Alternatives to the toothed belt

I'm building a lasercut BitsFromBytes reprap. The toothed belts were expensive and hard to find, so I decided to try ball-chain instead. However, it looks like I'd need drive gears specially designed for ball chain, the ball chain slips too easily on the default ones designed for toothed belts.

I tried wrapping the ball chain one or more times around the drive wheel, this helped to some extent, but the y axis is still slipping.

I tried with 1.3 mm nylon thread, but it seems to have too much play.

I've eyed steel wires in the hardware store earlier, but they didn't have any thin enough, and the ones they had didn't seem that flexible.

However, what about threaded electric cable? If it consists of many threads, it shouldn't suffer that much from metal fatigue, and withstand repeated bending. It's metal, so it shouldn't stretch very much. It's covered with plastic or rubber, so it has a nice grip on the drive wheels, especially if wrapped one extra time around it. And you could even use soldering (and optionally cable wrap) to create a near seamless joint for the z-axis cable loop.

Any thoughts? Would electric cable make sense? Any showstoppers?


Most thin cable I have lying around is single threaded, so I'll go shopping for some multi-threaded tomorrow and try it out. (I'm trying to finish the build fast so that I can demonstrate the machine at a local demo party next weekend - [www.altparty.org] ).

I tried with limited success to use fishing line made for catching Marlin this is very strong but still streches a little (too much) electrical wire will strech loads as it is made of copper not good in tension or with repeated bending, cables for robots which need repeated flexing are very expensive. I would recomend biting the bullet with tooth belts or making something to work with ball chain. Ball chain also streches but it doesn't loose drive when it does like cable will

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Ian
[www.bitsfrombytes.com]

... in past i built some plotters with steel-strings - here i found a german supplier for high-elastic steel-wires with high counts of single steel-fibres.

I have some samples and rolls with different diameters and elasticity.

The thicker wires (1.5 to 2mm diameter) i used for stepper-driven laser-plotters with a working area of nearly 800x600mm without noticeable elasticity ...

Viktor

I found some 1mm threaded steel cable, and tried that. However, it did slip even when wrapped a few times around the drive gear. It was also unpractical to handle, the bends were a bit too sharp for it.

I ended up using 2.6 mm ball chain, it's wrapped 1.5 turns around the x drive gear and 2.5 turns around the y drive gear, that seems to grip well at least when I tested it manually. It's also much nicer to work with than steel cable.

you could try to mold a pulley for these the same way the normal pulleys are made (check the wiki build page).

-Leav

Yup, did think about that a bit, but for now the ballchain seems to work when wrapped a few times around the pulleys meant for the toothed belt.

I must say i'm surprised.. I would have thought that under high speed direction switching it would easily slip.

are you applying tension to the chain in any way?

-Leav

Well, I have just tested it manually so far. Not sure how well it will hold up to actual usage.

I use the belt tensioner for the z axis, and tensed the x and y axis by tightening the chain once installed, by moving the idlers outwards.

I used to have a routing machine called a Woodrat. It used a steel "bowden cable" to move the workpiece past a woodworking router. The cable was wrapped half a dozen times around a plain steel shaft, about 6mm in diameter and could move a heavy piece of wood (I think the heaviest I ever worked would have been 30kg) against the router with absolutely no slippage.

The steel cable was very similar to the one that B&Q sell by the meter. The smallest that they sell is 1/16inch which is probably too thick for our purpose.

Again, a long while ago, I used to fly "control line" model planes. They use two wire cable connected to the model aircraft, kept under tension by the centrifugal force of the model (some models only used to fly a quarter of a full circle, the "pilot" would continually loop them back on themselves)

The cables are readily available in model aircraft shops try Best Service Stores

One problem that may be difficult to overcome is how you join the two ends together. You could solder them, or crimp them but that would add a section, albeit very small, that wouldnt run round the pulleys smoothly. It would also snag on any other loops that were on that pulley. You can increase traction without having to use several loops on each pulley by using a smooth pulley that has a wide elastic band around it, so that the cable effectively bites on the rubber band.

... i used different highly elastic steel-wires with diametres from 0.3mm to 0.8mm in my XY-Pen- and Laser-plotters.

For best traction i used aluminium-discs with 16 resp. 32mm diameter and 3 or 4 windings of the wire around.

