A new way to think about frame size and angle

[MeticulousMaynard]

@aluminumwelder

your sled weight changes from 38 lbs to 20 lbs. Not sure if that is a mistake or if you will be using a new lighter sled.

Good eyes. It is intentional. My current setup is certainly heavy. I found when I was calibrating initially, I got much better results from a heavy sled. This is probably mostly because this was before chain sag calculations were in the firmware, so eliminating as much chain sag as possible made it so the machine and the math lined up better. Also, with my shorter top beam, I got much more width out of the cut area with the heavier sled. I never really bothered changing that, given the scope of the upgrades I’m going to be doing relatively soon.

The Meticulous Z-Axis is a much lighter sled overall, and I’m going to see if it runs fine with just the weight of the assembly or if it will need additional weight as well.

@aluminumwelder

higher top beam gives improved top center performance.
wider motor top beam spacing gives improved bottom corner performance.

Of the two, I would prefer wider over taller. But, of course, getting the full performance over a 4 x 8 would be mint!

@dlang

if the forces required along the top are too high, a horizontal cut along the
top will tend to droop a bit (and hook up at the end commonly)

That sounds almost exactly like the type of deviation I was seeing when I was messing around with the max feedrate way back when.

@dlang

it’s possible that lowering the max force will make it less likely to wear out
the gears (pure speculation)

For what it’s worth, my machine was built from a Kickstarter kit. If I remember correctly, the gears where of a higher quality then, but I could be wrong.

@dlang

If you get the max force low enough, you may be able to try different
motors/sprockets and get more speed

It’s almost like you’re reading my mind! I did get the larger sprockets that you recommended in the thread I linked above. Combine that with the acceleration planning in the Due and I just might stand a chance using 2 flute tooling.

@dlang

But most of the trouble that we have seen has been in the bottom corners where
the gravity force is the limiting factor. In extreme cases, the sled doesn’t
move while chain is released (slack accumulates) and then the sled jumps,
cutting unevenly, rounding corners, etc.

That is especially a problem for my current, shorter top beam. Accuracy drops off pretty quickly outside of the center 4’ part of the bed.

@dlang

So, without lots of testing and reports, I focus primarily on increasing the
minimum force, and just check that the max does not get too high.

So what you’re saying is that, once again, I’m going back into testing mode? xD

What I am taking away from this is that it would be greatly beneficial to modify my frame to be able to handle up to 30" of Y offset. Maybe even more, depending on the math.

That’s interesting. I hadn’t really taken note of the minimum force before, but that makes a lot of sense. I’ll have to play around with the spreadsheet a little more and see what I can come up with. Do we have a threshold for how high is “too high” for the max force? When the spreadsheet makes the cell red? Are we in the land of speculation, and just not have enough data right now to know that?