Remember that time when you got that print going, then after it was done you realized the build plate was not in there? Well…I did the same thing.
So I expected a plate of resin to be washed up on the shores of my resin tank but there was nothing? If there is no metal build plate then nothing gets cured?
I don’t think the printer senses if the built platform is installed or not. But I suppose it could. I don’t remember anyone asking the question before… You’d think you’d have gotten an error saying “no build platform installed” if that were the case, though. And if it ran the laser, you must have a raft of cured resin in the tank. Are you sure you actually started the print?
If I understand you correctly, it got cured on the bottom of your tank. The good thing is, you didn’t waste as much resin as if you would with successful print.
I know you guys are going to call me a liar, 
but I scraped/scanned the bottom of the tank with a business card and nothing. I even moved the wiper. It ran the entire time I was upstairs and I even waited to see the first beams of light appear in the tank, then I left for the 1.2hrs it was printing.
I realized my mistake, scanned the resin tank like I mentioned and nothing.
I am really surprised there is no Off switch on the Form2. Or something that shoots the laser up and detects metal or not.
That sounds weird. So the laser passes through the tank without curing anything? Maybe a formlabs employee can elaborate more on this.
That is very confusing. If the build platform isn’t installed, the laser will still cure resin and it will adhere to the PDMS layer. This is why we have a prompt before starting a print along the lines of ‘make sure your platform is installed’. I don’t imagine many of us read the prompt after the first couple of prints and I’ve made this mistake once or twice. To be on the safe side, you might filter your resin and check the bottom of the tank to ensure that nothing is adhered.
yeap, I checked the resin, nothing is there. Since the metal goes into the liquid I would imagine something happens when it hits metal.
I have a ~405nm handheld 20mW laser I use to bond separate printed parts together with resin. I can 100% guarantee that the resin cures almost instantly when hit with laser light whether or not the resin is on a print, still in the tank, or on your fingertip (which I stupidly tried to cure with the laser and was instantly/painfully reminded that resin curing is a highly exothermic reaction). Since there’s no build platform present when I bond parts together, whether or not the build platform is present does not matter to whether or not laser light will cure the resin.
So if your print went to completion without a build platform, you should have a nice thick coat of resin on the bottom of the tank because if the laser hits resin, the resin cures.
The only explanations I can think of are: you do have a layer of cured resin on the bottom of the tank you’re not detecting for some reason, or the print didn’t actually proceed even though you think it did.
If the model you printed filled up the build platform, is it possible there’s a uniform cured layer of resin that just seems like it’s the bottom of the tank but really it isn’t?
Note, I’d be very cautious about using the tank for another print until you’re absolutely certain you understand what happened here. If there is a thick undetected layer of resin on the bottom of the tank, when the build platform descends to “zero” for the first layer of the new print, it’s going to need to push the resin tank down as far as however thick that remnant cured layer is, which it may not be able to do without damaging the tank or the printer.
The printer does not know if the build platform is there. I would expect cured resin on the PDMS that is easily removed with a gloved hand or a spatula. I can’t explain why it wouldn’t result in cured resin.
@BenFrantzDale Begs the question, why is there not a sensor to detect the build platform. Could be a simple microswitch by the clamp mechanism just to know its in place. May be worth considering for next-gen.
It’s a good thought. The simplest approach involves a bending cable which, while possible, adds cost and complexity and is asking for reliability issues.
Thank you guys for all of the info! I am wondering if it just ran through the paces and didnt really do anything besides raise the platform etc. I didnt watch it the entire time but I definitely checked on it. I have it in a fairly dark room so it was hard to see any build platform at all.
Thanks!
Isn’t the capacitive resin level sensor giving a different output when the build platform is fully down? I can imagine this sensor would respond a lot to the aluminium frame.
The sensor is only checking for resin level when the build plate is retracted.
I did this once and it did leave a mound of solidified material, I only let it go a short time so it was just the raft. I just scrapped it out and everything thing was fine. But if you got a lot of loose pieces that would be annoying to clean out of the resin tank.
Of course, otherwise you cannot measure the resin level.
So I’m saying… What if you don’t retract the build plate… Will the sensor change output due to the build plate being there? It’s a cheap and easy way to check if it is in place when starting a print.
Ahhh. I see what you are saying. Yeah, that seems like it’d be a good idea…