SkiBikePrint/Filamentalist

Filament Driven Passive Spool Rewinder/Buffer for 3D Printing Multi-Material Unit (MMU)

The "Filamentalist" Passive Filament Driven Rewinder

Filamentalist Enclosure Drybox Project Github

See video of 6 rewinders swapping here (plus Trident Blobifier): Filamentalist X6

Theory of operation:

The Filamentalist uses the axial force delivered by the MMU gear motor along the filament to load and unload to/from the filament spool. An adjustable spring clamp forces the filament against two o-rings that sit on the drive pulley to create a high traction interface. A one-way clutch style bearing locks against the drive shaft and rotates the filament spool to take up filament during an unload. For loading and print extruding, the clutch disengages allowing for effective free-spooling of the filament spool similar to a roller style spool holder. For unloading/buffering, some slip will occur between the filament and the o-ring interface of the rewinder to account for the varying diameter range of a spool from full to empty (full spool = max slip, empty spool = no/minimal slip).

Credits:

Discord user Thisiscam first made me aware of Muzi Xiaoyang's video of a filament driven rewinder (https://www.bilibili.com/video/BV1ZM41197fX/?spm_id_from=333.337.search-card.all.click). Through a long collaboration with Thisiscam, a great Beta dev/test team, and many design iterations/improvements on the Muzi Xiaoyang design the Filamentalist was born.

Additional Notes/Considerations

This rewinder is "almost" perfect, but not completely perfect. Things that you need to know include:

1. The ERCF gear stepper is doing the heavy lifting. Configure your gear stepper to run in sync mode with your extruder via Happy Hare settings.
2. A high torque NEMA 17 motor is recommended. Many in the Beta team ran NEMA 17's spec'd at 55 N-cm max torque and config'd them for 1-1.4A. Grafton's 40 tooth NEMA 17 mod is recommended (https://www.printables.com/model/692720-ercf-40-tooth-gear-modifiction). This may not be required so if you already have built your ERCF, try the Filamentalist with the motor you have and decide if you think you need more torque.
3. Several in the Beta team had space constraints that they wanted the rewinder to honor. As a result, one baseline width of the Filamentalist was set to use a 80mm axle length. It has a maximum spool width of 68mm and supports most standard 1, 0.5, and 0.25KG spool sizes and still be able to fit 6 rewinders across a 350 size Voron printer. Height was set to be as low as possible to fit some existing dry box designs although there is the possibility to make user modifications to to reduce height further if needed. Some spools such as KVP's are too wide to fit the 80mm design. If you use spools wider than 68mm there is also stl files posted for a 100mm axle length version. If you are using Autodesk Fusion 360 the provided .f3d file in the CAD directory is a parametric based model allowing you to customize the width of your rewinder to suit your max/min spool widths and/or to design around a standard available steel axle length (see instructions here parametric_model ).
4. Because the standard tuning of this design relies on some filament slip at the o-rings, the o-rings may ultimately wear-out. Testing and extrapolation estimates that the wear-out point is ~5K cycles. See the O-Ring Replacement section at the end of this document for o-ring swap/replacement instructions.
5. Due to pressfits for the 608 bearings, 8mm axle, and ECAS, printer calibration is important. A "Test Block" stl is included. It is recommended you print this first and test the press fits and measure the two small holes (2.7mm for cutting 3mm screw threads and 2.3mm for the filament path) to determine if you need to apply any scaling or changes to your extrusion factors in your slicer before printing. Due to varying ECAS supplier tolerances and varying printer tolerances some experienced cracking at the ECAS hole when pressing in the ECAS. If all other press fits work well on the Test Block but you experience cracking at the ECAS hole when pressing in an ECAS fitting, you can use an Xacto knife to lightly remove some plastic from the ECAS hole. If the ECAS is too loose you can use superglue to glue the ECAS into the Tensioner Mount (not the Test Block 😉 ).
6. Questions or input?
   • Refer to the FAQ (https://github.com/SkiBikePrint/Filamentalist/blob/9d7a90dc3dec40c67051558c80c616155eb8eba8/Filamentalist_FAQ.md)
   • Troubleshooting Guide (https://github.com/SkiBikePrint/Filamentalist/blob/9d7a90dc3dec40c67051558c80c616155eb8eba8/troubleshoot.md)
   • Filamentalist Discord group here: (https://discord.gg/uDcGxukRKd)