The ends of the wires were fixed to the moving head or sidepart and a spinning nut-tube for adjusting the tension.

Atached is a photo of two old gearheads i used for the laserplotter nearly 15 years ago ...

Viktor

That looks amazing quality there Viktor, very impressive!

What does 16 resp. mean?

I can see from your earlier message that you used the cable to move the moving head directly - in our application we turn a threaded rod so the issue of how we join the ends becomes important. I suppose we could spline the two ends of the cable together, but I simply havent got the skill to do that!

I like the idea of using two large washers with a rubber washer in between - Ive popped down to the local DIY store this morning and will give this a go.

Phil

That's how my plotter does it:
(nick was so kind to take a highres picture)
photos.nickfines.co.uk/misc/HP9872C_Top.JPG

And even old hp Scanners do it that way.

Also, there are powerlifters for car windows that are working this way,
so I guess you can say as long as you have the right cable and Motor you can move whatever you like

'sid

PS Finding the perfect pulleys is not that easy though, I'd love to have a set of the ones in the picture (no, I wont rip my plotter apart)

[EDIT]
some are 16 and some are 32mm (respectively, but I guess you don't use that term in this manner like we do )

Oh you don't need to join the cable ends, the ends are fixed to the frame.

Edited 2 time(s). Last edit at 08/12/2009 08:07AM by sid.

Hi Phil,

look at the images in this post: - [forums.reprap.org]

This are sketches of a laserplotter where i moved the X-arm with a wire-loop and the laser-head (Y-axis) with a 2:1-pulley, so i had to double the diameter of the disk for the Y-wire. This setup allows to fix both motors to the base and the moving parts are much lighter than the standard setup with the Y-motor sitting on the moving X-arm ...

Viktor

Thanks for that link Viktor, its odd to think that I was building almost exactly that for my A-level design project in 1980! I built a mock up with a very similar principle but in the end switched to screwed rods for the final plotter.

Sid, we would need to join the end if we used the cable to spin the threaded rod.

Phil

The method I like the best is the use of the balled chain there is a 2mm pitch version of this chain.

Im looking for a simple & easily repeatable method of how to make the drive wheels.

My curent thoughts are of using steper motor to position a plastic rod under a drill then drill step drill etc..

I also liked the cycle chain method

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Bodge It [reprap.org]
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BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

phil,
yes but who wants to spin a threaded rod with a cable

I thought it's either belt OR rod OR cable, not a combination of two or more per axis that is

'sid

The thread is about alternatives to the toothed belt, as it is quite an expensive item, not easy to get hold etc.

We ARE looking at spinning a threaded rod with a cable!

Phil

I like the milk bottle top idea, the ridges on the side have a 2mm pitch and it looks perfect for what we need.

The balled chain is great because the method of connecting the ends together will not stick or jam. I suppose thats true of any chain.

For the time being, Ive gone with two large washers with a rubber tap washer sandwiched in between. Im going to see how much grip a wire has on this "pulley"

Phil

BodgeIt Wrote:
-------------------------------------------------------
> The method I like the best is the use of the
> balled chain there is a 2mm pitch version of this
> chain.

> I also liked the cycle chain method

May I suggest that people try and designing a sprocket and chain system that can be printed.

Maybe using the same approach as Lego and have clip together chain sections

or

If you have Lego chain available, use that instead

Well it'll be much much harder to spin the threaded rods of a darwins z-Axis with
a cable than it is with the belt, and that alone is a not too easy task

If you have enough tension that the cable will not slip (even with 4 or more windings at each pulley) you will have enough tension to bend the threaded rods and this rising the friction in the cornerblocks making it impossible to turn them.

Even if you'll find the exact tension to make it move, you'll end up in a block, since the more windings you have on the pulley the less space you have left for the next rotation since the cable will move up and down.
Worst case it will jump over the washer and slips that very moment, best case it'll eat up the pulley slowly and slip somewhat later.
Both not fortunate

It may work on more accurate systems, with threaded rods that are fixed in ball bearings at both ends, since you can add just a little more tension to the cable without locking the threaded rod in a cornerblock.
On the other hand, that's exactly what's needed to make it easier to just use the belt

Oh yes, it's not cheap maybe; you're right.
But if you take a look at the dumpster section at ebay every once in a while you'll find extremely old scanjets for a dollar or less.
Two of those and you'll end up with four perfect pulleys, and enough belt
As a bonus you'll get four half inch steel rods 21" long, four fitting linear bearings and two stepper motors for the next project

And if you don't like that idea since it#s producing trash in your can...
just take a close look at the shops, I found, that the next bigger belt costs less than the half of what we use now.
There are different forms too.
So just buy the cheapest (think of the pulleys!!) you'll find there.

