[rcbamm]

hey guys, I was wondering if it will be good enough to use a belt driven setup for my X rails? I came up with a quick drawing of what I am thinking and how my CNC design will look from the side. My rails are going to be 54" long and to get a ballscrew for that length it's gonna be costly I was checking out the Acme Rods and found some one here in FL that sells them and those arent bad but I heard that they sometimes stall the stepper motors? and aren't as precise. I thought that pretty strong belt with pullys on both ends would be more "precise" and I think it might be cheaper. not sure, was also wonderign if any of ya had some good links on belts and pullys. I found a Robotic website that had a 1" x 90" belt for some thing like $98 and then the pullys are like $15 a peice and I was thinking, that is almost as much as a Ballscrew! but if there are cheaper belts I would check into them.


My drawing.... the belt and Pullys would go directly in the middle of the table and then I will have a support bar connecting the two bearing cars and then I will strap the belt onto that bar and then I will get my back and forward motion.



Note: this is a quick CAD drawing!


-Dan

[Kipper]

I'd be inclined to use 2 belts to prevent the "Y" from skewing... Have a look on fleabay for Carolbrent aka HubbardCNC as that seller lists open ended belts and suitable pulleys (not available to UK buyers...Grrr ) Also consider making a reduction drive using belts/pulleys for as backlash free an installation as possible (on the cheap) Oh and check out the linear slides with skate bearings they sell? hth

[rcbamm]

thanks for the reply but I can't seem to find any information on carolbrent or hubbardcnc got any links?

[Kipper]

Hubbard-cnc-inc Interesting stuff!

[rcbamm]

SWEET! this is exactly what I was looking for! thank you!!

[Kipper]

SWEET! this is exactly what I was looking for! thank you!!

If you buy anything ask why they don't post over the pond lol glad to help :cheers:

[rcbamm]

pong? lol

[ajmoir]

hey guys, I was wondering if it will be good enough to use a belt driven setup for my X rails? I thought that pretty strong belt with pulleys on both ends would be more "precise" and I think it might be cheaper. not sure, was also wondering if any of ya had some good links on belts and pulleys.

Hi,

I'm building a belt driven xy table, take a look here

I purchased my stuff from EconoBelt as usual I still spent the same but bought better stuff I went for wide L belts and steel pulleys on .5" shafts.

I had some custom brackets made at BigBlueSaw. These are adjustable to get belt tension. Also, my motor shaft doesn't have any lateral load but rather feeds a separate shaft in bearings. Steppers do not like lateral loads.

My take on the belts is that they work at lengths that ball screws cant, they more forgiving of poor tolerances.

My total cost per axis less motors is $200, the cost difference between a 4ft run and a ten ft run is peanuts compared to the pulleys and mounts.

[martinw]

hey guys, I was wondering if it will be good enough to use a belt driven setup for my X rails?


-Dan

Dear Dan,

For what it's worth (probably not a lot), I looked into belt drives for a small CNC MDF frame 3 axis router last year. Like other people, a belt drive on both sides of the main bed seemed a good idea.

I came to the conclusion that the stretch of the belts under dynamic loads might be a bit of a problem. This was partly because I found it quite hard to relate manufacturers' figures of belt stretch ( if indeed they gave them) to the forces involved in a machine that accelerates etc.

Kipper is absolutely right, by the way, that open-ended belts are hard to find in the UK. You people on the other "side of the pond" do not know how lucky you are compared to us in "rip-off" Europe.

Best wishes

Martin

[Kipper]

Dear Dan,

For what it's worth (probably not a lot), I looked into belt drives for a small CNC MDF frame 3 axis router last year. Like other people, a belt drive on both sides of the main bed seemed a good idea.

I came to the conclusion that the stretch of the belts under dynamic loads might be a bit of a problem. This was partly because I found it quite hard to relate manufacturers' figures of belt stretch ( if indeed they gave them) to the forces involved in a machine that accelerates etc.

Kipper is absolutely right, by the way, that open-ended belts are hard to find in the UK. You people on the other "side of the pond" do not know how lucky you are compared to us in "rip-off" Europe.

Best wishes

Martin

:threadhijack ahead: I found a supplier called Wyko in the UK that can supply me with them Martin....For a price

[martinw]

:threadhijack ahead: I found a supplier called Wyko in the UK that can supply me with them Martin....For a price

Dear Kipper,

Thanks for that. I do not wish to sound ungrateful, but the belt stretch stuff could still be an issue. I'm pre-judging it, sorry. Will take a peek really shortly.

Thanks again..

Best wishes

Martin

[Kipper]

If anyone wants to express an opinion (I've been wrong before lol) and I'm actually on topic for once Attached is a rack type system that seems "awfully good" Very generous .zip file size allowed! :cheers: admin.

