Removing bottom/top layers

[Hammerhead]

What settings would I use in Skeinforge to remove the bottom layer of one part and the top layer of a second part on any given print?

I have two pieces that I need to assemble together (think 'mirror image') each part having 10% fill.  Since they're being glued together, I need for the two faces which will be on the interior of the part to be printed with only the fill exposed when they're done, as opposed to being enclosed.

For example, if you wanted to print an apple, you slice it in half, but only one flat half is on the bed of the plate, the other cut flat half is facing up.  The half that's facing down needs to be printed without a bottom layer (only the fill exposed) and the other half with the flat side facing upwards needs to be printed with that side 'open face' with only the fill exposed.  This way, I'm not printing additional "solid' layers that will only wind up being glued together and never seen anyway.

Thanks!

[Joseph Chiu]

I'm not sure that it's worth all that effort to do this, but since you asked -- one approach that immediately comes to mind is to export the parts with so that the each half has an overlapping band with the other half and then run them through the slicer.  Then, discard the top layers of the lower object, and the bottom layers of the upper object so that they will join at the same layer  (I might even allow one or two layers of overlap so that when you acetone fuse them together, the melting of the plastic cosumes that extra thickness) .  You would specify the start and stop layers of the carving in Skeinforge to pick the layers you want to output.  

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[Hammerhead]

Joseph, it's worth the effort - at least for me - because I'm making parts for production and not printing fully filled layers will likely reduce print time by 25% or more.  If I'm unable to work this out, then my price will have to be so high to account for the additional machine time that the item will be too high for the customer and I'll lose the job.

By the way, turns out I've changed the design, and now I need to figure out how to print both parts open-face down but eliminate the initial 100% bottom layers.  In other words, I need to start the print with only the extra shells on the perimeter and go immediately to fill on the first layers, with both layers printing on the bed.

That said, I'm not sure what you mean when you say 'export the parts... with an overlapping band'.  Does that still pertain given the change in design?

[Joseph Chiu]

Well, it's based on something I read from ProtoParadigm's plastic T-slot beam (http://www.thingiverse.com/thing:10261) -- he prints out 100 mm segment at 101 mm lengths, to allow for material loss during welding sections together.  That is, when you mash the two 101 mm sections with ABS-dissolved mating faces, you squeeze out 1 mm of length from each end.  Then you clean up the "flash" when you are done.  

My point is that if you're ABS-welding the parts together (instead of gluing), make sure you have excess material to consume at the interface of the two parts...

[g. wygonik]

Try this:

• Duplicate your working SF slicing profile (RepG -> GCode menu -> Edit slicing profiles... -> Duplicate) and give it a fun name like "no bottom or top".
• Edit your new profile (hit the Edit button)
• In the SF editor, go to the Craft -> Fill tab
• At the bottom of the parameters, find the one labelled "Solid Surface Thickness (Layers)" and set this to 0 (zero)
• "Save All" at the bottom of the SF window, then close it

Re-slice your object with the new profile then view it in a gcode visualizer (like Pleasent3D). It should not have a solid layer at the bottom -- starts with just outlines and infill (see attached screenshot).

HOWEVER -- this will also make the TOP of your object not filled if it's flat. If it tapers to a close it will be fine (your apple example, and the "ornament" in my screenshot).

Good luck!

[Hammerhead]

Thanks for the suggestion, though unfortunately it won't work.

Per my prior message, I'm needing to print both halves with only the first layers 'open face' (fill only).  These parts are 2.5" x 4", rectangular shaped and flat on bottom and top.  Think 'matchbox' or something like that.  Need the bottoms to be open-grid.  Any way to do that?

On Sunday, December 16, 2012 11:43:33 AM UTC-5, g. wygonik wrote:

Try this:...

[g. wygonik]

Yeah - sorry. You only previously gave the example of an apple which is rounded and tapers at the top. Knowing you want a flat top changes things. :-)

If you can find a good profile for Slic3r to work with your printer (I can't for my ToM), it has separate options for how many solid layers at top and bottom; I've never found that for Skeinforge. :-(

g.