BOM:

(please read comments in the right column)

Qty per Site	Part	Example Source Reference	Comments
1	8mm dia. x 80mm Stainless Steel Dowell Pin	https://www.amazon.com/uxcell-Stainless-Chamfered-Support-Elements/dp/B0BC8VFSWD, Amazon Alternate https://www.amazon.com/Unifizz-Stainless-Steel-Round-Silver/dp/B09P9MC953?th=1 (sheared ends may need to be cleaned up), Aliexpress https://www.aliexpress.us/item/3256801518620991.html	Undersized shaft (7.93-7.97mm or 5/16" dia) works the best. 100mm length is more available and can extend out of rewinder, you can cut polished 8mm or 5/16" diameter stainless rod to length, or there are stls to make a wider rewinder based on a 100mm axle. Custom rewinder widths are also possible using the Fusion 360 parametric model and you can cut shaft to whatever length is desired. 8mm (or 5/16") diameter straight stainless tube is also an excellent alternative to solid rods as the are much easier to cut to length.
5	MR608 bearings	Can be obtained anywhere (Home Depot, Amazon, Aliexpress, etc.)	MR608RS, MR608ZZ, etc.
1	HF081412 One-Way Bearing	https://www.amazon.com/dp/B0C7TRFJBS, Aliexpress	8mm Bore, 12mm length, 14.2mm Diameter. Get the "hex" style.
1	ECAS press-in pneumatic fittings for the bowden tubes (like used in ERCF)		A locking clip is required and can be bought or printed (stl included)
2	O-rings	AS568 Standard size 211, Home Depot #110, https://www.amazon.com/211-Buna-N-Ring-Durometer-Black/dp/B000FN0W7I/, Aliexpress	In the range of 13/16" ID, 1-1/16" OD or ~20mm ID, ~26mm OD (~3mm cross section/cs), Nitrile Butadiene Rubber (Buna-N)
1	Spring	https://www.amazon.com/gp/product/B08FDYJLYC/, Aliexpress	Like in extruders - 304 Stainless Steel,6mm OD,1mm Wire Size,7.5mm Compressed Length,15mm Free Length,37.2N Load Capacity
1	3mm Heatset Insert	M3x4x5 like these: https://www.amazon.com/gp/product/B09MCW7ZN5	Voron standard size
1	3x35mm SHCS	SS Socket Head Cap Screw	Spring Tensioner Screw anything in the range of 35mm +/- 10mm should work. If building the alernate reverse access version then a 40-50mm length is recommended.
2	M3x8 SHCS	Stainless Steel Socket Head Screw	for locking rim rollers to 8mm steel axle shaft
6	3x12 FHCS	Stainless Steel Flat Head Screw	for Tensioner Mnt and Rear Axle installation 8/10/12mm lengths will work
3	3x18 FHCS	Stainless Steel Flat Head Screw	for Tensioner Arm clamp bearings and Tensioner Mnt pivot installation 16mm length will work
2	Rubber Band	https://www.amazon.com/dp/B0CPJPN41V , Aliexpress https://www.aliexpress.us/item/3256804772787208.html (120x20mm)	Size #94 (3 1/2" x 3/4"), any wide rubber bands in the 2.5"-3.5" size will work. Can combine multiples across face of rollers. Another excellent alternative is to cut bands from a bicycle inner tube. Mountain bike or "balloon" tire sized tubes for tires in the 1.75"-2.4" width work well. Cut at ~30-35% wider than face of Rim Roller.
var.	2.5mm ID PTFE tubing	Amazon, Aliexpress, 3D printing vendors	2.5mm ID recommended but you can try whatever you have. Length depends on the distance from your rewinder location to your ERCF inputs

Printing Guidelines:

General:

• Material: ABS or ASA (~170 gm per site)
• Print Time: ~8hr 17min (based on the Ellis PIF profile speeds, accelerations, and volumes)
• 0.2mm layer height
• 40% infill recommended. Linear style infills are fastest (rectilinear, monotonic, grid, triangles, stars, etc.)
• Wall Count: 4
• Solid Top/Bottom Layers: 5

Part Specific:

• Orientation suggestions are relative to the installed assembly orientation and are shown in the slicer images below.

