jhertzberg
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Posts posted by jhertzberg
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I managed to take the play out of the Z nut by putting a spare piece of plywood covered in tape in the socket of the Z stage. The Z nut is now stuck as intended
Any link for Oldham couplings on ebay EU? I saw they are going for roughly 20€ each
In a stock Ultimaker Original, the play is intentional, to allow the smooth z rods to keep the bed moving straight, even if the lead screw is not exactly straight. If you start to see bands on your prints every 3mm (the period of the screw), take the spare plywood out and see if print finish improves.
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3 points define a plane. 4 is one too much.
About the flex coupling for the z axis: I once used one too. But then I realised that the z position is never properly defined with a flex coupling. In the meantime I switched to an Oldham coupling and added quite some weight to the z stage.
I like the Oldham coupling idea. I seems to be a more straightforward way to deal with a not quite straight lead screw than getting fancy with the z nut housing. Given this, did you take the play out of the z nut housing?
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Three point leveling is far better. Thats why the UM2 uses 3 points. The (re)leveling has nothing to do with the springs; If this were the case, the screws would have to change length.
As noted before, in most cases it's because small warpings in the wood. This is also one of the reasons why the UM2 has a metal bed (Heated bed being the other).
True about the releveling being caused by the wood warping. The 3-point design I referenced anchors the two front points to the thick z-stage arms rather than the thin board in the middle.
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Hi guys!
IMHO - mod to 3-point leveling...
It's so easy to level the bed.
Take a look onto youmagine or thingiverse, there are a few mods also applicable on the original bed.
Can't agree more. I went with this one. The design calls for three strong ball magnets that hold the bed consistently in the same place. I hardly ever need to relevel after swapping the bed out. I also replaced the acrylic bed with glass. I had two panes cut for me locally. I use glue stick instead of blue tape, and get glass smooth bottoms.
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I'm using Murat's 3-point levelling for Ultimaker with magnetic ball bearings V2 (http://www.thingiverse.com/thing:84754 I feel dirty just posting a Thingiverse link now.) I find that I don't need to re-level, since the plate returns so consistently to the same place.
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The top two items [Alternative Repositories to Thingiverse. Two things must happen now. First, we all stop posting designs to Thingiverse, especially designs for improving printers. No one here has the time and money to keep their work from becoming Makerbot's. Second, the gloves have to come off. We need to educate the potential printer buyers we encounter why buying a Makerbot is a bad idea, including "They are a company that looks at what other people are doing, then runs out and tries to patent it as their own. This matters because if you support them, your next printer will cost more, not less."
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I disconnect one end of the bowden, hold it vertical, put one drop of sewing machine oil in the top, let it run down, then reconnect and feed filament. I can then print in FlexPLA (slowly). I think your design might act like a spring during fast retraction.
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I'd love to adapt this for the UM Original. Could you use rubber bands between the blue parts on left and right arms, on the opposing diagonal from the silver parts, rather than a locking mechanism? This might give you greater tolerance of badly sized or out of round filaments than a fixed locking position would.
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I have been fooling around with a tractor design, but not as far along as you, Ian. I am using three o-rings as the tractor, two on side, one on the other, to make a self centering filament path.
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Would the diameter allow you to cut the threads directly into the bowden with a die, and forgo a coupling entirely?
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Very interesting. Is it possible that you post a picture of your cardboard solution? My imagination still is a bit limited in the morning...
It's nothing to look at, just some cardstock folded under to damp the motion of the nut and to keep it from twisting into a locked position in the cage...
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I think the Ultimaker design fulfils this spec quite well, doesn't it?
I can't quite agree. When I first built my UM Original in January 2013, I had severe banding artifacts every 3mm. This was probably a combination of a not-quite-straight leadscrew, and a tight nut capture cage that transferred the screw wobble to the bed. I had to take a file to the wood in the cage to loosen things up, then add some cardstock folded in an accordion shape to keep the nut from twisting. Owen posted a design that solves this here.
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What are you doing for the leadscrew nut cage? I spent a lot of time trying to find the balance between holding it tight in place and letting it float. Too tight, and I get z-wobble artifacts. Too loose, and it can twist a little and lose z height accuracy. The ideal is a mount that allows the nut to move freely in x and y direction, but with no twist.
