They're going to be 60mm nema17 steppers from RobotDigg, pretty hefty torque at 92oz/in.

The Z axis will be threaded steppers, Tr8*1mm lead.

 

IIRC, the 60mm threaded steppers with a 500mm length were about $55, with a 2-3 week lead time.

 

My V-Slot arrives today!

On that note, I've made some significant progress with the design and have started filling out a Bill of Materials for the components.

Some of which I've already ordered today, so they'll take a few weeks to arrive.

The official build volume should be roughly 400 x 400 x 400mm, though the X axis would be limited to 370mm... I may re-design the X carriage somewhat to increase the movement to allow for the full 400mm on X.


Take a look at the updated Sketchup file and the BOM Excel sheet.

 

Thanks!

This is why I love doing most of the design pre-work in Sketchup, it allows me to figure out how it'll go together before I even order the parts...

 

I redesigned the X/Y Idler mounts at the back side of the frame to increase the strength and resistance against the belt tension.

I've oriented the parts so that the longest side is facing down, though you will need to print with support.

 

My order of V-Slot arrived today, packaged really well - it's like an early Christmas.

The technique I used to make printed parts with V-Slot key ways seems to work well - the printed part fits perfectly.

 

Got a surprise in the mail today, earlier than I expected from shipping in China..

The massive massive 400 x 400 mm silicone heat bed arrived!

And it's HUGE.


24 V, 200W silicone heat bed with 100k thermistor embedded in the middle, with 3M adhesive tape on the bottom.

For size reference, the box that the heater is on top of is a good 24" square - it's that large.


Coupled with a 1/4" aluminum heat spreader and borosilicate glass, and I shouldn't have any problem with uneven heating...

Also: Room-temperature resistance of the pad measured out at around 3.2 Ohms, or calculated at 180 Watts at 24V - I'm sure the resistance will go up to match the rated 200W as it heats up.

 

RobotDigg Santa delivered today!

Parts:

• Two TR8-2 Leadscrew Steppers, 8mm diameter 2mm pitch single-start, 500mm long, with 60mm Nema17 Hi-torque Steppers
  The nuts on them are acetal/pom nuts - not anti-backlash, but should be fine.
  
• Four of the same 60mm Nema17 Hi-torque steppers - 1.5A coils, 92 oz/in torque. Two for CoreXY, two for dual bowden extruders.
• 5 Meters of 9mm wide GT2 belt
• Two 16T GT2 Pulleys, 9mm wide and 5mm bore.
  
• 10 Meters of 4mm/2mm PFTE tubing
• Two steel NEMA17 stepper mounting brackets - They have 5mm-wide mounting slots on the back, I believe 20mm apart - though I haven't measured them.

 

Not as such... the Z axis is mostly stationary, typically only moving downwards during a print job.

If I were going to make this into a CNC router or the like, then a ballscrew would be more applicable due to the accuracy requirements.


I don't even have an anti-backlash nut on the lead screws yet due to the smaller lead/pitch of 2mm - though I think I did find a source if I needed one.

 

I've have been struggling to find a suitable controller/firmware combo that meets these requirements:

• ARM-based CPU
• 24V Input for Heat Bed and Hot-Ends
  
• CoreXY Support
• Multi-extruder Support (2+)
• DRV8255 Steppers for 1/32 Stepping Support
• Z-Probe & Auto-Bed Leveling / G29 / G30 code.

I think I've pretty much decided that a BeagleBone Black controller (full linux!) and a Replicape stepper cape/shield will do nicely, and the Redeem G-Code interpreter seems to be actively developed.

There also appears to be a "Reach" expansion board in the works, to add 3 more extruders/hot-ends.

http://www.thing-printer.com/product/replicape/

 

I've made a design change to the Mini-V Gantry plates that serve as the Z axis ends - by removing two of the wheels and chopping 15mm off the side of the plate.

The wheels would then ride along the inner side of the rails, allowing me to easily attach an acrylic sheet to the sides to form the structure of an enclosure.

One side will have the fixed wheels, the other side will have the cam-adjusting wheels.


This should also allow me to reduce or eliminate over constraining the Z axis rails by having too many wheels clamping on either side.

 

They're simple Sketchup components that I'm intending to print.

The bed and mount designs are still in flux - I'm considering using a sheet of Ultem 2300 as the print surface.

 

Not exactly - SmoothieBoard has A4982 stepper drivers rather than the DRV8825 stepper drivers I want.

I'm keeping an eye on the Replicape board and the python code / firmware that is in development, just haven't gotten around to ordering the hardware yet.

 

The Replicape board is the one I've been watching, good thing the price dropped from $179 to $99 - though I'm going to wait for the Revision B boards at the same price.

Although you still need to spend another $50 or so for the BeagleBone Black to power it.


Another thing that is nice about the Replicape is the Reach expansion board - which will allow for an extra 3 stepper motors and hot ends eventually:

http://www.thing-printer.com/reach-expansion-board-replicape-ready-review/

Hasn't been developed into production yet, though.


I also invested in their kickstarter for their Manga Screen LCD panel - HDMI and touchscreen for the BeagleBone Black / etc.


As for the 20mm V-Slot Gantry plate, try this Sketchup file - The components are from OpenBuilds, although I modeled the 20mm L-bracket myself.

 

The fixed bed idea is rather neat - I haven't cut my rails yet, so I may try to incorporate that somehow.

I've been experimenting with using the large V-Slot gantry plates for the hot end carriage, but the plates are really wide and would limit X travel unless they were cut down to be narrower.

I'll see if I can come up with something similar for a floating X/Y/Z carriage.