A few months of inactivity left the CNC-3018XL table parked in its homed position where the gentle-but-inexorable pressure of the switch lever displaced the foam holding the plastic actuator tab on the X-axis bearing enough that it would no longer operate reliably:
Putting foam tape in a highly leveraged position produces the same poor results as in finance.
The fix requires reorienting the switch so a solid block on the bearing can push directly on the actuator lever:
The block must curve around the bearing to give the tape enough surface area for a good grip:
The solid model for the new X-axis mount looks about like you’d expect:
I increased the home switch pulloff to 2 mm, although it’s not clear that will make any difference in the current orientation.
The OpenSCAD source code as a GitHub Gist:
| // 3018-Pro Mount for Makerbot Endstop PCB | |
| // Ed Nisley KE4ZNU - 2019-07 (using OEM machine axes) | |
| // 2022-02-02 rotate X block (after renaming axes to match new layout) | |
| /* [Build Options] */ | |
| Layout = "Show"; // [Build, Show] | |
| /* [Hidden] */ | |
| ThreadThick = 0.25; // [0.20, 0.25] | |
| ThreadWidth = 0.40; // [0.40] | |
| function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit); | |
| Protrusion = 0.01; // [0.01, 0.1] | |
| HoleWindage = 0.2; | |
| ID = 0; | |
| OD = 1; | |
| LENGTH = 2; | |
| //- Shapes | |
| // Basic PCB with hole for switch pins | |
| // origin at switch actuator corner, as seen looking at component side | |
| SwitchClear = [15.0,5.0,2.0]; // clearance around switch pins | |
| SwitchOffset = [12.5,9.0,0.0]; // center of switch pins from actuator corner | |
| PCB = [26.0,16.4,2*SwitchClear.z]; // switch PCB beyond connector, pin height | |
| //XBlock = [PCB.x + 10.0,PCB.y,20.0]; | |
| XBlock = [PCB.x,PCB.y,10.0]; | |
| XBearing = [10.0,26.5,28.5]; | |
| XPin = [10.0,20.0,10.0]; | |
| module XMount() { | |
| if (false) // side-push switch tended to slip | |
| difference() { | |
| translate([-10.0,0,0]) | |
| cube(XBlock,center=false); | |
| translate([0,-Protrusion,10.0]) | |
| cube(XBlock + [0,2*Protrusion,0],center=false); | |
| translate(SwitchOffset + [0,0,10.0 - SwitchClear.z/2]) | |
| cube(SwitchClear + [0,0,Protrusion],center=true); | |
| } | |
| else { | |
| difference() { | |
| cube(XBlock,center=false); | |
| translate(SwitchOffset + [0,0,XBlock.z - SwitchClear.z/2]) | |
| cube(SwitchClear + [0,0,Protrusion],center=true); | |
| } | |
| translate([1.25*XBlock.x,0,0]) | |
| difference() { | |
| cube(XPin + [0,0,XBearing[OD]/4],center=false); | |
| translate([-Protrusion,XPin.y/2,XPin.z + XBearing[OD]/2]) | |
| rotate([0,90,0]) | |
| cylinder(d=XBearing[OD],h=XPin.x + 2*Protrusion,center=false); | |
| translate([-Protrusion,-XPin.y/2,XPin.z]) | |
| cube(XPin + [2*Protrusion,0,0],center=false); | |
| } | |
| } | |
| } | |
| YBlock = [PCB.x,PCB.y,5.0]; | |
| module YMount() { | |
| difference() { | |
| cube(YBlock,center=false); | |
| translate(SwitchOffset + [0,0,YBlock.z - SwitchClear.z/2]) | |
| cube(SwitchClear + [0,0,Protrusion],center=true); | |
| } | |
| } | |
| ZBlock = [PCB.x,PCB.y,6.0]; | |
| ZPin = [20.0,10.0,5.5]; | |
| module ZMount() { | |
| difference() { | |
| cube(ZBlock,center=false); | |
| translate(SwitchOffset + [0,0,ZBlock.z - SwitchClear.z/2]) | |
| cube(SwitchClear + [0,0,Protrusion],center=true); | |
| } | |
| translate([1.25*ZBlock.x,0,0]) | |
| difference() { | |
| cube(ZPin,center=false); | |
| translate([ZPin.x/2,-Protrusion,4.0]) | |
| cube(ZPin + [0,2*Protrusion,0],center=false); | |
| } | |
| } | |
| //- Build things | |
| if (Layout == "Show") { | |
| translate([0,XBlock.y,0]) | |
| YMount(); | |
| translate([0,-XBlock.y/2]) | |
| XMount(); | |
| translate([0,-(ZBlock.y + XBlock.y)]) | |
| ZMount(); | |
| } |
The Smell of Molten Projects in the Morning 
I have had similar problems to yours and I have included a couple of raised bosses to marry with the holes in the pcb to lack everything into place – this may also give the tape a better chance since its no longer acting in shear, only in tension.
Food for thought?
Regards,
Simon
I’d surely go for shiny screws, rather than tiny printed posts, but it certainly seems like a good way to keep the tape from sleazing away under load. In this situation, though, it was the (mostly) unsupported tape under the actuator tab: a total botch.
Thanks for the suggestion!