• There are stls for both 80mm and 100mm wide version and a Fusion 360 parametric CAD model for additional custom widths. See "Additional Notes/Considerations" point 3 above for more details.

• If rotating the Filamentalist is not feasible for your required filament loading direction or you need a bottom feed capability (for example enclosure limitations or feeding through the bottom of a shelf) there is an option for a rear loading version which only requires printing the Tensioner_Mount_Rear_Load_80mm/100mm_[option] in the place of Tensioner_Mount_80mm/100mm part.

  

• Stl's are provided for optional clip-in style supports where no Base_Plate is needed and the rewinders are easily clipped in and out of (2) 2020 extrusions mounted 170mm center-to-center apart. This option is highly recommeded if your setup can accomodate this style type of mount.

  

• !! IMPORTANT !! This design relies on multiple press-fits for bearings, axles, and ECAS fittings. As a result, printer calibration is important. A Test_Block stl is included. It is highly recommended that you print this block first, check fits, and make adjustments to extrusion multipliers and/or slicer scaling if needed before printing the Filamentalist parts.

Qty per Site	Part	Pic	Orientation	Printed Supports Needed	Comments
1	Right_Support		Horizontal	N
1	Left_Support		Horizontal	N
1	Option: Right_Support_[2020_Clip-In_option]		Horizontal	N
1	Option: Left_Support_[2020_Clip-In_option]		Horizontal	N
1	Base_Plate_80mm/100mm_[option]		Horizontal	N	Optional part for a standalone unit not mounted to another surface
1	Idler_Roller_Axle_80mm/100mm		Horizontal	N	align flat of "D" to build plate
2	Rim_Roller_80mm/100mm		Horizontal	N	Dished side up.
1	Center_Drive_Roller		Horizontal	N	Recommend scattered seams for press fit-bore concentricity
2	CDR_Spacer_80mm/100mm		Horizontal	N
1	Tensioner_Arm_Left		Horizontal	N
1	Tensioner_Arm_Right		Horizontal	Built-in	Remove built-in support from the locking tab
1	Tensioner_Mount_80mm/100mm		Vertical (as installed)	N
1	Tensioner_Mount_Rear_Load_80mm/100mm_[option]		Vertical (as installed). Optional for rear loading if needed.	N
1	Idler_Roller_(male)_80mm/100mm		Vertical	N	Scattered seams
1	Idler_Roller_(female)_80mm/100mm		Vertical	N	Scattered seams
1	Axle_Depth_Tool_80mm/100mm		Vertical	N	Pocket opening up. Print with 100% infill for reuse strength and durability when building multiple rewinders.
2	ECAS_Clip		Horizontal	N	Tab up
1	Test_Block		608 Pocket facing up	N	printer calibration tool

Assembly Instructions:

1. Tensioner Mount Assembly

• 1.1 Install 3mm heatset insert into Tensioner Mnt.
• 1.2 Remove the rubber seal from the ECAS fitting.
• 1.3 Install the ECAS fitting into the Tensioner Mnt. It should be a moderate press-in. You may need to push it in firmly using the end of a 8mm steel shaft or printed rear axle shaft to get it to sit flush to the Tensioner Mnt mating surface. The sidewalls of this hole are relatively thin. Varying ECAS and print tolerances could result in the sidewall cracking. If this happens, use superglue around the ECAS and crack.

