nice, reminds me of the cnccookbook...
[www.cnccookbook.com]

'sid

I still go back to my suggestion of maybe designing a chain which can be prited, then use Polycapratone to make the gears

Found one suggestion on Thingiverse
[www.thingiverse.com]

Hi Phil

Yep thats the chain I liked it because of the colour too.. I have 4M here I intend useing Peek for strength. I was also going to try wood doweling as that could sanded down to size.

Looks like you got some ASDA chopping board .. its nice and easy to drill and work with..

Im only have to take a few photos of the Y slider mounts and motor holder then will post the next part of repstrap darwin.

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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]

Yep, good old ASDA!

I was a bit dismayed when you said that you didnt need all those 608 bearings as I had just bought 32 of them! I have since seen that a heavier build will need them so I am using them anyway!

Ive just had a few days away camping in a teepee which gave me a chance to think things through.

I am going to make a jig using two stepper motors, one of them will turn the shaft with the cog blank on it and the other will raise an lower the dremmel using an eccentric cam. The whole think will be automated so removing possible operator error.

Ill post results asap.

The cogs to keep the four z axis shafts in sync can be quite large - im going for 30mm diameter. The larger the better as it will strain the ball and chain less. I have to devise a way of joining the ends of the balled chain, Im thinking of using thin wire to splice the ends together with the correct spacing but im open to suggestions.

Phil

I started rebuilding Bertha to do the same.. I got carried away and made it a little bigger too... Ive not made any Drawings thou as I built it with left overs and some legs from some kind of Australian saw kit B&Q were selling off Cheap..

Bertha now contains a Micro ATX PC running Emc2 Linux so its realy a CNC machine.

Just figuring out the PSUs and the stepper controllers cooling system will pop up pictures soon probably on my tools blog..

I have two Darwins at the moment one with bike chain and bearings and one with the imperial black belt from the rrrf.

The bike chains will only work with a bearing drive system...

Bertha will now have a 400 x 400 x 140 mm work area.

Why do you need to join the ball belt just make the meeting point the carridge with out a join. If you lok in my blog you can see i have two pairs of belt width holes ~I would just use tiewraps like I have for the belt.. Bike Chain is diffrent tho it needs to be tensioned

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

---

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 will need to join the belt for the z axis, you need a continuos belt running round all four cogs.

Oh Im using 4 stepper motors for Z it was cheaper than bike chain and the original belt .. I cant think of a way of Joining the chain so that the join is like any other part of the chain.. Bike chain is easy to join but extemly heavy..

I got the Nema 17 motors at £12 each,

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

---

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]

Here is the link to the Y axis motor mount and slider for belt, ball chain or bike chain drive drive Bike chain requires a four pices of MDF to make a 4 sided construction fore the other two only two pieces of MDF

[repstrapdarwin.blogspot.com]

---

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

---

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]

Maybe I am being stupid

Has anyone considered a car timing belt for the Z axis?

Yes I know the teeth are bigger but doesn't that just mean bigger cogs?

They are cheap to buy and if you go down to the scrap yard they are ususally
given free. (my favorite price)

Stephen

P.s. Anyone know what the spec is for the timing belt on the bit from bytes kit v2.0.0.0 ?

-> Has anyone considered a car timing belt for the Z axis?

I was just going to suggest the same thing.
Any Garage worth its salt should carry those.
Unfortunately all the car repair shops I have connections to are closed for the weekend. I'll hit the shops first thing on monday morning. Maybe I can score some discarded belts to experiment with. can't get cheaper than free, right?

When I was in Saeco Precision a few weeks ago, I looked at their automotive timing belts, and there is 2 big reasons why we can't use them.
1) They're big, I mean really big, and seeing as we're trying to reduce the size of the thing that isn't a good idea.
2) On a lot of vehicles, the timing belt is ribbed differently, either laterally (length ways) or V shaped, neither of which would have enough grip.

Though do go ahead and ask, don't quote me on face value, as I only looked at a few belts.

One type of belt that you can use which is fairly common, or splice together is R/C car belts, and often you can get a pulley with a grub screw in it to lock down onto the shaft of a motor or something. I did ask my local shop, and while they are short, it shouldn't be too difficult to splice together, though I assume vulcanizing rubber glue, you know the type to repair punctures in tyres, would work for splicing. Vik did try with success R/C helicopter belts, these are longer as they go from the main rotor to the tail rotor.

