The consensus elsewhere is also an enclosure for reducing cracking, but industrial machines (which we can assume do it better) r
Go one forget and heat the entire enclosure 50-100C+. That should be the avenue we use to prevent cracking for large parts (that and better materials). Honestly you shouldn't have issues unless they're rather large parts or it might just be crappy filament.

As for adhesion, a combination of glue stick, kapton, hairspray, and/or abs glue will work for just about any material. Abs should only require glue stick + 110C bed (works for me). Hairspray also works, kapton can work, but sometimes needs help from the other methods.

Went back to my printer and noticed that the little bits of ABS from one extruder are, (yes!) embedded on the outside of the tall skirt.  The actual part is clean. not sure how to make sure this always happens, but . . .

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Update: The part finished printing late last night, so I just left it on the bed until this morning.  Everything seemed to work out - the part stayed on the bed and there was no pulling up at the end.

There is an issue with roughness in a certain section of the part's upper surface.  I've attached a couple of files (if someone can instruct me on how to place images in a post I'd appreciate it).

I think the roughness is more geometry related - not related to warping.  I might start another thread to open that up to more discussion.

http://www.simplify3d.com/support/tutor … and-brims/

I'd seen examples but couldn't relate the terms to the examples.  I design in SolidWorks, used to use an expensive Dimension Elite which was very good, but has only one 'dual extruder' and the second head was always used for support material, which was always a proprietary non-abs 'dissoluble' (in a nasty heated chemical bath).  It also used disposable platforms, and always used a raft.  It had a heated chamber and was really, really good for accurate parts.

But back to now.

Now that I know the definitions, I realize that last night I was intending to go the 'brim' method, and was trying to figure out how to add geometry to my model at 55 degrees so I could fit the brim on a model that completely uses up a diagonal area from the back left corner to the front right corner.

I ditched that idea and choose a raft instead then created a used a high wall skirt.  I actually made the high wall skirt higher than my part . . . just to keep things warm inside the skirt and slow the cooling of the part.

I've also made another jump (since I'm using the Duo) into using the second extruder for rafts and supports.  I had all kinds of issues with the second extruder not breaking off the filament when switching extruders.  I would get hairs and strings all over the part as a result.

And I did run into problems when I started today's print.  I had to cancel the print, clean the nozzles, and perform 'load filament' routines to get a good print started.

I also ran into something I haven't seen yet: The XYZ Software would report an 'unidentified cartridge' and wouldn't send the part to the printer.  I tried everything to clear it, then finally exited the XYZ software and started it up again and went through the whole print process again.

I like how jjc thinks though. some good ideas to try, plus a brim.

However on tall prints which take many hours to complete I've had delamination on high layers, in the corners of the print mainly, and I'm not sure what can be done against that. I've tried printing with and without fan, with the case open and closed... and still getting cracks.

Tried to print a new version of a bar like design that I've printed before.  It's long and narrow and this new version has a pair of deep notches into the sides of the part near the end.  Basically, there are masses of plastic on the ends that are 'separated' in a sense from the mass of plastic in the center portion of the bar.

Both ends have lifted up in two separate prints, causing me to cancel each print before they were done.

So I've added a raft, and I've also added a .2" wide 'wall' around the part, that is spaced .2" away from the part.  I've also gone from 90% fill to 30% fill.  BTW, the part is so long, I have to rotate it 55 degrees to place it diagonally across the platform.  I'm running the 2.0 Duo, so the platform is not as wide as it is deep.

The whole strategy is to try to keep the part at the same temperature as much as possible.

In the previous failed runs, the warping didn't start until the part was about 90% of the height of the part (about 1 in) when printed at 30% fill, and started at about 30% of the height when printed at 90% fill. 

My thinking is to:

1) reduce the mass of plastic in the middle

2) use a raft so the mass is not flat against the glass/glue

3) use a wall around the part to trap heated air in the gap

4) use a wall to shield the part from air currents at different temperatures.

It seems the whole trick is to balance cooling against keeping the part warm enough that the temperature gradient throughout the part is not severe.

I'll post again when this latest print is done.

But - some background:  I'm an engineer, and I started 3D printing from the other direction: using a Dimension Elite in a R&D Lab at a multi-national technology company.  I'm now running a virtual company from my home and I figured learning how to use the most inexpensive 'off the shelf' printer on the market might just help me understand a few things . . . and save me some serious bucks.  I didn't want to go the DIY route.

I'm doing product development, so warping is a big deal to me.  The Dimension Elite has a heated chamber with many fans, and the temperature of that chamber is held evenly over the whole chamber.

The Da Vinci doesn't come close to being able to do that out of the box.  The layer sticking to the bed is not as hot as the plastic coming out of the extruder - that's kind of obvious.  Another obvious thing is that there is a hole in the top of the printer above the extruder.  It's the 'handle' in the 'door' that is the top of the printer. Heat rises, so the temperature coming off of the extruder goes out that opening.

During the first layers, the temperature change between the bed and the soft ABS coming out of the HOT extruder (yeah, I'm ONLY talking about ABS) is from Warm (at the heated bed) to HOT (at the extruder).  Nearly all of my parts are solid throughout, and it doesn't take a rocket scientist to understand that the part you are printing is not going to be the same temperature throughout.  It's constantly cooling.  As it cools, it contracts.  The material on the bed stays hotter than the sides of your part as the part gets thicker . . . and the top of the part is always going to be the hottest place as the very hot ABS comes out of the extruder and quickly cools and shrinks.

From my engineering background, whenever you have a difference in temperature within a solid, the stresses between different parts of the solid that are cooling and shrinking at different rates is going to cause warping.  So it was no surprise that the ends of a long solid part would pull up from the bed.  During one early print, I left the front door open and the part curled up like a banana . . . starting with the front of the part closest to the open door pulling away very quickly.

With one part, with a minimum of glue, I found that as soon as I opened the front door, the part lifted up from the front of the bed as cool air entered the chamber through the open door.  YIKES!

What I've found is using low density helps a lot.  The many, many spaces inside the print help keep the temperature more uniform and relieve some of the tension between layers that are at different  temperatures through the build.

I think adding fans are a great idea, since they can circulate the air throughout the box and provide for a more uniform environment. 

I would think that the right idea is to have multiple small fans turning slowly to mix the air and allow the sources of heat (the bed, the moving extruder head) to raise the temperature of the enclosure to help keep the air inside more uniform and allow the cooling process throughout the part to slow down.

Just my two cents.

I tried lowering the bed temp to the point that it almost doesn't stick and I still get some warping.

Doesn't seem to matter if the door is closed or open. 

Maybe it is just the green filament.

http://www.amazon.com/gp/product/B009NQ … &psc=1