2. Tensioner Arm Installation

• 2.1 Lay the Tensioner Arm Right part on a flat surface. Slide the 608 bearing onto the bearing post. Place the Tensioner Arm Left part into the 608 bearing and rotate against the Tensioner Arm Right part making sure the alignment tab seats correctly at into the pocket at the bottom of the Tensioner Arm Right part.
• 2.2 Place a 3x18 FHCS (or x16, x12) through the bearing mount hole of the Tensioner Arm Left part and moderately tighten the screw into the Tensioner Arm right piece. Once installed verify that the bearing turns freely.
• 2.3 Place a 3x18 FHCS (or x16, x12) through the hole in the Tensioner Arm Left part at the "nose" end and moderately tighten the screw into the Tensioner Arm right piece.
• 2.4 Install the Tensioner Arm onto the Tensioner Mnt using a 3x18mm FHCS screw (or x16) . Tighten until snug and then back off until the arm rotates freely on the mount.
• 2.5 Place an M3 washer followed by the spring onto an M3x35 SHCS (or x30, x40) and slide through the slotted hole in the bottom of the arm assembly. Screw the SHCS into the heatset insert of the Tensioner Mnt. No tension should be on the spring at this point.

  • 2.5.1 ALTERNATE INSTALLATION: If the orientation of your Filamentalist makes it difficult to access the tension adjustment screw you can use a 50mm long 3mm SHCS coming from the bowden side of the rewinder with a lock nut with loctite, or a heatset with loctite on the other end as shown in the image below.

    

3. Drive Roller Assembly

• 3.1 Press HF081412 One-Way Bearing into Center Drive Roller. Orientation does not matter at this point.
• 3.2 Before placing the Rim Rollers onto the axle use a ball end hex driver to drive the M3x8mm SHCS through the hole in each hub of the Rim Rollers to cut threads into the plastic. Back the screws out a little to allow the axle to be inserted into the Rim Roller.
• 3.3 Install first Rim Roller onto the 8mm steel axle with dished side facing down as shown in picture above. Use the Axle_Depth_Tool to aid with getting the Rim Roller set at the correct distance from the end of the axle. Use a ball end hex driver to tighten the M3x8mm SHCS against the steel axle shaft. Only medium force is required as to not strip the plastic threads.
• 3.4 Slide the first CDR Spacer followed by the Center Drive Roller (with One-way bearing already installed) followed by the second CDR Spacer onto the axle.
• 3.5 Install the second Rim Roller onto the 8mm steel axle with dished side facing outward as shown in picture above. Use the Axle_Depth_Tool to aid with getting the Rim Roller set at the correct distance from the end of the axle. Use a ball end hex driver to tighten the M3x8mm SHCS against the steel axle shaft. Only medium force is required as to not strip the plastic threads.
• 3.6 It is very important that the one-way bearing rotates in the unlocked direction freely with low resistance . If the resistance of the one-way bearing is greater than the combined rolling resistance of the rest of the rewinder the one-way bearing will not disengage and freespool properly during filament loads resulting in loose coils on the spool. There has been limited instances of certain one-way bearings having too much resistance. If your one-way bearings don't spin freely in the unlocked direction then assess your shaft diameter to ensure it is not too much above 8mm and/or you may need to try a different brand of one-way bearing (5/16" or 7.2-7.6mm diameter is optimal).

4. Base Assembly

There is an alternate version of the base that clips into two 2020 rails spaced 170mm apart (center-to-center). It enables quick add/remove/relocate capabilities and requires no hardware to mount. You print all of the same parts except for the 2 base Supports that use the clip mount version (see "[2020 Clip-In_option]" versions in STLs directory). Assembly is the same.

Also, there is an optional "Base_Plate" part that mounts to the Supports and Tensioner Mount for a standalone application where the unit will not be attached to some other mounting suface. If installing the Base_Plate part, screw the Tensioner Mount to the Base from the bottom before installing the side Support parts, Drive Roller Assembly, and/or Idler Roller.

• 4.1 Thread the Idler Roller (male) and Idler Roller (female) parts together tightly. Press a total of (4) MR608 bearings into the Right Support, Left Support, and Idler Roller parts. The Axle Depth Tool can be used to aid with pressing the bearings into the deep bearing pockets of the Idler Roller. Ensure the inner races of the bearings in the Right/Left Support parts turn freely.

• 4.2 Place the Tensioner Assembly around the Drive Roller Assembly and screw the Tensioner Mnt onto one of the Support parts using (2) 3x12 FHCS screws (or x10, x8).

