J's Build

Mostly Printed CNC - MPCNC Your Builds
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Made some modifications to make it more rigid as aluminum and carbon fiber are materials of choice here.

Corner block I lowered nut trap, so I can get a little more tension on it before the PLA breaks.
Middle Z I made taller and longer also has the brace across the top. Z flex seems to happen here alot.
Milled some 3mm aluminum nema brackets on it(made on this machine), as the existing PLA ones couldn't handle the tension.
Extended the Roller F lock out to try and minimize gantry flex, keep it square. Plus the roller locks always broke
Changed to a 15HDT belt system, has a steel ply layer. To much wobble in the 6mm GT2 belt, which added to the chatter
Using 3 x TB 6560 3amp, two in parallel to running full amps on X/Y
Used supplied RAMPS 1.4 on a i3 Prusa build
Using GRBL 0.9 on Freetronics Arduino
Cheap 400W spindle, I dont recommend as its not quite powerful enough.
Using 2 flute HSS endmil 2mm-6mm

More pictures here
Thingiverse link

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Very interesting heavy-duty mods! I’ll definitely consider some of these if I ever get into milling aluminum.

What does the brace on the z tower look like?

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Z tower looks the same, but there is a heavy duty one that Ill probably do on next replacement

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Awesome, inspiring build! I might have to try some of your modifications eventually. I’d mostly like my machine to be a CF/aluminum sheet cutting workhorse one day.

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Oh, I guess I misunderstood the original description. What does this part look like?

Middle Z I made taller and longer also has the brace across the top.
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This is my Middle Z, Not the Motor Top mount which is what I thought you were talking about
Extended Middle Z

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I tried it alted, although great its a middle Z. If your getting chatter you should try my middle Z

Here what happens even when you tighten up real tight (see pic)

Screen-Shot-2016-02-21-at-9.06.52-AM.png

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So by bridging the gap on that old piece you are taking away the ability to adjust the tension on the z axis rails. If that was causing you chattering you should have been able to tighten the long bolts to help that out.

The new , currently recommended, part actually ties the 2 half of the middle assembly together in 3 places instead of just the one. The increased rigidity significantly when we started using it, it also allowed for much larger tools as they didn’t sag.

You should try the new part, you need 2 of them instead of 4.

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I did what you suggest with the bridged two piece middle Z. I even over tightened to the point of the pla being munched, tearing. Maybe its just the IE version that suffers from this problem, as the bore size is bigger(less plastic wall thickness). Either way if you grab the one of the Z poles and pull on it you will see the middle Z problem I am talking about(where the middle Z opens, even when over tightened)