TriMatical
Release status: preliminary
TriMatical - yet another linear delta printer project, design goals where mainly scalability and use of mostly commercially available components. Aluminum framing is well covered industrially, one can choose between many flexible profile systems, exploiting mass produced quality, relative cheapness and global availability. Overall design is loosely based on previous nice examples of linear deltas, namely the Kossel variations, that are generally using less rigid and smaller extrusions. Structural frame is made from MiniTec profile (45x32mm, 45x45mm can be used), Power-Lock fasteners and custom prismatic 60degree angle centerpieces. Frame volume should scale to 2 cubic meters without any problems.
Contents
Part drawings
- Solid Edge model up on GrabCAD
- Solid Edge model up on GitHub
- Kinematics video on YouTube
- Fastener locations in frame
- Frame stress analysis - 500N sideways FEA
Design highlights
- Linear delta printer
- Minimal number of custom components
- Relatively high stiffness
- No plastic frame components
- GT2 belt running on smooth side reducing belt interference
- Scalable to 2 cubic meter volume
Bill of Materials
Minitec components
- 3x 800mm MiniTec 45x32mm (20.1055)
- 6x 155mm MiniTec 45x32mm (20.1055)
- 6x MiniTec Power-Lock fasteners (21.1018 or 21.0818) [big 45x45mm frame with additional 12x Angle sheets (21.0018)
- 21x M3 square nut with position fixing (21.1309/2)
- 15x M6 square nut (21.1330)
Fasteners
- 6x ISO 7380 M8 25mm round head internal hex bolt (central triangles)
- 6x DIN 912 M6 20mm internal hex bolt (carriage physical end stops)
- 9x DIN 912 M6 16mm internal hex bolt
- 6x DIN 912 M5 12mm internal hex bolt
- 6x DIN 912 M3 55mm internal hex bolt
- 50x DIN 912 M3 12mm internal hex bolt
- 3x DIN 7991 M3 12mm bolt (countersunk, bearing plate fastener, directly under GT2 motor pulley)
- 3x DIN 912 M3 8mm internal hex bolt (GT2 belt clip fastener)
- 6x 60mm M3 threaded rod
- 3x 40mm M3 threaded rod
- 40x DIN 985-8 nyloc nut (3.8mm thickness)
- 6x washer DIN 125 M8 (central triangles)
- 3x washer DIN 9021 M6 (big belt idler)
- 9x washer DIN 125 M6 (big belt idler and motor mounts)
- 6x washer ISO 7092 M5 (5.3/9.0 small O.D. also DIN 433, small belt idler)
- 50x washer DIN 125 M3 (optional)
Custom parts
- 2x central 60 degree angle prisms - aluminum or steel (reinforced with 4x torsion locking circular disks in bigger frames)
- 3x carriage plate - aluminum (can be plastic, printed)
- 3x carriage plate belt surface - aluminum (can be plastic, printed)
- 3x toothed belt clip - aluminum (can be plastic, printed)
- 3x big idler wheels - turned plastic (not printed)
- 3x small idler plate - aluminum or steel (can be omitted and substituted with washers)
- 6x motor mounting clips - angle aluminum (can be plastic, printed)
- 1x effector - aluminum (can be plastic, printed)
- 1x hotend collar - aluminum (can be plastic, printed)
- 1x hotend circular plate - aluminum (can be plastic, printed)
Linear Motion components
- 3x 560mm linear rails with ball retaining carriages (IKO or other >=12mm wide rail systems)
- 5m GT2, 2mm pitch, 6mm width belt (3x Gates PowerGrip GT3 1830-2MGT or 1700-2MGT)
- 3x GT2, 2mm pitch, 10mm width, 20 teeth, 5mm internal diameter pulley
- 3x bearing 627N1Z (or other similar, big idlers)
- 12x flanged bearing MF105ZZ or MF115ZZ (or other similar, small idlers)
- 3x NEMA 17 stepper motors (Nidec Servo KH4248-B95101 or other)
Delta rods
- 6x 250...280mm O.D. 6mm I.D. 4mm carbon tube (carbon arrows can be substitute)
- 12x DIN 914 M4 20mm internal hex set screw (sharp point)
- 12x Traxxas 5347 rod ends
Base plate
- 1x >= 260mm diameter tempered glass or borosilicate glass disk
Electronics
- 1x BeagleBone Black
- 1x BeBoPr++
- 4x Pololu stepper driver modules, Pepper BeBoPr addon board with 5 drivers (for high speed systems - Granite Devices VSD-E modules with suitable servos)
Extruders
- Any suitable (E3D or similar), tool changer attachments etc.
Software
- 1x Machinekit
Special assembly tricks
- Use coarse aluminum (or steel dust) shavings and epoxy to torsionally lock central triangles. This gives under compression ~95 percent contact area between prism sides and MiniTec profile end. Additional upper and lower circular metal disks for central prisms rise torsional stiffness even more. One can use additional angle fasteners (MiniTec 21.0018) to increase 90 degree joint stiffness.
- Over-tighten slightly the setscrews going into Traxxas rod ends, this preloads ball joints and replaces typical spring preload used in deltas. To clarify - sharp ends of setscrews go towards the joint ball. There are also reports of fitting joint balls using thermal expansion (like bearings), resulting backlash free joints without preloading.
- Do not over-tighten linear rail bolts, if needed, use more bolts and square nuts.
- The motor mounts are fastened changing two of motor bolts to longer ones - loosen no more than two screws at the time and do not take motors apart (demagnetization risk).
- Front motor mounting angle is fastened to frame before it is fastened to motor.
- Use Sorbothane pads for motor vibration isolation. Do not forget pads/washers under motor mounting clip M6 bolt heads. The amount of dampening can be tuned by tightening. Oversize holes for M6 bolts slightly in motor mounting clips. Vibration isolators can be completely omitted if noisy printer is acceptable.
- Small idlers can be fastened directly to profile without the idler plate, if you can drill holes to profile accurately. Shim bearing height accordingly. MF105ZZ bearings need small O.D. washers, MF115ZZ can do with normal washers.
- Big idlers are light press fit to bearings. Use really tiny amount of Loctite 648 if fit is too loose. Belt preload can be done with just hand pressing the big idler down (down force max 8..10kg, use soft buffer) and tightening. Longest side of belt should resonate at around 50..80Hz (when gently pulled like guitar string).
