Solidworks Belt And Pulley

[Riitta Palazzo]

BeltChain Assembly Feature simulates a belt, chain, pulley or sprocket. Ithas the ability to include more than two components. This feature addsappropriate mates and relations to give you that desired rotational results. Itwill also create a sketch containing arcs and lines describing the path of thebelt.

Belt Members: In this section you can select edges of differentpulleys/sprockets which you have to mate. Multiple bodies can be selected. Asseen in the picture above, we have selected a groove edge of the first pulleyand it is correspondingly showed in the feature property manager. It also showsthe diameter of the pulley.

In the Properties section, you can give target length to thebelt, which makes a pulley change its position as per the length of the belt(you can notice the bottom pulley changed its position as we gave a target Beltlength.

Furthermore there are options to create a separate part forthe belt and to give thickness to the belt.After all this, click Ok and rotate any of theface of a pulley, you can see other pulleys rotating as per the belt, as shownin Below Picture.

2020 Update: It has been pointed out by a comment (thanks Ivanov) that the tooth profile described here, while looking close, is not within spec for a HTD timing pulley. While its probably fine for use with a quick and dirty 3d printed prototype, use of this profile may may lead to damage of your transmissions with prolonged use!

After having some trouble finding a clear guide on how to create the correct tooth profile for a HTD 5M timing pulley I have decided to create my own. This method will also work for a HTD 3M or 8M pulley, just change the pitch accordingly.

The belt has a 5mm pitch (peak to peak), a tooth height of 2.08 mm, a total belt thickness of 3.81 mm, a the tooth width is 3.05 mm, a radius of 1.49 mm and a valley radius of 0.43 mm. Note that the image below is one of many you will find online that shows an incorrect tooth profile! If you use the dimensions shown below to make the pulley in CAD it looks like that shown by SDP-SI with a flat valley.

Your reply is simply wrong. You are forgetting that the diameter was set exactly for the type of teeth dimensions from that doc sheet. So dividing 360 by the number of teeth to get the degrees between the center works perfectly. The calculation comes out spot on as I verified this.

On a curve, the peak to peak gets closer. Bend a belt for yourself and tell me if the peak to peak stays the same or gets closer, should be pretty obvious! Also, the drawings are not just some random ones by a 5 year old, but verified from the data sheets put out by the manufacturer, that should be plenty sufficient for 99.9% of applications out there for normal use.

This tutorial will cover how to design and print a pulley for a T5 belt for various shaft sizes. Although various outer diameters (OD) can be used, use one belt for all shafts for simplicity. Use a Nema 23 data sheet as a reference for the shaft dimensions [1].

Design pulleys with 16 teeth for the Moveo belts, so the tooth pattern below is appropriate. If designing a pulley with a different outer diameter, the 22.5-degree angle will decrease for larger OD and increase for smaller OD.

Sample calculation: a T5 belt has a pitch distance of 5 mm [5]. To ensure the arc length is 5 mm in a circle with pitch diameter 25.46 mm, the angle should be approximately 22.5 degrees. Use the Omni Arc Length Calculator to verify the calculation [3].

Create a cut extrusion through the entirety of the cylinder. This will create the tooth for the belt to fit into. Read further about designing pulley teeth on BrecoFlex [6]. Ideally, the pulley gap should be minimized to reduce backlash.

Create an evenly spaced circular pattern from the extruded cut in the previous step. Remember that this design specifies 16 teeth, as in Figure 4. If unfamiliar with circular patterning, the SolidWorks documentation has resources to learn it [2].

On the flat edge of the extrusion that was created, create a circular sketch and extrude cut through the entire design. The size of the hole should be 90% of whatever diameter set screw is needed. Remember that the 3D printer and the printing quality will affect small features like this. View Figures 7a and 7b as an example.

Next, increase the shaft opening slightly to make it easier for the shaft to slip in. Create a sketch on the extruded edge. Copy the pattern of the shaft opening and increase it by 0.25 mm. Now, extrude cut 10 mm. This will look like Figure 9.

Maybe something like "follow path" joint, will do? I was trying to "move" most simple examples using contact sets, but first it's a lot of calculations (even when I've made chain with zero clearance), second there still something missing in how contact sets works, there is a problem to freely rotate component. I've made a gear and I've wrapped a chain around (zero clearance), and I was able to rotate the gear for about 4 degrees, where if rotation would be equal to move it should spin without a problem.

Why I'm saying this? If we want to move chain with gears it will require to change how contact sets work, and even with that done, whole simulation will need a lot of computing. This is a reason why I think "follow path" should work, without forcing our computers.

If you want to position 2 or more timing pulleys or chain sprockets, you need to run a standard length belt or chain around them so you know the correct amount of slop to take up with the adjuster / jockey pulley. Solidworks does this rather nicely:

I appreciate that this is a fairly complex feature but you will probably need to think about how you will implement it in the longer term. In the meantime, I will either revert to Solidworks or possibly one of those pulley centre calculators. But the latter are not very accurate.

The first feature would at least calculate the length of the chain needed between two sprockets. Since a chain has to be some multiple of links (ok, you can have a half link joiner too) knowing that in the design phase is nice.

The next feature would be knowing how much flex would be in a chain path. For a given chain and pair of sprockets, the combination of links will have some degree of excess unless the axle spacing was 'perfect'. If the slop of the chain goes past some point, you then add a chain tension device to the system so the chain can't jump off.

A trickier part for simulation would be giving some range of stretch to the chain after that initial length. Again the goal would be knowing if some sort of adjustment is needed and how much adjustment would be needed.

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