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Pushing the edge of print volume

Discussion in 'General Questions' started by OutsourcedGuru, Jun 12, 2017.

  1. OutsourcedGuru

    OutsourcedGuru Active Member

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    I purchased this Robo C2 with a particular project in mind. It's basically a cube which is just shy of the X/Y print volume of 5"x5" of this printer. I carefully researched things before the purchase and was satisfied that I'd done my homework, so-to-speak. I've successfully printed many things so far, each with rafts. I've dialed in the z-adjustment and so each raft adheres beautifully.

    So then, I laboriously learned Autodesk Fusion 360, created the several components inside this cube, placed them, created all kinds of constraints and finally, finished designing the bottom of the box and exporting this as an STL file.

    I then next brought this into Cura and it isn't happy, noting that I downloaded and created the profile for the Robo C2 printer already. Cura indicates that it can't slice it because it exceeds the size of the print volume. Note that the cube's sides are each 120mm = 4.72".

    Researching this a little, if I turn off the raft in Cura (which would extend the X/Y a bit) as well as supports and then scale the X/Y down to 117mm then at least it will allow a slice to a GCODE file. Transferring this file to the printer and attempting to print it doesn't adhere in the least.

    1) It just feels to me that this printer (without a heated bed) with PLA pretty much requires a raft or it doesn't adhere (suggest any Cura tweaks if you have a no-raft fix for this).
    2) It would be great if I could convince Cura to print the maximum print volume instead of a fraction of it.
    3) It would be great if I could convince Cura to lay down a raft which only extends the X/Y by, say, 2mm only.
    4) I really don't want to have to go back into Autodesk and change the entire design to make it raft-friendly in size since I thought I had a 5"x5" print volume on this.

    The inside of the cube holds a variety of parts and I'm already pushing the limits to allow for internal cabling, etc. It would be nice to not have to re-engineer this. Also, there are external holes/ports and other contraints which I don't want scaled down.

    Any thoughts?
     
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I do not use a raft on any of mine (just throwing that out there). While every environment is different the leveling/Z offset is key to adhesion. I can't give you Cura tweak suggestions because I don't use it.

    Your bed may be bowed slightly in some way that causes you to need a raft (not ruling that out at all) but generically you do not need the raft on this printer.

    I bet however that there is a way to convince CURA to ignore whatever size limit it is imposing since you are sure you have the physical capacity for it (someone who uses Cura can speak up).
     
  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I did get frustrated with the auto leveling and how Robo was at the time tweaking it* and the firmware every other day (it seemed) so I eventually just manually leveled the bed and ditched auto leveling entirely.


    *the side effect of this was that the Z offset kept changing. I would get it dialed in and then -- another update and it is now "different"
     
  4. OutsourcedGuru

    OutsourcedGuru Active Member

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    You mentioned elsewhere that you "dropped the G29 code" (the auto-leveling routine). Can I assume that you're bringing the GCODE file into a text editor and commenting it out at the top of the file?

    What's frustrating is that for some files it does an auto-level, lays out the "tell" line up front (perfect adhesion), runs a second auto-level and then is too high for the first trace of what comes next.

    For this particular printout, the first (botched) line of the cube nearly coincides with the location and direction of that (good) tell line so I suspect the G29 is causing me this grief.
     
  5. OutsourcedGuru

    OutsourcedGuru Active Member

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    I'm also thinking about a wag-the-dog approach here in which I update the Robo C2 profile in Cura so that it thinks the print volume is 125mm x 125mm or similar. It may then do its calculations, dial things down and at least get on with it. I can imagine the printer laying down a sloppy-edged raft around the perimeter which yet produces a good part nonetheless. (I think they're just erring on the side of caution here.)
     
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Nope. It is done in the startup GCode section of OctoPrint and I edited that to remove it. I don't have anything in the startup GCode section of the slicer and OctoPrint does everything else (just not that anymore for mine)

    EDIT: for reference, in the OctoPrint UI...
    1) Settings (top-right corner)
    2) GCode Scripts
    3) Before print job starts

    That is the section that controls what is sent initially before a print job initiates.

    As I mentioned earlier the line at the front is in no way related to AutoLeveling since it does not even USE autoleveling rather it is printed as a specific absolute Z offset value (this is also in the OctoPrint startup GCode section). Most Z positioning done by the slicer is 'relative' positioning, but this one is an absolute number

    I have an LCD/OctoPrint combo on every printer I own these days (I really liked the Robo approach so I cloned it). So each machine has an instance of OctoPrint customized to it.
     
