1.75 mm vs 3.00 mm

I've only used 3.00 mm filament. However, there seem to be a lot of good reason to use 1.75 mm filament:

Then, would there be any reasons to use 3.00 mm filament (or not to 1.75 mm filament)?

I think I read it somewhere that 1.75 mm are a bit more expensive (because it's easier/faster for manufacturers to extrude 3.00 mm filaments), but all the suppliers I have seen either had the same price for both or had a very little difference in price between them.

Another possible disadvantage with 1.75 mm I can think of is that inconsistency in filament thickness/diameter may have bigger impact on it. For example, if the diameter varies by +/- 0.5 mm (in the same spool), it's difference of 28.6% vs 16.7% variation. Well, obviously my assumption is that this variation in diameter is nominal and constant regardless of the filament size, rather than being proportional to the size of the filament.

Also, to move the same volume of filament, the extruder will have to push more (longer) filament with 1.75 mm, and faster (to extruder the same amount at the same rate). This may cause the extruder motor to work harder and run hotter? Or, will that be compensated by the fact the motor now needs to use smaller force (therefore we may be able to reduce the driver current)?


I'm pretty sure this topic of filament size has been discussed before, probably many times. So, I apologize for asking it again - it may have been my poor search skill, but I couldn't find any thread about it... or, maybe I didn't search hard enough :p If it's more convenient for you, you can just give an URL for those previous discussions (as long as they still relevant and not too out of date).

Thanks!

I switched from 3 to 1.75 mm. At that time things like pressure /area seemed important, but ultimately i discovered that there is no real difference to me.

It really doesn't make a difference. The biggest issue IMO is if you are using a direct drive extruder or a geared extruder. 1.75mm is easier to directly drive with the limited torque of a direct drive extruder.

I think using 1.75mm and a direct drive extruder will probably give you more accurate control over the extruded volume, at least in theory.

The direct drive completely eliminates any backlash you may have had in the reduction gear. Also, since every millimeter of filament pushed through results in less volume you get finer control over the volume delivered.

The disadvantage is probably that you need a better, more accurately machined drive wheel for the filament, since everything needs to be scaled down accordingly.

Are home-made hobbed bolts used succesfully with 1.75mm filaments? I mean the ones cut by a Dremmel and such not the ones made on a CNC mill sitting in the living room.

I'm building my printer right now and chose to go with 1.75. Seemed to have some easier feed capabilities and some claimed accuracy (but I'm sure that could be argued).

But I'm now committed to the 1.75mm direction and have been researching the hobbed bolt question. I've found a few reports that indicated that they have made bolts intended for 3mm and they worked fine for 1.75mm. The reduction in pressure seemed to make up for the reduction in contact patch.

My plan is to make a relatively shallow hobbing in the bolt using the same techniques as for the 3mm and then put a shallow grove in the idler wheel if possible. But now that I think about it, I think the "idler" wheel is just a bearing so the "groove" may be difficult and impractical. But even with a shallow indent for the hobbing, the filament should stay centered in the middle of the grove.

But any experience or advice on prepping a bolt for 1.75mm would be greatly appreciated. Thanks.

Why not buy one pre-machined? They're like $10.

I made a hobbed bolt with a 4 mm tap, it is too fine to use with 3 mm filament. Maybe that would be a good pitch to use for a 1.75 mm extruder?

BTW, the groove in the idler bearing is a nice upgrade, it helps reduce stripping of the filament because you can exert more pressure on it before it begins to deform against the narrow contact patch of the 608 bearing.

So far I have not seen much that shows that 3 or 1.75 is better than the other. Maybe someone has some nice photos?

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Yvan

Singularity Machine

Thanks Yvan. I like the idea of the grove in the idler bearing too, but wasn't sure how to get it there. What technique did you use? If I had a lathe I could just chuck it and use a file, but my drill press chuck won't get close to holding the whole bearing. Maybe mounting it on a shaft and using a cutting wheel of some kind? Any good ideas?

I'll try a small tap (maybe 5/32 as it's close to 4mm). BTW, are there any good videos on hobbing a bolt? I've watched a couple on youtube but just haven't been impressed with the techniques (that don't utilize lathes). Thanks.