And if all that fails and doesn't satisfy your needs.

Just go ahead and do what nophead does; buy four cheap steppers one for each rod (2$ per stepper is cheaper than any other idea so far; and you'll have no more hassle with the z-Axis at all )

'sid

PS see hydraraptors blog: [hydraraptor.blogspot.com]

Hey Sid...

In the UK it costs a bomb to get stuff from the USA in postage then we get unofficially taxed by the post-office who charge about $16 just to collect the tax which is 15% is usually a tiny fraction of that charge.

The UK is not as big as the US so the amount of available resources are considerably smaller.

following your 2$ Ebay example shipping costs for 4 of those $2 motors is $25 + $16 (post office charge) + 15% Tax

So the UK cost for those four $2 motors is now about $50.

Then what if they don't work?

I guess its not too different from Australia when it comes to buying stuff from overseas.

So in the UK we have to be more inventive to keep the costs down.

So my $30 of RRRF belt cost me at least $60 just with postage it was still cheaper than the belt sold here though. That's why people in the UK are trying bike chains and sink (faucet) plug chains (ball chains)

Can you now see the reason for us in the UK trying to think of better ways to to move our axis than the very expensive belt.

I am using 4 Stepper motors for my Z axis drive the motors cost me $24 each e.g. £12 brand new. Nophead bought the $15 stepper from Makerbot then paid $16 post office charge and 15% tax that's over $30 total cost see thread.

Generally the majority of second hand steppers seen on ebay are from the USA.

I paid $30 for 4 of the new bare extruder boards in May its now August they still haven't arrived... from the RRRF in USA. See thread

Edited 1 time(s). Last edit at 08/15/2009 08:06PM by BodgeIt.

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Bodge It [reprap.org]
=======================================

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BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

Re the $15 NEMA17 motor, I did buy four plus some ABS filament, so even with the VAT and post office charge it was cheaper than the UK. They have changed to a different motor now though.

Yes the $2 motor is only cost effective for people in the US because the shipping is exorbitant. I bought 7 and the shipping was $42!

Same with the $7 tiny motors for Jameco.

Seems like you need to live in the US or the Far East to be able to buy cheap engineering parts.

Since most of the people building RepRaps are in the US and only a handful in the UK I figure it is worth evaluating these parts and blogging them.

I also have some samples of reclaimed motors sent to me from a company in the UK that scraps IT equipment. I haven't had time to evaluate those yet though. That could be a good way of getting cheap parts.

The four motors I use on my Darwin are actually scrapped from a German fruit machine (that's a slot machine if you are from the US).

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[www.hydraraptor.blogspot.com]

shipping is indeed something to consider;
but there's no need to order from overseas
(well, since you're on an island... ah you know what I mean )

the T2.5 belt for example costs twice as much here in germany (18.50 Euro/meter)
but the T5 is cheaper (8,55 Euro/meter) and there are no shipping costs at all.
go ahead take a look at maedler.de (since they have an english frontend, I guess they are willing to send across europe at least / probably for a shipping fee but surely no additional taxes)

You'll find some sites like that in GB too I'm sure
take a close look at farnell or digikey, sometimes you'll find good deals there too.

You can try it with a cable, but it wont work reliably, so you'll end up with another idea until you get the belt to work.
(Or like me don't get the belt to work )

'sid

Im not keen to try using cable.. my self

however for many many years nylon & cable was used for driving pointers dials and many other display contraptions.

Just look in any old Radio old TV, curtains in a cinema.. theatre etc. any old military electronics..

I look every where of bits to use for REPRAP when searching the internet thou its not often you find a European product sites the over whelming majority are US.

When you search you must have the same I'm guessing you filter to .de we filter to UK so its not often we see a .de site here is only by recommendation or from a UK based page.

