I've been experimenting with different unheated build surfaces for printing ABS. HDU foam works quite well, but unless you have a pretty thick piece, the top surface shrinks and causes the foam to warp when you print on it. The higher density foam is also rather expensive. I've now tried a few prints on 1/32" thick phenolic (McMaster XX grade). I've sanded the surface to expose some of the pby LoboCNC - General
billyzelsnack Wrote: ------------------------------------------------------- > Love it. I've made many MCAD experiments from this > concept > and your variation with the pivot is very > interesting. What's the build area? I like your plotter in the video. I had made a similar one a while ago (not nearly so nice), which, in fact was the inspiration for the feather printer design. Tby LoboCNC - General
Regarding play, at all of the pivot joints, I am using 0.250" dia nylon spacers with 6-32 screws. It turns out that by tightening down the screw, you can force the spacer to bulge a little bit to get a zero clearance fit. This would never work if you had any real load on the pivots, but they only ever see a few oz. of force.by LoboCNC - General
The screw hinges (I'm assuming you are referring to the funky Z motor mount) actually work fine because throughout the entire Z axis range of motion (about 5" at the extruder) the motor tilts only about 5 degrees - hardly any motion at all. The flathead screws stay firmly seated in the countersunk holes. I was mostly worried about backlash in the pivot points driving the table, but in the testby LoboCNC - General
Here's a new non-Cartesian 3D printer I designed. I call it the Feather printer because the total X-Y moving mass (the build table plus slider blocks) only weighs about 150g. The whole printer only weighs 2.5kg. I'm still working out the kinks, but as you can see from this video (youtube Feather printer video) it does, in fact, print. I built it using my Lobo CNC milling machine (see: ), anby LoboCNC - General
I'd like to announce the new Lobo CNC milling machine project I am starting at lobocnc.com. This is a light-weight machine, falling somewhere in-between a small desktop CNC milling machine (like Sherline, Taig) and a desktop CNC router. It has a 14 gauge steel laser cut and folded structure that is more rigid than the typical desktop routers -- capable of machining aluminum and brass, as welby LoboCNC - CNC Routers, Mills, and Hybrid RepRapping
Finally managed to do a quick test printing ABS on unheated HDU foam (the 48lb/ft^3 stuff). Is stuck really well. (Maybe too good.) I liberated it by sliding a razor blade under the part around the perimeter, and then it popped off with just a few tiny specs of the foam board stuck to it. Much less damage to HDU foam than to the lighter density foam in the video posted above. Of course, theby LoboCNC - General
Have Blue: Curious - it seems that common wisdom is that you need a heated bed for ABS. Printing on foam sheet seems like a much nicer solution than trying to keep everything hot. Have you tried higher density HDU foam? It is much harder than the PIR foam and may not suffer so much damage when removing parts. The smaller pore size of the HDU foam may also make parts stick a little less aggresby LoboCNC - General
This place seems to have a wide range of diameters:by LoboCNC - General
tenacious Wrote: ------------------------------------------------------- > What are the temp ratings on the HDU foam? Will > it melt if a heated nozzle crashes into it? The softening temp of HDU seems to be around 120C. In testing by hand with the nozzle at 230C, I pretty much just jammed the nozzle right up against the HDU with no visible marking. I suspect you'd need more prolonged cby LoboCNC - General
I'm still working on getting my printer together, but I do have an extruder to fool around with. I've been experimenting with different materials to see if ABS will stick to anything not heated. (I'm designing my own printer and a heated bed is proving to be inconvenient.) I've been test extruding ABS onto any random material I have laying around the shop. (It's remarkably resistant to stickiby LoboCNC - General
NewPerfection Wrote: ------------------------------------------------------- > The problem is that as that layer cools it > contracts, pulling on the layers below and causing > warping. To reduce the stress the entire part > would have to be warmed and cooled all at once. I'm not entirely sure about that. Let's say you've managed to build N layers that are stress relieved. You theby LoboCNC - General