Double Check that the one-way bearing of the Center Drive Roller locks when rotated in the direction of a filament unload (if using the Tensioner Mount Rear Load option then the one-way bearing must be reversed and operate/lock in the counter clockwise direction with respect to the picture above).

• 4.3 Insert the Rear Roller Axle through the same base part aligning the "D" shape end to the flat in the 8mm pocket of the Support. Ensure it presses all of the way in (you may need to tap it in a bit). Secure with (1) 3x18 FHCS screw (or x10, x8).
• 4.4 Slide the Rear Roller onto the Rear Roller Axle.
• 4.5 Install the opposite side Support part to assembly pressing in the D shaft end and securing with (3) 3x12 FHCS screws (or x10, x8). Make sure there is no spring tension on the Tensioner arm for this step.
• 4.6 Insert a section of bowden tube into the ECAS until it bottoms out/butts against the Tensioner Mnt behind the ECAS. Place a locking clip in the ECAS (if you don't have these, an stl file is provided to print the locking clips). 2.5mm ID tubing is recommended to ensure good stiffness and minimal "buckling" of filament in the driven filament path. Cut your section of tubing a little long for the location of the rewinder and the run to the ERCF slot position. You can fine tune/trim the length after installation of the rewinder.

It is recommended that you chamfer the inner edge of the tubing that is going into the Tensioner Mount with an Xacto knife or drill bit to ensure easy filament loading. Also, depending on print quality you may want/need to clean up the filament path hole in the Tensioner Mount by hand turning a 1.75-2mm drill bit and the bowden tubing hole with a 4mm drill bit.

Tuning

The standard recommended method for tuning the system is with the Tensioner Arm clamping force. The arm does not need an extreme amount of tension. To tune the spring force, lift the tensioner and insert a section of filament through the o-ring bearing interface and into the bowden tube. Hold the center roller by placing your thumb against the o-rings and try to pull the filament out. You want the slip force to be slightly more than what the overall system drag is, so you have to imagine the range of gear motor pull force vs rewinder drag and set a slip range in-between the two "imaginary" lines. Adjust the spring tensioner screw accordingly and err on the light side. Run the rewinder (see test code below). If loose filament is forming around the filament spool during unload, tighten the spring tensioning screw. If no loose filament is forming around the filament roll, gradually reduce the spring tension until loose filament starts to accumulate and then increase tension in ~1/2 screw turn increments until you feel you have the lightest tension that results in a tightly packed unload.

O-Ring Replacement

You may never need to replace o-rings. Testing and extrapolation estimates that the wear-out point is ~5K cycles. The impact of o-ring wear-out can be reduced by periodically swapping highly used rewinders with low use rewinders in your line-up. Also, o-rings with grooves worn in them can be swapped with their opposing partners to present the unworn side/face to the filament to extend the life of a set. For o-ring replacement, remove the Drive Roller Assembly from the rewinder (unscrew the (6) screws of the Right and Left Supports). Then unscrew the set screw on one Rim Roller. You can now slide the CDR Spacer and Center Drive Roller from the axle, remove the old o-rings (a dental pic works great), and install a pair of new ones. Reinstall the Center Drive Roller and CDR Spacer back on the axle and install the Rim Roller back onto the axle per 3.3 above, and re-install the supports.

Troubleshooting

Please see troubleshooting guide, reference the FAQ, or join our discord server (https://discord.gg/uDcGxukRKd) for more help.

Testing

Below are macros you can cut and paste into the bottom of your mmu_software.cfg or printer.cfg to test and tune your rewinders.

Happy multi-material printing and rewindering!

