Mark, what wheel plate are you using, I don't recognize it?

 

Hi Josh, great build idea! I can't wait to see how you solve all the belt issues. I admit that I've only glanced at most of the Core XY designs. They seem like a solution looking for a problem How ever, yours appears to be a much better (simpler) concept and anything over 300mm gets me excited.

One thing I wondered about is your use of a Nema 17 stepper for the Z axis? It seems to me, that with the load spinning 4 leadscrews and lifting a 400x400mm build platform with a kilo or two of printed material on it, the load may exceed the abilities of the humble 17. Perhaps a Nema 23 270ozin stepper may help avoid any problem. Since you only have one stepper in this axis with careful selection of the stepper you can stay safely within the limits of a Ramps chip. And even if you need to swap to a slightly stouter Ramps chip (4825?).

Keep up the great Work and please, keep taking pictures.

Larry

 

Well, I feel foolish! I know I read that you intended to have a fixed build platform and by the time I was typing I spaced it completely out!

Thanks for the pics. I know I really enjoy looking at all the different ways other folks solve problems and I'm sure others share my voyeurism too. Maker porn, I guess.

Be well!
Larry

 

Ah, yes, the second image in the galley list. Can't believe I never saw that before . Looks like a possible candidate for a dual extruder mount . Thanks!

 

Smooth, JOSH, real smooth! Love the design.

One thing you'll probably run into when you run the Z belt. You may need to place an idlers inside from each Z axis pulley just to force engagement of enough of the pulley for grip. No biggy the way you have it laid out.

Something to consider. You are running the two XY belts on different planes to avoid having to do the cross-over. But you have separated the corner idlers to two different positions and shafts. Can't you just stack one plane's idler on top of the other on those corners the same way you are doing on the X axis idlers for those belts? Something like this....

 

Keeping your 4 lead screws true to the bed and the carriage will be difficult moving them. I'd go with the idlers for tensioning (you'll only need one for the entire belt). I was thinking more about tooth engagement


As for the way the belts are mounted offset to the X carriage - I don't know yet. When I originally tested this xy carriage moths ago I had it set up so the bracket the belts tied to was back over the wheels and the belts were parallel to the x axis bar and the carriage wheels. That requires a wider x axis travel space, so I'm going to experiment with the offset. In both setups I'm not that concerned with the belts being parallel with the axis or the extruder plate, I'm thinking that the focus should be the force applied to the wheel axises to which the belts are attached via the bracket. If the applied force is equal everything else on the carriage should follow in place.

 

This looks a really interesting build - but my thoughts are on the single wheel on each corner for the Z axis whereas most other builds I see are 3 or 4 - have you done much testing with the Z axis?

 

richw I was wondering the same thing. But, if Josh is using 4 acme lead screws, w/bearings top and bottom, maybe the wheels are not even necessary. The 4 drive screws may be able to double as the 4 guides we normally think of using linear bearings/rods, or wheels/slots, for. Maybe....

 

Great looking build. its making me rethink my CoreXY build

 

Love your build - think you solved the gantry/pulley attachment problem in a much cleaner way than I did (though my design squeezes out a bit more build volume). Though I am satisfied with the result, were I to do it over again, I think I would opt for the more robust and simpler attachment and sacrifice the volume.

One hint on Z steppers, I am using the same size steppers and geared down my Z pulley 1:2. I'm not sure if I needed it or not, but I can tell you it is working fine as is using 1/32 steps with 8825 drivers.

 

This is looking AWESOME Josh! A really clean looking robot.

Using 20t/40t pulleys on Z axis for gear reduction will work, but it will also force the Z axis to use micro steps. 20 teeth produces 12.5 micron resolution, whereas 16 teeth produces an even number 10 micron resolution. A better pair would therefore be 16t/32t. Mark Carew posted a great article link on avoiding using microstepping for Z axis. Here's a couple of links I use for 16 tooth & 32 tooth pulleys w/10 day China delivery.

Rostock 16 Teeth 5mm Bore GT2 Pulley - 3D Printer Supplies: Stepper Motor, Lead Screw, GT2 Pulley n Belt, stepper driver and 3d printer parts. ($1.80)
GT2 Pulley 32 Teeth 8mm Bore - 3D Printer Supplies: Stepper Motor, Lead Screw, GT2 Pulley n Belt, stepper driver and 3d printer parts. ($2.10)

 

Josh

Disregard the rant on 16/32 vs 20/40. It's germane to using belts instead of lead screws. I had just woken up from a coffee/nap when I typed that and had been working on a belt driven concept earlier. Sorry bout that....

It doesn't matter which pulleys you use on OB Tr8*8-4 lead screws. As long as you have 200 step 1.8 degree motors at 1:2 ratio gear down you can do full stepping to achieve .1mm increment layer heights. 200 steps @ 1:1 = 8mm travel. 200 steps @ 1:2 = 4mm travel. 20 steps @ 1:2 = .4mm travel. 5 steps @ 1:2 = .1mm travel. (To achieve the same resolution with direct drive would require a 400 step 0.9 degree motor.)

 

the pieces that you are using to mount the acme screws to the base.
can you post a link to where you found these please.

 

Thanks.. the more i mess with my build the more it looks like yours! lol. hope you dont mind

 

Your solidworks file has alot of references. would you be able to post the references too.

 

Have a look here. hopefully you can just resave the file with references
2012 SOLIDWORKS Help - Save As with References