My Solar power system Inverters are from Holland and 3 of 6 solar Panels from Germany it is much better to buy from Europe if you can find what you want. I bought some bits from Conrad the andrino from Italy.

Edited 1 time(s). Last edit at 08/16/2009 04:56AM by BodgeIt.

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Bodge It [reprap.org]
=======================================

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BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

The main aim of my many many builds of 3D type cnc structures has been to make it affordable.

The strange thing thats has come about this search is that its is much cheaper to make RepRap Darwin than any other structure.

By cheap to build I mean at home without RP parts without special tools so any one can have or every one can build a Darwin with Lego like simplicity an extremely low cost I am looking now at a full cost of all parts below £200.

Using Method 3 the mechanics of Darwin fall to around £60 for the complete set-up.

You then need to add 7 stepper motors and the control electronics.. + PSU.

It has to be easy and simple to make so any one seeing the design for the first time says "hey i can make that it so easy" Once I finish my design using these simple nylon building blocks I hope that is the reaction a new commer will have.

NOte if you are Dyslexic do not use a spell checker without due care and attention it will change words like Darwin to drain.. and you need to re edit to correct it ..

PS As I left school at 15 to do an apprenticeship my grammer is extremly bad as well... When I have completed this project I will be posting the full instructions on the Wiki hope fully some one will quitely edit any ambigus or badly constructed sentances to make it simple and easy to read.

Edited 4 time(s). Last edit at 08/16/2009 05:35AM by BodgeIt.

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Bodge It [reprap.org]
=======================================

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BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

I look forward to your write up. I have a completed McWire (minus the extruder) but it seems to have one major limitation - the movement speed is severely limited by using drive screws. I may either try to convert the XY stages to belt driven or go for a different design altogether. Haven't decided yet.

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Help improve the RepRap wiki! Just click "Edit" in the top-right corner of the page and start typing. Anyone can edit the wiki!

I'm in much the same boat as NewPerfection. I've built a small cnc to act as my repstrap. (also want to do pcb milling)

Driving the stages with threaded rod is just way too slow. I would have to buy some really expensive multi-start drive rod from McMaster/Carr or use expensive belts. I'm hoping someone will come up with a way to use the ball chain. It's cheap!

Looking forward to seeing your write up of your current efforts. I'm following your blogs now. Sure like the lego/like stuff you're working on!
Arvin

^^ what I would like to do is get my machine running as-is, and print a couple pulleys to work with ball chain. I've been trying to find some pre-made but haven't had much luck.

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Help improve the RepRap wiki! Just click "Edit" in the top-right corner of the page and start typing. Anyone can edit the wiki!

After an interesting weekend (lets just say it involved being stuck on some cliffs until 3am and a helicopter rescue!), Ive made a lot of progress with CopperRap 2

Ive ditched the idea of using screwed rods for the X+Y axis, and Im going to use a toothed belt. The belts arent easy to get hold of and are quite expensive so Ive been looking for alternatives.

I have managed to get some plastic coated steel cable but as expected it slips quite easily. I also bought some ball chain and that seems much more promising as long as I can get a suitable pulley. The pulley must be quite small to maintain accuracy. I made some rough calculations and worked out that I can make a 14.98mm pulled with 16 "teeth" that will link in with the balled chain that I have bought.
This will give a resolution of 0.12mm per step.



It was made by spinning a piece of acrillic sheet in a drill and filing it until it was the correct diameter, then mounting it on a stepper and moving round in 22.5 degree steps. I held a dremmel with a suitably shaped bit and made a ball shape indent each time the motor stepped. It was very crude!



The gear was a good fit, and with a suitable jig, I can make high quality and repeatable gears.

I managed to test the gear, I tied six half litre bottles of water to the chain, and the NEMA 23 motor easily lifted them. I was about to video it, but cracked the gear when I was adjusting it - typical!

Edited 3 time(s). Last edit at 08/18/2009 12:26PM by philwaud.

Looking forward to seeing the video!

I was thinking more along the lines of nickel plated steel chain. If the cheap plastic ones will hold up long enough then that definitely is the way to go.

Adrian had used a stepper to make a similar jig. I would never have thought about it. I would have spent long hours measuring and still getting it wrong.

Going to try to make one of my own tomorrow. We'll see.