X Axis belt-better way to clamp?

[AbuMaia]

Interesting design Dave. How springy is the belt in that configuration?

[PyramidDave]

I can not take credit for the design, I just modified someone else's design to fit my needs. If you mean does it move it all, it does not. It is quite tight. I am using this same idea on a Y-bed clamp on the Y-bed I am designing & I do not think it even needs screws to hold it in place.

[PyramidDave]

I was checking this design with where the aluminum extrusion is relative to the holes that mount this part to the x-carriage. I do not this this will line up properly with the original wooden x-carriage or the modified plastic version because those bolt holes are lined up with where the top of the belt comes across. With this plastic belt clamp, those holes should probably be about 4.5mm lower on the carriage. I can certainly lower those holes on the plastic x-carriage, but will not work on the original wooden part.

[printbus]

I was checking this design with where the aluminum extrusion is relative to the holes that mount this part to the x-carriage. I do not this this will line up properly with the original wooden x-carriage or the modified plastic version because those bolt holes are lined up with where the top of the belt comes across. With this plastic belt clamp, those holes should probably be about 4.5mm lower on the carriage. I can certainly lower those holes on the plastic x-carriage, but will not work on the original wooden part.

Yeah, coming up with an alternative for the x-axis belt mount is a challenge because of how close to the v-rails the OEM belt mount bolts go. A problem with lowering the belt tie points is that it offsets the tie points from being aligned with the belt path on the x-idler bearings or the x-motor. The effect of this misalignment would be most pronounced on the x-idler side since the x-carriage gets closer to the idler than it does the motor, and since most of us already start with a misalignment on that end by adding the thickness of an idler pulley to the idler bearings. Depending on how much the belt ends are lowered, the misalignment can lead to a pretty hefty angle on the belt as the x-carriage approaches the x-idler. That angle could lead to the x-carriage getting tugged upwards a bit, and triangle math would likely suggest the x-axis steps per mm calibration would be affected at the very extreme end of travel as well.

[PyramidDave]

I took another look at this design to see if I could keep it better with space of the 2 extrusions & this is what I came up with. I would have to modify the hole pattern of plastic x-carriage design to make this work. See if you think this would work. The belt comes into the clamp horizontal, then I dip it down to clamp it. The top of the clamp in this setup would be about 2mm below the inside of the aluminum by my calculations. In the 2d screen capture, the extrusions are gray & the belt is shown in black.X-CarriageBeltClamp_rev11.jpgX-CarriageBeltClamp_rev11_Scad.jpg

[printbus]

Seems like that would be better, yes. Anything that keeps the entry point of the belt as high as you can. There's a nice simplicity to that concept.

In the early design stage of my x-belt mount that rhonal89 linked to, I was thinking of doing something similar as far as having the belt enter high and dip lower where it'd be easier to deal with a tie point clamp. I wasn't sure, however, what if any angular/twisting forces that would create so I kept looking for an idea where the clamp point would be as high as possible. It could be that any of these ideas would work fine with only subtle differences - I just tend to avoid possible concerns where I can.

[PyramidDave]

Here is what I came up with seems to work well for me. http://www.thingiverse.com/thing:861339
I have 3 versions of this, rev17, rev18 & rev19. Rev 18 is 1.5mm higher connection than rev17 & rev19 is another 1.3mm above rev18. If you are using that plastic pulley over the idler bearings, rev19 is probably the best of these 3 versions to use.

[lakester]

It so happens over the past couple of days I've been reviewing the options in this "category". Now if I can just bring myself to bring the printer down for awhile for updates, instead of printing semi-useful-non-printer-part stuff...

Question to PyramidDave: which CAD tool are you using?

[PyramidDave]

I know what you mean about taking the printer apart. I just took my the X-axis assembly apart to replace the X-motor plate & X-Idler plate with the plastic parts & also change the anti z wobble and backlash mount. I also changed this X-belt clamp to my newest version. I see a couple of small things I could change with X-carriage motor & Idler plate now that I installed them. Looks like they are going to work ok though.
I used to be a CAD operator using AutoCAD & their related products. I now use some free software for the most part. Draftsight for drawing the basic 2d designs. I use TurboCAD for converting STL files to DWG so I can use them in Draftsight. I also use TurboCAD for doing the 3d extrusions along a path since that has been the simplest way for me to do that. I then use openscad for putting it all together. I use blender occasionally for cutting down the detail on STL files I find on the Internet that have way too much detail in them. I also wrote visual basic program that I copy & paste the polyline 2d data from Draftsight to create linear extrusion commands in openscad. I find this to be faster than using dxf files imported in.

The visual basic program converts X,Y pairs in polylines to X,Y pairs like openscad uses, which looks like this:
X=0.00 Y=0.00 Z=0.00
X=0.00 Y=5.50 Z=0.00
X=10.50 Y=5.50 Z=0.00
X=10.50 Y=0.00 Z=0.00
To data that looks like this:
Ht = 6;
module PlineExtrude()
{
linear_extrude(height = Ht, center = false, convexity = 10)polygon(points =
[[0,0],[0,5.5],[10.5,5.5],
[10.5,0]]);
}
PlineExtrude();

[lakester]

Thx Dave, lotsa good info!