Why is filament line better than belts?

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In addition, we use spectra fishing line which produces higher resolution prints than using belts.

Can I ask another newbie question here, while I can see that belts may wear, and have a bit of play in the engagement of the teeth, why is fishing line going to produce higher resolution prints, from what I can see of it, the resolution will be down to the size of the belt, the slack or otherwise in the engagement of the belt with the pulley, and a host of other factors that are nothing to do with the drive, and everything to do with the slack in the multitude of bearings that are connected to the towers, the link arms and the related links. Even something as simple as some torsional twist in the towes will throw things off, if not corrected and locked so that it can't twist

Looking at some of the line based systems, they are using pulleys that are grooved, so the angle of the line between the drive pulley and the intermediate pulley on the tower is changing, which will (albeit only a very small amount) vary the length of the filament, thereby stretching it slightly as the tower moves away from the centre position of the filament.

Is this just marketing hype, or have I missed something fundamental here? I'm asking as I'm about to start building a belt based Delta Pi shortly, but if that's the wrong way to drive the towers, I could change it, but long experience with belts on all manner of things makes me think that there is not the issue with belts that is being implied here.



Thanks

Edited 1 time(s). Last edit at 09/01/2013 06:45PM by Irish_Steve.

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Irish Steve

I don't think that spectra gives better resolution than belts, as long as the proper belts are being used. I think the main reason for using spectra is that it's significantly cheaper than belts and pulleys. I still prefer belts simply because they are easier to work with.

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If you want to make a precise machine that doesn't need a lot of maintenance then belts are a must. In my book, there are two reasons to use fishing line. It is cheaper. It can do routings that belts can't. I would put precision of both belts and strings at about the same level. However, string creep and tension will change more between prints than a belt will.

For you I would say it was a decision between cheap or worry free.

Thought I'd chime in here as although there is no reference, it seems you're referring to the Deltaprintr if I'm not mistaken

There are a couple of reasons that we decided to go with strings.

1. Scaling printers is costly. Strings are cheap and therefore let people scale easily.
2. There is a SLIGHT improvement in using strings over belts. When a delta bot prints fast, even if everything is tightened properly, the teeth in the grooves of the pulley may still move ~0.2mm from side to side under fast speeds and especially if your platform is heavy.
3. Yes, strings do stretch. This is why we use a 65 pound tested spectra fishing line which only needs tightening about 3 times after you first assemble it, then it works fine.

We think that although it may not be "industry standard" to use strings in mechanical designs, it helps us drive down the cost tremendously and does help improve resolution when it comes to fast speeds.

We'll be at Makerfaire NY if you're interested in seeing it in person
We're going to be sending out an email soon with our booth number if you're signed up at www.deltaprintr.com.

-Shai

As an (electronic) engineer I find many components of RepRap printers heavily oversized and therefore also overpriced. If you develop a product you should always use the components that serve the given purpose - there is no benefit from overdoing that. Using linear rails for general purpose 3D printer is such a nonsense and even belt drives are not needed, exspecially with delta printers. The forces, the speed and the load that lasts on the arms is so minimal a simple string is all it takes. Save that money and invest it in some other components that still are not mature and improove them.
There is no reason to use belts or threaded rods, linear rails on those printers, it only makes them heavy and expensive. Only if you have very special applications that - by any reason - do require this.
We have seen belts in bikes and even motorbikes, but still today these remain exotic solution. With a string you are far mor eflexible when it come sto design. You can lay it around corners and place your motor anywhere, it is cheap, it is availabe worldwide no metric-imperial hazzle. You can print out all parts for your drive (exept for the string of course). Only the installation can become a bit of a fumbling procedure.
But in the intension of the RepRap idea: Make a printer that can print out itself - Make it cheap and widely available, strings are the way to go.
I find the usage of strings one of the great innovative introductions that took place at RepRap, that point into the right direction and i have not seen anything more convincing for that (lightweight) give purpose.

Edit: Maybe one could even use a filament from a spool(depending on the material) and simply use it as string, then all parts are printable or ready to use.

Edited 1 time(s). Last edit at 09/05/2013 02:54PM by maboo.

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shai
3. Yes, strings do stretch. This is why we use a 65 pound tested spectra fishing line which only needs tightening about 3 times after you first assemble it, then it works fine.

I'm planning to try Spectra and will pre-stretch it before installing it. Maybe I'll hang a 3kg weight on it? Or would it require more or less weight? I'm hoping this would allow the line to stabilize more quickly and require less adjustment when on the machine.

I wonder if brake cable (steel braided wire) would work in this situation? It should not stretch much at all under the loads a 3d printer can generate. Unfortunately the bend radius is large for those so the pulleys would have to be big.

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Modicum V1 sold on e-bay user jaguarking11

As a non professional I can only state from my own experience.

Strings are much better ..... on my guitar.

(b.t.w. I have never seen a guitar with belts :-)


whoehaa Thomas

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Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)

There are some steel wire in under 1mm. That may be a good choice to use in 3d printer.

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bunbun
There are some steel wire in under 1mm. That may be a good choice to use in 3d printer.

One thing that worries me about using steel braided cable is fatigue and work hardening. The more bends it has, the more it will work harden, it will eventually fray and break. What the limit for that fraying and breaking is I have no idea.

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Modicum V1 sold on e-bay user jaguarking11

Hi all,

I realize this is a fairly old topic, but I have a delta printer (that I love) with belts and am contemplating a spectra drive design. Couple of reasons...

My Dad lives across the country and I would love to share my printer with him. So I'm thinking about a baby printer. Belts are out for that.

But my current design uses a round (not toothed) idler pulley and the teeth create vibration at high speeds that is probably affecting the quality of my print. I have had to tighten the belts to prevent the teeth from jumping the drive pulleys so this only exacerbates the vibration.

I love the belts. Yes they cost a few dollars more. My printer only stands two feet high so they aren't that long. But the ease of assembly (and dis-assembly) can't be overstated.

Best of luck!

Ross

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You don't need a parachute to skydive. You only need a parachute to skydive twice.

You don't have to run the toothed side of the belt around the idler pulley. The Ormerod uses a half twist in the run of the belt that doesn't drive the carriage, so that the smooth side of the belt runs round the pulley. A further advantage is that where the two ends of the belt meet in the carriage, the teeth on the two ends are facing each other and can be locked together.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hi DC

I haven't heard of reversing the belt. Sounds interesting... I'll give it a try. As for mating the teeth, I've had great success attaching to the carriage by folding the teeth back against themselves and inserting a pin to prevent it from pulling out. Works great and I can still do the same with the belt twisted. Take a look at my posted pics.

Thanks again!

Ross

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You don't need a parachute to skydive. You only need a parachute to skydive twice.