timing belt instead of lead screw

[Swarfing]

For 6 metres it will cost you £120 quid. plus you will need other belts to get you geared to the right torch. I would not run these direct drive (way too fast) and for the money you could get 2 screws. I got mine from ERIKS which where cheaper but like i say by the time you add everything else it costs way more.

[deannos]

For 6 metres it will cost you £120 quid. plus you will need other belts to get you geared to the right torch. I would not run these direct drive (way too fast) and for the money you could get 2 screws. I got mine from ERIKS which where cheaper but like i say by the time you add everything else it costs way more.

ouch, back to screws then.

Thanks

[Jonathan]

Belts... advantage is less power required to achieve higher acceleration and speed (since kinetic energy of moving belt and pulleys is much less than a long rotating screw). For a long axis it should be a lot cheaper since you don't need as high torque stepper motor (unless you use a rotating ballnut like I did, then you can still use the small stepper, but that's completely irrelevant for an only 48" axis).

Disadvantage of belts is, as 2e0poz said, they stretch. Any belt will stretch, it's just some are more stiff than others. Different tension members, cross sections/pulleys all make a differenc. To get reasonable resolution (and thus accuracy) from a belt it is apparent you need double reduction to get the right ratio from stepper to belt. That's more pulleys (expense) and more belts to stretch! Due to the stiffness I doubt you would be able to cut aluminium with belts, whereas you could with a ballscrew or another type of screw.

That does however make belts great for something like a laser cutter or rapid prototyper where there are no cutting forces and the accuracy is not so critical.

[baccus61]

I have tried most of the forms of transmission out there and if you can afford it then get the ball screws or even a good anti backlash lead screw. The anti backlash lead screws are still good value for money and the polyacetal nuts are very good wearing. I have a 12 start leadscrew on my x axis and its great. Fast rapids and pretty good control when geared down about 3:1 on the motor.
A lot of people make their routers very accurate but if you are only cutting wood then it needn't be as wood swells and contracts with moisture in the air. It's only the positional accuracy that you need and not resolution. i.e it has to come back to the same spot all the time (no backlash or looseness in the mechanism).
I went from belts to leadscrews to ball screws over a year or two so it would have been cheaper right from the start to get the ballscrews and have a good machine from the get-go. if you want a machine to last for the next 10 years or so then go ballscrew or anti backlash leadscrew.
Some of the Chinese ballscrews are very cheap but you need a press and lathe (or Vee block with indicator) to straighten them out when you get them as they are like spaghetti and are all over the place. I don't have a preference for either but the leadscrews with polyacetal nuts are better in a dusty environment. I have ballscrews on my Y axis (long) and to keep the dust out I loop a leather bootlace over the screw twice with a 3/4" nut hanging off the bottom of it to add some weight and do this on both sides. It wipes the screw before the nut goes over it and keeps 90% of the crap out of them. I grease the screws and don't oil them. I also have a fairly good dust extraction system which I think for a wood router is absolutely necessary not just for the machinery but for your lungs.
Here in Australia a few years ago the Gov health agency listed ALL Australian hard woods as being carcinogenic. This would probably be the same for a lot of woods in other countries as well. It makes sense to combat this problem at the source and not later through medical situations. Prevention is better... Blah, Blah, Blah, as they say.
Don't get single start leadscrews as the rapid traverse is just not fast enough. It's good for a metal machine for cutting but not a wood router where you need rapid repositioning. Get something in the way of 4 start or 20mm per rev (3/4") and gear down your stepper to about 3:1. I wouldn't go under 10-15mm per rev as it just too slow.
Steppers work stronger and better at low revs and if you have 8-10 microstep drives then the accuracy is as good as you need.
I hope this helps you out somewhat.
If you want toothed belts then the only ones I would recommend are the TDH belts or the ones with the rounded tooth profile as they seem to fit better than the sloped sided ones. (Most photocopiers I pull apart have TDH belts so the manufacturers can't be wrong) I have bought most of the type of belts on the market and the rounded ones definitely fit the best. I only use the belts on fast moving stuff now like a laser head etc that has little mass or weight to push around and I use leadscrew or ballscrew for the rest.
Ultimately it come down to what you can afford but my recommendation is to go with a screw type of setup.
Richard.

[JAZZCNC]

Some of the Chinese ballscrews are very cheap but you need a press and lathe (or Vee block with indicator) to straighten them out when you get them as they are like spaghetti and are all over the place.

Not very fair that comment.!! I have bought literaly dozens of ballscrews screws from China and only 1 was ever so slightly bent and twenty minutes later straight.

[baccus61]

Thanks for your reply.
I have bought 3 ballscrews from China and all were bent and needed straightening. This was from 2 different suppliers. What's not fair about telling the truth?
Were your screws short or relatively long?. Mine were 2x16mm x 1.25M long and one was 600mm long.
The smallest bend was about 0.012" and the largest was about 0.120. Way off line for a ballscrew.
This is my experience with them. You obviously have had a much better one.
I use the ballscrews about once a week and have had no trouble with them but I also don't push them to their limit either. Only on a wood router and small metal lathe.
They all were VERY cheap compared to what I can buy in Australia so you get what you pay for. It took me about 1 hour each to align in the press and swap out to the lathe to check alignment and they are now about 0.005" true along the whole length.
I'm happy with the price and happy with the end result BUT only after a bit of work here at home.
If your supplier has sent you good ballscrews then post the name here so others may buy nice straight ones from them so they don't have to go through the process of truing them up. I have a pretty good workshop and, from what I have seen here on this forum, others may not.
I'ts just my opinion from my experiences.
Rich

[JAZZCNC]

Thanks for your reply.
I have bought 3 ballscrews from China and all were bent and needed straightening. This was from 2 different suppliers. What's not fair about telling the truth?
Were your screws short or relatively long?. Mine were 2x16mm x 1.25M long and one was 600mm long.

Sorry buying just 3 screws and deducing from this that all chinese ballscrews are rubbish hisn't fair.!!
I've bought lierally dozens ranging from 250mm to 1800mm in length in all sizes and in my experience they are very much ok and only had 1 screw bent and one that was machined badly.

It's no secret where I get my ballscrews from and I'm always recommending and saying they come from Chai at linearmotion bearings, I've also bought several spindles without issues thou I do recommend staying clear of the VFD's.

I agree they are cheap and you get what you pay for but they are more than good enough for DIY. Yes there will be bent screws just like there are fault spindles and VFD's but in the grand scheme of things and considering the numbers they must sell I think the overall percentage will be low.!
Saying all chinese screws are like spaghetti is incorrect, Others read this and are put off from buying from china and here in UK this can severly up the cost of building a machine.

Gud day. .:wave: