#lcd-sla-printer

Finally, a few months ago I finished another SLA printer (LCD based). And it works great, prints really well with way faster cure times than I thought. Now I think I can share my experience.

But to begin with, my goal was not to make the smallest and the fanciest device, but it was supposed to be quite adjustable, easy to work with and upgradeable if necessary (or if something goes wrong).

I started to with frame itself. I wanted to make it out of ordinary shelf components so I chose standard aluminum profiles (40mm x 20mm) (image: Profiles). I went for “box” design with two sections: bottom part for electronics and upper part for actual printing chamber. And now, after finally completing this printer, I must say that this design is really comfortable to work with: you can access all segments of the printer from all sides, you can do that very quickly with no stress. You do not have to disassemble the whole printer, when you want to adjust something that is deep within.

Profiles

Aluminum profiles were powder coated using self-made powder coating system (images: Powder Coating, Painted profiles, Powder Machine). It uses old CRT monitor transformer (50k V), paint gun is also 3D printed and uses “Nestea” bottles to feed powder. I was amazed how expensive are powder coating paint guns… and it took as one evening to make one for us.

Powder Coating

Painted profiles

Powder Machine

Profiles were joined together using my own design 3D printed “corners” (images: Frame Assembly, Frame Assembly_2). Each profile was also fixed with M4 screws to each corner. After joining profiles together, I had fully functional frame. See images.

Frame Assembly

Frame Assembly_2

Then it was time for Z axis (images: Carriage Head, Carriage Plywood, Carriage Top). I am a fan of thick linear rails, so I used here 16mm calibrated steel rods. I like thick rods since they compensate well any wobbles that come from usually curved thread. Stainless steel M8 thread was used. Head itself was redesigned “Cristelia” version. I did not like to use only two bearings for carriage, so I made my own carriage that uses 4 linear bearings since that brings way more stability into the system. Build plate and the rest of the head is “Cristelia” design. It is quite good although a bit bulky, but it works well. All in all, Z axis itself after calibrating it, was off only by ~10um within 10cm, i.e. after moving axis from 0 to 10cm, at the top it was off only by ~10um. Since everything was made by hand – that is pretty good. Disclaimer: my hands are not very well “calibrated” I was simply lucky this time :)

Bottom part and printing chamber was separated by hand-cut plywood plate (image: Carriage Plywood). I have chosen wood, since it is less expensive and easier to work with. I coated it with lacquer and it is just fine. At least when you need additional hole, you can make one easily.

Carriage Head

Carriage Plywood

Carriage Top

Now electronics (images: Inside, Dashboard)... First of all, my goal was to design electronics to handle 100-130W LED (I did testing at the end and it handled that power well). I use two PC power supplies (since I have a bunch of those): one for LED and one for remaining electronics (RPI3, Arduino, power for fans, steppers etc.). LED is powered using 300W step-up boost converter. Since I installed powerful 1 ohm resistor, I can measure current usage of LED circuit with voltmeter and with another regular voltmeter (measuring LED voltage drop) I end up having a nice dashboard, which helps me to see actually emitted power by LED and I need that, since I change LED power for my own reasons quite often. Another dashboard screen shows voltages of RPI3 and Arduino (helps to debug any issues). Everything is cooled using a bunch of fans from PCs.

Inside

Dashboard

Now, the LED part… It was (as expected) the most complicated one, where I spent most of my time. I also thought of using an array of LEDs, but after trying a lot of alternatives I went for a single LED. Moreover, it was way easier to work with single LED than with array. I was just not able obtain better results with an array than I did with a single LED. I will add image of light uniformity with single LED (image: Light Distribution). Although I designed everything for >100W LED, I use 50W LED (400-410nm). Since I still think of making daylight device one day, I think this power reserve might be useful later.

Light Distribution

LED assembly (images: Collimator, Collimator Top) consists of a large piece of aluminum plate (image: Heatsink For LED) with additional heatsinks attached at the bottom. PC fan is attached at the bottom as well. LED is screwed on the plate. Then there is first part of the whole assembly (everything is 3D printed, ABS) which holds Fresnel lens on top (see image: Collimator). Then there is second part – mid part, which had a purpose to be short and easily changeable if I needed to adjust distance between LED and LCD, so bear with me, but I did take a lot of precautions. It was easier to print another short part than entire assembly. Last part is top part, which is attached to a plate of black PMMA plate with a rectangular cut, which holds LCD display. There are a few fans to get cooler air inside, I am not really sure now that they are making some sort of impact, so you can say that they are useless, but… oh well: they live there and it seems they are happy. Interior of this collimator is covered with aluminum foil. Foil itself also did not make any serious changes/improvements since Fresnel itself collimated light, but, I would say, it was a little bit better. I did not observe some sort of light unevenness due to the foil (image: Light Distribution). LCD itself was placed into the rectangular cut of black PMMA plate – thus closing system. LCD is the same as used for YHD-101 (KLD). With this setup, I did not notice any heat issues at all. LCD is warm, but that is all.

Collimator

Collimator Top

Heatsink For LED

This LED assembly was fixed to plywood plate that separates bottom part from printing chamber (image: Inner Chamber). I used springs to fix that in place and springs also allow me some sort of adjustments. Another feature is that it helps me to avoid crashes if Z axis accidentally goes to low – springs will compensate that.

Inner Chamber

Frame was covered with milled orange PMMA, which is very easy to remove, when you need to access some parts of the printer. Doors are made out of piano hinge (image: Hinges) and door lock (image: Door Lock) is made using simple magnets and 3D printed parts. At the bottom of the frame, there are adjustable legs (image: Legs), which you can screw up and down to adjust the level of the printer.

Hinges

Door Lock

Legs

VAT I made was a mix of various designs, since I made a lot of them in recent years, this was just a rough assembly which appears to be working really well (image: VAT)

VAT

I have attached image of printed calibrations parts  (images: First Print Calibration, Motor) 

First Print Calibration

Motor