgg]

Getting nice cutouts or overhangs when 3D printing can be a chore particularly with bed slingers or single head core XY machines without an Automatic Material System (AMS). The trick to remember is some filaments will not stick / bond together with other filament types. If you are using i) PLA use PETg in those sections  ii) PETg use PLA. Where it will have to change from one type to the other there is no need to do all the support in the opposite filament type. All you need is 2-3 'top' layers in the opposite type. Just enough so it pops off nicely and gives a nice finish to the 'bridge' area. Obviously, if you are putting a support that does not go from plate to the part (say in a 'window' on a part you are printing) you will need to make the bottom 3 layers also be the opposite type.

This old school trick can be done with a bed slinger but you will have to babysit it and manually change / drain the filament in the head on every filament change. With a Automatic Material System (AMS) system it just does the necessary filament changes for you.

An example is that I wanted a particular side of a edge guide for the right side of the needle to be printed face down on the plate so the side that would have material rubbing against it was super slick. That meant the over hang would be nearly over 30mm from one side to another, unsupported. I was using 3d850 so I used PETg to fill that area and when the print was finished it just popped off leaving a nice crisp cutout.

The first photo shows the side that was face down on 3D plate to give that nice slick 3D finish.

The second photo shows the 4.25 mm deep cutout with the 30mm bridge.

The third photo shows the backside of the edge guide as it sits on the table top.

kgg