jmccorm
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Bug? RAFT seems to consider more than the object's base

Mon Sep 23, 2013 12:54 am

So I was printing out Voronoi Yoda...
Voronoi Yoda

When I previewed my gcode (and subsequently printed it on the printer) a problem arose with the skirt.

Image
It seems that too much is being considered for how the skirt should be made. Instead of looking at the layers which may be touching the build platform, it is building a skirt based on the overall profile of the object from a top-down perspective. Aside from wasting excess material, in this case, it also impacts the maximum size I can have for my object. I want to have a good 1cm skirt and also print the Voronoi Yoda as large as possible, but those two are now conflicting goals.

If the skirt was being printed more sensibly, this wouldn't be a problem.

Bug, unexpected feature, or am I doing something wrong?

EDIT: Changed subject to reflect that I'm actually talking about the raft and not the skirt.
Last edited by jmccorm on Mon Sep 23, 2013 8:54 am, edited 1 time in total.

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jimc
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Re: Bug? Skirt seems to consider more than the object's base

Mon Sep 23, 2013 6:57 am

I believe thats the way the shirt should be. That wont effect the size of your object. The skirt is the outer border of your project no matter what the base shape and size is. If the top of your part is bigger than the base you still cant increase the size because the upper layers will be ouside your build dimensions.

jmccorm
Posts: 13
Joined: Tue Sep 17, 2013 12:36 pm

Re: Bug? Skirt seems to consider more than the object's base

Mon Sep 23, 2013 8:49 am

Crap. I mixed the terms raft and skirt. Let me correct myself.

Actually, aside from the unnecessary raft material (which I do not want), it is still a problem. I want the outer border of my project, at the top, to be at the edges of the print area. I have to subtract my maximum size by two times my (raft+skirt) offset in order to make the print, even though it shouldn't technically be necessary, since I only need the raft to hold down the object on all sides. So the maximum size I can this object is now additionally constrained by an artificial limitation imposed by the raft mechanism calculating its area on something other than the base. If I want a nice big 1cm raft for a top-heavy object, I have to reduce the X/Y size of the object by 2cm.

So, yes, I know why it is happening, but the way that the raft is computed seems wasteful, and the unnecessary overage actually takes away from my build area in a print where it should not.

While I had this problem going on, I made another discovery. While Simpilfy3D Creator prevents you from arranging an item which is too big for the bed, it doesn't give any warning if you create a raft+skirt which is too big for the bed. I anticipated this problem and looked for it (because I was paying careful attention to the problem above and my tolerances to get the maximum object size I could) and I decided to see what happens when I tried to print with a raft+skirt that draped over the build area. It'll print beyond the bed. Going in the other direction, it'll hit the kill switch. :)

It might be nice to give a software warning ahead of time if the raft+skirt exceeds area of the print bed.

jmccorm
Posts: 13
Joined: Tue Sep 17, 2013 12:36 pm

Re: Bug? RAFT seems to consider more than the object's base

Mon Sep 23, 2013 6:11 pm

I settled on just printing it at 200% rather than trying to see how close I could get to 225%.
Here is an image which demonstrates the large unnecessary raft:
DSCF5736.jpg
So much wasted plastic. (And it also takes away from how big I can print the object.)

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jimc
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Re: Bug? RAFT seems to consider more than the object's base

Mon Sep 23, 2013 7:36 pm

i see what you mean. that print in the pic looks funny. looks like a pile of ooze melting into a puddle.

jmccorm
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Re: Bug? RAFT seems to consider more than the object's base

Mon Sep 23, 2013 9:38 pm

jimc wrote:i see what you mean. that print in the pic looks funny. looks like a pile of ooze melting into a puddle.
It looks really weird partially printed, but I like the look of the completed piece. (Come to think of it, the completed piece looks pretty weird, too.) With my current settings, I'm looking at 22 hours of printing so I'm unlikely to do another one of these unless I want to make a gift for someone.

I think I've found my killer app for 3D printers: gifts!

jmccorm
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Re: Bug? RAFT seems to consider more than the object's base

Tue Sep 24, 2013 5:12 pm

Finished. 24 hours, 20 minutes. I have to clean up the print -- it wasn't designed for clean 3D printing. There was a lot of bridging going on. This thing stuck to the borosilicate glass so tight that I had to rest it in the deep freezer to get it free. (And people seem surprised when I say that I print ABS directly to glass?)
DSCF5769.jpg

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jimc
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Re: Bug? RAFT seems to consider more than the object's base

Tue Sep 24, 2013 6:00 pm

Jm, what are you using on the glass to help adhesion?

jmccorm
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Re: Bug? RAFT seems to consider more than the object's base

Tue Sep 24, 2013 7:14 pm

jimc wrote:Jm, what are you using on the glass to help adhesion?
Nothing. Here are the things that I do:

General prep --
1] Clean the bed with windex
2] Wipe the bed with a microfiber cloth
3] Level the bed extremely well with feeler gauges (left,right,up,down, then diagonals)
4] Measure my bed distance with feeler gauges, compensate for my layer height, and set an Z-axis offset that matches in the G-Code settings tab

For a print --
1] Bring the room temperature up to 80-85F
2] Wipe the bed with a microfiber cloth (but not hard enough to alter the leveling)
3] 2-layer raft at 50% infill
4] Manually stabilize the bed temperature at 110C
5] Manually stabilize the extruder temperature at 220C (overshoots, falls, then slowly works up to the correct temperature)

Some of this may be overkill, I'm sure. Often times I don't even need the raft. But I use it if I am printing something very vertical or if I've got tiny little pieces on the bed which a fast swipe of an extruder nozzle could knock around. For that same reason, I've also lowered my XY speeds by 25% and I'm noticing a lot less knocking sounds during the rapids.

This print was a little unusual in that I noticed an artifact during printing. I was really close to the bed, it seemed, and an irregularity in the borosilicate glass became visible. No problem though. It all smoothed out on the next layer of the raft.

Image

sir-mike
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Re: Bug? RAFT seems to consider more than the object's base

Sat Sep 28, 2013 9:10 pm

Hi all,
I used a random part to show my simple solution for small rafts just divide the print, see picture and factory file.
raft.png
Attachments
Wall-E_Scaled.factory
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