Only one side of the timing belt would touch the sprocket (see image attached).
Hi!
When there is a motion in Y axis, the z axis belt and internal gear (black) are kind of locked to each other and will move along the y axis.
So, only when you supply power in the z axis motor, the black gear will rotate.
Did I understand this right??
Since the earlier reply is bit conflicting. When the platform is moving in Y direction, we’d not require second motor running as well (if black gear and white belt are locked in place while moving in y direction)?
Motor 1: Y axis
Motor 2: Z axis
Motor 3: X axis (not really discussing this)
Motor 1 is located at one end of the rig and connected to a timing belt (#1), and the traveler is fixed to one location on this timing belt.
Motor 2 is located at one end of the rig and is also connected to a separate timing belt (#2)
On the traveler, there is a sprocket which meshes with timing belt #2 (ONLY at the top, NOT at the bottom).
This sprocket is connected directly to a bevel gear (#1), and this bevel gear turns a second bevel gear (#2) which is connected to a lead screw.
Therefore if only motor 1 rotates, this causes the traveler to move along the Y axis. Since timing belt #2 is not moving, the sprocket rotates, causing the lead screw to rotate as well.
If motor 1 AND motor 2 rotate in the same direction, the sprocket’s position with respect to timing belt #2 stays the same; therefore the sprocket will not rotate, even though the traveller is moving.
If motor 2 ONLY rotates (motor 1 is fixed), then the timing belt moves, forcing the sprocket to rotate.
I get it now. We have to run both motors at the same rate for above to hold true, right?
Thanks for your help!! 
I’m very bad at visualizing.
I’ll make a detailed model.
I’ve looked at several stepper motors in the market, but would you be able to help pick the parts, later on??
Correct; if you want the bevel gears to NOT turn, you need to operate both motors in the same direction.
Hi Benson,
-
I have found a motor. (Nema 17)
canadarobotix.com/robot-part … 0steps-rev -
Big Easy Driver
canadarobotix.com/sparkfun-b … v-2a-11876 -
Shaft diameter on NEMA 17 is 5 mm, so I’m looking for a timing pulley and belt.
robotdigg.com/product/9/GT2- … h-5mm-Bore
The timing pulley is metallic since the motor is situated outside the experiment box. I’m finding the end pulley (plastic) on sdp-si.
It says this pulley can support up to 7mm belt width.
Timing Belt: robotdigg.com/product/10/Ope … h-GT2-Belt
Will this motor and belt be able to sustain the load? The weight will be under 1 kg.
- I have changed the design a little bit and put the bevel gear system underneath the platform.
i.imgur.com/Z4bgQQT.png
i.imgur.com/yVVokqV.png
but I couldn’t find the bevel gear set online (in Plastic). Do you have any recommendations?
Edit: Found this store selling bevel gear set, but the vertical gear doesn’t have gear features to place the belt.
teausa.net/Portals/0/uploads … r-Sets.pdf
Sincerely,
Kev
68oz-in and the timing belt is roughly 7mm radius (0.25in?), meaning it can sustain a load of F = T/R = 272oz (17 pounds)
Hi!
I’ve a question regarding the vertical motion. I’d like to avoid the free fall situation. For example, the slide holder will fall down due to gravity and free motion. If I supply power through motor to hold the position, will the motor burn, or is there better solution?
The design looks like it’s coming together! In all likelihood yes, the motor would probably burn. Can you add a counterweight?
The vertical slides are made of acrylic and will wight about 500 grams.
We can add counterweight, but may not have much room (1-1.5cm).
How about a counter balance, or a counter spring?
Alan KM6VV
Careful with a spring though because the force it exerts depends on the extension (i.e. not constant).
Changing the vertical slides box to this: i.imgur.com/b5A2Jua.png
I’m sure weight will be less than 250 grams.
Will the motor be able to hold whether on or off?
It should be able to hold, but keep in mind that all motors need time to cool off; so if it’s always working (to keep the traveller at a certain height), it will heat up, which will reduce its lifespan.
Hi!
I just cut the parts today and weighted them. It is going to be around ~250 grams.
I’m curious how would I be able to hold the position? By Keeping the motor on, or detent toruqe is enough? It is 2.2 N.cm. The motor for vertical motion would be always working, maybe 5 hrs a day although it may not be continuously, I’d like it to hold position for 1.5 hrs continuously.
canadarobotix.com/datasheets … GHM809.PDF
A bit of experimentation at this point, but a counterweight will always help. The motor will not last long if it’s in operation for 5 hours continuously.
Just experimented with the motor. It seems to be more than enough to hold the position when not in motion but now I am wondering if it is possible to hold the position while moving only in longitudinal direction. I agree counterweight should solve this.
Motor will not run 5 hrs continuously, 1.5 hrs continuously at the most.
Hi Coleman!
Can you help with this? The belt is slipping for vertical motion. I have tried to add smooth rod on one side to increase the tension but it still slipped.
img.ctrlv.in/img/14/08/11/53e8ed3e231ec.jpg
img.ctrlv.in/img/14/08/11/53e8ed5b8f2ef.jpg
img.ctrlv.in/img/14/08/11/53e8ed72e426b.png
Edit: I had removed belt clips before taking these pictures. That is why belt seems loose.
If the belt is slipping at any point, you need a belt tensioner which has teeth (and ideally a spring to provide force).
Hi Coleman,
Here’s the final version. The video size is bit large as I haven’t compressed it.
Thanks for your help. I’m controlling the motion with two switches.
Do you have any suggestions? The motors are little bit noisy due to improper mounting. I couldn’t find right screw length and haven’t cut the screw to avoid damaging it.
dl.dropboxusercontent.com/u/444 … 1%20PM.mov
Thank you very much for your help.