-> When I was in Saeco Precision a few weeks ago, I looked at their automotive timing belts, and there is 2 big reasons why we can't use them.
1) They're big, I mean really big, and seeing as we're trying to reduce the size of the thing that isn't a good idea.

I'm pretty sure the automotive belts can be cut into narrowewr strips using a jig and a sharp blade.I'll have to try on monday.

-> 2) On a lot of vehicles, the timing belt is ribbed differently, either laterally (length ways) or V shaped, neither of which would have enough grip.

What you're thinking of are drive belts. timing belts have to be ribbed perpendicular because any slippage would mean instant death to the engine.

I've thought of RC car belts (currently building a belt driven buggy), but their teeth are around 2.5 mm which would make printing pulleys pretty much impossible (not to mention that I have yet to build a printer). Also I think a bigger belt should be easier to splice.

Anyway I think it's worth a try. I'll experiment a little on monday and post my findings, whether positive or negative.

Just bought 2M of timing belt. The cost? $70. ($USD60)
But they will deliver in two days.

If anyone wants to bulk buy this stuff the keywords for a google search seem to be
"synchronous belt t2.5" with t2.5 being the pitch in mm

Checked out the car timing belt situation and found this great site

[www.dzbelt.com]∂=220&page=19

Shows that VW golf III (1h1) has a timing belt pitch of 8mm width 19mm (can we cut it down). Code AA-TOP: 133S8M190A

[www.dzbelt.com]∂=220&page=38
Shows a Fiat Panda has a timing belt of pitch 8m width 15mm code AA-TOP 125STDN8M150. Bit it has a strange tooth shape.

[www.dzbelt.com]∂=220&page=31
Shows a timing belt for the lancia delta 9.5 pitch 18m but nice shaped tooth

Also found this
[www.6mm.com]
Which gave lots of techy advice.

Stephen

I managed to score a timing belt today, for a VW 1.9 TDI engine.
Looks good so far, the pitch is about 8mm, and the trapezoid teeth will allow or easy pulley construction and the total length should amount to about 1 meter.
The only problem i can see so far is that the pulleys will have to have at least 3-4 cm of diameter.
Unfortunately I won't have time to experiment until the weekend rolls around.
I'll keep you posted of any progress.

Hi

>- I managed to score a timing belt today, for a VW 1.9 TDI engine.

Did you get it from a breakers yard? If so did you notice any useable
cogs on the engine?

The idea of having high quality metal cogs intergrated into the reprap seems
to me to be a good idea.

Stephen

... i've found small chainwheels and chains in different sizes and lengths (smaller formfactor than bike-chains) in old copiers - there are many other usefull parts for repstrapping too ...

Viktor

-> Did you get it from a breakers yard? If so did you notice any useable
cogs on the engine?

I got the belt from a garage that I used to work for. I'm pretty sure that just about any car repair place will let you sift through their trash for used belts (or will keep the next one they change just for you) if you ask nicely. The gears however are too big and too massive to be of any use in a machine the size of a repstrap. I have an idea how to make simple pulleys from mdf using nothing more than a drill press. I'll give it a try over the weekend end then post the results with pictures.

Edit: due to some personal stuff this week I didn't get anything done, now will anything be done over the weekend. I'll keep you posted.

Edited 1 time(s). Last edit at 09/25/2009 04:28AM by Corbarrad.

I'm using these little chains:

[greenarrows-shed.blogspot.com]
[greenarrows-shed.blogspot.com]

I'm not sure they worked out much cheaper than timing belts in the end thought.

I like it greenarrow
But still to expensive for our 3rd world reprap person.

Must trot down the car junk yard and see if a engine timming belt will work.

Stephen

I'm curious, because I just had a silly idea involving ball screws. Ball screws are really neat, low friction, low backlash linear motion devices.

What if you printed a plastic ball screw assembly, filled it with steel ball bearings and printed the threaded ball screw rod? My first thought was, thats silly, it would bend like crazy, but what if you stiffened it with a cheap normal threaded rod? The ball screws would wear away imperfections in the plastic and you would get much faster linear motion with ~ hopefully ~ similar degree of accuracy.

The whole thing might need to sized up a bit to get the precision necessary, but it could be worth it.