Armstrong, the parallel SCARA 3D printer.
Current version is the A1. It's already capable of printing actual objects, but is very much in the prototype/alpha stage.
NOTE! The STL files may be out of date at any given time. If you want to reproduce this, use the SCAD files instead.
Concise contruction instructions:
- Print plastic parts. You need: 1 x arm11 1 x arm12 1 x arm22 1 x arm21 1 x z-carriage 1 x z-end-bottom 1 x z-end-top 1 x z-end-support 2 x circspline-spline 2 x circspline-motor-mount 2 x flexspline 2 x wave-rotor 4 x mendel-rod-clamp (from Prusa 2, not included here) 1 x mendel-coupling (from Prusa 2, the Z rod to motor coupling, not included)
Everything else except the flexsplines should print fine with 0.25 or 0.3 mm layer height. The flexspline should be printed with 0.2 layer height, 2.0 W/T parameter, one perimeter, no extra perimeters. Retract minimum length should be set to 1 mm to force retraction when infilling the teeth. Slic3r normally does full infill for the teeth regardless of the infill solidity, this is fine.
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Assemble the arms. 2.1. Left arm, middle joint, from top down: M8x50 bolt, washer, 608 bearing, arm11, 608 bearing, washer, arm21, washer, locking nut. 2.2. Right arm, middle joint, from top down: M8x50 bolt, washer, arm22, washer, 608 bearing, arm12, 608 bearing, washer, locking nut. 2.3. Final (end effector) joint, three times: M4x20 hex key bolt, arm21, 4xwasher, 624 bearing, washer, nut. The 624 bearings should run smoothly in the groove of the arm22.
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Mount arms onto the z-carriage. 3.1. For each: M8x50 bolt, washer, 608 bearing, flexspline, arm11 or arm12, 608 bearing, washer, z-carriage, washer, locking nut.
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Tighten the nuts so that there is no play but the arms move without effort.
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Insert six M4 nuts in the nut traps of the z-carriage.
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Place the circsplines on top of the z-carriage (may require some fiddling or forcing into place) and check that they mesh with the flexsplines.
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Mount NEMA17 motors in the motor mounts using M3x8 conical head (sunken) screws.
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Assemble wave drivers. In each end: M4x20 bolt, washer, wave-driver, washer, 624 bearing, washer, wave-driver other screw hole, washer, locking nut. The wave driver length is critical. The included STLs have 52.75 mm total outside dimension. This should work fine at least initially. When the drives have been run for some time, wave drivers with larger dimensions may be needed (in 0.25 mm increments) to get rid of backlash. The drivers are for motors with 20 mm shafts with double flats. Other types of motors may need redesigned drivers.
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Assemble the motor mounts into the z-carriage, 6xM4x20 bolts and washers are needed. The wave drivers should insert nicely into the flexsplines when the motors are rotated a bit by hand when inserting them.
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Insert 4xLM8UU linear bearings into the z-carriage, use M3x20 screws and nuts for each.
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Construct the frame. Anything L-shaped and at least 80 mm wide will do. Just mount the z-end parts with M8 bolts. If the L-part is sufficiently supported, the z-end-support part may be omitted. The height can be freely chosen.
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Mount the 8 mm smooth rods with the bar clamps and M3x24 bolts, nuts and washers. Place the z-carriage at the same time and check that it travels freely on the rods.
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Insert a M8 nut into the z-carriage and screw in a M8 threaded rod for the Z travel.
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Mount the Z motor with M3x8 sunken head screws and attach it to the M8 threaded rod with the coupling.
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Place the print bed in the frame. The print area is 200x120, with the nearest Y position being 82 mm from the centerline of the arm base joints.
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Mount the extruder. The arms will accept a groove mount extruder with small diameter. Tested with J-Head Mk V-b. The mounting bolts have the standard 50 mm pattern. (M4 bolts)
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Do the electrical connections and upload the Marlin SCARA firmware.
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The printer should now be ready for use.