Suggestions for Modified "Dolly" Printer 300x300x300 Dual Extruder 24v

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lee.deese
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Suggestions for Modified "Dolly" Printer 300x300x300 Dual Extruder 24v

Post by lee.deese » Sun Nov 26, 2017 8:39 pm

Hey All!

I'm really enjoying my Geeetech i3 and am impressed with many of my HatchBox Filament prints :D

While still very new to the hobby, I'm interested in Tom's Dolly Build and wondered if a 300x300x300 24v dual extruder materials list or build has already been done.
Tom references 24v should be accepted by "most of these parts" but I'll need more specifics.

I'm fine to go MKS Gen instead of ramps, but the boards I see only show 1 plug for an extruder even though description shows 2 extruder capable.
( https://www.ebay.com/itm/222615581571 ) either that or it seems like only 1 z axis motor plug, not sure...

I understand going 24V can be a problem, but I also know that DC to DC converters (up to 3amps) exist and wondered if that might be a solution.
How can we step down from 24v to the parts that max out at 12v? (I'm assuming the DC to DC converters wouldn't be a reliable solution)

Anyone that has already completed or knows where a 300x300x300(ish) dual extruder printer build already exists, would you please provide a link so I can check it out?
And just in the interest of sharing information, I stumbled across this .05 micron large format printer.
(just for reference) https://folgertech.com/collections/3d-p ... inter-kit
In the mean time, I'll keep reading! Thanks to you all!

-Lee

chumm
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Re: Suggestions for Modified "Dolly" Printer 300x300x300 Dual Extruder 24v

Post by chumm » Mon Nov 27, 2017 4:02 am

lee.deese wrote:
Sun Nov 26, 2017 8:39 pm
I'm fine to go MKS Gen instead of ramps, but the boards I see only show 1 plug for an extruder even though description shows 2 extruder capable.
( https://www.ebay.com/itm/222615581571 ) either that or it seems like only 1 z axis motor plug, not sure...
It's the latter, the plugs in that pic are X, Y, Z, E0, E1. You can wire dual Z motors in series and connect to a single driver: https://www.instructables.com/id/Wiring ... in-Series/
lee.deese wrote:
Sun Nov 26, 2017 8:39 pm
I understand going 24V can be a problem, but I also know that DC to DC converters (up to 3amps) exist and wondered if that might be a solution.
How can we step down from 24v to the parts that max out at 12v? (I'm assuming the DC to DC converters wouldn't be a reliable solution)
A switching or buck converter that utilizes an inductor should be good, better than a voltage divider made with resistors which wastes extra energy converting it to heat. Buck converters will have slight variation in the output voltage as they are basically constantly switching current, but it shouldn't have any noticeable effect.

Some more info on buck converters:
https://www.pretzellogix.net/2016/11/14 ... usb-ports/

You can get all 24v parts though, I use 24v without any conversion (on a single extruder/200x200 printer though.) Fans and heating elements are the only things that can be inconvenient to find in 24v, Digi Key is a great source for finding fans, though the number of products they sell can be daunting. All other electronics should be fine, the MKS-Gen has onboard 5v auxiliary outputs so you can run things like a Raspberry Pi straight from the board.

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lee.deese
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Re: Suggestions for Modified "Dolly" Printer 300x300x300 Dual Extruder 24v

Post by lee.deese » Fri Dec 01, 2017 10:07 pm

Thank you, chumm!
I've actually read a few of your post. You're very helpful and knowledgeable. Thank you again!

Thank you for the fan link on Digikey. So then, the board I choose should take 24v as well as the heated bed... I'll make sure...

I've begun to buy pieces here and there. I'll just take my time to get this together.

Since my 8mm rods are 36inches, I'm thinking, I'll simply halve them for 450mm axis, this may provide space for possible larger bed in the future.

And I think I'll go with .9 degree stepper motors.
I was convinced when this guy said he gets better resolution with .9. I choose to believe him. (see Yoda, scroll half way)
https://hackaday.com/2016/07/06/build-a ... workhorse/

I'm happy with the Geeetech so far.
I'm using bundled slic3r in repetier, but I've seen where I need to learn more about slicing and retraction to help some strings I'm having.

Anyway, enjoy these sample prints.

thanks again to you and everyone!

-Lee
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chumm
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Re: Suggestions for Modified "Dolly" Printer 300x300x300 Dual Extruder 24v

Post by chumm » Fri Dec 01, 2017 11:28 pm

Prints look nice! A note on 0.9 steppers: I also saw that post and bought 0.9s for my first printer. I'm not entirely convinced that there's a significant benefit to the maximum resolution possible, which makes that comparison picture very strange. Using DRV8825 drivers with 1/32 microstepping, my motors have 320 microsteps per mm. If I had 1.8 motors, they would have 160 microsteps per mm. So, the difference in resolution becomes 1/320th of a mm, which is definitely imperceptible to the eye. Further, you'll get more imperfections than that from belt backlash, even on the tightest setups. Having twice the steps per mm also means it takes twice as many instructions from the microcontroller to move your motors, which causes them to have slower maximum speeds (and in one case I had recently, crash the board when trying to move too fast during auto leveling!)

That said, I think the answer to using 0.9s is probably to reduce microstepping to be more in line with a 1.8 degree motor, so running DRV8825s at 1/16 or just using A4988s which max at 1/16. This should give slightly better accuracy since the physical steps built in to the motor will be more accurate than the estimated microsteps of the driver, while also allowing you to operate the motor at normal speeds/processor strain. Just remember that we're talking about microscopic differences here, you will definitely not see the benefits shown on Mr. Yoda, it's a totally bogus claim.

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lee.deese
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Re: Suggestions for Modified "Dolly" Printer 300x300x300 Dual Extruder 24v

Post by lee.deese » Tue Dec 19, 2017 4:32 pm

Thanks again, chumm!

Your advice and reasoning is VERY sound.

Just considering the environmental variables make 0.9 steppers seem unnecessary for MY work, anyway. When you consider variances in filament and other factors for blemishes on a print, you've helped me convince me the 0.9 aren't worth the extra money for me... for my application anyway.

(and when I consider that I'm satisfied with my "cheap" Geeetech prints it helps return me to what I'm really after is a second printer (of similar quality) but larger bed, bed leveling and dual extruder. I just figured if I were to build another 3D printer, I'd invest in "better" parts.

Your experience with the board crash is worth gold to me. Thank you!

I've made myself coss-eyed spending so much time looking at designs and choices for the x-y-z axis. I finally decided to eliminate the 8mm drill rods (already purchased locally, lol) and chose the 2020 extruded aluminum... Now, it's time to cut my 12meters of 2020 to lengths I need. And I had to laugh when I found the Tronxy X3 frame was essentially what I had envisioned. All that time and late nights considering frames via web (and openbuilds https://openbuilds.com/ etc) and of course it's already been done. https://hobbyking.com/media/file/t/r/tr ... e_v.03.pdf

Anyway, I've purchased a dual extruder from eBay (who knows if it's REALLY 24V capable as advertised) and a 24V 300x300 heated bed.

I certainly wouldn't mind buying metal (are they called carriers?) but looks like I'll need to print those in ABS as so many have warned.

Hopefully, I'm through the worst spot in the build, making frame decisions, and I'm certainly having fun thinking and doing during these colder days in North Carolina (USA).

It's a fun hobby (chasing that perfect print) to do while I wait for outdoor Radio Control fun to continue.
And AND, I've learned a LOT which is good for self esteem and life experience.

-Lee

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