I've used both, but I prefer 1.75mm. The main reason is that it's more flexible and resists movement less. It's usually better for a bowden setup because of this. Also, I like that it moves through the hotend faster due to lower volume. This could reduce the melt zone, but that might be negated in a jhead because you have more insulation.

So far I've used variations of letting the bearing spin on an 8 mm shaft while I cut a grove with a Dremel tool and abrasive/cutoff disk.

Last time, I used a small nylon brush as a friction brake to control the spin of the bearing. It can rotate way to fast as it tried to follow the high rpm cutoff disk.

iquiz, I'm not a big fan of bowden setups because they add another layer of play or slack in the chain. I should try one though, just to see how it all works out.

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Yvan

Singularity Machine

cobrageek Wrote:
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> I've found a few reports that indicated that they
> have made bolts intended for 3mm and they worked
> fine for 1.75mm.

MK7 is made that way ... and it works very well.

regards,
mihai

I don't know the equations required myself, but I'm sure there are some people on the forums who have or have the ability to calculate which diameter of filament is actually more efficient at extruding. By that I mean which requires the least force to push through a standard sized(.35mm) nozzle at a certain rate while heated to a certain temperature. My thought is that 1.75mm filament would require less force, but you have to account for the fact that to extrude the same volume of plastic as 3mm filament in the same amount of time, it would have to be fed much faster, which would also result in more resistance while trying to squeeze through that nozzle. It may very well be that both sizes of filament take about the same amount of force to extrude. I can't know for sure unless I do some more research. haha

What I know for sure is that using 1.75mm filament does allow your extruder to more more precisely control the filament. I'm going with 1.75mm plastic for my first personal printer because other than physical differences, I think that it's getting harder to find wide varieties of 3mm filament in more stores. It's also going to be my first experience using 1.75, might as well jump into new territory and experiment.

Thanks Yvan. I'll try the cut-off wheel option and probably add some resistance to the bearing to keep it from "just spinning".

Mihai, I've thought about the MK7, but I wasn't sure how it would work in the current extruder. Isn't it larger than the bolt? How do you put this in without changing the layout in the extruder?

Bowden tubes definitely add backlash, so that is a negative... but it is possible to make them work just as well if you put effort into it and spend some time trying to understand it. As an example, the Ultimaker is capable of some fantastic prints and it uses a bowden setup. Bowden is just more natural for some printers.

Yvan Wrote:
-------------------------------------------------------
> So far I've used variations of letting the bearing
> spin on an 8 mm shaft while I cut a grove with a
> Dremel tool and abrasive/cutoff disk.
>
> Last time, I used a small nylon brush as a
> friction brake to control the spin of the bearing.
> It can rotate way to fast as it tried to follow
> the high rpm cutoff disk.
>
> iquiz, I'm not a big fan of bowden setups because
> they add another layer of play or slack in the
> chain. I should try one though, just to see how it
> all works out.

cobrageek Wrote:
-------------------------------------------------------
> Thanks Yvan. I'll try the cut-off wheel option
> and probably add some resistance to the bearing to
> keep it from "just spinning".
>
> Mihai, I've thought about the MK7, but I wasn't
> sure how it would work in the current extruder.
> Isn't it larger than the bolt? How do you put
> this in without changing the layout in the
> extruder?


Instead of adding friction you can offset the cutting disk such that its axis is tilted about 20 to 30 degrees from that of the bearing. This will also give the groove a rounded profile which will better match the filament.

Even if the bearing rotates freely the wheel will still cut into it because the two are not rotating in exactly the same direction.

I attached a drawing to clarify what I mean:

Thanks for the idea lister. I just did it this over the weekend and it turned out quite well. I used bigger cutoff wheel so much of it needed to be done with the wheel aligned with the bearing. I used some friction to get it to spin slower than the cutoff wheel, but I also tilted the wheel some to round things a bit more and make a nice sine wave curve. I think it turned out very well and when combined with a shallower concavity in the hobbed bolt seems to work well for the 1.75mm filament. I haven't tried it yet to actually extrude because I don't have the hot end wired yet, but it seems to have excellent grip.

