Projector focus

[Kattejuice]

Hi, I'm new to DLP printing and I have some questions about calibrating a few things.

After following the assembly guides I got to focusing the projector, which I did as best as I could using the included scaling charts.
One thing that concerns me, however, is that the best focus I could get was with the focusing-dial all the way to one side. In other words, I don't know if it is optimally focused since I cannot overshoot and see when the focus gets worse again.

My first calibration print did turn out well, but not perfect, and (apart from some failure caused by breaking supports) so did my second and third attempt with some figurines.
I should try making the calibration piece again and see if I can improve my settings.


I'm using a P1500 in the front-most position with all the acrylic washers as described in the assembly guide.

Should I try moving it back by one hole to focus better? And wouldn't this affect the print resolution?

[Kattejuice]

Heres the first print

Sorry about poor quality, taken from my phone.
The smallest of the 5 columns didn't print other that a "blob"/string right at the bottom. Some of the other columns are broken by me playing with them(I'm surprised how flexible they are, that's so cool, haha!). The smallest hole is clogged, and so is the last wall. Theres some visible layer lines along the sides. Other that that I think it came out fine.

[Affi75]

If you try moving the P1500 back one position you will at least get past that overshoot so you can ensure that you have the optimal focus.
I guess it lowers the maximum resolution a notch but you can easily loose more details due to an out of focus print than that few percent of reduction in resolution will affect it.

[Scatterplot]

You'll lose a little bit of resolution, but not much.

I had a similar issue with my prints; I ended up having to go way higher than the suggested starting cure times, so it can really depend on your projector. Move it back a notch and see if that helps, if not move it back two notches. Your resolution will get lower but it's already incredibly high, so you shouldn't see much quality loss.

If your smallest post didn't form, increase your cure times to try to get it to cure more. That will also help improve the sharpness of your print, as undercured resin ends up blobby rather than sharply cured.

[Kattejuice]

Thanks, I'll try that then.

[goopyplastic]

A longer cure time (enough to fully form each of the posts, it's ok if the smallest one is a little floppy) will get rid of a lot of the ridging too. When undercured during the separation stresses the edges of each layer can get roughened. Great job so far!

[Kattejuice]

Ok, so I moved back the projector by one hole, increased cure time to 3600ms (makerjuice sample resin), disabled anti-aliasing and got this:

All the holes go all the way through (however, first one blocked at the bottom layer, but that was expected.) All columns printed to full length, and the smallest one supporting its own weight, although very "sloppy" to the touch.
The last wall is nearly clear form the others, but has a little blob in the middle. The scratch from C and across the walls is from the rinsing, where I must have hit it across something.
Letters are much sharper now. There are still noticeable layer lines, especially on the 45°front slope.

Big improvement, but not perfect yet.
I should mention that I still didn't see any overshooting when focusing, but it seems to be very good right now, so I might be in focus. Should I try the third hole as well?

[goopyplastic]

What layer height are you using? 100micron .1mm you will see layer lines.

The last wall will never be unconnected like the other walls with the current resins we use, I believe this is primarily because you lose contrast inbetween two objects. For example it is really hard for the projector to projector to display dark black inbetween two close white objects.

[Scatterplot]

Try higher exposure times (assuming you're on 50 micron layers). You still look a little undercured (to my rookie eyes lol). I had to go up to around 4500-5000 ms to get my Makerjuice to reliably print supports!

[Kattejuice]

I'm using 50µm layer height. Oh well, its conforming to hear that the last wall is tricky, since I didn't get it
I'll try some longer exposure times then.