Gear reduction set-up

[scrambled]

Hi all-

At this point, my CNC plasma cutter is at a standstill. The linear bearing that I ordered will not arrive until June 9. So, since I have time to kill, I am going to start to build the gear reduction/ drive unit.

What is the best gear ratio I should use? Where is the best place to purchase the parts needed to build the gear reduction set-up?

Can you post a picture of your gear reduction set-up so that I have an idea or 2 to start with.

Thanks



Steve

[Torchhead]

Steve, I am working on a deal to start having table parts (motor mounting plates, gear (belt) reduction kits,Floating Head (plasma) Torch Holders and some other kit components precision machined and to offer them as part of our PlazPak and RouterPak lines. The components will be in the form of bolt-together kits and are going to be precisioned machined by commercial CNC equipment. If the components are popular, we will expand it to include other drive components and possbly a rail system.

Time frame on the motor mounts and belt drive components is weeks (not months). The major delay at this point is doing the exploded drawings and manuals (:-)

You can contact me next week off-list to get some pix and preliminary pricing.

TOM CAUDLE
www.CandCNC.com

[bullethead67]

I'm building a plasma table too and don't know much on what I need for gear reduction. I found some 28:1 gearboxes with a 1/2 in shaft that I'm trying to figure out. I read that most of my cutting will be below 300 ipm and I plan to use belts. am I on the right track? I want to use servos and drive the gantry with 2 (one for each side) I'm hoping to keep accelleration and change of direction speeds up to help burn better pieces. I have a brother that works in a machine shop so he is making me free parts and going off the solsylva belt drive design
ps I HAVE NO IDEA WHAT I'M DOING. SO I'M PRETTY MUCH BUILDING AS I READ POSTS. be nice

[DeviousMW]

Originally Posted by Torchhead to start having table parts (motor mounting plates, gear (belt) reduction kits,Floating Head (plasma) Torch Holders and some other kit components precision machined and to offer them as part of our PlazPak and RouterPak lines.

Tom,

I too would be very interested in the motor mounts and gear reduction setups. I need multiple gear reduction units to drive my X and Y using Nema 34 steppers with 1/2 shafts. This would be for rack and pinion. At least a 3 or 4 to 1 reduction. Please let us know more as this materializes.

You plaz pak minus motors is already on my short list once I get closer to the electronics stage

Thanks,
Mike

[massajamesb]

Look into www.mcmaster.com and look at their timing belt/pulleys, .2 pitch works, at least 1:2.5 reduction or higher, i.e. a 10 tooth on the motor shaft, and a 25 tooth on the driven shaft. I would go higher if you can find the pulley, say a 50 tooth pulley for a 1:5 ratio.
Chain and sprockets could also be used, or planetary gearboxes, if you can find them cheap enough.

[Bigtoy302]

How wide of belts are people using?

[Robin Hewitt]

Gear reduction really depends on how fast you want to go, how fast your steppers are prepared to go, torque required for accelerating/decelerating the axis and rolling resistance.

As your steps per second increase your torque falls away, there has to be a limit to how fast you can reverse the current in the motor coils and still get useable torque.

Unless you have a graph showing revs/second against torque, for a small motor I'd suggest holding the motor shaft between finger and thumb as a rudimentary friction brake then wind the speed up until there is no useable torque left. That gives you a number to work from.

Calculate a gear ratio that gives you the required inches per second then work back to find your step resolution and be prepared to compromise.

My 3.6" Escap steppers, wired in series with a 24 volt drive, clack out around 5 rps in half step, useable torque is fading fast by 4rps. I want 200 inches per minute, 3.3 inches per second so 1"/rev looks about right. Half step resolution 0.0025".

For this kind of power most any pulley belt combination is fine. The real load comes when you stop the motor and it applies it's full holding torque while the axis wants to keep moving. Unlikely to shear teeth off the belt, but it will try to ride up and apply a severe side load on the shaft. I know small pulleys are cheap, but can you get enough shaft inside them so it isn't going to bend?

[Perp]

Hey Guys, I just got my Plaz Pak 4 set up via UPS Friday and I got to say it sure looks great. Very well protected with excellent packing techniques. If you are thinking of buying from Tom I would say you won't be disappointed. I can see from the attention to detail that the people who built these components took great pride in there work. The servos are mean looking too, I think I won't be lacking any power here.

Now I just need to make a little time to start building.

As far as the reduction goes I am looking into either a 10:1(per Tom C for the 850oz servos) belt reduction or a 10:1 low backlash planetary gear head. The gear reduction head is pricey at around $850.00 each, but it appears to be clean, compact, and ready to run. The belts would require a jack shaft and double sets of pulleys, plus possibly fixed tensioners to ensure proper tooth engagement (minimum tooth count contact). I will be watching this thread to see what you guys come up with.