Friday, July 17, 2026

 

Using Raking Light To View Resin Droplets

Fired up the μRepRap after nigh on a month, and after damp weather following an air conditioning failure. Still in good alignment, so I had a go at a resin print.

As expected, the steeper angle on the probe used produced a bigger droplet size (hey, it was what I had fitted at the time). This may seem counter-intuitive, but I've seen this before and  I suspect that a thicker probe tip pulls more resin back due to capillary action. The deposited first layer was approximately 8-10μm thick. Here's a shot of me doing a few tests of micromugs:


The takeaways from that run are:

Raking light from the top camera (now angled in at 45 degrees or so) is causing reflections at the contact point between the resin and the slide. This was a suggestion from a fellow Fab Labber. This, together with the 4K microscope, allows coated probe contact to be visualised relatively easily compared to previous efforts.

The first layer appears to be substantially thicker than subsequent layers. This is a slight problem, because current slicers all let you set the thickness of the first layer by determining the standoff distance to the bed for the first layer, and with μRepRap, the layer always starts at zero. Prusaslicer does seem to have individually configurable layer heights though, so I'll have to play with that.

Eventually this is going to need custom software, but I currently don't have the resources to manage that and I'll have to fake it.

PS I'm feeling fine now, but have to go back in hospital in a week to be introduced to some tiny little cameras so they can figure out WTF is going on. I hope they're narrower in diameter than my microscopes!


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