Post-curing Underwater


#22

The sun is very bright where I live, I tried leaving my prints nearby a frosted glass door and it works like magic. I might make a small box with one side open using white A4 paper.


#23

I am a new user to this Forum, and i can’t figure out how to make my own thread, So I’m just going to post my question here and hope someone can help.

Has anyone used the (print from your pone feature)
I have looked for Formlabs phone apps and found nothing
I can’t find anything on youtube or this community forum


#24

“Print from Phone” is more of a consumer-oriented feature. FormLabs printers are really targeted at commercial users. Developing applications like this would have limited (if any) value to the target user. You can check the status of a print on your phone via the Dashboard website feature if you have a Form2. I don’t think Form1 printers support this functionality, though.


#25

I know this is an old post but want to see if anyone else has the issue of parts during other colors when doing this method. I have clear parts that turn completely frosted and black parts that turn perfectly grey. I thought at first based on this thread that I might just have hard water so I tested it with distilled water and then with deionized water, both having the same effect.

Anyone else see this issue?


#26

Clear parts will always turn out frosted because the surface will end up slightly rough compared to what’s needed to get a perfectly clear part. When the part is initially finished, it has liquid resin still on it which fills in the roughness so when you clean it then it shows what the surface is actually like.

As for black–make sure you don’t expose the print to light until it is cleaned and rinsed off and submerged in water. If you have the light on then any part that has water on it will start curing before the rest which will change the surface color. Also, make sure you have clean IPA since over time it will end up with resin in there and that can leave residue on your print.


#27

Seems like as soon as I put the part in the water it starts to discolor. I need to change the IPA out for clean, hopefully will get some tomorrow.


#28

Since I am using this method my parts got some “milky” areas so I put some Dishwashing liquid in the water. Solved the problem.
Please try and tell us wether this stops your decoloring.


#29

If you want to reduce the discoloration try distilled water. It will have a lot less contaminates that will cause issues.


#30

Also, you don’t need to cure it in water very long to get good results, it just needs to cure the outside of the print, if you put it in there for a few minutes that’s all you need. Also, don’t use hot water.


#31

what’s your Idea about put in ultrasonic included water and also included IPA?!


#32

From what I understand using IPA in an ultrasonic cleaner can possibly cause a fire, so probably not a good idea. It should be fine with water and there’s some other cleaner (I think called Yellow Magic) which can be used in an ultrasonic cleaner.


#33

I’m not a fan of filling the tank in an ultrasonic cleaner with IPA directly as it really is a fire hazard.

There is a work around that some have been having success with.

  1. Partially fill the ultrasonic tank with water.
  2. Place the part to be cleaned in a ziplock bag and cover the part with IPA.
  3. Put the plastic bag in the cleaner, turn it on and run as normal.

This method will clean parts that are larger than the cleaner tank because the IPA in the bag can stick out above the top of the tank. The Ultrasonic waves (and vibration in most of the cheap machines) will travel through all of the liquid fairly well cleaning the entire part.


#34

coat printed object with glycerin or Vaseline and cure


#35

#36

I have just tried curing clear resin in 55 celcius water, it works really well, no stickyness and nice finish. I dont understand why underwater curing is not promoted more?


#37

Wanhao publish the use of water as part of the post cure procedure for their resins. We tend to use other things that work even better. Such as glycerine or liquid paraffin. Both have a (slow) solvent effect on uncured resin as well as speeding up the post cure on the surface.

The surface tackiness is caused by oxygen inhibition stopping the cure on the surface. Water, glycerine or liquid paraffin stop that effect. IPA tends to leave a very thin dilute solution of the resin on the surface which is VERY difficult to cure in air, the effect is worse as the IPA becomes saturated with resin.

This article explains the issue with oxygen inhibition in post cure very well: https://www.sciencedirect.com/science/article/pii/S0109564117313696

To quote part of the article:

Abstract
Objective
It is known that after light-initiated free radical polymerization of a dimethacrylate monomer system, the curing continues for some period of time after the curing light emission has stopped (so-called delayed post-curing stage, DPCS). It is also known that during free radical polymerization, the presence of oxygen effectively inhibits polymerization of monomers. However, less is known of the influence of oxygen inhibition of light initiated polymerization during the DPCS. The aim of this study was to determine some polymerization related properties of a resin system during the DPCS.

Methods
Monomer systems of BisGMA-TEGDMA (60/40%) with light sensitive initiator-activator (camphorquinone-amine) system were polymerized by light-initiation (wavelength average 430–480 nm) with a radiation intensity of 1200 mW/mm2 for 20 s on the ATR sensor of the fourier transform infrared (FTIR) spectrometer. After light curing, the samples were divided into two groups: the DPCS stage was allowed to continue in air (O2-exposed group) or the samples were protected from the direct effect of air (O2-protected group). The degree of monomer conversion (DC%) was monitored from the sample surface up to 360 min from both groups of samples (n = 6). Sample surfaces were additionally analyzed for surface microhardness (VHN) at four time-points corresponding to time-points of the DC% measurement (n = 6).

Results
After ending the light-curing of 20 s, i.e. during the DPCS, the DC% still increased from 50% to 65% in the O2-protected group, whereas no increase was seen in the O2-exposed group. Surface microhardness increased from 2.99 to 9.10 VHN of the O2-protected samples and to 4.80 of the O2-exposed samples during a 6-h period. Surface microhardness differed significantly between the groups (p < 0.005). There was significant correlation between the microhardness and DPCS (O2-protected r = 0.950; O2-exposed r = 0.940, p < 0.001). A correlation was also found between degree of conversion values and DPCS time (O2-protected r = 0.941; for O2-exposed r = 0.780, p < 0.001).

Significance
The results of this study suggested that O2-inhibition of free radical polymerization of dimethacrylate resin occurred after ending the curing light emission. This correlated with a lower surface microhardness of the polymer when the DPCS continued under air-exposure.


#38

Just to give another easy to unerstand / cool example of the role of oxygen as an inhibition layer for UV curable resin printing :

Carbon basically uses this oxygen layer to pass the laser through resin without curing it, avoiding the peel operation completely. It’s basically curing in “midair”.

Too bad they have a very closed approach to the 3d printing market and curtail their technology behind a subscription paywall which makes using one of their machines a $100k/year affair…