Two motors, each with their own drivers and sharing the same Step and Direction signals and two motors being run by the same driver is not good practice. (More details in Section 7 here http://www.openbuilds.com/threads/electronics-101.693/)

Tweakie.

 

Exactly my point. I wish I could get away from it and they say that using two drivers, instead of one, causes sync issues even more. All I know is that two motors using the same driver is just bad all around.

 

Who says ??

Tweakie.

 

Well, Josef Prusa for one. I asked him why he went with two motors driven by a single channel (driver) and that was his answer to me.

 

Just modified my original post, after re-reading it, to correct my error.

Basically, when using two motors to drive a single axis you need to have one driver for each motor, they need to be slaved, they need to be 'homed' to synchronize position and you need to manage any disable events applied to the drivers (i.e. homing again after any disable event or not using disable at any time during the current job run).

Tweakie.

 

More work with a better outcome. As it is Z had to be turned up to almost double (strange it wasn't exactly double) what the other drivers current was. I am just surprised the Z driver hasn't blown.

 

Yeah, there is that - I'm basing the idea off of something like this:

http://q3dprinter.com/rxl.htm

Again the linear bearings are what constrain the platform to rise/fall equally at each corner.

With 8 V-wheels at each corner, they'd have to have some level of clamping force to prevent the wheels from deforming or preventing the ends from racking.


The other thought I was having was to rotate the Z plate by 90 degrees, and use the wider 40mm portion of the rails as the bearing surface rather than the narrower 20mm surface.

Or possibly the addition of the harder polycarbonate wheels: http://openbuildspartstore.com/openbuilds-xtreme-solid-v-wheel/

 

On a 3d printer do you really think you would need that?

One thing I never understood are these printers with only one side supported and the X axis moves to the side with no support. Ahem, yeah, you would never catch me buying something like that, lol.

Here is another joke (poor people who bought, or are buying it) but a printer by QUBD is made out of laser cut cardboard EVEN THE HOTEND is supported with cardboard. *shudder*

 

Probably not, I'm mostly looking into it for the H-gantry / Core XY system and trying to design something that can do a 300 mm cubed build volume.

 

My next build I am going for a bigger heated bed as 200x200 is just a smidge too small to do the things I wish to do. Oh, and I am going to try to get more even heat which is a bit of a task but I do have some ideas.

 

I think I've come up with a variation on this that I am liking.

It's more or less the same, except that the box frame and Z gantry are both rotated 90 degrees, and a the XY belt paths are mirrored/flipped/inverted with the crossover belts riding along the inside of the back frame rather than on the outside of the back frame.

All of the purple 20x40 lengths are 500mm, easy pre-cut lengths - the rest are cut shorter.


I may decide to replace the Z gantry wheels with a set of the Mini-V end plates, and / or the mini-V rails and wheels: http://openbuildspartstore.com/mini-v-plate/

 

Part of the purpose of the design is that you eliminates ghosting that come from the y axis shifting back and forth.

 

Ghosting?

 

Ghosting a.k.a. Vibration a.k.a. ripple a.k.a. shadow is the axis vibrating as it attempts to come to a stop. Any number of mechanical things in that chain will contribute to it, the springiness of the belt and rigidity of it's mount, any bounce back from the stepper and even mechanical rigidity of the entire frame along that particular axis. You can combat it by lowering the moving mass, stiffening the mechanics, lowering the speed, and/or lowering the acceleration.

This design lowers the moving mass.

 

Ahh, yes and that can get pretty high. You will see that in the print as the lines will be wavy.

I am lucky as that is the only issue I have never had.

Oh, how hard is this design to have a level bed? On my I3 rework I had to go to Automatic Bed Leveling as I could not ever level it (using a dial indicator) and I spent over 200 hours (sometimes over 16 hours in a single day) trying to level it. Flat it is (has to be for ABL to work) but never level.

 

Looking at your design for my first 3d printer build. I've been doing research into reprap designs, specifically the prusa i3 design. I looked into the i3v from makerfarm, which lead me to Openbuilds, and to your C-Bot design.

I've looked into kits such as the iv3 from maker farm, the Prusa i3 Rework from Replikeo, and other prusa kits. I'm on a budget so I would source all the parts separately to save on costs.

That being said, since this is my first build, do you think I could get your c-bot built correctly, or should I go with the a widely supported reprap design? I realize reprap would be a good learning experience, but I'd rather learn on your design.

 

I have an I3 Rework Single Frame (Aluminum) and let me tell you go with the c-bot. I spent over 200 hours trying to level my bed alone and I never managed it so I had to go to ABL (Automatic bed leveling) and man was that a chore to implement. It was such a chore (I am no dummy about electronics and programming) I had to go to a forum to get help and all of that is just the tip of the iceberg in the garbage issues I have had to deal with. I use 8mm chromium steel rods from Mitsumi (the 22 dollars a piece ones (not including shipping)) and using the V-Rail system you can eliminate the need for that. In my instance the C-Bot would be less expensive with a fair amount of less trouble too.

Now, the only issue with the C-Bot, for me, is cutting the extruded aluminum perfectly straight and cleanly. C-Bot is less demanding with that due to the printed parts but that brings up an issue for you if this is your first printer...how are you going to get the printed parts??? With an i3 the parts, and all in one kits, make it very easy to have something but there are no c-bot rp sources that I know of so as a first printer it would be very hard to source that.

 

Thank you very much for your input.

I have a Da Vinci 1.0 that I should be able to print decent parts with. I've been playing with it for the last couple weeks. Mostly learning the ins and outs of loading custom Repetier firmware on it, and doing some small prints. The little blue pick axe in my profile picture I printed with the Da Vinci.

You have motivated me to continue filling out my own BOM and see what my final cost will be and go from there.

Thanks again!

 

"Looking at your design for my first 3d printer build."

Ahhhh, I took that to mean this was your first printer so you should be golden then and you will be much happier using a printer designed around V-Rail than any I3 and all of its variants. That is my opinion at least.

 

Carl,

Going over your BOM, I calculated about $400 in Openbuilds parts. Is that correct?

 

Carl, I know this is going to sound crazy, but I love the color blue for your printed objects. Where did you get it? I want to buy some.

 

hey guys, good job after
3weeks I've received the V-slot - so I will start cutting them anysoon,

looking for the motor,

is those are the one suggested ? (68oz)

Nema 17 Stepper Motor,2Phase, 68oz, 4wires

Step Angle: 1.8 degree

Voltage: 3.1VDC

Current: 2.5A/phase

Resistance: 1.25Ohm/phase

Inductance: 1.8mH/phase

Holding torque: 0.48N.m 68oz-in

Rotor inertia: 68g-cm2

Detent torque: 280 g-cm

Number of wire leads: 4

Weight: 0.36Kg

Length: 48mm

just wanted to make sure I order the correct one

 

what is you're current speed with you're actual printer if you don't mind asking?

looking at that sheet, the one I was looking are pretty low, not sure if its the right motor, the goal is to print faster with high accuracy has I have already a K8200 printer at home that I'm happy with

 

thanks Carl,

searching more - I had found a good deal for 5x 70oz motor - here is the link:

http://www.aliexpress.com/item/HOT-...T47-1684A-5kg-cm-70oz-in-1-68A/782779071.html

is those are good? I usually print a normal speed with my Vellman but if I could end up at 130% why not

thanks