High temp resin printing problems FORM 2


#21


Ok so I got close yesterday the firs pic is the one i printed at .05 res with all numeral fillets removed set at a steep angle… I got the ejector pin hole I wanted but you can see some bad striations and some of the numerals didnt really come out. I tried printing again at .025 res and at a shallow angle "my thinking being that the internal faces are what i want to turn out the best, and at steeper angles one or more faces are closer to parallel to the print bed. anyway you can see it failed… I also attached a pic of a similar mold printed in flexible… I actually have gotten better results with the flexible than the one pictured, its all i had on hand atm. IT was printed at a steep angle at .025 res. Im wondering if i could use another material, like grey pro or tough if that would work as a mold, im using two part resin at warm temps, no more than about 100f so im starting to wonder if this just wont work with the high temp resin?

Thoughts?
     Thanks

#22

Are you sure the optics are clear? Looks like a print done on a fogged pdms.
Blobbing and distortions are also a sign or an under exposed resin which fogged pdms, clouded glass or main mirror can also cause.


#23

I have no experience with high temp resin but I agree with @KenCitron : this looks like there’s an issue with the ammount of light getting to the part.

Have you tried printing this :

and looked at the result ? This .form file tends to exaggerate the issues related to the path of the laser and will help in telling whether you should clean anything. In all cases it’s a good opening point for a Formlabs ticket if you want to speed things up.


#24

thanks for the Tips I will try out that print pattern.

before I embarked on this latest round of mold printing, I did clean the print window with PEC pads. It had a faint haze that I could only see with a flashlight. I also looked into the machine to see if I could see anything on the mirror “i didnt see anything” I have had many successful prints uning the high temp material before but this one really is confounding. honestly I’d love for a dirty mirror or window to be the problem. I have a print runnning right now but i will revist this when its complete.

I will advise when I have more to report, but in the meantime i really appreciate any ideas.
thanks


#25

Close, but no cigar. this is the same file at .025res. i just set it at a steeper angle… I got ok resulds except for the distortion.
I checked the window and the internal mirror with a flash light. there was a some slight straking on the window but it was very faint. i cleaned it up but it was very faint. but the mirros are clean and i dont see any dust inside the printer.


#26

I still don’t know why the surface looks so blobby. Do you really need 25 micron? I use 50 usually even with small text as most of the modes are at angles so your more reliant on the laser spot size and xy minimum feature size. Finer layers usually useful on very small objects. Build lines are not so bad on sla as compared to a polyjet system which usually have very evident build lines and tend to have ratty edges (because the resin is sprayed like an ink jet printer).

Model like that I would actually try 100 micron.


#27

I’m not married to the 25 micron, but it seems to be the most successful of the various failures. I’m open to trying it. I was afraid of losing numeral detail


#28

25 micron would be necessary if you had tiny features that were vertical on models orientation. XY resolution and feature detail makes up majority of the model as that doesn’t change on the printer and is determined by the laser spot size.


#29

Well I tried printing this in grey pro just to see what happens, i also set the res to .1 mm. I also printed these little brackets just before the mold print with no problems same resolution as the mold test.
Im starting to wonder about the triangular hole in the print. Just for some backround… I printed this in flexible many times last summer with good success. I am also starting to wonder if the new firmware may play a part?!
The main print window seems to bave some faint “abrasion” marks for lack of a better word, where some kind of coating mmight be worn off maybe? but it is so faint as to be almost impossible to see withouth the aid of magnification. I also have printed may prints besides the mold with no problems… when i upload the mold to preform it detects no errors BTW.

nope|500x500


#30

The freaky thing is that it only appears to effect the faceted cavity.

If it were optical- then shifting the position of the print should change the location of the flaw… but the vents and separation planes appear to pint perfectly.

One test I would suggest is to post the actual model and let one of us try and print it to see if we are getting the same results.
That would at least identify if it were the model, versus your machine.

If other machines get a similar result- then we can know its model.
If only machines running the latest software have the issue then its the software.

I am still running Preform 2.17.1

PS- have you considered printing a positive model of the die and making a platinum silicone mold for casting?


#31

PS- looking at the better example- it does not look like your numbers are correctly drafted for casting a rigid material in a rigid mold.

This looks like something that would be better printed as a positive for a high durometer rubber mold.


#32

yeah The model is still suspect… with that in mind I made some changes to my original this moring after my morning post. i dont THINK its a shifting model but who knows.

  1. I am running 2.19 preform my old molds were on 2.17.1 as well
  2. I printed this new part today with the small changes to the numerals, please note the buldge on the outside of the mold “this face should be smooth”. so this is another mystery. The setting is .1mm res
  3. i had thought about printing a positive, but am hesitant because of the support poits being left over affecting the quality of the finisshed mold.
    Ill post the file later once this post has some time to digest.


Ill post the model later.


#33

Hum, have you checked for cupping ? Are you able to share the STP file with Formlabs so that they can check if the file is good or not ?

I would still print the test print linked earlier. Your printer could still have optical issues and this print makes the laser pass several times over the same area to increase the consequences of such issues. It is also possible that that simple successful model you showed photos of could print successfully but the increased complexity of the letters in the dice mold as well as the possible cupping could lead to issues.

The model as you said might be causing issues. I would try to make a completely new file from scratch, maybe just with the shape of the dice without the numbers and print it with the same orientation.

By the look of your part, especially the last two trials, my money if still on low laser power (=pollution on the optical path, or dying laser but that’s unlikely and obviously not good news).


#34

you can print a positive with no support points on the relevant surfaces.

Its call a split master.

So, imagine the opposite surface from your Die mold.
That would be a solid block, with its UPPER surface being the negative of the separation line in your existing model- and instead of a cavity, just HALF the positive die form sticking up out of that separation line.

As if you poured resin over the entire separation surface and cavity of a ‘good’ print of this die mold.

Your vents would show up as Positive forms sticking up out of the separation plane. And so would one half of the die as a positive model of the die.

For the opposite side of the die you produce a second inverted model- capturing one side of the separation plane and the other half of the die sticking out positive as a model.

You end up with two blocks you can print with the separation plane and each half of the die as a positive model. These can be oriented on the printer with the precision surfaces down facing and so avoid contact points and their inherent distortions.
You then pour a high durometer platinum cured silicone on each of these blocks- and when you peel the two silicone parts off- they will fit together and form a mold.

Platinum silicones can be found that have near zero shrinkage and they can handle the temperatures you plan to cast at.

The only reason for a rigid mold on something like this is if you plan to use an injection molder at hydraulic pressures.

Conversely- you could also use the Split master to cast a metal filled resin to make the mold halves- if you need to injection mold the dies.