Keith Davis published a new build:

Read more about this build...

 

STLs, BOM, Tutorial, etc. when it's completed. I've decided to try it with a direct drive instead of a bowden first so I'm still making changes to parts.....

 

That's kind of the whole reason for publishing here Well, that, and of course, I get to use whatever improvements you perfect. This is the pirate ship

 

I'm going to try a 17 40mm long. I originally just installed one I use on my OneZ. It was late at night when I got it on. Time for a beer. I sat back to look it over, took one swig - and it hit me to reverse it all. The beer is still sitting there, one swig short, flat and warm. Stayed up all night reprinting the carriage (multiple times), extruder body, extruder lever and by doing so moved the center of gravity for the extruder motor 56mm closer to the Z axis side. Before and after pics



Don't know if that will help, but it can't hurt and I had the room on the left to do it.

Also, decided that the joint between the 20x60 frame and 20x40 Z axis upright was not as rigid as I want. So while printing the extruder pieces, I tore the thing completely down and married those two together with a Vatican wedding. First, Openbuilds ships 20x60x250 with square cuts on both ends. So, I threaded the top and bottom channel ends M5. Then I ran M5x10mm flat head screws into those threads leaving 4mm out. I then bore two 4mm holes in the 20x40 through both channels at 10mm and 50mm up from bottom. Sliding the 20x40 slot down over the two screws in the 20x60, I could then reach through the two holes with a hex key to tighten the screws. This joint is solid and perfectly perpendicular.



So why stop there! I drilled two holes in the slots on the Y axis frame piece, slid 2 M5x6mm screw and slide nuts into the 20x60 top slot, slid the Y frame piece slots over those screw heads and cinched it all into place through the holes. Now the Z axis and Y axis are rigidly perpendicular with each other.

What I really don't like about a bowden is the retraction dribbles, especially with flex or when doing support. That's why I'll try ANYTHING to get a DDE working if possible.

Time for a beer again. Well, not THAT beer.

 

I agree on the price and size. But, they are going for a niche market, you know, the cool guys who carry their 3D printer in their cargo pants pocket. The Bukito weighs 7 lbs (without the power brick which is in the other pocket) and PLA only. Simplrbot now weighs 9.5 lbs with heated bed and power supply integral. I think if I can't get it out to 8x8 build area, I'll go for 6x8, 6x10, or 6x11.5 (Makerbot size) since Y axis length is immaterial. I'm just looking for a cheaper, easier way to build a full size printer, not a mini.

 

Thanks for the link. But the Titan is way over-priced. It uses a 3/1 gear ratio to enable that 18.4 oz.in motor. And Thomas Sanladerer claims that motor works at 3/1 reduction.

Rather than that, I'm toying with adapting Sonny Lowe's extruder on his cantilever printer.


Sonny is using a 2/1 gear ratio with a Nema 14. It looks like he's using 32/16 pulleys. But, a 50/16 would produce a 3.125/1 ratio and Robotdigg has the 50T for $3.00. The 50T is 38mm in diameter while the 32T is 25mm, so it should fit on Sonny's design with slight modification. And end up a whole lot cheaper than $64.

 

What 14 are you using? Do you know the oz.in or Ncm? And the weight?

I think I'm going to go with 126mm belt and 16/50 pulleys from Robotdigg and the 17 David pointed to. It's weight is 140g and at 3.125/1 ratio will produce 57 oz.in. That may be lighter than a 14 at 1/2 ratio producing 50+ oz.in range.

That belt calculator is cool! It's slightly more accurate than my printing the pulleys, mounting on a extrusion and counting the teeth on a belt wrapped around it. Thanks!

 

Sonny, David

I should get that pancake Nema 17 (20mm) tomorrow (Thanks David). By the 25th I should have a 50T 2GT pulley and 126mm belt to run against a 16T for a 1/3.125 ratio (Thanks Sonny for the calculator link). This should cost $6.80 for pulleys, belt, and bearings more that my regular extruder.

Here's how I'm going to try to use them. Pretty unorthodox! One thing about mounting the drive mechanism on the back of the motor - the screws on the back go all the way through the motor and screw into the front flange to meet the front screws, so there may be some need to micro adjust the depth. This has room for using an E3D with the standard pipe fitting keeper (the brassy looking part) for running 4mm PTFE all the way from the MK8 drive gear to the E3D barrel. I don't think I'll need a guide going into the drive gear, but it's trivial to adapt the pillow block there if needed. The two red bearings supporting the drive shaft from the 50T pulley to the MK8 are 5x11x4 or maybe 5x10x4 from the mini-v-wheel kits. While I'm waiting for the 50T pulley and belt I'm going to remove the nozzle, print a pulley, and use a thick rubber band just for testing.



Back to the Simplrbot. This extruder will be perfect for it if it works as envisioned. But, I realized that I can add a bit of extrusion and use cheaper wheels and use the same basic layout to build an adaptation of my OneZ 13 that will be $120 cheaper to build, is 3 inches narrower that my i3, and only $3 more than the Simplrbot. So..... when I get this light extruder assembled later this month I'll go ahead and finish up the Simplrbot, but I'm concentrating on a OneZ i4 in the meantime.

 

I ceased working on this Anthony.

Using a direct drive 40mm extruder was OK, but there was vibration artifacts in the print from front to back. What was happening - on non-print moves the X axis vibrated the direction of that move and continued when extrusion resumed. The cause was using a printed plate for the X-Z wheels. Using a metal plate would correct it but add cost to the unit, something I was not willing to do. Because established retail price range for a cantilever printer is low, that added expense was a deal breaker. I don't design for amusement or personal use but for marketing.

The mini belt driven extruder also had the same problem. But I was disappointed with that mini extruder, it weighed in only 4 oz less that the full sized extruder, for double the cost and complexity.