I'd guess that delamination in the middle of a print is resulting from the same internal stresses that cause warping, or that also cause parts to want to peel off the table. So yeah, maybe you don't a have a high enough temp. in your build chamber. (Also could be that the layers aren't stuck together well enough to begin with.) I Guess my idea is is that rather than trying to keep everything hby LoboCNC - General
I'm still working on building my first 3D printer, but I am a little perplexed by the heated build platform and cooling fan issues. It seems that the common way to prevent warping is to use a heated table (or a heated build chamber) to keep the part in a constantly relaxed state just near the softening point of the plastic. It strikes me that this is a little at odds with wanting to cool the extby LoboCNC - General
One interesting thing to think about with the tooth profile is the comparison with timing belts. Conventional trapezoidal tooth timing belts have a much lower load rating than the HTD style belts with the round tooth profile. I wonder if that applies to driving filament? On the split hub, yes, doing the normal thing of using a hub collar over the split hub does make it foolproof. I'd seen thby LoboCNC - General
Gerard Choinka Wrote: ------------------------------------------------------- > Looks nice > a traction test like this > - > and-no-traction.html would be nice Thanks for the link - this blog has just the sort of data I was looking for. I'll see if I can't rig up a test rig to get some numbers for comparison.by LoboCNC - General
Here's a filament drive gear that seems to be less prone to clogging that the standard V-groove hobbed gears: The teeth have a circular profile which seems to eject filament shavings better than the V-groove formed with a tap. I made this on my little CNC mill (Lobo CNC mill) using a 0.032" dia end mill . The OD of the toothed portion is 7mm. Overall, it seems pretty grippy. The other innovaby LoboCNC - General
I'm working on my own extruder and hot end (see , although I've made a few mods) and finally have something that works OK. This is going on a very minimal 3D printer I'm designing and I'm aiming for print speeds of 60mm/sec. I'm able to feed 1.75mm ABS reliably at about 225mm/min with a hot end temp of 230C. I can do 275mm/min if I crank the temp up to 245C. (It has a 0.4mm orifice nozzle.)by LoboCNC - General
I think I am starting to understand better what you are getting at with the overall heatflow issue. How about this: I've replaced the nut at the top of the exposed PTFE with an aluminum tube with a short threaded section to grip the PTFE at the cold end. The PTFE will be fully supported and the cold section heatsinking will be brought all the way down to the torlon collar. With this design, Iby LoboCNC - General
knowbusiness Wrote: ------------------------------------------------------- > Contact me through eBay I sell the SG2 hot end, if > you would like, I will donate one to your cause. > I will change my listing to accept "best offer" > and you will pay the lowest eBay allows + > shipping. Thanks for the kind offer. So far, our home-brew hot end seems to be working OK, but if it starby LoboCNC - General
After a bit more testing, it does look like if I let the extruder sit idle for 5 min or so, the melt zone does creep up above the torlon collar. As long as I'm pushing filament, though, the melt zone stays restricted to just above heater block. With extended use (say, 45 min), and with more or less continuous feeding, everything is well behaved. It seems like this would be OK for normal operatby LoboCNC - General
Thanks for the suggestions. I'll do some more long-term testing and see how bad the heating is of the upper section of the PTFE liner. By my calculations the thermal conduction up the PTFE tube (if it were completely insulated) would be less than 0.1w. The conduction up the 4-40 screws is about 1w but they screw directly into a fair amount of aluminum. My gut feeling is that small amount of hby LoboCNC - General
I'm working with a group of high school students on a 3D printer design as an engineering exercise, the only problem being that I have no experience with 3D printing. (I'm and engineer that's done lots of machine design, though.) The hotend/extruder seems like the trickiest part, and I wanted to get a handle on that first. We're on a budget so I wanted to see if we could make the extruder (weby LoboCNC - General