Preheat before mixing

It’s been a few weeks since the last time I ran my printer. I now see that when it starts up, it has a preheat cycle prior to attempting to move the mixer. It also seems to have a “recovery” behavior if the mixer detaches in a sweep, where it goes really slowly for the next set of sweeps when the mixer arm detaches.

Both of these things address issues I whined about a couple of months ago. My printer is in my basement workshop, heated to 64ºF. The mixer always detached during the start up mix, because the resin was cold, and I’d have to stand there for 10 minutes to move the arm back in to position, while I waited until the resin loosened up enough.

The problem is, the printer doesn’t appear to have the wattage it needs. My resin started at 28ºC and rose to 31.1ºC in about 5 minutes, after which it stopped going up. I aborted the print after about 10 minutes of no further temperature increase and restarted with the same result.

I have the plastic bag the printer shipped in, that I put over the printer when I’m not running it so dust and other debris doesn’t collect on it. I slipped that over the top of the printer and down to the base while the preheat was stuck at 31.1ºC. Temperature immediately started climbing. Took it another 10 minutes to get to the 33ºC target. I turned the heat up in my basement HVAC to get it the last couple of 10ths of a degree and the print finally started.

So the question is, what temperature is the minimum that the printer can handle and still get the resin to the target mixing temperature in a reasonable amount of time? Do I need to preheat my basement to 68ºF before attempting to start a print?

When I first received my Form 3 in early February, some days my workspace was in the upper 50s and the machine was able to reach the target temperature. So I’m not sure why you would need 68 F for your machine to function properly.

I would also note that it appears the pre-heat before mixing only applies to certain resins. I only have Rigid 4000 and Color resins to test, and new jobs sent with Rigid 4000 do pre-heat before mixing, but the jobs where Color resin is selected do not.

What behavior are you seeing and with what resins?

Tough 2000 only. There’s another thread I started on the symptoms so I won’t repeat the detail here. But when the resin is cold, the mixer arm can’t be dragged through it, it detaches. Now the printer says it’s preheating before moving the mixer, which was the kind of change I was asking for. Except per above, my machine seemed incapable of hitting the target 33ºC resin temp without some assistance.

Ran another print this afternoon. Printer reported resin temp at 27ºC at the start of the print. My ambient was maybe 16ºC. Temp had barely come up a single degree after 5+ minutes. Slipped the plastic bag over it and the temp started to climb more quickly. At 31.5ºC I removed the plastic bag and the temp immediately dropped back to 31.1ºC and was pretty stubbornly stuck there after a few additional minutes waiting. Reinstalled the plastic bag and the temp got up to about 31.8ºC before it appeared to stall. Turned up the heater for the room to 25ºC with fan on high and after a few minutes more the resin temp started to climb again. Took nearly 30 minutes to get the resin from 27ºC to 33ºC.

I dunno, maybe the heater on my printer isn’t working correctly. But based on 2 prints observation it sure doesn’t look like it’s got the wattage to deal with ambient temps much below around 20ºC…

I run my printer in an environment where ambient temps run below 20C during the winter. In fact, I’ve run lots of prints over the past winter when ambient was ~10C. I have it enclosed in a utility cabinet that has some low wattage heat cables taped inside. These prevent the ambient temp from dropping below 10C, even when it’s 0C or lower outside (I’m in Vancouver, Canada). Once the printer warms up, the ambient temp in the cabinet gets up to 15-20C.

I do have a cover for the Form 3. I suspect that without this, the machine would have more trouble heating as you’ve seen. I got my cover from Digital Deck Covers (link below). It’s really a perfect cover, and it’s strange that not many people on this forum know about it. It also helps reduce the smell for those who are printing inside. You could easily cut a hole in it and 3D print an exhaust adapter for a fume extractor as well, which would likely capture all the gross smells without having to build any enclosure. Not a problem in my case, but good for people to know.

I also encountered issues where certain resins froze or had significant increases in viscosity because of the low temps. My work around for “pre-heating” was to just start a print without the build plate attached, because once a print is started, the convective heater turns on.

I ran a print this evening, but I turned the thermostat up in my workshop (Sensibo remote control) before I started orientation and supports in Preform. So it ran maybe 20 minutes before I started the print (was nowhere near 70 by then, but it was at least a few degrees warmer). Resin temp at start was 27ºC as always. And I still needed to put the cover over the printer, but it only took 20 minutes to preheat instead of 30. So from now on, when I’m getting ready to do a print, I’ll crank the heat up for 30 minutes beforehand.

I also can’t get my printer heated past 31.9 in a room where the ambient temperature is 22.

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