Printing a matrix of long and thin cylinders


#1

I want to print a structure made from many small cylinders, akin to a bed-of-nails, with about 30mm length, a diameter of 1mm and a distance (centre to centre) of 2mm. This is necessary for an engineering research project in the field of microwave technology.
There are two unexpected things that happened and maybe someone has experienced something similar or can offer some advice on possible mitigation strategies.
Number 1: During the overnight printing process a peculiar symmetric pattern had formed from groups of four pins sticking together. They could be seperated quite easily before curing, but remained in the deformed position at that point.
(Point no. 1 surprised me especially, since a previous print in a Form 2 did not exhibit this behaviour)
Number 2: The curing process lead to another deformation of the pin structure, which resulted in an „outward spread“ of the tips of the pins. This gets more noticeable the further the pins are to the edge of the matrix.

Ultimately, it would be desirable to achieve as much uniformity as possible.
The layer thickness is 50 microns, Clear V4 was used and the model was printed without any support structures.

Thanks in advance!



#2

These are very tall and thin structures, so some deformation is expected. The warping during curing described in #2 is likely due in part to uneven light intensity reaching the models. More light hits the outer surfaces, causing them to contract more than the inner surfaces which are somewhat obscured by other parts.

If your application can tolerate it, I suggest adding some “custom” supports - model some thin cross-bracing between the pillars. You’ll need some experimentation to find out how many you need and how thick, but I’d start by placing them say half-way up, and again at three quarters. Don’t orient them 90 degrees to the pillars, rather have them angled up/down (e.g. think X cross-bracing between posts). Make them in both X and Y dimensions. This will result in a loosely lattice-like structure that will stay more rigid during the print. The cross-bracing can be small enough that it easily snaps off after the print, and if needed you can sand away any remnant stub.


#3

Do you need it to be in 1 piece, monomaterial? > Otherwise: what about printing separate “concentric” squares or rows and glueing? That way UV radiation can reach more evenly if cured separate too.
Cyanoacrylate bonds extremely wel and this geometry seems extremely suitable for that approach.

Side note: Isn’t 30x1mm at the limit of the recommended geometries? (as per: https://support.formlabs.com/s/article/Design-specifications-for-3D-models-form-3?language=en_US)