Belt vs Gearbox drive system

[Redgoatfab]

Been looking at all the different build here and see that they are all belt drive systems. I am guessing that the begest reason is cost of gearbox systems.

Other then cost what is the pro and con with Belt vs Gearbox?


I am in the proces of desinging my table 5x10 cutting area with a little extra for future tool additions. Looking at gearbox drives it seems to me that it would be much easier to do a gearbox system then a belt system. Looking at www.kelinginc.net and there NEMA 23 gearboxes.

The other thing I was reading is Arc min of backlash. What should we be shooting for arcmin for a plasma table.

For the electronics I will be using the candcnc BladeRunner Dragon-Cut 620-4 kit. They seem to really have a good product based on everything I have been reading.

I have only been working with Soldworks for a short time, so if you want to look at the design send me a pm would love to hear what other solidworks users think of it.

atached is a jpeg of the main assembly.

Gary

[WSS]

These are good GB's:

Planetary Gear Box gearbox manufacturers gear reducer Canada USA Australia

I purchased three of them for a retrofit on our table to fit up to a CandCnc servo system. 12:1 ratio for this servo system gives me a 800ipm top end, which is plenty fast for me. I have it squeezed down to top out at 680ipm.

A dragoncut is stepper I think. A 3:1 is the preferred ratio it seems for steppers.

The arc minute we have is 10 and it has smooth quite motion with no detectable backlash (yet LOL).

WSS

[Redgoatfab]

So I have been busy in Solidworks getting everything lined out for the ganty happy with frame. Just been sorcing parts and getting very thing drawn up.

I am goign to use a gearbox set on all but the Z movment motor. The main gantry frame is 80/20 extruded 60x60mm. I am goign to use SBR Supported Linear Rails and Ball Bearings from Glacern Machine Tools the mounting holes for there linear rails is 30mm to its a perfect fit for the 80/20. Using the block for cncrouterparts to mount the rack.
THC is goign to be with 4" Plasma Z Axis, Linear Slide from K2cnc.com. Gearboxs are from Planetarygearbox.net.

Here is a few pictures of the assembly in solidworks to give you all an idea of where I am goign with this.

Also what should a gantry weigh complete? 100lb to much or about average?

Gary

[Ubatoid]

Hi Gary, I cant give you a yes or no to the gearbox question, only my findings when I was designing my table. I was originally going to go to gearboxes and spent an age researching which type I wanted and the right ratio and backlash was suitable but had to give up in the end as I just couldnt seem to get any serious dialog going with any suppliers. Wether it was the fact that I only wanted 3 units totalling 1800 US or that perhaps I was asking stupid questions, who knows? but in the end I fell back on belt drives. Zero backlash and a fraction of the cost.

I do have to say that from all the suppliers I contacted, Anaheim seemed to be the best of the bunch. Good luck with the table and those are some nice Solidworks drgs.

[Redgoatfab]

Thanks Ubatoid

Right now I am kinda at the same point you were. Been hard to get the info needed so think I am going to go with belt drive system. Looking at using cncrouterparts.com bent drive system. Doing everything possible to cut down on weight.

Will have some updated solid works drawing soon. Should have the money to order the parts very soon.

Gary

[I Lean]

If it's not too late, you might try to change your design so the gear racks face down everywhere--the one with the teeth up is just asking to catch crap and make your machine "jump" over it.

To contribute to the original question a tiny bit--I use belt reductions on my table. I think I'm into all the parts I needed for 3 transmissions about $120 total.

[jimcolt]

The majority of high end industrial cnc plasma machines use planetary low backlash gearboxes and inertia matched AC brushless servos as it is important to have excellent acceleration (at least 40 miligees) at speeds up to 350-400 inches per minute. Some of these industrial machine need to carry relatively heavy payloads with multiple plasma and oxyfuel torches (up to 4 plasma and up to 16 oxy-fuel) as well as bevel heads, torch height controls, etc.

Many of the lighter weight gantries that only have one torch head are perfectly suited with precision belt drives, linear recirculating bearings and either steppers or servos for drives. Acceleration at maximum cutting speed is still important....so size the drives accordingly!

I get a lot of emails regarding the high cut speeds of plasma on thin materials....and that many of the low cost entry level machines get unstable beyond about 140-150 inches per minute. The best cuts on 16 gauge steel will occur at about 350 inches per minute or faster....if you cut slower you get more heat input, a wider kerf and higher chance of dross.


Jim Colt Hypertherm

[I Lean]

The majority of high end industrial cnc plasma machines use planetary low backlash gearboxes and inertia matched AC brushless servos as it is important to have excellent acceleration (at least 40 miligees) at speeds up to 350-400 inches per minute. Some of these industrial machine need to carry relatively heavy payloads with multiple plasma and oxyfuel torches (up to 4 plasma and up to 16 oxy-fuel) as well as bevel heads, torch height controls, etc.

Many of the lighter weight gantries that only have one torch head are perfectly suited with precision belt drives, linear recirculating bearings and either steppers or servos for drives. Acceleration at maximum cutting speed is still important....so size the drives accordingly!

I get a lot of emails regarding the high cut speeds of plasma on thin materials....and that many of the low cost entry level machines get unstable beyond about 140-150 inches per minute. The best cuts on 16 gauge steel will occur at about 350 inches per minute or faster....if you cut slower you get more heat input, a wider kerf and higher chance of dross.


Jim Colt Hypertherm

What do the high end industrial machines use for their linear motion? (since you mention linear recirculating bearings for the entry-level stuff most of us have...)

[BTA PLASMA]

All those gear boxes start with low backlash. None of them last forever and they get worse and worse just like a belt drive if your not using a quality belt you will get stretch. For tables that arent ran 24/7 there are budget chinese reduction boxes sold all over the internet that work good...good enough for a while.


Rail is most often used and computed for load values. The heavy machines need a truck and rail with minimal deflection. Reciprocating ball trucks are often used like Hiwin, THK, IKO..ect. When PROPERLY equipped with scraper/wiper combos these last a long time but require grease.