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I'm not really sure if I'm asking the right question here, but I just made a noob mistake of buying 3 mm filaments instead of 1.75 mm. I have a Makerbot Replicator 2 which I've been using and so far it is pulling in 1.75 mm quite well.

Is there any way I can still make use the 3 mm filaments, or do I need to use the filaments on different models? If it is the latter, which particular model is able to pull in 3 mm filament well?

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  • $\begingroup$ Alvin, you will need to research. I know of no comparison site which lists printers based on filament diameter. $\endgroup$
    – Davo
    Feb 3, 2017 at 14:36
  • $\begingroup$ Thanks, Davo. So far, what I have learnt is that I need to mod the extruder and nozzle to be able to use the 3mm filaments. $\endgroup$ Feb 3, 2017 at 14:53
  • $\begingroup$ Research also if modifying the extruder will void your warranty. $\endgroup$
    – Davo
    Feb 3, 2017 at 15:58
  • $\begingroup$ The extruder shouldn't need to be changed, I would have thought that just the hotend (and maybe the nozzle) would need to be changed. $\endgroup$
    – Greenonline
    Feb 4, 2017 at 2:02
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    $\begingroup$ Return the filament (or sell it) and buy the proper diameter. Save yourself a lot of trouble. $\endgroup$
    – Gunslinger
    Feb 4, 2017 at 12:26

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This is not a definitive answer (and has turned into a ramble), as I have not yet had to change my filament size.

However, initially, I would have thought that only the hotend and the hotend's nozzle would need to be changed, from one that can handle the 1.75 mm filament to 3 mm. If the extruder is spring loaded, then it should adjust itself to the thicker filament, without a problem. If not, then you may have to do a slight manual adjustment.

However, after doing some further reading, there may be other factors that need to be considered, such as:

  • Extruder gearing;
  • Melt time (which would imply a different feed rate)

It could be worth having a close look at the aperture of your hotend. If, in the unlikely situation, it looks as if the hotend would accept 3 mm (or if you could remove the lining so that it can), you may not need to actually change any hardware, but instead just try tweeking the feedrate in the software, because as your nozzle is less than the width of the filament anyway, then it will be fine for both 1.75 mm and 3 mm. A 3 mm filament would require more heating, and therefore a slower feedrate than a 1.75 mm feedrate. Once the filament has melted, so long as the pressure from the extruder is sufficient, then the molten filament should come out of the nozzle. However, this may be a less than satisafctory method and result in some dubious prints.

There is an interesting thread on the RepRap wiki, 1.75mm Filament vs 3mm Filament, that discusses most of the points above.

It should be noted that the advantages of 3 mm filament has over 1.75 mm are that it is:

  • cheaper
  • stiffer (less flexible) and thus "easier" to push through the hotend.

As an aside, one interesting point raised in the thread, is that maybe a smaller extruder can be used, for the narrower 1.75 mm filament, thus resulting in a lighter print head. I am not sure how true that is.

This article, Converting a 3D printer from 3mm to 1.75mm, does the reverse of what you want, and comes with a video. It states that, as you have already found, that the hotend needs to be changed:

The printer [Thomas] is changing out to accept 1.75mm is the Lulzbot Mini, one of the most popular printers that would ever need this modification. The only required materials is a new hot end suitable for 1.75mm filament, a 4mm drill, and a few wrenches and allen keys. It would be a smart idea to get a hot end that uses the same thermistor as the old one, but that’s not a deal-breaker as the problem can be fixed in the firmware.

Alternatively, you could leave your printer as it is and use a 3mm to 1.75mm filament converter, which may be a bit of overkill for just one reel of filament1.

The bottomline

To be honest, is it worth the hassle, time and expense of having to modify and re-calibrate your printer (or worst case, change the model of the printer), just for the price of a reel of filament (assuming that you did not bulk purchase a bunch of reels)? It may be better to stick to one filament size (i.e. your original size) for all of your projects, and so resell the reel of 3 mm and stick with the 1.75 mm printer and buy the correct filament2.


