MK2S Molly (Multi Material Dolly) Build Log

Anything goes! Cheap or expensive, FDM or SLA, DIY or Commercial.
Tal_Esh
Posts: 3
Joined: Sun Oct 15, 2017 10:29 pm

Re: MK2S Molly (Multi Material Dolly) Build Log

Post by Tal_Esh » Sun Oct 15, 2017 10:33 pm

Really interesting & awesome work you have done there!
I had a question about the dual gears setup, doesn't adjusting the idler's tension effects the gears' mesh?
Will too high distance between the gears greate backlash or inconsistent movement of the idler one?

TheBat
Posts: 13
Joined: Thu Jun 15, 2017 12:18 am

Re: MK2S Molly (Multi Material Dolly) Build Log

Post by TheBat » Mon Oct 16, 2017 9:56 pm

Tal_Esh wrote:
Sun Oct 15, 2017 10:33 pm
Really interesting & awesome work you have done there!
I had a question about the dual gears setup, doesn't adjusting the idler's tension effects the gears' mesh?
Will too high distance between the gears greate backlash or inconsistent movement of the idler one?
Yes, If they move too close it can mesh hard and cause extra friction, and too wide and it may skip, but so long as the mesh is engaged, there shouldn't be enough tolerance that will cause major torque issues in the system. The only real difference between this solution and the prusa one is that my gears are plastic. If Prusa thinks it's worth shipping and putting on the mk3, my guess is that it is a viable solution.

Tal_Esh
Posts: 3
Joined: Sun Oct 15, 2017 10:29 pm

Re: MK2S Molly (Multi Material Dolly) Build Log

Post by Tal_Esh » Fri Oct 20, 2017 8:20 am

TheBat wrote:
Mon Oct 16, 2017 9:56 pm
Tal_Esh wrote:
Sun Oct 15, 2017 10:33 pm
Really interesting & awesome work you have done there!
I had a question about the dual gears setup, doesn't adjusting the idler's tension effects the gears' mesh?
Will too high distance between the gears greate backlash or inconsistent movement of the idler one?
Yes, If they move too close it can mesh hard and cause extra friction, and too wide and it may skip, but so long as the mesh is engaged, there shouldn't be enough tolerance that will cause major torque issues in the system. The only real difference between this solution and the prusa one is that my gears are plastic. If Prusa thinks it's worth shipping and putting on the mk3, my guess is that it is a viable solution.
Ok got it, so when designing the parts - what was the gap between the gears that allowd perfect mesh?
(what is the theoretical filament diameter when the gears' pitch diameter's circles are tangent to each other)

TheBat
Posts: 13
Joined: Thu Jun 15, 2017 12:18 am

Re: MK2S Molly (Multi Material Dolly) Build Log

Post by TheBat » Fri Oct 20, 2017 10:44 pm

Tal_Esh wrote:
Fri Oct 20, 2017 8:20 am
TheBat wrote:
Mon Oct 16, 2017 9:56 pm
Tal_Esh wrote:
Sun Oct 15, 2017 10:33 pm
Really interesting & awesome work you have done there!
I had a question about the dual gears setup, doesn't adjusting the idler's tension effects the gears' mesh?
Will too high distance between the gears greate backlash or inconsistent movement of the idler one?
Yes, If they move too close it can mesh hard and cause extra friction, and too wide and it may skip, but so long as the mesh is engaged, there shouldn't be enough tolerance that will cause major torque issues in the system. The only real difference between this solution and the prusa one is that my gears are plastic. If Prusa thinks it's worth shipping and putting on the mk3, my guess is that it is a viable solution.
Ok got it, so when designing the parts - what was the gap between the gears that allowd perfect mesh?
(what is the theoretical filament diameter when the gears' pitch diameter's circles are tangent to each other)
I don't have an exact number for the best possible mesh, but when dealing with small gears, there is a neat trick that I learned from RC cars. When gapping gears, put a small piece of paper between the gears then push them and tighten them to a fixed tension, then roll the paper out from between the gears.

In this case however, the mesh distance is not fixed and fluctuates between the sweet spot (hopeful right at 1.75mm) and +/- the tolerance of the filament. I think the worst case here is the filament is too large case, since it will push the gears apart and lose traction completely, I can possibly do some tests to see what the maximum size is for this setup. The other case where the filament is too small is less of a problem because of the addendum circle of the gear. This will allow the gear to mesh a bit tighter than if it were completely pointed. So there should be a bit more leeway when it comes to filament that is too small.

When I was actually designing my gears, I just looked up the official gears, and took some pixel based measurements to start and then did trial and error to find a tooth shape and size that worked best.

electrafide.design
Posts: 1
Joined: Mon Mar 05, 2018 3:05 pm

Re: MK2S Molly (Multi Material Dolly) Build Log

Post by electrafide.design » Mon Mar 05, 2018 5:32 pm

First off... dude great job on the DIY multi-material mod!

You're 100% right, $300 to get a seemingly Rube Goldberg-esque upgrade (I know, I know, J.P. has defended its merits and makes some valid points), that in some cases needs to waste up to 80% of the total filament used in a print... doesn't feel bad, just somehow doesn't feel great. The same kinda "ugggh" like if you paid for a new expensive car except when closing the door it sounds like tin cans rattling instead of a proper, solid *thud*... if that analogy makes any sense.



However, if you had some spare time, I had a few questions/thoughts & it'd help a TON to hear the opinion of one of the only ppl I've found that's successfully pulled off this particular upgrade this thoroughly.

So, my questions for you:
BTW, an important detail to mention beforehand... tl:dr til bold... I just got an MK2S kit (silly I should I have waited 2-3 more months to get the MK3)... But for financial reasons, Chase Bank starting to block Bitcoin, and other things; I kinda had to pull the trigger. Lo and behold the E3D heatblock came DOA anyways, so I haven't even been able to print anything yet. They're kindly sending a whole new hotend at least. But in this period of limbo, I've realized more and more I'll need multi-material capability not to feel buyers remorse. Bottom line: the upside is I'll have an extra E3D V6 Full hotend that I can repair to working-order and use for any upgrade.

So which sounds best to you according to my print needs?
1) Attempt your way. But have to invest in a hotter heating element, maybe the P100 thermal sensor, and most importantly a $99 Ollson Ruby nozzle. I need the ability to print with normal stuff, but very frequently with abrasives (especially carbon fiber) and higher temp stuff like PC.
2) Don't merge the feeds, thus not requiring the extra geared extruders. Secure both new and repaired E3D V6's to a carriage for a "Double Barrel" print head. Lose some build area in 1D (~30mm-ish X-Y)... but this time no need for the ultra "on steroids" hotend... just one with a $20 steel wear-resistant nozzle, leaving the other one brass for smooooooth flow.
3) "The Diamond"... nifty, but I can't make heads or tails about how people feel using it on a daily basis. Even less info about how well it plays with others (a.k.a. abrasives).
4) Any clever solutions you might have?



Haha, so I'm gonna apologize in advance for the length of this post. But if you covered it all, thank you for reading. And any answers/advice to go along with it would be massively helpful and appreciated. Also if you'd rather continue dialogue via PM, totally up to you.


Regards,
Dave

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