marker pen driven over an 8x4 sheet help.

Quote:

---

Originally Posted by wiatroda

eg belt 3M pitch belt driven with 15 tooth pulley gives you 45 mm of axis movement per revolution of driving pulley.

---

My experience is 15T is too small for a machine this size.! Problem being the number of teeth in mesh is on the lower safe limit. It will work ok but the belt wears prematurely.
Obviously a plotter has very little work to do so the load is light meaning it won't be so much a problem but if it was to be used for cutting wood etc the force's will eventually tell there toll.
IMO for the sake of few more quid, and it literally will be £1 or £2 per pulley, and seen as gearing is required either way then it's just not worth not doing.!

Quote:

---

Originally Posted by John S

The link posted by Wiatroda,
Is for steel reinforced.

---

Sorry I meant standard 'circular' belts, not cut belt like that...

Quote:

---

Originally Posted by JAZZCNC

IMO for the sake of few more quid, and it literally will be £1 or £2 per pulley, and seen as gearing is required either way then it's just not worth not doing.!

---

Where do you get them for that price? Not worth making my own for that money.

Quote:

---

Originally Posted by Jonathan

Sorry I meant standard 'circular' belts, not cut belt like that...

---

Dare I ask why you want steel?

Thanks for all the tips guys i can see im not going to be short of advise and thats a good thing, my next step will to knock up a cad drawing for you guys to rip apart!

Quote:

---

Originally Posted by Jonathan

Where do you get them for that price? Not worth making my own for that money.

---

Sorry Jonathan thats does read miss leading doesn't it.!. . . I meant £1 or £2 more.

Hi there can you tell me if there is any issues with using fixed rack of teeth rather than belts , can you drive the stepper motors along a rack of fixed teeth ? just wondering if its cheaper im looking a allot of belt for an 8 x 4 could i half the amount needed by switching to a fixed rack set-up?

Quote:

---

Originally Posted by Danny

Hi there can you tell me if there is any issues with using fixed rack of teeth rather than belts , can you drive the stepper motors along a rack of fixed teeth ? just wondering if its cheaper im looking a allot of belt for an 8 x 4 could i half the amount needed by switching to a fixed rack set-up?

---

Hi Danny,

What I think your referring to is (R&P)Rack & pinion.!
There are no issues as such and it's often the prefered setup for longer length machines due to technical issues like whip etc with using screws, also it's slightly cheaper.

If by halfing the amount you mean only using R&P on one side then NO Bad idea.!! . . With a machine of this width, even thou the load will be light, you will potentially suffer from racking which could cause sticking and inaccurecys. Driving from one side is bad and not recommended even for machine of this light duty. . . . Drive it from the centre and it will be ok.

That said R&P does come with it's own set of requirements.!!. . .It still needs gearing for resolution thou not quite so larger 2:1 - 3:1 max, larger motors are needed because it's quite inaffecient this also means larger more expensive drives which in turn require higher power supplies.
On a techinical side it's far less efficient than timing belts with much more backlash (Timing belts are very low to zero backlash) and it's noisy as hell.

IMO for your light weight machine needs you won't get better or cheaper than using timing belts. R&P will certainly be far more expensive and perform far worse on a techinical basis.

Don't know what machine design you have in mind regards belts but let me just point out you don't need looped belts.? . . . Just a single length fixed at each end and looped around 2 rollers and the drive pulley is all thats required up each side.

If you look around you tube you'll see what I mean something like this http://www.youtube.com/watch?v=VPlyTTFo6w0

Jazz has covered the pros+cons of each pretty well.

Belts should work out far cheaper, and remember you can always buy a longer belt and cut it into two.
You also don't a wide belt given the relatively low forces needed.

For example, in the old HPC catalogue I've got here, they do upto 2500mm belts in HTD5, which could be cut to give you one side of the long axis, along with enough for the short axis, then you just need a shorter belt to cut open for the other side.

Quote:

---

Originally Posted by m_c

For example, in the old HPC catalogue I've got here

---

If your buying from HPC then you have too much bloody money.:rofl:

Find a local bearing dealer they will more than likely have belt on the shelf and sell you the exact lengths you need. . . I find they like to dealing cash with things like belt n bearings as it's easily lost.:whistling:

You got one of those bearing suppliers aswell? :heehee:

I know HPC isn't cheap, but their catalogue is a very handy reference to have. I've only ever bought one item from them, which nobody else could supply quickly, and they weren't that much more expensive than the other options.