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Safety...
The Loctite plastic bonder Mike mentioned should work well. They call it an epoxy (probably because it mixes in 2 parts like epoxy) but it is actually methyl methacrylate (MMA). It is highly volatile, nasty stuff to work with, but it does seem to stick to all but the most slippery of plastics quite nicely - almost acting as a solvent. Devcon's Plastic Welder is another commonly available versi
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LoboCNC
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It seems like a lot of people are missing Mike's point here - it's not about the bell, or how long it took to design the bell, or exactly how unique the bell is. His point is that if you start with a design someone has graciously posted for everyone to use, with only the small caveat that you acknowledge the source, you acknowledge the source. How hard is that?
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LoboCNC
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In a word: No. I tend to use OMC motors (https://www.omc-stepperonline.com/) which are quite reasonably priced, actually have data sheets, and are easily ordered on-line. I've also used SureStep motors from Automation Direct (https://www.automationdirect.com/) which are pretty nice but a little more expensive. That said, I've also used a lot of random eBay steppers (Wantai, etc) that are prett
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LoboCNC
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OK, here's another version of the anti-ooze valve that eliminates the complex extruder motor driven actuation and instead uses the differential extrude/retract pressure to operate the valve, as leadinglights suggested. It uses compressed air in a small chamber in the heater block to push the valve pin against the inside of the orifice during retraction, when the inner pressure filament pressure
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LoboCNC
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QuoteLykle
afaik, the retraction does not suck the molten filament up into the heat block.
It simply relieves some of the pressure, but there is no negative movement of the molten plastic.
So yeah, closing the needle will have a pulse effect of pushing some filament out.
That can be used, by retracting early and closing the valve slowly, using the pushed out material to finish the track.
That
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LoboCNC
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Quoteleadinglights
Whether the pin pushes any filament through the nozzle or not would depend on if the filament retract was effective before the pin closed off the nozzle.
In the case of the floating nozzle, since the lifting of the nozzle to meet the pin is done by retracting the filament, I think there would be nothing in the nozzle to be pushed out. Incidentally, the nozzle being lifted wo
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LoboCNC
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Quoteobelisk79
QuoteLoboCNC
Actually, it turns out that ooze, and pretty much all other 3D printing factors, have little to do with gravity. The viscodynamic and thermal forces are far greater than the weight of the filament. Printing upside down, even bridging, looks pretty much the same as printing right-side up. Oozing, in particular doesn't care about gravity. The biggest factor I've foun
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LoboCNC
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Quoteobelisk79
Since that thing prints upside down, do you even notice much of an ooze problem?
Actually, it turns out that ooze, and pretty much all other 3D printing factors, have little to do with gravity. The viscodynamic and thermal forces are far greater than the weight of the filament. Printing upside down, even bridging, looks pretty much the same as printing right-side up. Oozing, in
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LoboCNC
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Quoteo_lampe
Wouldn't the pin push filament through the nozzle each time it closes the channel? What would be the chamber pressure after unretract? There could be a gap in the filament.
If you would guide the pin sideways into the nozzle, you could again use a straight melting path.
I'm envisioning that the pin will be inserted as the filament is being retracted, so filament should be being suck
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LoboCNC
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Quoteobelisk79
I wonder how that zig-zag path you've got the material passing throuh will affect pressure and neccesary torque to push the filament through. Of course the concept could work quite well if you decide to create a prototype.
I'm not too worried about the zig-zag path. My current printer (UDIO printer) uses a right-angle extruder which has given me no problems at all in the year or
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LoboCNC
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Quoteleadinglights
One thought though, using the identical arrangement but with the pin fixed so that the 'O' ring and gap don't exist, but having the nozzle sprung and floating so that when the filament is retracted the nozzle also retracts and seats against the pin. The above problems of the 'O' Ring and gunge-blockage still exist but the mechanicals would have been simplified.
Mike
Are you
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LoboCNC
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I know the idea of an anti-ooze valve for the extruder nozzle has been discussed here before, but I haven't seen much beyond hand drawn sketches. The idea I am thinking about, illustrated in the photos, involves a stainless steel wire that is used to plug the extruder orifice from the inside. The wire pierces the heater block and is sealed with a silicone o-ring. My idea is to actuate it direc
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LoboCNC
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Quotedc42
Avoid MXL pulleys and belts unless you are willing to pay for pricey Western-manufactured pulleys. The Chinese so-called MXL pulleys I have come across have the wrong tooth profile. The MXL belt has wider gaps between teeth than the width of each tooth, therefore the teeth on the pulleys needs to be wider than the gaps, otherwise you get horrendous backlash.
You probably want to avoid
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LoboCNC
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You can get 2mm pitch belts longer than 2m, but there will be only a couple of specific lengths to choose from. Slightly more selection, maybe, if you are willing to go to MXL belts.
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LoboCNC
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Before rebuilding your printer, you might want to look at how much moving mass reduction you will actually achieve as compared to the increase in belt length. Generally, you want to reduce the moving mass to reduce ringing from the springiness of the belts. If you cut your moving mass in half but end up doubling the belt length (thus halving the belt stiffness), then you haven't really achieved
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LoboCNC
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How is your extrusion system different? How does it work? We'd love to see pictures or diagrams.
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LoboCNC
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Quoteicefire
I was looking at some existing CoreXY designs (no need to reinvent the wheel here) there is this one that caught my eye:
I like a lot that the heated platform is supported on both sides and is driven by two motors. This adds a lot of stability to the Z axis.
I don't think this printer is really a CoreXY. It uses the cross-rod configuration like the Ultimaker printers. BTW, does a
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LoboCNC
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Quote691175002
This is actually a pretty neat idea, but its very hard to actually implement because it crosses the machine/slicer boundary.
The slicer doesn't have enough information to do this unless you probe the bed and send that that heightmap back to the slicer (and then reslice and export g-code).
The 3d printer board really does not want to do this because its would require duplicating a
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LoboCNC
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QuoteGRAYWOLF
QuoteLoboCNC
From what I understand of automatic bed leveling, the out-of-levelness is compensated for by converting the simple X-Y motions for each layer into X-Y-Z motions. However, it seems like constantly moving the Z axis up and down will invite all sorts of surface irregularities, especially if the Z axis has even the slighted hint of backlash.
Given that most out-of-levelnes
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LoboCNC
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One other thought I had regarding the initial level mapping is to first lay down a single thick perimeter line and then use a camera to measure the resulting line width, which would be inversely proportional to the bed height. Although when I print gold translucent filament on Kapton tape, the first layer lines are nearly invisible. If you only need to level periodically, though, a high contras
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LoboCNC
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Quotedc42
That's an interesting idea. I can see two possible issues:
1. It will only work if the amount by which the bed is out-of-level is smaller than the first layer height. For example if you print using a 0.4mm nozzle, then you are limited to nozzle-to-bed height in the ranger approx. 0.05 to 0.35mm. So you would probably use a 0.2mm first layer height, then it could handle variations of +/
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LoboCNC
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From what I understand of automatic bed leveling, the out-of-levelness is compensated for by converting the simple X-Y motions for each layer into X-Y-Z motions. However, it seems like constantly moving the Z axis up and down will invite all sorts of surface irregularities, especially if the Z axis has even the slighted hint of backlash.
Given that most out-of-levelness is only on the order of 0
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LoboCNC
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No.
The tool paths are all fixed at print time. The only parameters you can change are those that don't affect the tool path - things like speed, acceleration, extrusion rate, etc.
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LoboCNC
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For what it's worth, I just measured the backlash on my big (350x350mm) H-drive printer that uses MXL belts at less than 0.01mm. Belt stiffness and structural stiffness are going to have a much bigger effect on accuracy than the timing belt backlash.
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LoboCNC
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I've had the same set of neoprene/glass MXL belts driving the spindle (1000-3000 RPM) of a homemade milling machine for about 15 years. I don't worry much about belts wearing out.
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LoboCNC
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QuoteSkrogh
If you really do want to try this approach out, why not get a commercial tubular ceramic heater?
The has one, but I've seen the heater type on both Aliexpress and Alibaba.
You will still face the issue of the coil being significantly warmer, than what you are trying to control the temperature of - namely the plastic in the extruder.
I'd be tempted to try a ceramic heater, but crucia
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LoboCNC
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Quotethe_digital_dentist
The OP's drawing looks a lot like the hot-ends in my CubeX Duo printer. They are not very good. I don't know if the volume for molten filament is too large or the heat zone is too long, but they drool continuously. The wire has some sort of glass fiber insulation wrapped around it, and the coils are covered with some sort of cement like substance. They commonly fail s
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LoboCNC
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Quoteleadinglights
The idea has possibilities but I think that nichrome is not a good candidate. Nichrome has a very high resistivity, about 120 x 10-8 Ωm this means that you don't need a lot of material to give your required resistance. Little material = little surface area = not much area to conduct the heat from the wire - the point that Skrogh made. The second point is that nichrome has quite
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LoboCNC
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QuoteSkrogh
I think the issue here would be that the nichrome wire will be significantly warmer, than the rest of the construction.
As you want things to heat up quickly, and heat transfers faster, the greater the temperature difference.
So reading off the temperature of the nichrome wire would not give any useful information.
If the nichrome wire is wrapped directly onto the thermally conducti
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LoboCNC
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Has anyone tried using a single nichrome wire for both heating and temperature sensing of the hot-end? It seems that many types of resistance wires have a relatively high resistance change with temperature (although not as dramatic as thermistor) that could be used to sense the temperature during the off-cycle when the wire is not actively driven. This would eliminate the need mount a thermisto
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LoboCNC
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