1 See also Conversion of 3mm ABS filament to 1.75mm

2 See also Tom's answer to Conversion of 3mm ABS filament to 1.75mm

See also Can 1.75mm filament be used in a printer that takes 3mm filament?

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  • $\begingroup$ Thank you for taking your time to actually write it like a literature review, even. I'll still need to experiment on it. I've actually upvote your answer nonetheless, but my reputation is too low to show an effect. I am looking into changing the hot end first. Wish me luck. $\endgroup$ Feb 4, 2017 at 3:01
  • $\begingroup$ @AlvinHerawan - Not a problem, it was interesting for me too. Yes, you need 15 rep points to upvote. I've just given you 5. Remember to revisit this post when you have enough rep... Good luck! :-) $\endgroup$
    – Greenonline
    Feb 4, 2017 at 3:31
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    $\begingroup$ Sure thing, @Greenonline . After visiting several websites, forums and hearing all the answers given, I've decided to accept your answer. $\endgroup$ Feb 6, 2017 at 20:47
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    $\begingroup$ The extruder hobbel bolt (or whatever is used) is usually shaped round to better grip the filament. The radius of the teeth won't grip 3 mm filament at all, therefore it will likely skip or skid very easily, especially given the increased grip required for 3 mm filament. 1.75 <> 3 mm is a complete overhaul of anything related to the extrusion path. I did it. $\endgroup$
    – FarO
    Feb 23 at 15:15
  • $\begingroup$ @FarO - You should post that as an answer... it's useful info and should have more prominence than just a comment... I'll upvote it. $\endgroup$
    – Greenonline
    Feb 23 at 16:36
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Well... Usually when one buys a 30 dollar roll of plastic they don't replace a 1k machine..

That said you can change out the extruder. The extruder is what matters. So if you have a Prusa i3, you can go and buy say a e3d hot end that is made for 3mm.

Usually we see 3mm on Bowden printers like the Ultimaker. Everyone else has moved to 1.8.

I would just toss this on craigslist and get the correct plastic.

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  • $\begingroup$ Yeah, agree with you ... I was just curious with this 3mm size. Of course I'd rather toss the whole spool ... perhaps find a use for it somehow, someday. $\endgroup$ Feb 6, 2017 at 20:43
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Late to the party here but I am doing this exact thing. I stupidly bought like a dozen rolls of 3mm filament for about $6 a Kg. I think trying the switch should be fun...but I have 7 printers so its no big deal to tinker on one of them.

What you need to do is modify the extruder. I have done this successfully using the crappy plastic extruders which come with most budget printers. You have to drill out the filament path to fit the 3 mm filament. It does get a little tricky to get the filament to run through nicely.

You actually do not need to modify your hot end other than your Bowden tube and your nozzle. Regular Bowden tube is 2 mm ID and 4 mm OD, so you just order 3 mm ID and 4 mm OD tube. Please note that this plan will not work for an all metal 1.75 mm hotend.

For the nozzle you can often find 3 mm compatible nozzles. Unfortunately they don't seem to be made for the MK10 hotend. So I simply ordered big ole 1 mm nozzles made for 1.75 mm and I am going to drill out the back for the 2.85 mm (3 mm) filament.

I am excited to see how this all works. You can get some really good deals on 3 mm filament and I suspect that it will actually work much better for things like TPU since it is significantly more rigid due to the increased diameter!

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Any modern and decent drive gear (single or dual) is shaped round (concave) to better grip the filament.

enter image description here

Some are flat, but only the cheapest and least performing ones.

enter image description here

(from Reprap wiki)

The concave part designed for 1.75 mm filament will be too small to accept 3 mm filament, it will grip it so weakly that it will skip or skid very easily, especially given the increased grip required for 3 mm filament.

1.75 <-> 3 mm is a complete overhaul of anything related to the extrusion path. I did it so I know...

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