Another Belt Configuration

[Max Metz]

Thanks for a very informative reply Improbable Construct.

Your detailed response has given me much to think about, slowly I am getting a picture of all the things to consider.

Tonight I tried to put all the bits together; maximizing the x-axis travel, keeping the belts low, getting the greatest surface area of the pully covered with the belt - all without interfering with the other functions of the machine.

This is where I am at so far, using Edward's single idler configuration with the front idler in the existing position, combined with your lowering of the rear idler. Instead of shaving off the steel plate, perhaps removing some of the aluminium on the x-axis Makerslide plate would be easier - both sides of the plate for a dual belt Y axis configuration.

To allow extra latitude when placing the rear Idler wheel , adding 3 x 1mm washers to the idlers brings them out clear of the Makerslide V-wheels, this is a little of Tom and Edward's idea of using the V-wheel bolts - it reduces the amount of interference from the belt on the overhead x-axis assembly (the depth of cut needed into the overhead aluminium plate, not the length ) and as such keeps the maximum y axis travel at the rear without having to cut into the aluminium plate above too much.

Here are tonight's drawings.

MyBat Shapeoko 003 Alt Belt setup 1.jpg (143.05 KiB) Viewed 455 times

MyBat Shapeoko 003 Alt Belt setup 2.jpg (85.77 KiB) Viewed 455 times

All this assumes a belt thickness of 2mm or less, I couldn't find a any reference to the belt thickness. Best regards.

[Max Metz]

Disappointed about cutting into the aluminium plate and the tight fit in my last effort, it occurred to me today that it might be better to move the problem to where there was more space and access, so when I got home this afternoon I drew this up.

MyBat Shapeoko 004 Alt Belt setup 1.jpg (195.91 KiB) Viewed 433 times

The bottom two idlers keep the belt below the pulley and dictate where the action is (where the belt feeds in and out), the top idler acts with the other two to get the belt in a position where it will have greatest contact with the drive pulley - two tasks divided between 3 idlers.

MyBat Shapeoko 004 Alt Belt setup 2.jpg (149.86 KiB) Viewed 433 times

Using the front V-wheel bolt, lengthened to around 33mm+ sets one corner of an equilateral triangle with decent space (around 5mm) between the idlers while allowing easy access to the arrangement from the front and simple hole drilling of the two new holes in the steel plate.

To locate and drill the two new holes; perhaps cnc an mdf template with the existing front idler hole and front v-wheel together with the two new holes, bolt the template to the steel motor plate using the existing two holes then use the mdf template as a jig to drill the two new holes.

This arrangement also needs a new 11mm nylon spacer for the rear and top idlers to match the idler on the V-wheel bolt, perhaps a 3/4" nylon spacer cut to 11mm with a small $10 tube cutter.

MyBat Shapeoko 004 Alt Belt setup 3.jpg (116.54 KiB) Viewed 433 times

The arrangement adds quite a bit to the cutting area, both sides with a dual pulley motor/shaft y-axis set-up. Still have to work out how to secure the belt either end of the machine.

So in total, 3 new longer bolts (33mm+), two new holes, 1 additional idler assembly and two additional 11mm nylon spacers (cut from 2x 3/4" ones).

[JCPhlux]

hey that looks good. Now I just have to find someplace to buy the extra idlers and belt that don't charge an arm and a leg for shipping.

[edwardrford]

Wow Max, I can tell you put a lot of time and effort into coming up with the configuration.

Do you think the idlers you have in the triangle formation need to be a perfect triangle? It seems that as long as the top idler is low enough to provide an exit path low enough for the belt to not interfere with the carriage, it should work. Now, with that said, I'm all for symmetry and would probably try to get the idlers in a triangle as well.

Regarding the 'how to clamp the belts down: I think you could use a modified version of Rob's belt clamp, like @improbable construct is using.

mbc.jpg (88.79 KiB) Viewed 425 times

Hardware
Both the idlers and belts can be had from inventables.
They both say 6-week leadtime right now. I'll try to find out what the current status is on both parts.

Smooth Idlers: https://www.inventables.com/technologies/smooth-idler-wheel-kit
MXL Belting: https://www.inventables.com/technologies/open-ended-neoprene-belt?recommended=true

-Edward

[JCPhlux]

yeah 6 weeks plus $8 shipping is a bit extreme. If I had a need for more parts I could spread that cost but for one or 2 parts is is allot.

[Max Metz]

Thanks John.

When you are on the other side of the ball like me, $8 shipping would be a blessing! lol I might ask Inventables if I buy the extra idlers (4 in total for both sides) and belt (1 extra Y axis length) from them would they would throw them in the box with the Full kit I ordered, no 48 in the second round. Might save a bit of postage.

[Max Metz]

Thanks Edward, though most of the work and information came from right here; especially from Rob, Tom and yourself.

As for symmetry in the triangle, I had to stop myself from making it a Golden Triangle - 1 wide to Phi high. lol

Thanks too for the source of the parts mate and for pointing me in the direction of Rob's neat belt solution. Like you, Rob has some fine ideas, plus the ability and nerve to put them into practice. Robs clever and successful moving of the idlers was the catalyst for my interest, I just tried to develop his already working solution.

ps. I am assuming that by Rob you mean Improbable Construct, because really this is his idea and the credit should go to him.

[Tom Smith]

I would like to take this opportunity to suggest that we set up a forum topic listing alternate sources for the parts we need, especially for those who are not in the U.S. that might benefit from more local suppliers.

Along those lines, I would also propose that the parts list in the wiki be populated with specific data pertaining to each part?

For example, in addition to "M5 - 4 Feet of belting, available at Inventables", add "Open ended neoprene belt, 0.08 inch MXL, Width: .25 inch"

I will try to do this one myself, but having clearer part specs in the wiki would help if/when Inventables is not an option. Hopefully this isn't stepping on anyones toes, I know that an objective with ShapeOko was to have only a few suppliers...

Tom

[edwardrford]

That's a good idea Tom.

Yes, one of the objectives is a low number of suppliers. However, another objective is availability, which IMO trumps the #of suppliers objective. After all, if the parts aren'ta vailable, nothing else matters

Edit away.

-Edward

[Max Metz]

I should have mentioned that the belt thickness I am still assuming is 2mm, could someone check this on their machine as if the belt is too thick the configuration will not work - it looks pretty thick in Edward's link. Thanks.

Edit: I imagine the pitch is the distance between the lines on the belt not the thickness.