Oddly shaped holes?
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Hey all,
Just added some upgrades to my printer in terms of the gantry (CoreXY layout). Now I'm getting some odd shaped holes in this piece I printed. Any ideas?
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belts tight? slop somewhere? With the printer homed (axis motors locked) try and wiggle the printhead to see if there is slop someplace.
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I'll double check but I cranked the shit out of them last night when I put it back together.
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More often this happens because there's a pulley that's loose on a motor shaft. Either way, I'd agree that it looks like backlash as the holes have two opposing sharper sides and two with a smooth radius.
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-ok belts are set. Make sure they are , or all the rest have no sense.
-Maybe too hight temp? Try to print a small cylinder with fan on and one with the fan off and see if they have the same shape. The corner of the wall seem have too some sort of blobs.
-Do you designed this part? If you designed this part , how did you exported it? (ex. I use FreeCAD and I have several option for export the mesh, and if I select wrong options (low detail for preserve the file dimension) it come to a poor STL , especially for curved lines . Ex , till a circle come close to a octagon) .
-Max resolution for the slicer? (I use CURA and I can set it properly) In the slicer preview the circles are really rounded?
-Just for check , look that the right voltage of the motors are set in the config.g. -
You aren't by any chance using steel core belts on the XY mechanism, are you?
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@giostark said in Oddly shaped holes?:
-ok belts are set. Make sure they are , or all the rest have no sense.
-Maybe too hight temp? Try to print a small cylinder with fan on and one with the fan off and see if they have the same shape. The corner of the wall seem have too some sort of blobs.
-Do you designed this part? If you designed this part , how did you exported it? (ex. I use FreeCAD and I have several option for export the mesh, and if I select wrong options (low detail for preserve the file dimension) it come to a poor STL , especially for curved lines . Ex , till a circle come close to a octagon) .
-Max resolution for the slicer? (I use CURA and I can set it properly) In the slicer preview the circles are really rounded?
-Just for check , look that the right voltage of the motors are set in the config.g.-I'll double check the belts.
-Temp may have been too high. I don't have a part cooling fan yet. That still needs to be added.
-STL quality is fine. Max mesh quality in solidworks.
-Voltage is fine.@ChrisP said in Oddly shaped holes?:
More often this happens because there's a pulley that's loose on a motor shaft. Either way, I'd agree that it looks like backlash as the holes have two opposing sharper sides and two with a smooth radius.
I'll check those. They should be tight though.
@mrehorstdmd said in Oddly shaped holes?:
You aren't by any chance using steel core belts on the XY mechanism, are you?
No I'm not.
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If you overtightened the belts and did one after the other, you may have pulled the gantry out of squareness. I would try loosening the belts again and then tightening them step by step, and avoid putting too much tension on them.
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I think I found the issue. The head is tilting back and forth. I guess the carbon fiber rods aren't large enough for the 12mm igus bushings? Does anybody know where I can find 12mm aluminum rods? Hollow, preferably.
I also tightened the shit out of the belts and now it's a lot louder and making a kind of grinding noise?
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@Surgikill too tight is definitely a thing. maybe back up a little. you want it tight, but not as tight as you can possibly get.
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you can use the gates app to tighten the belts, it works by listening to sound your belts make when you "pull them" and tell you to tighten or loosen them, similar to all those guitar tuning programs only for belts
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@arhi I'll give that a shot. Thanks for the tip. Do you have a link? I'm on android, having a hard time finding it.
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@Surgikill Maybe you can tighten the bushings. Cut the bushings lengthwise and make the bushing holder's clamping force adjustable with a screw.
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How can this small play affect only small circles and not all the rest of the print?
In theory at each segment change it should slide a little...
The holes are more or less regular and look like an hexagon. (a little melted but not that much, so the hight temp should not be the culprit for the hexagon shape )
Belts must be tied properly but the problem imho lied elsewhere.
The slicer resolution is fine? (should be set at least as the nozzle size. Maybe is bigger?)
Really curious to see what it is
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@giostark Small circles cause rapid direction changes which throw the loose parts around more than larger features of the print. It probably affects the larger features, too, but is more visible on the small ones.
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@mrehorstdmd Yea, there are issues on the other parts, but not as bad. Any idea how I can fix the wiggle? I'm not sure if the aluminum rods would fix it.
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@Surgikill I think it's this one:
https://play.google.com/store/apps/details?id=com.gates.carbondrivecalculatoror this
https://play.google.com/store/apps/details?id=com.gates.pttoolkit
both can be used i think
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@Surgikill As I posted above, clamping the bushings down a little tighter on the rod would help. If they aren't made to be tightened, cutting a slit with a saw will allow them to be tightened by modifying the clamps that hold them to have screws that let you squeeze the bushings a little tighter on the rods.
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@mrehorstdmd They're held on with zip ties, so not sure how well that will work. it could be a printer issue besides the gantry. I have a print running right now so I can't mess with it. I've attached a picture, maybe that will help.
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Are those maybe the type of bushings that require a certain amount of compressive force on them to get them to fit properly on the rod?
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@Surgikill As you have discovered, zip ties are not a particularly good way to hold components of a precision mechanism together. I'd start with a redesign of the extruder carriage that allows those bearings to be securely fixed and also squeezes them down to fit the rods better.
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At minimum, I would add a rubber band and some nailing wire !
(sorry, couldn't resist)
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@mrehorstdmd Yea that's not happening. That is the redesign. I looked into bolting them on, and I lose a shitload of print volume, which is the whole point of this printer. I used the same design previously, and didn't have an issue. Also why I used 4 of them, instead of 2.
It's also hard to see, but there is a cutout for the linear bushings to line up in. Those zip ties are only holding it in that groove.
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@Surgikill Then you're back to looking for rails that match the diameter of the bushings. Good luck- you're going to need it.
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@mrehorstdmd They're 12mm rods. I don't think that's the issue. As soon as this part is done, I'll show it to you, but after loosening the belts up a bit I don't see the carriage wobbling anymore, but the artifacts are still pronounced, even on large circles (3" diameter)
