RepRap: Blog

Layers, like an ogre (ref. Shrek et al., 2001). As with most experiments, before attempting a multi-layers print I conducted a trial run using a robust, relatively blunt old probe just to find my unknown unknowns.

The test object was an 8x8 hollow square of voxels spaced at 30μm, layer height set to 10μm. The test pattern turned out to be largely irrelevant due to the size of the probe tip, and an ill-defined square was what ended up being printed, and I ran out of resin at the end of the square. No matter, trial run isn't it? The experiment continued.

A single layer object was left as a one layer control, the probe moved over 500μm, and a second object printed in the same manner.

After the first "layer" the probe retreated to the resin reservoir and the UV LED was activated for 12 seconds. The probe was then dipped, and became over-saturated so I wiped it on the reservoir edge. Not ideal, never mind, soldier on.

The probe then returned to the object origin and was manually lowered until a change in the meniscus of the resin on the probe was seen, indicating contact. This occurred at a probe height of 10μm. The test pattern was then recompiled and printed at that height. Set as before with UV.

After recharging the probe a third pass was made. As anticipated, contact was made at 19μm height, and the pattern compiled/printed. In theory, resulting in a 30μm high object. This was then set for 3 minutes under a 4W UV LED lamp 40mm distant.

So, the result. The slide was put in a slide holder, and inclined at a slight angle under the binocular microscope to get a side-on view of the ill-defined blob. Here I have a comparison between the single-layer and three-layer objects:

Glass substrate is on the left side.  Looks like the layer heights determined manually are approximately correct. Doesn't look so nice from the front, so I'm not calling this a "successful" print, but it was a useful experiment.

Takeaways:

Repositioning of the probe after dipping is accurate to within detectable error.

The aluminium foil reservoir adequately protects the resin, and shields the probe so it doesn't set solid.

The UV LED does not take out the microscope camera.

Blunt probes are no good for accurate resin deposition.

Resin layer with a blunt probe depositing >30μm diameter dots roughly 10μm thick.

More care needed to keep the resin reservoir film at an absolute minimum thickness (swab with a cotton bud if needed).

Printing needs to happen centred more over the UV LED in the bed light well to speed curing time.

Even if accurate layering turns out to not be possible, it appears that creating thicker areas can be achieved, allowing for foldable structures to be generated.

Need to print a proper jig to hold slides at an angle for imaging.

 

What's next? The olive harvest. Nature does not wait for the schemes of men.