Yes you are correct, frame isn't limiting factor in speed. I'm running rapid moves at 250mm/s and could do higher but there is lot of moving mass and printer is waving my work table! I have printed with faster speeds, but print quality is always weaker then. When printing fast the start of extrusion looks ugly and some ringing is showing. Main reasons to ringing are wavy printbed, moderate quality linear bearings(they weren't as good as I thought), non supported rails and rubber belts. Even though I have 12mm chromed rods, I can bend them pretty easily just by pressing it down by hand and that isn't good thing.

Nowdays I can't machine parts by myself so I need to get along with these problems and I usually print around 50-60mm/s and I'm pretty happy with it. Print quality is good and I don't need to tweak calibrations at all!

As far as I know, Smoothieboard can handle 24VDC, so it wouldn't be a problem! At this point I still don't need upgrade for higher voltage.

Do you have any information of your printers online? They sound interesrting! I might also have one bigger printer project coming. If it begins, printer will have over 300x300 build area and I'm planning to use nema 23 steppers also.

I would expect a frame like this be able to go much much faster than 150mm/s - the belts are probably the limiting factor.
I achieved that kind of speeds reliably on a heavily modified Prusa V1 at high accelerations (i think 3-5k, cannot remember) without severe loss of quality and no ringing.

Your limiting factor on speed will eventually be the drivers & voltage, you'll need 24VDC after a certain point - that's basicly where i got stuck with RAMPS 1.4 last time around. But there's now easy solution on RAMPS board
For Smoothie you need put headers in and use external, afaik it cannot take separate supply for the drivers Which is such a shame as digital current control is sweet!

Before you get to that point, add heatsinks & cooling fan for the onboard drivers, heatsinks for all the steppers and basicly just run them at the highest current you can make them reliably work, find the spot where they start failing and come back 20%
Cooling affects that most heavily.

Voltage as i understood is the ultimate limiter of speed due to back EMF, eventually the back EMF generated by the steppers when decelerating will be too large and eventually the voltage difference from back EMF to supply vanishes and you'll miss steps.

My next build is going to have 36VDC driver supply voltage with 4.6A Nema23 stepper motors which are 3N-m or 425Oz-in, so a bit above 4 times the torque the Nema 17s linked on this thread.

Because all steppers are basicly wound for the same speed, which translates to about 1200rpm with half steps (measured in PPS), eventually no matter how much larger motors are put in, you can't get more speed unless you sacrifice resolution
Precision is largely determined by how sturdy the frame & drivetrain is.

Knowing what i know now, it still amazes me how i managed to drive so much performance out of the Prusa V1 design, which has wobbly X axis and super strong Y axis, esp without lateral supports!

With Nylon i got out flawless prints at 180mm/s print speed (tho design was round) with straight cylinders snap fitting together so well that people didn't know they are snapped together unless i showed it to them

Do you think that smoothieboard website is a bit unclear..?

Well, I'm certainly always challenged when I'm trying to find stuff on it :-).

Thanks for the info about the display (though I always have my print next to my computer, so adding a display is a long way in the future, if ever :-).

And I also soldered 1A voltage regulator so I can use printer without USB or 5v power supply. I bought board itself and GLCD-adapter pre-soldered so there wasn't anything else to solder. However here is guide for it: http://smoothieware.org/rrdglcdadapter

Do you think that smoothieboard website is a bit unclear..?

This whole package weights just under 300 gramms which are about same as normal sized stepper motor. Altough weight isn't so important thing in my printer because there is no printed parts in strucutre, so moving mass is higher than usual in any case. But many little weight savings makes a big difference in the end!
I have printed couple test prints and it seems promising. It can easily achieve 30mm/s retractions and print over 150mm/s!

I bought also smoothieboard for it! And as usual, here is video:

So, I've made most of new moving parts, installed new steppers(ACT-motors, 0.52Nm), Faced all aluminum profiles to exact length and made threads into them. Frame was way easier to assemble with these new corner brackets that you can see.
I made bronze bushings, but it's impossible to get rails so straight that they will run smoothly. So I paid pretty much to get good guality LME12UU linear bearings and it really was worth it! They run very smoothly and not too much slop. Also made heater blocks from E3D drawings for becoming hotends. And here is photos:

https://dl.dropboxusercontent.com/u/526 … _28759.jpg
https://dl.dropboxusercontent.com/u/526 … _11728.jpg
https://dl.dropboxusercontent.com/u/526 … _12434.jpg
https://dl.dropboxusercontent.com/u/526 … _31687.jpg
https://dl.dropboxusercontent.com/u/526 … _55458.jpg

And here is heater blocks. I guess they are cheap copies of E3D since they did cost only time for me Now I need to design and make new hotend and extruder. Desing is in good shape already!

