Raspberry Pi 4 Experimental Resin 3D Printer -- Episode 414

I think you guys are overthinking the tilting bed/vat design I am envisioning. I'm thinking of a hinge, with a hinge pin of drill rod (small diameter precision polished shaft) allowing a machined aluminum hinge body, with a reamed hinge hole .0005" larger than pin diameter, and a light torsion coil spring, to aid in return to beginning position, against a set of adjustable stops, opposite the hinge, on the corners of the vat. This will allow the bed/vat to tilt, and peel the FEP from one side, when the Z raises up, it will peel off, starting from the hinge side, as it cannot raise up, with a stop allowing the vat to only raise a certain amount on the movable side. The MOAI printer seems to use a tilting vat, where the right side (looking at the printer from the front) is hinged, and the left side tilts down, likely on a very small ball screw, then raises back up to the starting location, I think I can mimic this action without the use of any additional electronics, just using the 'sticktion' (my made up word for the quantitative amount that cured resin sticks to FEP) and the torsion spring to return to zero, I would just need to set the retract height with each layer to allow the Z axis to travel slightly more than the travel allowed by the vat stops.

Pretty much all resins I encountered stick to Glas and most plastics, there are silicones used for laser based printers.

Those don't work as well with msla anecdotally.

Your welcome mate.

Just trying to shoot a thought across, the resins used in SLA printers, do they stick to glass?  If not have you investigated using a vat with a glass base?

In regards to a tilting bed, you could use a titling platform mounted on two ball screws, as ball screws depending on the quality have an accuracy of up too .001mm or 1um, perfect for resin printing, the reasoning for two, one at each end, you start to lift one screw until a desired angle is achieved, then start the other screw, but I don't believe support is available in the firmware to do this at this time,  And to keep track of the ball screw position, you could fit rotary encoders or, magnetic encoders with a diametrically magnetised magnet feeding a AS5047D https://www.mouser.com/datasheet/2/588/AS5047D_DS000394_2-00-347336.pdf  magnetic encoder which runs over SPI, this encoder has an error of +/- 0.8 degrees, but if you use a calibration routine you can get this error down too +/- 0.1 degrees.  But Z screw accuracy is critical with a resin printer.

Clem, have you look at investigating a feedback for positional accuracy on your V2 printer?  If not the above mentioned encoder might be worth investigating.

thanks for the update, a very handy chart!

Thank you very much for your comment.

the size of my printer was mostly determinded by what screen was availbale for a given pricepoint and within time.
I agree that 4k is not needed for decent qualitiy in structural parts.
My main focus was to avoid FEP completelly but I'm certain that your approach with FEP on a bigger screen should be workable, but you might be limited wit hsprint spoeed as the time it takes for the fep to peel increases with larger diameters siginificantly. (basically stretch to Area ratio).
the tilting Bed might be a godo approach to ensure even sufraces, but keep in mind that you need to build a very precise sy<stem as the vat has to end upü exactly at the right position after every tilt. (take a look at the SL1 designg by prusa3D)

Iḿ already working on V2 of my printer. this time it is much smaller (still a bit bigger than the cheap printers onthe market) but it omits FEP completelly< and might be a bit faster if eveery thing works out as planned. Of course there wil lbe a video about it.

Found this video on youtube and you have inspired me to try to merge parts of your design with another design, the FDM-printed SLA-printer, by youtuber Tinkering On Steroids. I would like to create my own SLA printer, but the issue with TOS' design is that the cost to build is equal to, or higher than, the cost to build a far larger printer like yours. I have sourced a used 17" lcd pc monitor for nearly nothing, and although the resolution is only 1280x1024, I think it will work quite well for my needs, I do not require perfectly smooth prints, however I prefer the versatility of SLA parts as far as strength goes, compared to the often very weak FDM parts I am used to. I also though want more build volume than the 5.5" screens can provide, so for this I think the 17" monitor will do nicely, especially considering it is nearly square in dimension, I think I will make the vertical travel 300mm, to make the total build volume approximately 250x220x300. However I intend to stray from your design and use FEP film, and a tilting vat, similar to the tiny SLA models of printer. What do you think?

If you want I can speak to my local supplier, and see if they can source the index matching gel, and get back to you with a price.

My contact at the supplier is always willing to help me out with fibre optic's as he owes me a favour or two

I'm always happy about comments on older posts as it keeps them relevant and I often go back to those projects.

You are right!

I have heard of such gels before but no way to source them it didn't even seem that our local Fibre companies use it.

I'm currently working on the version. Two of this 3d printer and have some ideas that might eliminate the need for a specialized liquid.

Hi Clem,

Sorry for posting in an older project of yours, but whilst I was posting on your latest project I had a light bulb moment, as I do work with Telecommunications in my day job, I recently did some fibre optic work for a few clients and used field terminated connectors, sorry for the long intro but I'm getting to the point, these field terminated connectors use an INDEX MATCHING GEL so to match the glass fibre to the polished glass in the connector.

So the idea I have is, if you can source the index matching gel used in field terminated fibre optic SC or SC-A connectors, its designed to have the same index as glass, and being a gel, its denser than the resin, and the index gel only needs to be a thin layer.

So that would be the best stuff to use.  But I don't know why I did not think of it before, but thanks to having a recent client getting fibre optic work done, it came to mind again.  But the difficult part is sourcing the index matching gel.

Regards
Paul

Edit: did a quick search and found this https://www.fiberinstrumentsales.com/fis-matching-gel-4-oz.html

and this https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=354

and this TechOptics - Index Matching Gels

and this https://www.newport.com/f/index-matching-fluid

even found this