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Discussion in '3D printers' started by Keith Davis, Mar 26, 2014.
A Prusa i3 design running on Open Build's mini V wheels
Keith Davis published a new build:
Read more about this build...
That is a great looking machine. How do you think it will price against the makerbot? Also where are most of the electronic components coming from.
Makerbot? I hadn't even thought about makerbot. Their high price reflects their market dominance, not the value of the machine. On the other end of the scale, I can compete with Printrbot and still turn a profit. The components come in around the mid $500 range when all parts are bought retail. The actual sale price will be just as high as the market will bear, somewhere close to assembled Ord Bots.
As for electronics, it will use the new Azteeg X5 (mini) from Panucatt (I'm still waiting for them to ship their kickstarter batch so they can fill new orders.) The small, but powerful enough, NEMA 17s are from QU-BD (min v wheel guide systems have less drag than linear bearings) and the NEMA 14s are from Pololu. Heat bed is from Sainsmart.
Excellent work Keith - a beautiful machine.
I second that Keith, great job and much success on your campaign.
Keith, i'm thinking about adopting your Y axis belt system.
Because it's off centred (not in the middle of the carriage), the forces on the carriage are not "balanced".
I can imagin that over time, some play can occur on the carriage wheels running on the extrusion because
the carriage not only wants to move back and forth, but also wants to twist a bit.
Have you ever run into problems with that?
I have a little over 1000 hours on a printer with that design, and no play in Y carriage wheels has developed. There are lots of printers that use an offset for the Y axis (printrbot, cube, up!, makergear m2, etc). The makergear uses wheels that are a lot smaller that the OpenBuilds Solid V Wheels. The others use linear bearings.
A nice thing about using wheels instead of bearings is that wheels can be adjusted as they wear. I have a printerbot that got wear in the linear bearings for the X axis and the same thing happened on an OrdBot's X axis, both after 5000 hours. The Ordbot was easy to adjust, the printrbot required bearing and rod replacement. By definition, most X axis designs use an offset belt and have a much smaller distance between bearings/wheels accentuating the effect you are referring to.
The main thing is having a truly parallel set of slots for those wheels to run in. I tried using two 20x20 extrusions separated by printed spacers. No go, the two sides were never parallel enough and that did cause wear. That's why I use a 20x60 for the center. I actually think a better setup for wear would be to use three wheels - two stationary and only one adjusting on the other side half way between the other two - creating a triangle, which is more rigid and automatically squarer than trying to get equal tension on two adjustable wheels. Deezmaker uses that concept with OpenBuilds wheels on their Bukito. But I haven't tried that on a Y axis.
Take a look at my other printer design http://www.openbuilds.com/builds/oneupsolid.1222/ on the third picture. You will see a different variation of the concept there. I'm cutting the extrusions for assembling that design this afternoon.
Thanks for your informative answer!
Such an offset configuration it will be then
A single 80x20 of 60x20 as a y axis rail was already in my design, so i made a good choice there.
If you plan on using the OpenBuilds Build Plate, look it over before deciding on whether it will be an 80x20 or 60x20. The pre-drilled holes fit 60x20 exactly. 80x20 holes are not there, if memory serves me correctly.
It's a pleasure to share!
Are there any plans or drawings issued for this printer yet? I note that you said you would issue some soon. It would be great if you can.
Proteus. I discontinued that model a few months ago. The design of the printed bracket connecting the X axis bar to the Z axis bearings is too flimsy after 1K hours of operation. I'm finishing a redesign using V Slot extrusions and Mini V Wheel Kits for Z axis. Much stronger and more rigid. The redesign also places the X axis motor in the center of the X axis bar, evenly distributing weight and torque along that axis. I'm just now completing an auto-leveling mechanism for the new design.
I'll post links to the new design here when I release it.
Many thanks for that feedback. Very useful and you confirmed some of my thinking. Whilst I am new to this I have been trying to gather as much info as possible before making my own mistakes/ I like the sound of the central X axis motor. i resume you are going to use a rack and pinion movement. The only thing i couldnt figure how to do was easily mount both extruder and x axis motor without both interferring. i also had some concerns about the flexing of the cable and wanted to minimise this. The mini v wheels for Z axis again sound good to me so i will be interested to see your next prototype.
Rack and pinion moves the motor. We certainly do not want that weight moving on a high speed x axis. My x axis motor is stationary with the belt above the top v wheels (actually anchored to those v wheel axles). Here's some picts and the Sketchup file
X axis front
X axis rear
Excellent thanks for that. This is almost identical to the conclusion I came. Unfortunately mine is still on pen and paper at the moment. For the Z axis I was going to mount the wheels directly on to the X axis cross bar (V groove) rather than mount a separate mini plate to simplfy the design a little but having seen your drawing your method looks a bit neater.