Fitting a Drive Belt on a Printer Bed, Easiest Method?

[andyF5LHE]

Been trying to figure out which toolset is the best for this. The length of the belt cut is 800mm (x6mm/wide x 6mm/tall) long. I have a 300x300 bed. Can't print a circle, strips with connectivity would have weakness, what about some sort of connected spiral/coil?

Tried my hand at just pathing it out with sketch lines then filleting and a sweep but getting the length to connect right is a real hassle; even then I'm not 100% sure my line is the length it should be with the arcs..

Anyone have a thought I'm missing on doing this easier?

[g-andresen]

Hi,

maybe MST sketch tools  can help:

günther

[andyF5LHE]

Ah, no mac version unfortunately. That would at least help me know if my length is right. Good thought!

[g-andresen]

Hi,

for an easy belt run, you could solve it like this. It would also have to be possible to implement it for a different arrangement.

Calculate distance for belt pulleys

günther

[etfrench]

A circle with a diameter of 254.647908947033mm will have a circumference of 800mm which should fit on a 300mmx300mm bed

[andyF5LHE]

Sorry, I was just giving a generalized large number, the real size is 958.55mm which is 305.211 -- so I exceed it by just a bit to be a perfect plot.

[etfrench · Accepted solution]

Draw a rectangle slightly smaller than your print bed. Fillet the edges with an arbitrary radius between 95mm and 100mm.  Calculate the length of the curves (2*PI*Radius). Subtract that from 958.55.  Divide that by 4.  Set the length of the straight lines to the result.

If you want to print different size belts, move all of the calculations into user parameters.  The above will work for any belt up to 1200mm (except that would have very square corners 😀 ).

[g-andresen]

Hi,

i have the impression that you have not dealt with the process shown in the screenshot (#4/8), otherwise you could calculate the distance(s) in the parameter table with the real length and the involved arcs of the rolls.
The procedure can also be used with other arrangements such as those of @etfrench .
@etfrench Using MST Sketchtools is not an option because the TO uses a Mac.

günther

[etfrench]

I actually used Excel to do the calculating.  MST Sketchtools was just used to show the results.  In any case, using parameters can eliminate the manual calculating.

[andyF5LHE]

Working through the details now. Lost power and internet for a few days due to area tornados. Let's see how I can apply all of this now that I can actually work. 😄 Thanks for the pointers.

edit: oh yea, definitely not familiar or comfortable at this time with user parameters. I see the benefit immediately.

[andyF5LHE]

Ah! Thanks for this. My approach was far too convoluted I see now for what is pretty straight forward. I do have a few other belts to do and this gives me a template/preference setup to get them done much quicker.

[andyF5LHE]

Stupid question, but when measuring the radius, am I measuring that into the center of the curve? or into the flat?

[andyF5LHE]

I've been trying to understand this a bit better because I realized I made a belt that fit due to stretching properties of TPU but wasn't the right way to solve the problem (I basically forgot a step, hah.)

Here's a square fit to 275mmx275mm

If I get the radius of the corner it's 150.514mm

2 × Pi × 150.514 mm = 945.70mm

Now here's where I get lost, you say to take that number and subtract it from 958.55 -- then divide it by 4..

The results are pretty much null. ((958.55 − 945.70)/4) = 3.21

Where am I going wrong?

[etfrench]

You have the fillet radius set to 100mm.  Since there are four of them, you can consider the length of the modeled belt path to be a circle with a radius of 100mm plus the four straight sides.  Since you know the total length of the belt, you can subtract the circumference of the circle from the total length to get the length of the four straight sides.