hollow channel

[Sebastien_Lani]

Hi

I'm trying to print hollow channel (see drawing below) and except for the channel of 1mm I'm not able to get the channel open. The sizes are 0.25, 0.5, 0.75 and 1mm of diameter.
In contrary I can get a 0.1mm structure or opening when its not embedded in a printing.

I tried cherry, solusproto and spotHT-A black resins with different parameters but not all.

Does someone has some ideas?
I know there is a lot of possibilities. I'm showing also some pictures of prints, one for which I had cut the piece and one for which I start a print at half of the channel to observe it more easily.

Sebastien

[mongerdesigns]

I have printed 25 micron deep and wide channels using SolusProto, but they were open channels on top of the model, so I think what you're trying to do is possible.

Use SolusProto, tilt the model at 45 degrees to eliminate internal overhangs, lower the layer exposure time a bit.

Also make sure your channel is not close to the base. Because that area gets overcured so it sticks to the platform.

[M-Williams]

Also make sure your channel is not close to the base. Because that area gets overcured so it sticks to the platform. .I totally agree . learn it the hard way when trying to print faberge like eggs.

[rkundla]

From a general printing perspective and not just the Solus, I would say that exposure and focus are primary factors.

Setting the exposure right for the negative feature (the channels) may prevent you from printing the positive feature (the pins) correctly. It's a game of give and take.

What would be neat is something like the B9 software, where they have the over cure, which is where they leave the edges displayed a little longer due to the lack of surrounding active pixels providing additional light energy. You need a under cure where the interior channels are turned off earlier to reduce the amount of light energy overall.

[mongerdesigns]

The main issue here is that the tubes are close to the base. Move it up on supports, make sure the focus is sharp, and you can even lower the exposure a bit.

[Sebastien_Lani]

I did try all proposed except the tilt that I will try soon. Also with or without supporting structures.

The tubes are all fine, so it is not for me a problem of XY over-exposure but more a z over-exposure (but maybe I'm wrong).
I was wondering what is the minimum thickness of cured resin to block UV light, according to fail prints that have fully stuck on the film shall not be so thick. Need to measure that next time.
Also what is the thickness of uncured resin to stop UV completely... maybe I need to print at 100z to avoid exposing the channel but I tried channels of 1mm deep, 0.25mm to 1mm wide with the same results...

So I will test to till the sample and I will post the results.

Thanks for your tips

[Sebastien_Lani]

I don't know if it was due to the fact I tilted the sample or from the rinsing process but I was able to get 3 of the 4 channels open.

Normally for rinsing these parts, I'm connecting the input tube to a rubber tubes and a syringe and pushing isopropanol inside. For this last printing, I was still not able to rinse the channels so I tried to push air and after "pressing a lot" some resin was flowing outside and then I was able to rinse with isopropanol.

I did the printing with cherry 30z exposure 3000. Will try also with the solus proto now.

So thanks again !

[nzfinescale]

I'm having similar issues. Not that this is a problem for me exactly, more a case of tuning and optimisation.

Small channels are not really the issue for me (it is more that close features can fuse) but it is obvious (under magnification) that parts are fat and voids are narrow. A 0.5mm wire is 0.65mm when printed. Anything less than about 0.5mm hole does not remain open. A 10mm wire is 10.15mm when printed so it is not a print area calibration issue. Prints are otherwise good so I don't think it is focus, and I've checked that too.

This is SolusProto 25/25/25 using recommended profile except I have dropped exposure to 1200ms and AA to 2. On the last test I reduced the projector brightness from +10 to -10 and this looked like it improved the fine channel performance a bit (it was late, so haven't evaluated it properly yet).

I have the latest Vivitek 1188 (I think) projector. Is this brighter than earlier models? if so, a need to rework of the profile is to be expected.

One possibility suggested by Mark, that I have not fully explored, is that the resin may not be adequately mixed. In this case pigment content in the vat may be low (and thus uv penetration is higher than expected).

The other thing I've wondered about is how the anti alias works. I guess this could contribute to the issue.

I'll be looking into this later today - will report back if I make progress.

[reify]

The profile was likely created on a projector that already had quite a few hours on the bulb. Since yours is brand new try dropping the exposure time a bit.

[Sebastien_Lani]

I had not yet calibrate the solus proto in term of size. I did it for cherry resin for which I had observed an over cured volume of 30um in XY but compensate by general shrink of the piece (2-3%).

I had less over cured resin with black spot A HT resin.

When comparing the pieces with the solus proto resin and cherry clearly over size in XY is higher.
For doing hollow channel with solus proto I m currently using 800 and 10z and the part is cures enough. I guess I can still lower the exposure.

Sébastien