Help with the Design

Community General Discussions
6

I get it now. We have to run both motors at the same rate for above to hold true, right?
Thanks for your help!! :slight_smile:

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??

7

Correct; if you want the bevel gears to NOT turn, you need to operate both motors in the same direction.

8

Hi Benson,

  1. I have found a motor. (Nema 17)
    canadarobotix.com/robot-part … 0steps-rev

  2. Big Easy Driver
    canadarobotix.com/sparkfun-b … v-2a-11876

  3. 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.

  1. 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

9

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)

10

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?

i.imgur.com/ILZpkkM.png

11

The design looks like it’s coming together! In all likelihood yes, the motor would probably burn. Can you add a counterweight?

12

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).

i.imgur.com/JIzQZ1R.png
i.imgur.com/ZKJef3q.png

13

How about a counter balance, or a counter spring?

Alan KM6VV

14

Careful with a spring though because the force it exerts depends on the extension (i.e. not constant).

15

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?

16

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.

17

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

18

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.

19

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.

20

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.

21

If the belt is slipping at any point, you need a belt tensioner which has teeth (and ideally a spring to provide force).

22

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. :slight_smile:

23

Could you upload the video to your YouTube page and make it public?

24

youtube.com/watch?v=OZEr6aPQrXg

I’ll make a better video later on. The stepper driver just fried this afternoon.

25

It seems to be working well actually - not sure what you need advice about?