[gcode_macro rewinder_test]
gcode:
    MMU_TEST_LOAD LENGTH=50
    {% for n in range(20) %}

# cycles currently set at 20, i.e. range(20).  You can changes this however you chose.
        MMU_SERVO POS=DOWN
#        MANUAL_STEPPER STEPPER="gear_stepper" SPEED=300 ACCEL=400 MOVE=800
        MMU_TEST_MOVE SPEED=300 ACCEL=400 MOVE=800
# change the SPEED and ACCEL as you see fit
        MMU_SERVO POS=UP
# to stop a macro mid-cycle you must use the e-stop.  This dwell allows you to hit the e-stop while the servo is up so that you can pull the filament out of the ERCF while the printer/macro is stopped
        MMU_SERVO POS=DOWN
        MMU_TEST_MOVE SPEED=300 ACCEL=400 MOVE=-800
        MMU_SERVO POS=UP

    {% endfor %}


[gcode_macro rewinder_test_multitool]
gcode:
    {% set gates = [5] %} # [0,1,2,3,4,5] move between these gates
    {% set test_load_length = params.TEST_LOAD_LENGTH | default(50) | float %}
    {% set repeats = params.REPEATS | default(20) | int %}
    {% set speed = params.SPEED | default(300) | float %}
    {% set accel = params.ACCEL | default(400) | float %}
    {% set length = params.LENGTH | default(800) | float %}

    MMU_HOME

#    MMU_TEST_LOAD LENGTH=50
    {% for n in range(repeats) %}
        {% for gate in gates %}
            MMU_SELECT GATE={gate}
            MMU_TEST_LOAD LENGTH={test_load_length} # preload gate for a bit of length
            MMU_TEST_MOVE SPEED={speed} ACCEL={accel} MOVE={length}
            MMU_SERVO POS=UP
            MMU_TEST_MOVE SPEED={speed} ACCEL={accel} MOVE=-{length}
            MMU_EJECT
            MMU_RECOVER

        {% endfor %}
  
    {% endfor %}

Version History

Versioning convention. V"X"."Y"

• "X" represents a major change in form, fit, or function. An increment in "X" may not require that existing built units undergo rework but the new parts will generally not be compatible with past version rewinders.
• "Y" represents a "step rev" or minor revision. These are generally small "tweaks" for improved printability and/or assembly and typically would not require reprint/rework for existing rewinders. If there are cases where a step rev may incrementally improve function on existing units in the field this will be called out in the releas and on the discord channel.

V1 - 5/17/24 - Public release into ERCF V2 RC2 repository

V1.1 - 5/19/24 - Update to CAD and stls for Tensioner Arms to remove potential filament catching point during endless spool ejection

V1.2 - 5/20/24 - Reverted Center_Drive_Roller to cylindrical press fit hole (vs hex of V1 and V1.1). Revised 608 press fit pockets of Idler_Roller_(male&female) parts for both 80mm and 100mm width versions for improved press fit.

V1.3 - 5/20/24 - Added bevel to internal step on Idler_Roller_(male) part for 80mm and 100mm versions to improve printability. Updated the .f3dparametric file, step files, and stls for 80mm and 100mm versions.

V1.4 - 5/21/24 - Shortened threads on Idler_Roller_male parts by 1.5mm to remove slight interference. Updated CAD, 80mm, and 100mm stls.

V1.5 - 6/4/24 - Slightly deepened 608 bearing pockets in Idler Roller parts to prevent potential side loading binding due to print/assembly tolerances. Reprint not required for existing functioning units.

V1.6 - 6/12/24 - No mandatory reprints/rebuilds required: Updated CAD parametric model and 80/100mm step files because two Tensioner Mount-to-Support holes were getting "buried" in the 100mm version. Updated the Tensioner_Mount_100mm stl file as well.

V1.7 - 6/13/24 - Opened up c-sunk hole on Tensioner_Arm_Left part pivot screw hole to allow for full seating of a FHCS head and use of a 16mm long screw. A new stl for Tensioner_Arm_Left ans new f3d and step files are included.

V1.8 - 7/2/24 - Removed notch/gap in axle pressing tool that shouldn't have been there. 80/100mm stl's updated as well as f3d and stp CAD files.

V2 - 7/22/24

1. Added Rear Load option Tensioner_Mount (works as bottom load too)
2. Removed threaded Rim Roller option and converted Rim Rollers from press-fit to set screw style.
3. Add 608 bearing inner race clearance back into Supports.
4. Added ~2mm of additional bowden capture in Tensioner_Mounts

To DO