[Clinton Hoines]

You can indeed input how many layers used for solid layers in SF. But it is for both top and bottom not one or the other.

 

 

Clinton

[whpthomas]

You can also remove the top layer manually. Enable skeinlayer in the RepG profile editor under analysis, scroll through the layers and write down the Z position of the layers you want to delete. Then in the GCode, search for that Z position and delete everything above it (below it on the page) but leave the final bit of code labeled end.code in the comments. Its only about 10 lines or so right at the bottom of the page.

[Hammerhead]

No worries - it was my mistake.  Actually, I gave that example before I had finished the design work and realized that it wouldn't work the way I hoped.

So, to reiterate - I need to print this with no bottom layers - I need the top layers only.  If anyone can think of a way to get it done, I'd be grateful.

Thanks!

[hellphish]

There might be a manual way to do it, which I don't think will scare you much :) You could try to splice gcode from two profiles together. I believe you can set 'carve' to only do a range of layers. Set the first round to slice from 1-3 (assuming 3 layers solid thickness) with no fill. Then do another slicing 1-999999999 with the fill settings you want. After it is done, replace layers 0-3 with the gcode from the first run. Should be pretty painless.

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[Lucas Saugen]

or possibly just remove the first 3 layers of gcode and raise your platform to compensate the missing distance. You should know the exact distance. If layer height is .27 x 3 layers = difference.

You could also build your object with that extra distance in mind.

just a thought but I might be thinking about that wrong.

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[Doogiekr]

Just out of curiosity, if this is something your designing (ie, not someone just handing you an stl that is hard to modify), is there no way to design it to print the way you want? At least for me, I would want it to be designed to print the way I wanted and not rely on SF to get it "workable".

On another note (this is from my experience with Rep1 so not sure if it applies to the Rep2 or not) ... for my own parts that need to be bonded together I have always found that its better to have the "mating" sides on top... if I have them on bottom then the initial "squish" that happens on the first layer means they don't seem to mate perfectly... I have had much better results by putting the mating side up, but again that's with my own Rep1.... YRMV

[g. wygonik]

FWIW, I had a quick look through the Skeinforge fill.py code and was able to add a new parameter to the UI -- Top Solid Surface Thickness (figuring I'd use the one there now for "bottom"). I could not, however, get the code bits working to make the two do their own things; there is a lot of code in there that would seem to make sense only to those that a) already know how Skeinforge is coded, and b) are more familiar with Python coding than I am (it's not high on my list of languages to learn).

I do think it could be done, and possibly quite easily. I'm not sure who we could petition to get this in as a real feature. Splitting these two would allow for things like KISSlicer's "vase" setting -- several layers at the bottom, no fill, no top layers -- and would generally be cool.

g.

[Hammerhead]

Yeah, that'd be great - especially for mirror-imaged parts which fit together such as mine.  Not sure who we'd send the suggestion to, though, either.  Would that be Dan?

On Monday, December 17, 2012 12:13:59 AM UTC-5, g. wygonik wrote:

... I'm not sure who we could petition to get this in as a real feature. Splitting these two would allow for things like KISSlicer's "vase" setting -- several layers at the bottom, no fill, no top layers -- and would generally be cool.

[Dan Newman]

On 17 Dec 2012 , at 7:23 AM, Hammerhead wrote:

> Yeah, that'd be great - especially for mirror-imaged parts which fit
> together such as mine. Not sure who we'd send the suggestion to, though,
> either. Would that be Dan?

You'd contact the SF folks or MBI. While it may not be hard to modify
SF's Fill plugin, there's the issue of getting the change distributed and
that's up to MBI and/or the SF folks.

Also, you can of course hand edit the gcode to remove top layers. (Removing
bottom layers has issues such as needing to change the Z heights for
all subsequent layers.)

Dan

[Lucas Saugen]

Actually if you can get away with just getting rid of the top layers instead of the bottom layers you can just use the zpause option in Sailfish.

Dan

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[Hammerhead]

Nope.  Unfortunately it has to be the bottom layers, because they're the most flat and even, for the purposes of mating parts together.  Also, the model in question has 'steps'.  Placing the part face down, the steps would overhang, which wouldn't print right.