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I wonder if you could adapt the http://www.thingiverse.com/thing:112718 on Thingiverse to act as your sliding blocks, since you could pick the optimal pitch. There is already a design there that uses 623ZZ bearings at a 38.5 degree bearing angle. The challenge will be block clearance and drag from the unpowered side. I suppose you could either leave belts for power transfer, or add two more motors, but that might defeat the purpose.
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Can't say if it would be. I suppose if you kept the head mass very low (eg. 5cc syringe) and printed slowly, with a fine enough needle gauge, you could exceed the precision you'd get with plastic. Are you thinking of printing into agar? I saw where someone printed into jello with a syringe, so you might even be able to get around overhang problems if you programmed your STL to retract the syringe and print in voxels instead of dragging it around.
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There are several syringe mounts for the UM1 on Thingiverse (see http://www.thingiverse.com/search?q=syringe+ultimaker). Would that work? If you need higher volumes, there are also peristaltic pumps there.
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As mentioned over in google groups, I pull the filament through a straightener as a I respool.
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I was told by my glass shop not to get tempered. While it does hold up against impacts better, it handles thermal stress worse. Either go all the way to borosilicate (eg. Pyrex) or go cheap like I did with ordinary 1/8" window pane glass. I paid $10ea., cut and smoothed to UM1 bed size. Unless you are in NYC, my shop won't be much help to you.
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Unless you are a woman. They can do that. At least they pretend to...
It has to do with their thicker corpus callosum, or so my wife tells me. :???:
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On second thought, reed switches probably won't work. There's way too much motion. It's probably better to KISS and move the endstop function to the printhead. Mount the mechanical switches on each arm of the crosspiece, and then cartridges would need to include extensions on their mating sides to press the switch.
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I think that for challenge #1, a more compact version of Jelle's cassette system would work (http://www.thingiverse.com/thing:25836). Rather than lasercut wood, I'd go with a minimal printed central crosspiece to preserve as much print area as possible. I like the idea of having up to four locations for attachments.
I'd like to keep the amount of fussing to add and remove cartridges to a minimum, so you could quickly pop them off and on. I'd prefer the option to use clips or magnets to hold them in place when forces are not too great (like for fans), but use screws when needed (like for heavy paste extruders). Perhaps print a coarse knurl on the mating surfaces on the crosspiece and print a complementary knurling on the cartridges to keep them from slipping and to help align multiple heads.
We'd need to make endstop triggering idiotproof when a cartridge protrudes into previously free space. The current solution of triggering with the slider blocks hitting mechanical switches won't work as-is, but I wouldn't want to give up the maximum margin of cartridges in all four corners all the time. So, in addition to the current stops, we may need a proximity sensor on the outer edges of each cartridge to detect when it is about to hit a slider block. Perhaps if blocks have magnets, we could use a cheap reed switch on the far corner of each cartridge.
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your right about the 1 to 1 thing Robert.. true !!
but...if you had a good system where the rubber belt or wheel was under a movable spring system like your design ! then I think the slip factor would be relativly low... and .. this all has to be simply tested but I cant see at the moment a monster loss in quality from this...
PS we have to address the flow of filament into the extruder more... i can hear my pla bashing around the back of the ultimaker 2 right now and that aint good for smooth flow... :sad:
Ian :smile:
It may be tough to fit, but how about using two belts in a miniature double conveyor, sort of like a double belt press, but symmetrical? The belts could be grooved down the middle to keep the filament on track.
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Will do, but that will be after I finish converting to direct drive.
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Hi Owen,
The two I had seen at Thingiverse both mount the syringe on the head. In the other, the extruder motor pulls a strong thread back through a bowden to pull the plunger down. Of the two, the second seems more robust, and I have the parts for that, but with both I'll be dragging around a lot of weight on the head, and clays probably require more force on the plunger than can be had by pulling a string or pushing PLA. Those designs look more appropriate for frosting. My holy grail would be to be able to feed clay continuously, but that may be neither practical nor necessary.
Hey jhertzberg
I think you'll find on thingiverse some designs that use a syringe that is connected to the bowden and the normal feeding of the filament pushes the plunger. Very simple.
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This. IMO, retraction only works for a little while if the block is kept heated. Eventually some melt will ooze from the undesired tip. Another solution that comes to mind is to direct cooling (eg. fan airflow) to undesired tip to form a small plug, then allow time for that tip to reheat when it's called for. It might be tough to calibrate.