[mrsa]

I want to build o cnc co2 laser 1200mm x 1500mm for engraving purposes.
The max engraving speed will be 2000mm/sec the load is small (only laser head) because it will be with flying optics design.
I will use timing belts & pulleys but backlash is unacceptable because the machine will be used for high accuracy egraving so >=0.1mm backlash is problem.
What timing belts & pulleys with small pitch exist that have high accuracy ?
I found very cheap in china HTD 3mm pitch polyurethane with steel cores timing belts & aluminum pulleys
but i want to know it there are more accurate options ... with smaller pitch if possible ...
What teeth profiles are suitable for this application ?
What about kevlar vs polyurethane vs rubber timming belts ?
Which is more accurate & durable ?
---
Now i saw servobelt system and i think that maybe this is better.. Can i used it a laser engraver ?
Thank you.

[skrubol]

GT2 is supposed to be an improvement on HTD for low backlash and I believe is available in smaller pitches. Belt drives over that distance may still cause a lot of vibration due to belt stretch and oscillation (belt will oscillate like a guitar string,) depending on acceleration.
I think servobelt might be a good fit for something like this.

[mrsa]

Ok i found GT2 2mm pitch what about belt PU with steel cores or rubber with fiberglass cores also what width belt to get 10mm 15mm 20mm 25mm 30mm?
Also to put it horizontally or vertically (horizontally for sure causes oscillation) ?

Now i have a machine with 1600mm movement in X axis(belt is about 3600mm length) with HTD3M (3mm pitch/15mm width) belt and at 300mm/s has 0.2mm backlash without belt oscillation because belt is positioned vertical.
Another machine i have with 700mm movement in X axis (belt is about 1700mm length) with HTD3M (3mm pitch/10mm width) belt and at 300mm/s has no backlash with a lot of belt oscillation because belt is positioned horizontally.

The problem with servobelt is that the motor must move with head and this will add extra inertia to head also must add cable drag chains so the complexity will be increased.

For example this https://www.youtube.com/watch?time_c...&v=qeyyOV66Uvo what belt is? (width/teeth profile/material)

[ger21]

The wider the belt, the more rigid it will be.

[Al_The_Man]

Google Goodyear Eagle pd they are made for high precision timing belt applications.
Al.

[RCaffin]

GT2 is backlash-free when correctly tensioned, so 0.1 mm is not a problem. The wider the belt, the stiffer it is.
But a GT2 belt drive over 1500 mm is a bit more than I would wish to try.

Cheers
Roger

[mrsa]

The X axis movement will be 1200mm so belt will have 3000mm total length the load is the laser head(very small) the speeds will be up to 2000mm/sec - 3000mm/sec.
What belt is suitable for this case ?
For example this machine what belt has ?
https://www.youtube.com/watch?v=wRVmkgZil50

[ger21]

To get a definitive answer, you'd need to talk to an application engineer from a belt manufacturer.
Be prepared to be able to provide a lot of information, as well as well defined expectations.
The simple answer, is just use what everyone else does.

[mrsa]

I know that the most easy answer is to use the belt that use an existing machine that works fine.
The machine in the previous video what belt has ? Also for example trotec speedy 500 what belt has in X axis ?
Now iam between GT2 20mm width or 30mm width polyurethane with steel cords reinforcement.

[Al_The_Man]

For belts that go the length of the gantry, I have used the BrecoFlex line, made particularly for this application.
Al.

[cyclestart]

Now iam between GT2 20mm width or 30mm width polyurethane with steel cords reinforcement.

If pulley diameters are small check if the belt manufacturer recommends steel reinforcement. Steel is strong but not the best for every application.
/www.megadyneamericas.com/reinforcement-options-for-timing-belts

[mrsa]

The pulleys diameter width will be 25T about 15.4mm or 30T about 18.6mm
http://ae01.alicdn.com/kf/HTB1OFl2aK...sq6ydZXXaY.jpg
http://ae01.alicdn.com/kf/HTB1P.TPk1...dq6zDnVXad.jpg
I know that other laser manufacturers use kevlar belts
but i can find only rubber with fiberglass reinforcement or polyurethane with steel cords reinforcement
so my options are 2.

[RCaffin]

Several mfrs make Kevlar toothed belts, usually with polyurethane. Do a web search.
As Gerry suggested, you need to talk to a staff engineer.

Cheers
Roger

[skrubol]

The laser engraver shown in that video was working in raster mode (scanning back and forth at a constant speed.) You can get away with a lot more backlash and belt stretch when running that way than in vector mode (cutting or etching thin lines,) because the laser is moving at a fixed speed when it's working. Also the other axis can be much slower if you're only working in raster mode, as it only needs to inch the gantry along.

[coherent]

With the light weight of the laser gantry I doubt you'll have any issues with any of the modern timing belts like those used on lasers and 3d printers. The steppers and belts (or simular) used on my small laser are extremely precise at even higher speeds and they are pretty basic. You didn't say, so I'm not sure what you are planning to do that you are concerned about accuracy. After all the gantry is only carrying a mirror and lens and there are no cutting forces involved. I'd take a look at some place like here: https://www.lightobject.com/Search.aspx?c=64 and find something similar to your planed build see what size/type gears and belts etc., are used. They may even be a source for parts...

[mrsa]

The load is minimal but the acceleration & speeds are high
acceleration up to 3G
speeds up to 3000mm/sec

So the belt must be very rigid flexible & accurate
The trotec speedy 500 is similar X axis length & head load and has similar speeds & accelerations
What belt uses this machine in X axis ?

[Al_The_Man]

New Video https://www.youtube.com/watch?v=LXGFTls0xgs
Al.

[skrubol]

Some 3d printers use a similar design for the X-Y axes. Has advantages for low force, high speed, high acceleration systems, as no drive motor needs to be moved around.