[rcbamm]

Dear Kipper,

Thanks for that. I do not wish to sound ungrateful, but the belt stretch stuff could still be an issue. I'm pre-judging it, sorry. Will take a peek really shortly.

Thanks again..

Best wishes

Martin

I thought about the belt stretching.... but then, I'm only gonna be cutting mostly foam and balsa wood. once I get my table working properly and precise then I will try out some hardwood for firewalls and landing gear plates etc.. but if I can start cutting foam and balsa wood I will be a happy man

[ger21]

If anyone wants to express an opinion (I've been wrong before lol) and I'm actually on topic for once Attached is a rack type system that seems "awfully good" Very generous .zip file size allowed! :cheers: admin.

Make sure you're sitting down when you get the price.

[ger21]

I thought about the belt stretching.... but then, I'm only gonna be cutting mostly foam and balsa wood. once I get my table working properly and precise then I will try out some hardwood for firewalls and landing gear plates etc.. but if I can start cutting foam and balsa wood I will be a happy man

Check out www.sdp-si.com for a lot of good belt info.

If you take a look at the threads from Joe's design router, they're all using or switching to 1/2-8 2 start acme. Best performance for the price, and easier to implement than a belt drive.

Just a guess, but I'd say at least 90%-95% of the homebuilt routers here use acme screws with great results.

With a belt drive, you'll likely need a gear reduction which adds to the complexity.

[rcbamm]

this is what I have in mind for right now....

package: CNC 3 axis Stepper motor Drive system http://cgi.ebay.com/CNC-3-axis-Stepp...QQcmdZViewItem


belt: about 20ft of the 3/8" WIDE 0.20XL open ended timing belt.

Pully for stepper motor: 15 teeth 1/4" bor .2p http://cgi.ebay.com/CNC-Timing-pulle...QQcmdZViewItem


reduction pully: i would probably get three of these and put them side by side for reduction then the other one for the belt drive. the third one would be for the return pully on the end of the router table. 30 Teeth 1/4" bore timing pully. http://cgi.ebay.com/CNC-Timing-Pulle...QQcmdZViewItem

and probably a 60 tooth kevlar timing belt for the reduction. http://cgi.ebay.com/CNC-TIMING-BELT-...QQcmdZViewItem


I add this all up two times so I can have every thing for the Y rail aswell.


how does this look?


-Dan

[harryn]

Hi - I am in the "studying / planning " stage of a belt drive setup as well.

I did a search of the forums, and someone (sorry, cannot remember who to credit) pointed to these guys.

http://www.brecoflex.com/?CATID=1&SC...T10&codeName=M

After a lot of reading of there site, it seems that the belt company recommends
- The AT style tooth
- I picked the -10 series (for powerful tooth strength)
- Steel reinforced for minimizing stretch
- They also have a special tolerance tooth shape for reduced backlash applications (3 actually, 1 std, 1 better, 1 best)
- The tighter tolerance belt teeth also match better tolerance pulleys

Interestingly, they claim that the steel reinforced versions do not need stretch compensation, just "pre-tension".

Belts are in every size you can imagine, up to 6 in wide.

I have not yet priced them out, so that part is still open for sticker shock, but my initial thinking is to use 100mm (4 in wide) so that the the belt can take up some of the (likely) slop / vibration in the system. Some of this is of course wishful thinking.

[martinw]

I thought about the belt stretching.... but then, I'm only gonna be cutting mostly foam and balsa wood. once I get my table working properly and precise then I will try out some hardwood for firewalls and landing gear plates etc.. but if I can start cutting foam and balsa wood I will be a happy man

Dear rcbamm,

I didn't wish to pour cold water on the entire idea of belt drives. Far better men than me have had good results.

If you take a peek into the guts of $70 ink-jet printer, you will see a tiny belt driving the print head. The print head sprays stuff with incredible accuracy.

Good luck,

Best wishes,

Martin

Martin

[randyf1965]

harryn,

Any pricing from http://www.brecoflex.com/?CATID=1&SC...T10&codeName=M ???

I want to do a belt drive is 3/8" wide enough for the y axis? MIne is 65" wide so I was looking at 3/4"

[harryn]

Hi - I have not asked for pricing yet.

The belt drive site has a calculation setup for belt selection - I have not run the numbers yet. I think it has more to do with how much force you need than Y dimension.

I made an guess (based on comments in threads by others) that the gantry would have a mass approx 50 Kg / 100 lbs, and be driven by at least a size 23 motor, or in my case, more likely a size 34 - so approx 400 - 500 oz - in of torque. Only logic is that is what other people seem to be using.

I am toying with using a really wide belt (2 x for each axis) so that the belt tends to help stabilize things, at least that is the idea - so I am thinking 3 or 4 inches wide. Probably way overkill, and the idea might die once budget reality starts to hit.