It's not the heat, it's the humidity

[Gary Crowell]

One week old Replicator with a new(er) build platform.  I always set it to 110, printing with ABS.  The first few prints I did with a raft, but I never saw a sticking problem, so the couple of dozen prints since have been raftless.  I was wiping with acetone before every print, but finally stopped doing that - if anything the prints were sticking too well.  It has taken a lot of force to remove some, and I've broken a couple of objects trying to get them off.  The platform was trammed multiple times initially, and has appeared to remain in alignment since.

Everything was working swell... until today.

Like somebody turned a slippery switch, nothing sticks.  Wipe with acetone.  Tram the platform (it wasn't far off).  Nothing sticks.  (haven't tried a raft yet)

The temperature in this room has been between 68-75; today it is 75.  The only difference I can see is that today there is an afternoon thunderstorm, and the humidity is in the mid-40's.  Previously it had been 35% or less.  I've had a meter in this room the whole time, so I'm quite certain of the change.

My Kapton tape is getting nicked up, so I'm going to try a change on that next.

Gary

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Gary A. Crowell Sr., P.E., CID+

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[Joseph Chiu]

The Replicators are made with plywood, which obviously can swell with moisture*.  I suspect you may need to re-calibrate your Z-depth.  Even 0.1mm difference in Z height can make or break a print.

(*I once had a bedroom door that you can rely on to swell and shrink just-so between summer and winter humidity - the door would shut nicely in cold dry weather, especially during snow season, but would need a shove during spring rain season, and would catch during the rest of the year.)

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[Jack Coats]

Some trivia for the day...

Not that it doesn't happen, but the plywood expand/shrink is minimized BECAUSE it is Plywood.  The thinner the ply's the less likely the expand/shrink of the individual ply's will transmit to the overall piece.  Wood tends to expand/shrink along it's long grain axis more than it does cross grain.  The opposing cross grain is what limits the amount of movement.

You are right, wood does expand/contract, plywood, chipboard, and MDF do much less of it than solid woods.  The best plywood for non-stretching are currently considered Baltic birch, appleply (imported vs domestic versions of similar plywoods, etc because they have few if any voids and are 'hardwoods' on all layers.

[Txoof]

Making sure your Z-height is spot on is a great place to start.  Failing that, you can try adjusting Raft > Base > Base Nozzle Lift over Base Layer Thickness.  I had a large thin print that refused to stick.  Adjusting that setting made a huge difference.  

I was having trouble with my Z-height on my TOM so I switched over to a Z-height minimum probe: http://www.thingiverse.com/thing:19204  

Before each print it zeros the Z-height.  This has made the largest contribution to the quality of my prints.  I don't have a Replicator, but I assume you could hack something similar to work.

[Joey]

While plywood has limited expansion in length and width, it expands in
thickness about the same as the wood it's made from. So a large change
in humidity might cause a noticeable change in the calibration
(depending on the thickness of the panel, a thicker panel will of
course change more in absolute thickness). Also, using "hardwoods"
doesn't always help with respect to expansion or strength, balsa is a
hardwood after all.