[Solved] Making the MK3 3mm instead of 1.75mm  

RE: Making the MK3 3mm instead of 1.75mm

I will need to change the entire hotend setup, as the 3mm is larger all over.

RE: Making the MK3 3mm instead of 1.75mm

Buy an E3D-V6 in 3mm, a set of Bondtechs in 3mm, and take a drill to the filament path thru the extruder. Or, grab the scads and modify the extruder body parts to accept 3mm. Then all you'll nee to do is play with extrusion ratio to compensate for the increased flow 3mm gives.

I've not done this swap, but looks like an easy parts swap (with some cable mods to get lengths right). Trim the MK3S IR flag, and you're set.

ps: one might ask why...

RE: Making the MK3 3mm instead of 1.75mm

Hi Tim,

Thanks a lot 🙂  That's what I have worked out needs doing, but like you say - always good to have more than one opinion. Why am I doing this - because I have just completed a 68 hour continuous print, standing 335mm high, using the MK3S single mode. As this size range is going to be a commercial venture, I have decided that 3mm is more of an advantage to me, at least on one printer (the other remains MK3S MMU2S). According to some confusing maths, a 3mm printer produces the same volume of printed material as a 1.75mm in roughly 1/3 the time and with far less wear and stress to the machinery involved (at least, that's how I understood it).

I think I will have to modify the internal size of the extruder housing, and the 3mm heatsink has a larger external measurement than the 1.75mm, but that's no biggy.

RE: Making the MK3 3mm instead of 1.75mm

You should probably also shift the filament path to the right about 1 mm relative to the drive shaft Bondtech. R4 filament path alignment is already  poor with 1.75 mm filaments but keeping the same centering while increasing to 3 mm is will really deflect filament rightward when it hits the Bondtechs.

RE: Making the MK3 3mm instead of 1.75mm

Duly noted, thanks for your input 🙂

RE: Making the MK3 3mm instead of 1.75mm

As for volumetric flow, that's a hot end limitation - as far as I know - so the actual max flow is not related to filament diameter: rather, it is X cubic mm per second. And for the V6, it's somewhere around 12 to 15 mm3 per second continuous.  It's related to how much heat the hot end can get into the nozzle to melt plastic. And the larger volume extruders, like the Volcano, do this by increasing nozzle contact area (longer nozzle and threads).

RE: Making the MK3 3mm instead of 1.75mm

Why didn't you consider a native 3mm like LulzBot?  Still highly rated.  Could be a fun challenge though. 

RE: Making the MK3 3mm instead of 1.75mm

Wouldn't it just be easier to go for a E3D Volcano and 0.6 nozzle instead? 

RE: Making the MK3 3mm instead of 1.75mm

Because I don't have a spare $5000.

RE: Making the MK3 3mm instead of 1.75mm

I don'n know - that's why I started this thread, to find out what needs to be changed to make the Prusa a 3mm. I've heard of the Volcano, but not researched it. Thanks for the suggestion, I shall look into it 🙂

RE: Making the MK3 3mm instead of 1.75mm

really switching filament diameter doesn't do much for you , the key is how much/how fast you can melt filament in the hot end. it's all about thermal transfer in the nozzle/hotend

RE: Making the MK3 3mm instead of 1.75mm

As a young boy I had a brilliant idea to make shoveling faster. When I showed my father my diagram of a shovel with a forked handle and two heads he asked, "Why not make a bigger shovel?" 

Crushed in one sentence.

RE: Making the MK3 3mm instead of 1.75mm

I thought the limit on throughput was due to the amount of material that can be melted with the heater in the hot end.  Increasing the heater size to melt more filament would likely require a larger power supply.

Steve

RE: Making the MK3 3mm instead of 1.75mm

Good point, steven-p8 - should I remain 1.75mm and merely increase the nozzle diameter? Atm I'm printing with a 0.6mm Ruby, 0.3mm layer and the print quality is vastly improved on the 0.4mm. But it that's the action to take, will I need a Volcano or similar, instead of E3D V6?

guy-k2: Sorry, I don't get the meaning - I'm trying to use a bigger shovel, are you supporting or deriding my endeavor?

RE: Making the MK3 3mm instead of 1.75mm

actually the volcan0 hot end is only 30W , but the heater cartridge  is oriented vertically next a brass nozzle that's twice as long as the stock v6 nozzle

RE: Making the MK3 3mm instead of 1.75mm

My interest in this would simply be to use the boatload of 3mm filament I have... I got a Lulzbot Mini 2 first, and have collected quite a bit of awesome filament -- all 3mm.

Not that big a deal, I'll use it up eventually with the Lulzbot. I like the MK3 better though, and wish I could use some of the more exotic stuff -- wood, metal fills for example -- on it. Until the 3mm is gone, I'm not going to duplicate the more esoteric materials in 1.75 until what I have is used up.

RE: Making the MK3 3mm instead of 1.75mm

A big part of the reason for the shift to 1.75mm from 3mm was the increased proportion of surface area directly exposed to the heat. With a thicker filament, you're having to wait longer for the heat to transfer to the inner filament to melt. With the same size heater cartridge, I wouldn't expect the same size heater block to melt filament any faster. What I think you're trying to do is increase the maximum volumetric rate of the hotend, so look into the E3D Volcano and SuperVolcano hotends.

3D Solex produced their "Matchless" nozzles which split the filament into 2 channels for melting to increase speeds (sadly they're apparently out of business as they haven't shipped my nozzles in 60 days -- I blame Voj). They've got an interesting write-up, just don't go trying to order one.

RE: Making the MK3 3mm instead of 1.75mm

The biggest disadvantage I see to have 1.75 and 3mm printer is that you have to buy the filament twice. I would always keep my printer line up the same size.

RE: Making the MK3 3mm instead of 1.75mm

Buy a Volcano Upgrade kit, under $50 on Amazon, then use your existing heater and thermistor to save time and energy. 

https://e3d-online.com/volcano-upgrade-kit

ps: I think the mod requires some changes to firmware Z-Axis limits.