What do you really get for a $350 desk top engraver ?

So i have been looking at a lot of belt drive idea's after doing this build. i have been playing around with a open ended reduction idea's and think i have something that would work and get a lot more from a smaller width belt. the down side to belts when you have some forces at play are what i believe to be minor flexing of the belt engagement into the drive pulley, belts just are not rigid like a ball screw in this respect so you either have to go to a wider belt or figure out a way to get more surface contact with the smaller belt.

Tommy i know how you do your reductions and i have looked at your designs quite a bit. The omega configuration on the open-ended side is a good way to get a few extra teeth engaged and is the basic configuration on my build minus the reduction. what i have built works mostly because the motors are oversized for the size of the machine. Keeping the design simple was a good base line to see what works and spot the tiny issues. for me it's surface finish between step downs
the idea i want to test is something like a serpentine belt reduction for open ended belts that would do away with the closed loop belt reduction on the drive shaft of the omega configuration that i see you using. my thoughts with a serpentine configuration is you end up with a lot more surface area in contact with the toothed pulley's which i would think would translate to a stiffer drive system.
I did some rough sketches to see what kind of footprint it would have and it seemed pretty compact  doing a 3 to 1 reduction with 3mm pitch belt. roughly 4.5 inched by 7.5 inches.

Try this, by far the best belt drive system

that kind of system solves the surface area contact so you get the most out of a belt, but it does not look to be a reduction from what i could tell. The idea i have could be configured to work the same way though.

when you get into the servo side of things the encoders are a lot better than what you find on these cheap closed loop steppers and the reduction is less of a big deal as long as the motor can do it[s job.

for what i built i have far more potential speed than space to ramp up to my top end speed so a 3 to 1 reduction would land me in the 4,000 micro step range with a .0002 resolution. one other thing would be the extra torque on the X axis which is powered by a single motor. the tandem axis has a lot more grunt with 2 motors.

tommylight wrote:

Try this, by far the best belt drive system

I agree. Servobelt is a really clever idea. I have designed a few systems that stole the idea (but not built them), Including one that used a belt mounted on an arc for a rotational axis. 

i have seen some rotation reductions with ring gears and arc tooth belts that looked interesting. i was looking at size requirements and it is pretty compact and low profile but it's only around a 6 to 1 reduction. my thought would be plus 2 axis configurations or robotic arms having a use for something like this. The problem i see is on the programming side with CAM is the software being so expensive beyond the 3-axis hobby use Cam i use at home.

The commercial 5 axis CAM on average is probably somewhere in the ballpark of 10K per year which is out of reach for most on a hobby level.

machinedude wrote:

i have seen some rotation reductions with ring gears and arc tooth belts that looked interesting. i was looking at size requirements and it is pretty compact and low profile but it's only around a 6 to 1 reduction.

You could consider planetary gearboxes. These are not expensive out of China,
We wanted to use a 5:1 gearbox on a retrofit recently but we had to keep the original mounting geometry to a NEMA23 motor.
WUMA gears did a custom version with an 8mm dia shaft (usually 14mm) and a custoom shaft length. They charged an extra $10 for that but the total was still only USD $77 per gearbox. We bought 3,