yep, done that, the “shelf” is well fixed & the standard auto supports plus a few carefully placed ones seem to work
I originally set Chitubox to the defaults for FNG, which to be fair has worked pretty well for nearly everything I’ve printed. Typically the prints when I wash them are the stiffness of a nice cheddar. Sort of firm but deformable, and ten minutes in the uk box makes them good and solid.
Current exposure time is 2.5s with no rest times before or after lift, and 0.5s after retract. As I’m doing it for fun, it doesn’t really matter if it takes a bit longer (different if your business depends on throughput, or you need another printer for capacity) so I will increase the exposure to 2.75s, ie 10% more.
I think you mean “high” viscosity, ie it’s sticky, not runny. I can see this being an issue with models with considerable cross sections. Not sure it’s a problem with thin sections like the wagon, except perhaps the floor, which is 1.75 thick.
i invested a tenner or so in an Amazon lizard heating mat. I don’t think the lizard’s nationality is relevant. It does increase the temperature but by only a couple of degrees, I got to 21 or so, though the mat is warm to the touch, I guess the heat transfer to air is poor. I will cobble up something with the mat, a thermistors similar, and an Arduino, and feed it an amp or two more.
thanks for this Mick.
I do have dual speed lift, but incremental change is the order of the day. I’ve put in a rest before lift of 0.25s, coupled with the 10% increased exposure. I’ll leave the other settings for now. A second more exposure is clearly possible, but will add nearly 30% to the print times. As I said, it doesn’t matter, but I’d prefer not to if I don’t need to.
I’ve also slightly thickened the model, again 10%, it’s now 0.55mm shell, which is nearly an inch at scale! And I’ve amended the cutout for the doors, so the door edges are still there, but they don’t go right through.
15 degrees from horizontal lengthways and transversely
Right, back to Chitubox and fingers crossed…
Okay, a lot going on here and a quick glance at your proposed new figures will almost certainly result in the bin monster being fed I'm afraid.
I'll jump between points as I think about them, adding 30% more print time, think about this, if the wagon takes 3 hours to print it'll then become four, if the wagon fails you'll print again which makes six, by my logic six hours to print fails is worse then four to print successfully.
Default Chitubox exposure is miles out, for me anyway, that was the biggest breakthrough I found, I had warping all the time and decided bugger it I'll go wild, here's the stash of VL80 bodies, each about 10-14 hours so not only a lot of waste resin but days, weeks of lost time.
So six wagon bodies and you're just getting into it I'm afraid
Another point, at some stage you should ask yourself if 3D is the right medium, if it consistently fails then there's a high chance it can't be printed. Most people send me CAD files to print and I send them back as unprintable, because they draw to scale. Some people say just print it and then I hand them a big bill for all the fails whilst searching for the optimum orientation, their WTF response is uniform, mine is told you so.
Then they make the necessary changes to suit 3D printing and suddenly it works....go figure. In short, you can't model and print scale thicknesses, you're going to have to accept some sort of compromise if you persist in 3D printing.
Supports, sad to say no where near enough where it counts (high load areas) I'm afraid, more supports = more strength = less model movement under hydraulic forces, oh and 21° is cold and the resin is thick so you need to ramp up delay and exposure times, the hotter the resin (some run around 28-30° which is considered a good level for FNG), typical supports for large objects is thus.
A typical (short sighted) argument is look at all that waste, so people cut back and then end up throwing it all in the bin because it failed, wake up, it's not a waste if it results in a 100% finished product as opposed to dozens of fails.
Compression forces, watch this video I did this morning, I read somewhere the compression forces are up over 50KG for the first few base layers, less as the model works it's way up, that's also partly due to the longer supports flexing (and not the Z axis bending) under compression load, flexing supports result in model movement which result in pressure waves and warping.
The DTI is fixed to the top of the Z mast, the backbone of the machine and it's strongest point, I started a few seconds before the first layer and the first step is to go to home (maximum compression), you can see how much force occurs as the mast flexes backward as it tries to compress the resin, you can feel it by hand too. The next step the machine takes is to lift a few mm and go back down the first layer height, in my case 50 microns, you can see the pressure come off and back on again.
If you had a more accurate DTI and higher speed camera you can see the pressure is still reducing once the bed plate has stopped as the resin evacuates the cavity, this is where you need the on delay setting, you're running 0.5 seconds, not worth it, waste of time, for your thick cold resin you need 4-5 seconds at least, I run 3 seconds at 25°C, word on the urban grapevine is 2 seconds for 29-30°C.
You'll have to fast forward to about 1 minute to see the peel forces and then the lowering for the next layer, nothing like the base layer but still quite a lot.
Rest after print or lift, debatable, some/most say it's pointless, I run 1.5 seconds and could see an improvement in thin parts being straighter and stronger, your mileage may vary.
Lift speed, in the lower region the slower the better and the length (distance) is important, you're looking for about 7-9mm of total travel and I split mine 4 & 4, some do 3 & 5, three being the lower section. The lower section is important, this is where the build plate is lowest to the FEP and where most of the forces are starting to occur and this is where you need to be going the slowest, for base layers which are not detail critical then I run 50mm/min, for the detail part layers I run 40mm/min, that's both lower and raise. For the upper section I run as fast as possible to gain some time back, in my case 200mm/min.
Exposure time, I over expose a little, two reasons, I want strength in the part in the future and make sure all of the resin is actually fully cured and second I like the sharpness and lack of warping in the final product. Exposure varies between machines, I believe there's a little pot on the motherboard and they just twiddle it near enough in the factory and send it out.
If you read the forums and such like the best setting is 2.5 seconds at 50 microns, I run 3.7 to 4.2 depending on resin temp, my base layers are set to 57 seconds, to date I've had 0 adhesion to base plate or parts breaking away. I could never run at 2.5 seconds, lowest I could ever run was around 2.8 so I expect my pot is trimmed a little lower, even then, all my models looked like yours, bin fodder.
Orientation, I'd not run as low as 15° for both axis in a dual axis set up, I'd run that as one of the dual axis angles but the second (in the longest plane, in your case wagon front to rear) I'd be looking at 24° minimum and somewhere around 33-36° optimum. For single axis orientation then that depends on the object shape and layer lines or forcing them to an area where it's easier to clean/smooth them. If they're on a curved surface then take a look at the VL80 and you'll see the lowest point (where the final layer lines appear) is right on the brow over the windscreen, clear of any details and easy to smooth off.
Feel free to tweak 0.25s and 10% but you might want to invest in one of these
On the other hand, go crazy and just slam one shot at much higher exposures and more bigger supports, I mean, what's the worst that can happen, it fails and joins all the others in the bin
finally look at your delay times, that thick ole resin is still moving once the bed plate stops moving, give it a chance to ooze out and stop moving under compression, by the same token, give it a rest before you yank it off the FEP, poor old model doesn't like being ripped off the second the UV light goes out, it's still solidifying so give it a chance to do what it needs to do, then lift off the FEP.
