Replicator: first layers print poorly

[Zak Kus]

I've had my Replicator for about a week or two, and have been pretty happy with it. 

However all my prints have the same problem, which is that the bottom layer or two are very crappy, for lack of a better word. The threads are barely bound to each other, and often there are threads out of place (take a straighter path when it should do a curve). After that though, it prints beautifully. This is a problem for my current project, since the part everyone sees is the bottom layer (there is a large overhang if i flip it, and i dont know how to deal with that...)

My initial theory was that it was a heating issue, so i cranked up the print bed's temp to 110 and enclosed the printer, which actually helped some warping issues, but the first layer is still pretty shotty. 

Anyone have any tips for dealing with this? One thing I would like to try is a raftless print... though my print bed is currently warped, and haven't been able to successfully go raftless yet (hopefully a replacement bed will arrive soon).

-Zak

[Zip Zap]

"straighter path when it should do a curve" - That's more a firmware/software issue.  All these upgrades called Marlin, Jetty, etc. attempt to resolve all that by decelerating the extruder instead of the current abrupt stops.  Go to Reprap Wiki for more info on Marlin and other upgrades. 

The other problems your facing such as layer separation can be resolve by switching to PLA, more preferably colored PLA.  Clear PLA is more challenging.  Get a sample roll and compare.

In other words, more refinements steps exist. 

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From: Zak Kus <zak...@gmail.com>
To: make...@googlegroups.com
Sent: Monday, April 23, 2012 6:51 PM
Subject: [MakerBot] Replicator: first layers print poorly

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[Jamesarm97]

"straighter path when it should do a curve" - Also happens when the z height is not low enough. The filament does not stick well when it is moving in a circle and is pulled and creates a straight line. I have seen this before and just experienced it just now. I had to re-level the hbp and then lower the height a few times before the first circle printed fine. It was printing correctly for the first few inches then had the last part pulled straight as it was printed because it was not sticking to the platform. I went from 123.6 to 123.705 to get it to stick and print ok.

[Paul Davis]

I started with the same problem.

Try raft-less (helps the bottom layer) and reducing the feedrate speed (25mm/s) and reducing the layer height. It will increase print time.

The settings hbp-temp/extruder-temp/feedate/layer-height/etc become a bit of an art. After a while you'll get a feel for the options to adjust depending on the model you are making. Some times extra shells and infill are great, other times the same causes excess warpage.

Though annoying, I always recommend recalibrating the platform before every build.

-Paul

P.S. Please share your results and settings. We are all learning. If you are printing something from thingiverse, leave a comment with your settings and a picture.

[Travis]

I get that when there's too much clearance between the build platform and the print head.  The filament being deposited doesn't stick to the previous layer, so it gets drug until it does.  The final result is a filament that 'takes a shortcut'.

If you're print platform isn't planar at temperature, you can have more clearance in some places than others.  I've had to designate a smaller portion of my platform for printing until my new platform arrives.

[Ben_R]

No, that sounds like the first layer not sticking the platform, and the nozzle pulling the filament around. 

[Zip Zap]

My Cupcake and unleveled aluminum unheated platform is not reliable either.  I end up babysitting the first layer by turning the z motor pulley to move the nozzle up at certain points to avoid bumping into any PLA oozballs.  Then I do some final manuel adjusting before letting it go.  The builds I do are not intricate figurines so I don't really care about layer perfection.  I just don't want any collisions to throw off the build and end up with an offset object.

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From: Jamesarm97 <armstro...@gmail.com>
To: make...@googlegroups.com
Cc: Zip Zap <zza...@yahoo.com>
Sent: Monday, April 23, 2012 7:06 PM
Subject: Re: [MakerBot] Replicator: first layers print poorly

"straighter path when it should do a curve" - Also happens when the z height is not low enough. The filament does not stick well when it is moving in a circle and is pulled and creates a straight line. I have seen this before and just experienced it just now. I had to re-level the hbp and then lower the height a few times before the first circle printed fine. It was printing correctly for the first few inches then had the last part pulled straight as it was printed because it was not sticking to the platform. I went from 123.6 to 123.705 to get it to stick and print ok.

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[Travis]

If it's just the first layer, then I agree.  He said "first layers", so I was visualizing this happening on the 2nd, 3rd layer, etc, which, for me, went away when I re-leveled my platform and only used the part that was mostly planar.

[Zak Kus]

I've removed the raft, and reduced the feed rate and layer height by quite a bit... The first layer print quality seems much better, however the print keeps snagging. My warped print bed is definately causing me some headaches. I've move the print to the corner where its a little easier to level (dip seems to be in the middle). We'll see how that goes... I think ill just let it run through the night at hope for the best.

[Zak Kus]

yeah, i watched it. The toolhead goes where its suppose to, its just the thread doesn't always want to stick. Likely a leveling/warping issue....

[Mark Cohen]

That is because you are not a starting close enough to the build platform. Recalibrate the z by adding in increments of about .01 to the stored z value on the motherboard settings till it is working correctly. You know you have it right when the first layer is flat and it looks a bit like they overlap. Too close and the second layer will look a bit fuzzy.

Sent from my iPhone

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[Zak Kus]

Where do you go to tweak these motherboard settings?

I was able to get a successful raftless print, which looks much better. I did several things at once, but i think the key was that i move the print to the corner (to avoid the warped mid section) and re-level with just focus on that corner. I also lowered the feed rate to 20 or 25, set the heat bed to 115 (seems to be about 10 degrees cooler in reality), and lowered the layer height. Much much better but still a little less than the subsequent layers. (ill post a comparison when i get home).

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