[posix]

it's (well, will be) a belt-driven door-sized v-groove gantry router.

x-axis 2500mm, usefull around 2300mm
y-axis 1600mm, usefull around 1300mm
z-axis 700mm, usefull around 400mm

I have aquired some monster nema34 steppers (http://www.arceurotrade.co.uk/projec...-010-00500.pdf) and have ordered some G201s. According to my calculations I will be needing a power supply exceeding G201s voltage so I think I'll settle for 75V and 12A but probably just need 10A. I'll need a volunteer to help me verify my calculations regarding PSU requirements.

Belts are optibelt alpha linear (http://www.optibelt.de/fileadmin/bil...ar_Opti_GB.pdf) T5 25mm, pulleys 20-tooth T5 25mm, starting off with no reduction and will see about needing reduction. The arrangement will be a DIY version of servobelt with kind permission from mike.

The build is actually almost over. The rough stuff is over, now I need to manufacture some mechanisms for belts and fine things like that.

What else? Oh yes, I'll post some detailed graphics and photos later on but just to tell you I've come up with an interesting approach to straightening square steel tubing to be acceptable for linear motion - just wrap it up in wood and plane the wood to the desired dimensions at your local cabinetmaker shop (they have these super-duper precise scm machines that only do that all day) - et voila! super precise super straight rails!

Wish me luck guys!

[posix]

btw this will be an open design so that anyone can implement it. I'll post drawings later.

[harryn]

Hi - neat project - I especially like watching belt drive setups, as that is what I am trying to do as well.

The Brecoflex guys are big believers in the AT vs T style belt, and their calculations sort of push your size + power of system into AT 10 x 25mm size belt. I wonder if you have worked through any calculations in this area, or even better - have experience with this belt (certainly cheaper, that is for sure) and of course the 5mm allows for smaller dia pulleys.

I assume that you will have 2 parallel belts driving the X axis with the pulleys fixed to common shafts?

That is an interesting idea for flattening out the steel - I was thinking of using self leveling epoxy, but wood might have some other advantages as well.

Interesting project to watch.

Take care,

HarryN

[posix]

no two parallel belts, only a single one - look closely at the first picture, see the stepper on the underside of the gantry? although I do have dual-shaft steppers, for the moment I'm going with a single belt down the middle of the table on the underside. when the machine starts making money it's easy to "upgrade" if the need arises, but I always believed dual-drive approach was an overkill - all it takes is some careful designing to ensure the gantry doesn't skew. which is my current preoccupation - trying to think of the best way of "boxing in" the gantry so it doesn't skew. It seems I've gone with the wrong material - namely plywood, two layers, sandwiched together - and it's flexing. 24mm and it's still flexing! this is not good. Hopefully I can come up with something simple that will stiffen it all up.

[posix]

some new images :wee:

[Jason Marsha]

You may have to build a torsion box, like Joes 2006 or Lionclaws machine, for the gantry.
Another idea could be "U" or "C" channel aluminium gantry as in the belt drive from Soysylva.

[posix]

this setup is just to get me going. then I'll be rebuilding it. without a cnc machine it's proven rather difficult to get something cut/machined the way you want/need it to be. the gantry and x rails are actually rather stiff - it's a rectangular 40x60mm steel tube "wrapped" in solid oak. tube is stiff as is, on it's own. the reason for wrapping it up in solid oak is to get the straight edge and cut the channels in it to hold/support the aluminium angle for v-rollers to ride on. noone has a mill/grinder big enough to make sure the 40x60 sides are flat enough but a friend does have a wood planer that's big enough - so an idea was born. steel "core" and wood "skin", work on skin to get the flatness you need.

but these buggers are heavy! and that's why they will be replaced with torsion boxes as soon as the machine is up and running. geckos have arrived (thanks janice), steppers are here, need to build a power supply for it (but will start off with 2 or 3 ATX psus in series to get it going). waiting for belts and pulleys to arrive. optibelt is not an "optimal" company to order from. 4 weeks lead time for T5 belts and pulleys. not optimal at all.

the table alone is something around 120kg! heavy indeed. heavy is stiff. I don't like heavy, I like stiff, not heavy. torsion box it will be.

[posix]

also working with aluminium for the time being is not an option - it's expensive and I don't have a good enough/precise enough machine to work with it. once this first revision is up and running with torsion boxes then I'll be looking into other materials and areas where it could be bettered.