    #6 mark tomlinson, Jun 12, 2017
    Last edited: Jun 12, 2017
  7. OutsourcedGuru

    OutsourcedGuru Active Member

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    Alright... researched the GCODE related to rafts. I'll attempt to turn on the raft in Cura, then edit/replace...

    raftOffset,3

    ...with...

    raftOffset,0

    ...which in theory ought to create a raft which does not extend at all beyond the part. The argument is the extent in millimeters around the perimeter of the part's first layer.
     
  8. OutsourcedGuru

    OutsourcedGuru Active Member

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    The setup for the Robo-specific Cura install indicated that they wanted you to nuke everything in the start/end g-code settings and so I didn't even think to look at the OctoPrint level for startup GCODE. d'oh!

    Thanks. I'll check this out. (Honestly, I might suggest that we should all put a GCODE to reset the z-increment to 0.1 at the end of every job as a sanity check to minimize later stupidity when jogging the adjust.)
     
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  9. OutsourcedGuru

    OutsourcedGuru Active Member

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    Okay, wag-the-dog appears to have worked. Went into Cura's printer profile settings for the Robo C2 and tweaked the print volume settings for X/Y, increasing them from 125mm each to 135mm. This allowed me to then set a raft with the default 3mm offset (since it was impossible to knock that down unless I wanted to build Cura on OS X, presumably). This approach then allowed it to slice without complaint and then setup the raft.

    Given that I was pushing the boundaries it was necessary to immediately snag the tell off there since it was occupying the same space as the closest run of the raft itself. And the job is off and running now.
    Screen Shot 2017-06-12 at 5.40.36 PM.png IMG_0103.png

    But honestly, would you really call that "on the edge"? I wouldn't. This printer will be tweaked some more, mark my words. ha
     
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  10. OutsourcedGuru

    OutsourcedGuru Active Member

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    Many hours later, here's what I've got. Looks like a bit of curl on the edges/corners. It feels like the raft did extend the 3mm around three of the four sides but not on the right-hand side. This made removing the raft from that side pretty difficult, requiring me to basically chisel off the raft with Count Spatula.

    Not a bad first design attempt in Autodesk Fusion 360 for me, in my humble opinion. I can now dial this in on the port openings and placement of the internal parts, which fit almost perfectly on this "v1".

    Any countermeasures for the curling? I'll let you suggest some things but I was thinking that I could pause after the raft's down, then apply three bed clips on each side, then resume. I'd have to design/print some bed clips, of course.

    IMG_0102.jpg IMG_0103.jpg IMG_0104.jpg IMG_0106.jpg IMG_0107.jpg
     
  11. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    When PLA curls on a no-heat bed it is usually (but not *always*) a filament problem.
    If you can, try another spool.

    You can try reducing the extrusion temperature a small amount too*, but like I said this is normally a filament issue.



    *say 5 degrees
     
  12. OutsourcedGuru

    OutsourcedGuru Active Member

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    I've only got the Robo-branded filament at the moment. Do you have a trusted brand that you prefer for PLA? I've heard good things regarding ColorFabb but it would be nice to go fetch a spool of white, come to think of it. But I'd also like to get one of the exotic ones with carbon fiber to see if it behaves any differently in this situation.

    I'll dial it down five and see if that changes the situation, thanks.
     
  13. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Colorfabb is a Cadilac filament lots seem to like Hatchbox as well.
    If you go with an exotic I suggest sticking with a better brand, but for regular stuff most are decent. Yours could just be an older spool...
     
  14. daniel871

    daniel871 Well-Known Member

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  15. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I agree that most of the (large piles) of filament I bought from eBay was not only cheap, but it worked like a champ.
    I still buy PLA cheapest I can get. Only the specialty ones do I pay more for... well that an anything I am printing on the darn delta. It simply will not print the cheap stuff. I have to run Colorfabb through it.
     
  16. OutsourcedGuru

    OutsourcedGuru Active Member

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    Interesting (reading that eBay link)... and thanks for the info, guys. So I just researched the soft PLA and I'm guessing that I need this for a breathing tube for one project and a bendable microphone extension for another. Before this, I was thinking that I'd have to do something exotic with meshing to allow some flexibility.
     
  17. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    If you need flexible look for SemiFlex: https://ninjatek.com/products/filaments/semiflex/

    It is easy to bend, but it is firm enough to print fairly easily. NinjaFlex is just 'floppy' not 'bendable' :)

    With the direct extruder on the Robo R2/C2 you probably can probably get by just printing it slowly. No tube modification likely needed. I can test it later this week and see.
     
  18. OutsourcedGuru

    OutsourcedGuru Active Member

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    I'd be trying to print something flexible like this: http://divermag.com/wp-content/uploads/2014/09/DIVER-old-regulator.jpg
    So think, "old-school scuba". Looks like this particular one was formed from rubber in two halves and then melted together, I'd imagine.
     
  19. OutsourcedGuru

    OutsourcedGuru Active Member

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    Alright, second run of this. Printed up four clamps to hold down the edges of the raft (to prevent part curl like last time). Now that I had the first part, I was able to go back into Autodesk Fusion 360 for a lot of internal tweaks and finishing. In Cura, did some post-processing of the GCODE for a pair of pause-at-heights: 8.9mm and 32mm. The first would be so that I can add the clamps and the second is so that I can remove them. Cura printer profile settings tweaked again, this time the X/Y min/max offsets, backing each off by 5mm and then increasing the X/Y print volume by 7mm each to allow it to slice. I've noticed that it isn't maxxing out on the right like it was before, so that's a good sign. Ultra-high quality, Robo White PLA, 25% infill.

    IMG_0143.jpg IMG_0145.jpg
     

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  20. OutsourcedGuru

    OutsourcedGuru Active Member

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    So well before the official z=9mm pause event I'd added, the curl started up in earnest on the far left side so I thought I'd start to apply the clamps as soon as I could. Added one to the front corner, since it was still too early and the printhead assembly was still printing the 3mm-filleted bottom edge.

    IMG_0147.jpg

    I kept trying to gently add clamps along the left but the printhead's return to that side of the part would usually compress things just enough so that the clamp would drop off. It's okay, I kept putting them back on.

    IMG_0149.jpg

    If you clamp down too much, you take up the slack between the corner magnets of the bed and the assembly it's riding on, resulting in a bad z-offset. So, easy-as-it-goes is the best approach here, adding slight pressure while the raft is still pliable. It eventually pays off. There becomes a point where the up-curling then forms an upward pinch which holds the clamp firmly in place and it stays on its own without fail. That pause-at-height was completely unnecessary, it would seem...

    In fact, that pause-at-height kicked off at around 3:30am and I went in there, things were looking reasonably good at 4am. It had slowly extruded some waste plastic but all in all, it looked okay. I should have noticed, though, that the extruder was sitting roughly near z=0 close to the bed. Since the clamps were in place I then pressed Resume on the LCD. I guess I put too much faith in that pause-at-height Cura script, unfortunately.

    Next, it started to drill itself into the plastic and the bed at the back of the part. It didn't raise Z first and then skip over the part as you would expect. In a panic, I aborted the job... dragging a molten trail of plastic in its wake at the same time as plummeting the bed to the bottom-most position. I started knocking the clamps off in a race to the bottom, only to find that it had trapped one underneath so I had to fight that one out. So, 4am and I'm now fully awake without coffee.

    IMG_0151.jpg IMG_0153.jpg IMG_0154.jpg IMG_0155.jpg IMG_0156.jpg

    Things learned:
    * Never trust someone else's script and their defaults. You should understand exactly when the inserted G-CODE runs and what happens next.
    * Whatever can go wrong, will go wrong.
    * The clamp concept works great when it works. The corner which didn't get a clamp curled the most, as seen from the vertical photo. The curl is only barely noticeable in the other four corners. I don't like the way the bottom of the clamps work for this.
    * That diagonal scarring on the bottom of both parts suggests that my bed has a diagonal ridge but I'd like a second opinion on that.
    * This printout would have taken 56 hours if it had gone all the way. I can't really be inserting pauses into jobs this long because a lot can happen if the extruder is sitting in the wrong place or the bed is trying to crash through a downed clamp.
    * I can push the X/Y max settings another 2mm for each and open things up another tweak, allowing more of a grasp on those raft edges.
    * The 3mm bottom fillet on the part helps to lower the curl rate, so it would seem.

    I dunno. I might make clamps with a lower head profile so that I can add them as soon as the raft is laid down. But I'll need to modify OctoPrint's ending G-CODE to prevent a bed dropout to bottom and further, to test that theory before I run another multi-day job.
     

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