Thanks for the tips.

You guys are correct, the offset angle adds a nice curve which matches the profile of the filament. I still use some source of friction though, because the bearing still spins way faster than it should. The start 'rattling' when they spin too fast!

Edited 1 time(s). Last edit at 09/30/2013 04:01PM by Yvan.

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Yvan

Singularity Machine

Instead of a cutoff wheel you can use a small-diameter grinder attachment. This way you don't apply as much force in the "spin" direction of the bearing.I used one that was only slightly bigger than the groove I wanted to make. Just tilt it a bit and you still get the bearing to turn but it turns rather slowly.

Interesting, so something like a small grindstone? I have some of those for the Dremel, but I don't know if they are hard enough to cut a bearing race. They are rather cheap, maybe I need to get harder ones.

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Yvan

Singularity Machine

so ive been thinking about this a lot recently and come to the conclusion that 3mm is better for high volume extrusion because you have a lot more grip over the filament, and obviously it is bigger so you get more.

i've never had much luck with the wades extruder and the 8mm hobbed bolt, it is really too small for both sizes ,just worse for 1.75mm, i use all 1.75mm with a machined hobb directly driven from a nema17 stepper with a fixed distance idler bearing and it simply doesn't stop, the key to good reliability with it is to have a idler bearing of a similar size to the hobbed area driving it, the only way to stop my extruders now is to turn off the hotend or press the nozzle into the bed ,and even then it'll skips steps for hours before comming close to stripping filament

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im working on a new extruder, its going to use a huge hobbed set of washers, the filament will be pushed onto the hobbed surface by a set of small bearings which will allow a large contact area, about 90 degrees around the hobbed surface, instead of just one small point. now the reason this will be good is because, it will have more surface area to grab onto the plastic, but it wont deform the plastic because it doesnt need to be pushed into the teeth as hard. in turn this will allow the filament to remain unsmushed through the bowden tube and hot end which will eliminate jams and other issues.

why? because im tired of having to fiddle with the extruder during prints that can take upwards of 24 hours, and because then they can take less time because i can push more plastic through.

Im still using 3mm but one thing that will surely be better is the ease 1.75 will come off the reel.
When im getting to the end of a 3mm reel the printer is practically climbing up the filament.
Perhaps my workshop is a bit too cold.

the 3mm probably wont like the big wheel though it might need an even larger one.

btw the wheel would only be for a bowden setup.

also i have zero interest in printing pla, I live in arizona, pla melts in my car haha, its really useless. abs polycarb and nylon are all fairly flexible, the polycarb isnt as flexible but it doesnt mind being bent at all.

Edited 1 time(s). Last edit at 11/12/2013 04:40PM by aduy.

I found 3.0mm is better with soft filaments

I was thinking, I use 3.00mm on a bowden setup, i think maybe the thicker stuff is a bit easier with bowden, i could be wrong tho

With some filaments I had the problem that 3mm breaks. Does anybody has the same experiences?

Thanks

All of my PLA filament is hard, i need to bend so many times to break it,
I once had some glow in the dark PLA, it was totally different, It would simply break easy, for example,
It would break by bending it once to far in my hand,
It would break from the extruder pressure bolt, also from the bend in the bowden tube.
Dropped the spool and ended up with an unusable spool as it had breaks through out the whole thing

It was very old and never kept in air tight container, I had it when i first got my printer, went out and stocked up on plastic but could not use it, layed around for 6 maybe 8 months.
When the stuff was brand new, it was fine, but never used much, it was ultra low temp,
All my PLA i get now gets is pretty good, i never have it long enough to go bad, i can use a spool easily within a week.
Never had this kind of issue with abs or nylon

Edited 1 time(s). Last edit at 11/14/2013 07:00PM by nechaus.

if the filament was really too brittle you could heat it at the point where it unspools.

The extruder i developed can do both filament types, 1.75 and 3mm, no problem at all, i call my extruder "Bulldog XL"