300X300 Need help

Hi,

I'm planning to build a printer based on wilson. I would like to know how much I can scale the build volume without loosing mechanical rigidity and acceleration. I'm planning to use bowden system with dual extruder set up. on y axis i will be using heater pad with aluminium plate.

I have been reading the forums and found out that 8mm rods is not strong enogh for further scaling. But i have doubt the lulzbolt Taz is also using 8mm smooth rods right but they are getting a build volume almost equal to 300X300 why is it so?
Even if i can get volume of 250X250 I will be very happy. I'm new to machine designing and machine engineering, If you can provide me any guideways that will be very helpfull. All the helps will be appreciated and thanks in advance.

The TAZ 4/5 use 10mm rod but it would be nice if they used 12mm as there is a tiny amount of flex in the current setup. So, no, 8mm is not enough. Use 10mm minimum or 12mm if you have the budget.

Thank you for replying,

12 mm rod means i have to use more powerful motors on Z axis also right. with 8mm rods can i achive 250X250 without much flex problem??

On the static parts, no problem. On the X gantry too, because it's moved slowly by the Z axis leadscrews, so it's no big deal. The most extra weight will come from the moving bed. Even if you only extend the X and Y dimensions by 50%, its weight will increase of more than 225%. When you want a big printer, it's wise to choose a design with a static bed, or a bed which moves only on the Z axis. On the carriages, one part of the weight you will gain will be mostly on bearings, and a bit on plastic parts, but not significantly. You can use brass bearings or polymer bearings to save on weight, and surely go under the weight of the LMxxUU series, with a smoother motion. Some 12mm rods won't flex when supported at a 380mm distance. Don't worry about the rods weight for acceleration. But you surely need to upscale your aluminium profiles too, for structural purpose, and also to stand all the dynamic stress induced by your large moving bed. Good luck

Edited 1 time(s). Last edit at 04/12/2015 07:40AM by Zavashier.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

My printer is just what you describe- 300x300 with bed moving in the Y axis. I have had to take some extreme measures to get the bed motion under control. I started with 1/2" round guide rails, brass bushings, belt drive, and a medium sized NEMA-23 motor and ended up with linear guides, ball screw drive, and a big NEMA-23 motor with a DSP driver and 32V power supply. It works beautifully, but it can get costly, it's very heavy, and it's pretty noisy.

Use a design that moves the bed only in the Z axis. I think the CoreXY architecture is good. If you're going to print ABS, design the frame to be easily enclosed and keep the electronics away from the heat inside the build chamber.

I like smoothieboard for control, too.

@ the_ Digital_Dentis
I am interesting on yor setup!
What type of electronic boar do you have?
And how many NEMA 32 do you use?
I am trying to figure out if Nema 17 + RAMPS 1.4 would be enough to run such a big platform!
My project is targeted to Cartesio type with Z axis hotbed movement

Thanks a lot

My machine moves the bed in the Y axis. I am using a SmoothieBoard for the controller. X, Y, and Z axis motors are all NEMA-23. X and Y axis motors have their own 32V power supplies and DSP driver modules. The Z axis has a single motor driving two screws to lift the X axis.

There are a lot of factors to consider when selecting the electronics, including cost, ease of making connections to the board(s), ease of updating firmware or making changes to the machine's configuration, ability to network the controller, current capacity of motor drivers and heater switches, I/O's for future hardware add-ons in the printer, etc. I was using Arduino/RAMPS to run my printer, so yes, it is possible to drive NEMA-23 motors with it, but switched to smoothieboard initially for the ease of connecting to it, but immediately loved the firmware and configuration update methods (recompiling firmware for Arduino was a PITA). I don't use the networking, but may do so in the future, if I can figure out a use scenario that makes sense for me. The faster CPU allows higher steps/sec rates (100k for smoothie vs 40k for Arduino) in the motors which translates to allowing finer microstepping to reduce vibration from the motors, while maintaining print speed. Smoothieboard's on-board drivers are limited to 16:1 microstepping, but step/direction/enable signals are brought out to headers so it's easy to connect external stepper driver modules. From what I've read, the Arduino is operating at about its limit in terms of what it can do, so future add-ons may not be easily accommodated. The processor in the SmoothieBoard is no where near its load limit and should easily be capable of future add-ons and improvements.

The proper way to select motors is to calculate required torque using something like this page: [www.orientalmotor.com]
Once you know the required torque, you shop for motors that meet the spec. Once you know what motors you're using, you make sure their electrical specs fall within the driver specs on the RAMPS board or whatever you're going to use to drive them.
An easier way to do things is to see what others have used for similar set-ups, copy it, and hope it works as expected.

Thank you T_D_D for fine explanation!
I retreat to start my project the reverse way!
I started to gather all components as for Prusa i3 , but having already aluminum rails that could stand 4'x4' ..yes 4 feet
I though, I could go about 400mm x 400 mm size printer....
Well, I might just go the smaller version and gain experiences and them to rebuild the bigger one, if ever.
Really appreciate your feedback and time spent!,,,,
THNAKS A LOT,

@Zavashier

I ditched LMXUU from my first prusa itself, they have that play which creates lots of mess. I'm now using used teflon bushings made from a rod using lathe.
And yea I have seen your comment on related post regarding engineering a machine so i understand its not a easy job. Actually i was expecting advice from you . Now i'm thinking about going with 10mm rods with nema17 5.5Kgcm motor and DRV8825. Whats your opinion with that?

Now I'm looking at abuild volume of 200X300. 200 on X axis and 300 on Y axis.

@ the_digital_dentist

Thank you for nice explanation. I would like to know did you tried that set up with smooth rods? If you did, then what was your experience with that?

I'm planning to build a core XY after it with 300X300X300 build volume with smoothie and stuff also. Since you have been using both, what about the learning curve from Ramps setup to Smoothie?
Tysm for that link

Here's what I did originally: [mark.rehorst.com]

Recent changes, not yet added to the web site include a complete rebuild with ball screw drive on the Y-axis and linear guides added to the X and Y axes to replace the 1/2" round guide rails. I upgraded the electronics along with the mechanics, so I never tried the external drivers, 32V supplies, etc. on it when it still had the round rails.

@ the_digital_dentist

Its a big and nice engineered machine I like it . I'm looking into simple setup. what dia rod you were using with round rails???