Pigments, layer heights, intensity questions.

[goopyplastic]

I have been trying to work out some good exposure times, pigment concentration etc. for lower layer height prints.

I am wondering if anyone has insight into how light intensity, cure time, and pigment concentration inter-relate.

My DLP is focusing about 2300 lumens into 51.2x38.4 (50 micron) area, and I am aiming for .05mm layer heights and lower.
My cure times are very fast with makerjuice subg+, subflex, subsf. With stock pigmentation I have the problem of not being able to reign in overcurring, as I dial the cure down the print falls apart, but still overcurred (ie. not accurate, overgrown features etc..)

I have been solving this with extra pigmentation but am having to use quite a bit, for example 4x the red pigmentation of standard subg+ with cure times of 1.25seconds at .05mm
I know others can print at .05mm just fine with stock pigmentation subg+ but have longer cure times and less light intensity (miicraft).

Would less intense light source + longer cure times = less need for pigment?
Would accuracy be better in general with less intensity + longer cure times?

Just curious if any of you have been down this road, or have any suggestions.

It seems like b9's answer is pigment load, the cherry pigment they have looks to be some pretty dense stuff.

[anthid]

I am having the same problem. I am using B9Red resin. I have exactly the same build area as you, but interestingly my projector is way less powerful, a cheap 1100 lumens one. Probably the optics doesn't block UV as well as new projectors.

I have tried to project in various gray tones rather than pure white, with no results. I think that when projecting gray instead of white, the light is still white, but projected less micromirror cycles, so the result is the same as lowering curing time. I cant control light bleeding and eventually the part doesn't cure.

I also tried to project in pure blue (the light have to pass trough color wheel, so I hope it loses some power), also without results. Probably in this case i have to rise curing times, but abandoned this route in favour of pigment concentration.

Adding pigment (and projecting in pure white) the problem was less evident, but still present and the amount of pigment i had to use was huge. 5-6% concentration by weight.

I am now waiting a new pigment to arrive. I will test to rise pigment concentration + blue light + raise curing time.

I am courious if you have resolved the problem or have some new findings to share.

[goopyplastic]

I will say that a more modern higher contrast projector doesn't seem to suffer from this nearly as much. I am testing some Acer's and they don't seem to have the problems that the old Dell I was using had.

That said I tried using some MadeSolid resin with my Dell and it became less of an issue as well. Seems like maybe pigment has more of an issue with this compared to uv blocking dye.

[@A2]

Where do you think the divide is for the quality of the print surface finish based on the contrast ratio?

Is there noticeable difference between 10,000:1 vs. 15,000:1, given a 0.10 mm resolution?

I'm considering the following two projectors:
1. Acer-h6510bd, Contrast ratio, 10,000:1, http://www.projectorcentral.com/Acer-H6 ... or-pro.htm
2. Viewsonic PJD7820HD, Contrast ratio, 15,000:1, http://www.projectorcentral.com/ViewSon ... or-pro.htm

[anthid]

I dont think that contrast ratio has a role in this problem. Contrast ratio is related to how truly black black pixels are. With low contrast ratio, we would expect poor edges definition, but I am not getting this problem, in fact I have focused the projector very well and am having an outstanding X-Y definition (remember that UV light focuses a bit further than visible light, aprox 5% in my case). For the records, this is my projector:

http://www.projectorcentral.com/IBM-iLM300.htm

So @A2, from my experience, discard contrast ratio as a choice factor.

And @goopyplastic I bet that the difference you are seeing is related to UV blocking capabilities from both projectors. Specially when is the modern one which behaves more in line with resin reactivity.

[adambx]

I'm having exactly the same problems as you guys. I have the acer H6510BD and I use borosilicate glass formy vat bottom which is totally UV transparent. I tried stock red pigmentation of SubG+ with down to 400ms cure time @50micron and i have lots of Z bleeding. The undersides of my parts are pretty washed out and blobby while the top side is crisp. Image printing an upside down pyramid, the edges are totally round. With the regular pyramid it's perfect.
I have thrown in a bunch of pigment (white, black and red) Now the material is pretty dense but still I get blurred down facing features with 75micron Z height and about 1.3s Curing time...
I don't know how others are able to print nearly transparent parts and not suffer from this issue..maybe i'll try a piece of glass in between the projector and the vat to block some more UV.

Also tried the grey and blue projection image to no avail.

Has anybody found any solution yet?

Cheers,
Adam

[anthid]

Hi Adam. I solved it adding pigment. It is the only way. At first I used Spot-A pgiment, but I reached almost 7% concentration without noticeable results. After that I tried almost all things you can imagine, but nothing worked. You can block some light before it reaches the vat, but once it reaches the vat, if the pigment concentration is not enough, you'll gonna have light bleeding.

I purchased maker juice pgiment (http://makerjuice.com/product/fire-red) and I nailed it at 1.75% concentration (I'm using B9-Red resin). As you have SubG+ resin, are you using MJ pigment? You have to shake it very well before using it, but as I said, it worked for me.

[adambx]

Hi,

thanks for the affirmation. I've been adding more and more pigment now and it works quite well. I've used up all my MJ EZ Pigment (Red). Now I'm adding generic white pigment for epoxy resins...can't tell you where to buy because i still had some at the shop. But if it works out, i'll Post results and sources. The MJ pigments are quite expensive and I believe comparable products cost way less in larger quantities...

It is also better to have some pastel-ish colours to see the details of a model. (everthing you get by mixing it with white).

Cheers!

[goopyplastic]

[muringa]

Hi guys, firts post here!

Which pigment you guys use?