Guru
Joined: 31/07/2019
Location: AustraliaPosts: 330
| Posted: 07:43am 17 Dec 2020 |
Anyone used a resin printer?
ie where resin is photopolymerised into a solid.
Senior Member
Joined: 10/01/2016
Location: United KingdomPosts: 214
| Posted: 09:22am 17 Dec 2020 |
Yes; stereo photolithography is the term. A bath of photopolymerisable resin sits over an LCD matrix which shadow-masks an ultra-violet light source. As sequential "frames" are exposed, a platform rises vertically with the resin bath, bringing the printed object into existence.
The advantage is far greater resolution and surface smoothness than can be achieved with fused deposition printing. The downside is that it is slightly messy to clean up the thing afterwards. The printed object needs to be washed with isopropyl alcohol to remove unpolymerised resin and then post-cured to increase the level of polymerisation to gain full strength. I have a machine that washes and post-cures.
Another advantage is that this enables metal objects to be cast. The object can be fabricated in a burn-out resin and then treated like a conventional wax pattern for investment casting.
What precisely do you wish to know?
Guru
Joined: 31/07/2019
Location: AustraliaPosts: 330
| Posted: 10:50am 17 Dec 2020 |
Why doesn't the polymerising resin stick to the window where the UV shines into the fluid? I guess in that configuration the solid is connected to the platform and floats/rises in the liquid resin ? What is used for UV, are UV leds adequate ?
There used to be many CAD/CAM diy'ers on this bbs, wondering if they have given up on it..
Senior Member
Joined: 10/01/2016
Location: United KingdomPosts: 214
| Posted: 01:09pm 17 Dec 2020 |
It is a matter of differential surface properties, as you are guessing quite correctly. The window is a stretched film of FEP (Fluorinated Ethylene Propylene Polymer) a.k.a. "Teflon". The platform surface is roughened steel. The resin sticks preferentially to the roughened steel and releases easily from the flexible FEP film. The latter is a consumable item but lasts a good time if it is cleaned properly between runs.
Just as LEDs have mutated from tiny little red things to full-on floodlights and car headlights, the same applies for UV LEDs. Actually, to activate a film of resin that is 25-100 microns thick requires only quite low energy UV. The trick is to keep the exposure dose above the activation threshold where solidification is required but below the activation threshold in the bulk of the resin where some light diffusion in the resin bulk is inevitable.
I had the pleasure of working at university with the one of the inventors of the UV activation system; Jo Jaworzyn who worked at ICI in Macclesfield where the system came from. The original intent of the UV activation system was to overcome the problem of painting ships. Successive layers of paint do not easily adhere to the last coat and hydrolysis and debonding was/is a problem. The original idea was to paint the whole ship hull in one coat and then light-activate the entire surface using an array of UV fluorescent strip lights. A number of problems prevented this application and it went onto the shelf for several years until the dental materials division became aware of it and the first light-activated dental filling materials was produced. The hazards of using a mercury UV lamp in the patient's mouth, albeit via a light guide, was remedied when a new activation chemistry sensitive to blue light led to the material used today.
Onto the reasons that the initial enthusiasm for 3D printers may have waned somewhat. Firstly, the fused deposition systems are basically rather crude. The resolution is poor and the generated surfaces are rough. Builds take hours. 3D design software is challenging. The scope is therefore rather limited. As I have already described, the UV system is just a little bit messy.
I have three laser cutters; the largest can handle an 8 foot x 4 foot sheet of 1/2 inch ply; the smallest allows me to cut acrylics with accuracy in the region of a few microns. I can run up a design on screen and hit, literally, the "print" button and in a few minutes the component is made. Sometimes I may find that a fit of two components is a little loose or too tight; I can wind back the dimensions by, say 50 microns and then hit "print" again. I find that in my model making the lasers are used far far more often than the stereo photolithography system.
Guru
Joined: 31/07/2019
Location: AustraliaPosts: 330
| Posted: 03:36am 18 Dec 2020 |
Thanks - interesting stuff. I see Jaycar are $elling them now, nice bit of tech.
Guru
Joined: 07/08/2016
Location: United StatesPosts: 508
| Posted: 01:57pm 19 Dec 2020 |
For me the first time I heard " Santa Claws Machine" was by Donald Lancaster.
Years ago and I think Chrysler used something like Don's "Santa Claws Machine"
to prototype carburetors.
Regular Member
Joined: 31/01/2020
Location: FrancePosts: 70
| Posted: 06:31pm 20 Dec 2020 |
I get a Elegoo Mars 2 Pro some weeks ago and for the price you got very good results.
The resin i get is from elegoo too , it polymerize in 3 sec , it's allot faster than printers that don't have BW Screen :)
The printing area is 129 x 80 x 160 , it's not really big but it was for see how it work ;).
The next i take will probably be the elegoo saturn with a bigger printing area.
The slicer is important too , actually i get Lychee Slicer , it made the hard work for me with the auto rotate and placement for optimize the parts support.
Guru
Joined: 31/07/2019
Location: AustraliaPosts: 330
| Posted: 10:31am 22 Dec 2020 |
Does the polymer resists etchants ? It would be a quick way to put a thin resist layer on a pcb...print it directly using the photopolymer.
Regular Member
Joined: 31/01/2020
Location: FrancePosts: 70
| Posted: 02:25pm 23 Dec 2020 |
It resist isopropanol for sure :) , it's the only product i use for clean the prints.
Now for the layer on a PCB it's not the good thing to do , the 1st layer have the elephant foot aspect (wider).
With 50µ pixel size it's probably possible to rework the slicer output to make the trace thinner so it match the real trace size for the 1st layer.
Newbie
Joined: 15/09/2022
Location: United StatesPosts: 2
| Posted: 05:00am 19 Sep 2022 |
A resin printer, regular FDM printer with PLA or PETG would be better for this.
See https://43dprint.org/3d-printer-for-miniatures/
Printed parts will never be as good as commercial injection molding, but if you do want to print a customised box it is relatively easy - but you will need to be familiar with 3d CAD software, or just print other people's designs. Also bear in mind that commercial boxes use flame-retardant plastic. AFAIK, all DIY type 3d printer use polymers that are not flame retardant.
I've designed some boxes with OpenSCAD, printed in PETG on Prusa Mini. They are good enough for hobby use, mainly for small projects. For larger projects it's just quicker/simpler (and probably works out cheaper) to buy commercial boxes.
Guru
Joined: 31/03/2022
Location: United StatesPosts: 327
| Posted: 09:42pm 19 Sep 2022 |
Resin Printers are Verry toxic I have a brand new one I won't even open Research their safe use before getting one
Admin Group
Joined: 31/12/2012
Location: New ZealandPosts: 8872
| Posted: 06:52am 20 Sep 2022 |
I'm playing with OpenSCAD at the moment for making project boxes, so if you would be prepared to share some of your design files for me to play about with, that would help me learn how to use OpenSCAD.
Welcome to the forums, BTW.
Senior Member
Joined: 07/06/2022
Location: United StatesPosts: 266
| Posted: 10:36am 22 Sep 2022 |
I would recommend perusing the GISTS of Ed Nisley... he's a decent maker of SCAD designs.
Ed Nisley Gists