Setacci con maglia quadrata

This project originated as a proof of concept for building a (non-professional) tool for investigating the physical characteristics of soils and clays for raw earth constructions/plasters.

It consists of a set of 5 sieves with square mesh sizes of 1.5 - 1.0 - 0.75 - 0.50 - 0.30 mm (mesh thickness 0.40 mm, equal to the nozzle) useful for roughly evaluating the particle size distribution of clays, powders, and granules. The sieves can be arranged in a cascade to estimate the particle size distribution (assuming no chemical/electrostatic interactions with the plastic of the sieve).

The components of this project were designed to be used with a "vibrating sieves" device, but that's another story…

Technical note: to quickly create the mesh of the net, I used a "modifier" on the bottom of the sieve and set the "sparse infill pattern" to "Grid" with different values of "sparse infill density" depending on the sieve (without Bottom and Top layers). 

The design of the sieves and screws was studied to avoid supports.

To estimate the correlation between the slicer's "sparse infill Density" (D) and the Mesh Size (LM), I used an empirical approach: once an arbitrary value of D was set on Bambu Studio, I took a VERY magnified screenshot of the "Preview" of the first layer. Then, using graphics software (GraphicConverter), I measured the LM size from this screenshot (calibrating the software on the mesh thickness, which is exactly 0.40 mm, the extruder nozzle). The calculated D and LM values were processed using non-linear regression techniques (StatGraphics) on a set of 8 data pairs with D values between 90% and 28%. The best mathematical model resulted in the type LM = a + b/D (see graph; R2>99.9%).

The extimated values for the 5 sieves were:

Almost identical results are also obtained through 2nd-order polynomial regression.

The advantage of this approach is that by modifying the "sparse infill density" values, sieves with any square mesh size can be quickly obtained (for example, if I wanted a sieve with a 3 mm LM, I would simply set D=17% (3=-0.40 + 57.2/D)).

The mesh size is obviously approximate, but despite not having suitable instruments, I tried to measure the LM on the 1.5 and 1.0 mm sieves with a vernier caliper, and the results are good. For the 0.5 and 0.3 mm sieves, the mesh size is negatively affected by the "Grid" infill construction method, as the nozzle crosses the filament already deposited on the plate, and the square mesh becomes distorted: see the photo below.

Net 0.5 mm

Net 1.0 mm

Net 1.5 mm

The 0.3 mm sieve presents serious issues with the 0.4 mm nozzle, so I'm planning to test with a 0.2 mm nozzle and, if successful, I will add a specific printing profile just for this sieve (printing times increase enormously).

To improve the quality of sieves with an LM smaller than 0.75 mm while keeping the 0.4 mm nozzle, I believe many tests are necessary with materials other than PLA (or different types of PLA) and by trying to vary the printing speed and perhaps also the extrusion temperature and/or the plate type (all my tests were done with the BL Cool Plate SuperTack).

Nevertheless, in my opinion, these sieves can still be used for comparative tests (however, I would exclude the 0.3 mm sieve as the occluded or heavily deformed meshes could skew the data).

The length of the bolt is designed to assemble all 5 sieves together with the lid and bottom, but nothing prevents shortening it by cutting the screw to the desired length using the "CUT" tool in Bambu Studio (avoid resizing). I have added a plate for a shorter screw suitable for assembling 2 sieves + bottom + lid.