K8200/3DRAG dual motor Z axis with M8 rods

thingiverse

Yet another tweak for the K8200 Z-axis to stop wobble, this time using standard M8 stainless steel rods and an anti-backlash system featuring regular M8 hex nuts for those who already have a different stepper motor and flex shaft coupler on hand and want to make minimal modifications. No need to adjust the steps/mm value and while this adjustment may not significantly enhance print quality, it at least prevents the M8 threads from wearing down by distributing the weight of the extruder arm (on the original design all its weight is only supported by one(!) M8 hex nut, which isn't well-suited for linear motion systems). Similar to floyd871's design, mine utilizes the following components: Motor holder: http://www.thingiverse.com/thing:167650 Upper Z-Carriage Holder: http://www.thingiverse.com/thing:175137 To document all the modifications I've made on my K8200 visit: http://www.thinkering.de/cms/?p=469 and http://www.thinkering.de/cms/?p=534 Instructions Besides the printed parts you will require: -another M8 stainless steel rod. Its material is tougher than that of the steel nut and will slice through irregularities. - An M4 threaded rod for cutting into pieces and attaching the anti-backlash nut box to the arm extension - 8 M4 nuts and washers -An M5 threaded rod for cutting into pieces for mounting the arm. Then you'll also need 8 M5 washers and hex nuts. Alternatively, six 20mm M5 bolts will suffice -an "M8 spring" you can find in hardware stores. Look at the photo above to see which one I acquired. Cut a piece of about 3cm and bend the cut end away from the center so that it doesn't get caught between nut and threaded rod while rotating. - Five M8 hex nuts (two for mounting inside the box, two for securing the axis on top printed mount [use washers as well], and one optional one for counter tension on the flex shaft coupler). - Four short countersunk M3 bolts with washers and nuts to assemble the printed motor mount. - Four short (10mm max.) M3 bolts to attach the motor to the mount - Four 10mm M5 bolts to mount the motor mount to the frame. Two can be salvaged from the original Lm8UU linear bearing holder at the end of the Z-axis arm -a total of eleven square M5 nuts for the extruded profiles (six for the arm extension, one for the top bearing holder, and four for the motor mount. - A NEMA 17 motor -A 5->8mm flex shaft coupler -An 608z ball bearing for the rod -Lubricant for the rod Assembly advice: -Don't make the anti-backlash assembly too tight and ensure it moves smoothly along its entire length before attaching. -Increase the motor current a bit. I set my motor voltage to 670mV, which worked fine. -Connect the second motor in parallel to the first one. For the motor I had on hand, the following modification allowed it to spin in the right direction: Flat cable -> Motor wires: Blue -> Green Green -> Black Yellow -> Red Orange -> Blue Once everything is assembled you can print and attach the M5 and M4 caps to the bare threaded rod endings.