And video of moving printer:

I haven't ordered steppers, since from omc-stepperonline postage would be insane. I'll just order wantai 4.4kg/cm steppers which I can get reasonably from ebay. I have now these so there will be great improvement anyway http://www.ebay.com/itm/251592343083?tf … lgo=origal

I have motors more similar to this on my Hadron

http://www.omc-stepperonline.com/3d-pri … -p-17.html

and they are bulletproof performers swinging around an almost 2 pound payload with the Bulldog extruder.

Only negative thing is that they are shipping from china, so I need to pay import duties if order costs over 22 euros. But they are still pretty cheap.

What do you think about this motor? http://www.omc-stepperonline.com/nema-1 … -p-21.html
There is 2.1A and 1.2A version of that motor. With 2.1A my stepper drivers will probably be very hot, but is there any benefits why I should choose 2.1A motor over 1.2A? 2.1A motor does have lower inductance. Does it matter?

Here is a source for a good variety of stepper motors...cannot attest to the quality yet, but some other members do recommend them:
http://www.omc-stepperonline.com

I've been suffering with lack of motivation with this thing, so I there is no progress in part manufacturing. Though in last couple weeks I found my motivation and pretty much designed the modifications!

Here is changes:
-Linear rails from 12mm chromed rod
-Linear bearings from brass or bronze
-CoreXY belt system (GT2)
-Aluminum bearing holders/X-ends/everything
-Direct drive extruder
-New watercooled hotend

I desided to go with CoreXY since there is lots of work to do anyway, so it doesn't matter. There is so much more pros with it, comparing to H-belt assembly. Carriage twisting haven't been problem with my H-bot design, but I wan't still change to CoreXY for increased stability. It will have also shorter belts, so there might be less stretching and more accuracy. Only negative thing is that it might be difficult to set exactly same tension for each belt, but I don't worry about it!
As you can see from my great drawing, it isn't ordinary CoreXY path. I'm doing it in two levels like Fabtotum(http://blog.fabtotum.com/blog/2014/04/0 … -to-share/). And motor location isn't in  stationary 180 degree turn of belt as usual. Belts are going from behind and they are not crossing. I think it's great thing! In demo drawing you only see one belt but it's not different from another, only going 10mm lower. With this kind setup I can keep the same style belt tensioning blocks with very easy access in front of printer.

Negative thing in these modifications are that moving mass is doubled comparing to existing design. CAD software says it's about 1.4kg + bolts, extruder etc. I'd say that is acceptable for (hopefully) increased stability and accuracy.
I'm making direct drive extruder because it's easy and reliable solution for first. I don't want to play with tons of problem at the same time. So when printer itself is running well, I start to develop different kind of extruders(Nema 8 stepper is waiting..)

If I'm lucky, part manufacturing starts in next week! If someone sees any problems with my CoreXY design let me hear that! I thought that the angled path you are seeing in demonstration doesn't matter since it's in fixed place? It's rough demo, so if I'd go with that those pulleys would crash. In real desing there is more room

You can also suggest some good stepper motors! I'm looking for powerful and fast enough motors. Maybe 60mm long versions?

Second thing is the springiness of extruder driveshaft. Retraction is okay, but oozing with faster printing speeds(+100mm/s) is driving me crazy! And that is because springiness creates kind of backpressure, so shaft turns a little more before retraction.

But I have plans. I'm going back to good old ground rail, but not with chinese linear bearings. I'll make some tests with bronze bushings at first. Maybe also with some plastics, like POM or Nylon? If they doesn't work, I might go with IGUS DryLin polymer bearings or good quality linear ball bearings! I'll stick with H-bot belting as I believe that I'ts good with rigid machined parts.
I'm not leaving my flexible driveshaft extruder, but I'll start designing whole new with Nema 8 stepper motor and high ratio gearing! Lets see what will happen.

Today I finally figured out why the print dimensions came out wrong. And feeling idiot! Steps for motors weren't correct. I trusted that 20 tooth pulley will need 80 steps and that's it. Shouldn't trust to quality of those pulleys. Just saying that dimension errors is bit sneaky with "corexy" configuration!
I started to calibrate those steps and was getting closer until fan wire did hit mosfet. Well, with some magic smoke I could confirm that my (second) ramps board is broken. My friend tried to fix it but no luck with it. I ordered new one and if I'm lucky it is here in Friday!

I've been also dreaming of smoothieboard.. When I get my printer "ready", there might be a little bit room for faster CPU
I don't want to fry 150€ board with this kind of mistakes.