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Just another 330x330x300 Ultimaker with direct drive dual extrusion

Posted by jerryjs8 
Re: Just another 330x330x300 Ultimaker with direct drive dual extrusion
May 04, 2018 07:29PM

Go to Thingiverse, and search Scoot68 and you will be able to access the complete model of the beast.

Always Printing,
Re: Just another 330x330x300 Ultimaker with direct drive dual extrusion
May 09, 2018 07:23AM
Got around to printing some dry boxes for filament to hang off the back of the printer. Been holding a lot of workshops for 3D printing at work and doing a roadshow with our prototyping program, so it's got to be put up a notch in the professionalism department :-)

PETG shouldn't have a lot of problems with shrinkage and delamination, but that's what the glue is for...

Then... the horror of it... my Duet Ethernet gave up the ghost :-(

So until that gets sorted out I'm back to using the CTC for a while. Really missing that auto calibration right now!

EDIT: Contacted Duet3D for a warranty claim and they got back to me within half an hour. I get to return the faulty controller and they are sending out a replacement ASAP so I can get back to printing, great customer service!

Edited 3 time(s). Last edit at 05/09/2018 08:55AM by jerryjs8.

Build Log - DDDE 330x330x300mm Ultimaker
Re: Just another 330x330x300 Ultimaker with direct drive dual extrusion
September 11, 2018 05:54PM
Hello! I saw that for the x and y axes you used 10mm bars ... how did you solve the rotation problem (print resolution issues: sort of: 16-teeth vs. 20-teeth pulley) ?! Your pulley is 32 teeth! Another aspect would be the use of the direct drive for the x and y axes ... I think it would bring some benefits to the one with the intermediate strap, plus that way I would be able to pull the engines out of the enclosure that is being printed. . One last point would be using of 8mm carbon fiber rods instead of steel ones?! Thank you
Re: Just another 330x330x300 Ultimaker with direct drive dual extrusion
September 22, 2018 10:23PM
Hello ssh18,

For the drive ratios I used 16 teeth on the stepper motor and 32 teeth on the shafts giving me a 2:1 reduction. This basically halves my resolution, but doubles the torque for the "small" stepper motors I've chosen. Since I'm using 0,9° motors, my steps/mm are 200, which is the number of steps per rev on a normal 1,8° motor. The 10mm steel rods are somewhat heavy, the rotating mass is quite small and in the sliding gantry you can see in a previous posts that I already compared 8mm steel to 10mm steel and 10mm aluminium rods. Although the weight should be a negative, the lighter more flexible rods resulted in more ringing around sharp geometries. It would be nice to go 10mm carbon fiber, I guess, but the current setup seems to be not worse than what I've tried so far.

IGUS does carry carbon fiber rods, but after talking to a couple of IGUS representatives I was not able to get a good suggestion for what bushings can be used for carbon fiber rods. Best answer I could get was "Try some of our products and let us know." Odd, isn't it? They produce linear rods, but what is the recommended linear bearing/bushing to use with them? Since my last conversation with IGUS they have published the following report: [www.igus.com] saying that their J260 bushing is the best fit for carbon fiber. If you look at the material properties sheet, it lists the Coefficient of surface friction, dynamic, against steel at µ 0.06 - 0.18. (notice they haven't the static value, nor updated the dynamic coefficient against carbon fiber). The static coefficient of Teflon against steel is 0.04, meaning the slip-stick effect is as low as it's going to get with commercially available materials. IGUS bushings are horrible at this, and were the largest cause of ringing I found while building this machine. (Take an IGUS bushing and just slowly slide it on a steel rod from a dead stop. You notice it sticks quite a bit until it starts moving) Until there's a proper line of linear bushings developed for carbon fiber, I'll just stay away for now...

As far as direct drive, you could couple the motors at the ends of the driveshafts, but the only benefit would be a higher resolution if you keep the 0,9° motors (400 steps/mm) but also the need for higher torque. If you are hinting towards the backlash of the intermediate belt, I would be more worried about the 2mm step in the GT2 profile than the influence of theoretical stretch in a 180 tooth closed belt. As for the only benefit of placing the motors outside of the casing, the housing plates are only 6mm thick, which allow me to simply turn the motors and mount the motors on the outside. Their driveshafts stick out enough to mount the pulleys on the inside of the housing. But as long as I'm not printing PEEK and sustaining an ambient air printing temp of 150°C, then there's really no need to relocate them to the outside.

I hope I was able to answer your questions. If there's anything I wasn't able to explain clearly, please let me know! Otherwise, stay tuned for updates, I've been busy, but not actively posting. Kinda have to juggle priorities between work and play winking smiley

Build Log - DDDE 330x330x300mm Ultimaker
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