00str00der

From RepRap
Revision as of 16:53, 1 January 2014 by Free (talk | contribs)
Jump to: navigation, search
Crystal Clear action run.png
00str00der

Release status: working

00str00der firstever 1.JPG
Description
The RepRap Wiki 00str00der page.
License
GPLv3
Author
Contributors
Based-on
Categories
CAD Models
External Link


The 00str00der is a belt-driven, gear-based, open-source extruder design intended for RepRap 3D Printers. It uses a precision linear-drive system to drive a hobbed bolt (or similar drive that grips filament/material), which in turn supplies filament to a nozzle used for 3D printing. The inspiration and research for this work was a natural progression based on existing open-source designs and is a result of collaboration between Lee Miller and Terawatt Industries (Colorado, USA). It is based on previous geared-extruder designs such as Wade's Geared Extruder, Adrian's Geared Extruder, and others; as well as Terawatt Industries' experience with RepRap drive systems.

<videoflash>_vMh1Gb-snw</videoflash>

Summary

The designers first shared concepts for the component in 2012, and agreed to collaborate on design and testing in January, 2013. Lee Miller designed the first 00str00der for an H-Bot-style 3D Printer (TBA) with Bowden-style extrusion. Free Beachler of Terawatt Industries revised the design to work with a PrismX by supplying the Sheliak X-Carriage design. Both designs are being converged (rev. C) and a mounting plate has been added to attach this extruder to carriages like [http://www.thingiverse.com/thing:18657].

Background

The 00str00der is designed to be affordable while offering greater precision, durability, and speed compared to extruder designs based on printed gears. It uses a small closed-loop GT2 belt to transfer power from a NEMA17 motor to a M8 hobbed bolt. GT2 pulleys are used on the NEMA motor and hobbed bolt to achieve an approximately 4:1 gear ratio. PLA and ABS filaments are driven by an M8 hobbed bolt, as is 'traditional' in the related designs mentioned here.

Terawatt Industries has tested and calibrated this component on a PrismX running at infill speeds up to 400mm/s. The 00str00der was first tested and proven on a PrismX 3D Printer in March, 2013 by Terawatt Industries. In April 2013 tests with the 00str00der on an h-bot in Bowden configuration were performed by Lee Miller. It performs exceptionally well in both configurations. On the PrismX it printed approx. 250+ hours total in March-April 2013.

I'll say qualitatively: it's difficult to drive a reprap (Prism, MendelMax, whatever) fast or hard enough to stress the 00str00der's drive system noticeably. During prints the nozzle experienced problems before we could drive our machine fast enough to stress the 00str00der or frame. During simple extrusion tests we hit speeds in excess of 1500mm/s; as noted before the nozzle shows problems performing at this speed.

The primary advantages to this design approach include:

  • The belt-driven system is very smooth, therefore resistance in the drive system is decreased. The positive side-effects from this are several including: faster drive, more accurate drive, potential for smaller/cheaper/lighter motors such as NEMA14.
  • The belt-driven system can be precisely calibrated. Instead of marking filament and attempting to measure travel inside of the robot's gantry (frame), we can measure the width of the hobbed bolt, and use a calculator for the rest.
  • The belt-driven gear system is very durable. Printed gears shed PLA/ABS material within 100 hours of printing. The belts and pulleys are rated for 1000s of kilometers and more.
  • Set-screws on the GT2 pulleys work more effectively than most set-screws on printed gears. Last longer too.
  • The ratio of gears can be adjusted. One-to-one (direct-drive) can be achieved with a set of 36T GT2 pulleys.

Some disadvantages to this system include:

  • The gears can't be printed, they must be sourced. This means we can't hack a new kind of herringbone gear and print/test it on an extruder. Purists will note, however, we can print decent GT2 pulleys in certain contexts...
  • All the other disadvantages that come with using non-printed parts such as: finding suppliers, specifications, availability, lead-time, etc.

Mechanical Construction

Materials

NOTE: Refer to the "Version History" section for information about the 00str00der's change history. These photos and BOM lists are not always current. However, the variations in the 1.x versions are slight and photos from older versions should still assist in assembly.

Version 1.0 BOM: http://kitbom.com/terawattindustries/00str00der-extruder-v10

Version 1.1 BOM: http://kitbom.com/terawattindustries/00str00der-extruder-v11

Printed Parts

See Terawatt's 00str00der Github repo for slicing instructions.

Quantity Description Comments Diagram
1 extruder block
00str00der block
1 extruder idler block
00str00der idler block
1 adapter plate optional - for mounting to www.thingiverse.com/thing:18657 - not needed for Sheliak X-Carriage
mount adapter plate

Non-Printed Parts

NOTE:

  • hardware BOM has changed in version 1.0; refer to "Version History" section.
  • pulley sizes have changed in version 1.1; refer to "Version History" section.
Quantity Description Type Comments
Drive System
00str00der-13.jpg
1 65T Plastic GT2 Pulley, 8mm bore, 2mm pitch, 6mm width Drive System 8mm bore for hobbed bolt; metal pulleys are OK; note: if this pulley does not have a set screw you will need an M8 nylock nut for the hobbed bolt
1 17T Plastic GT2 Pulley, 5mm bore, 2mm pitch, 6mm width Drive System 5mm bore for NEMA motor; metal pulleys also work; must have set screw
1 GT2 Belt, 88T, 186mm length, 2mm pitch, 6mm width Drive System +/- 1 tooth works OK
Feeder
00str00der-22.jpg
3 608 bearings, skateboard bearings Bearings
1 M8×60mm hobbed bolt (65mm works better perhaps) hobbed bolt M8×60 doesn't make it through the pulley completely, 65mm is perhaps better
1 M8 Fender Washer Fastener originally used since fender washers are slightly thicker than standard, optional
4-5 M8 washers Fastener to space the large pulley clear of the extruder base
1 M8 nylock nut Fastener optional - not pictured - I recommend using the set-screw on the M8 GT2 pulley to tighten things
Idler
00str00der-19.jpg
1 608 bearing, skateboard bearing Bearings the 608RS are resealable, so if they get clogged with plastic the bearing cage can be cleaned, and re-assembled.
1 M8×20 Threaded rod
1 M3×30 button-head cap screw Fastener mount idler arm to extruder block
2 M4×50 socket-head cap screws Fastener for idler tension
3 M3 nuts Fastener one (1) for button-head screw
5 M3 Fender washers Fastener one (1) for button-head screw - std washer is OK
2 ~4mm ID springs Spring Sized to fit over an M3/M4 bolt, unsprung length of 10-12mm, each spring providing 25-35N load. For a given filament drive force, you'll need about twice the spring force - i.e., if you want 100N of filament drive, your springs need to push with about 50N each.
NOTE: Some users have their extruders working without springs, but springs are recommended. Even better than springs are rubber gaskets. It can be tough to find good springs - often a local hardware store has an assortment and something in there might work. Also check with the recommended vendors.
'Hotend Mount
2 M3x30mm button-head cap, hex-head, or socket-cap screw Fastener NOTE: extruder block is revised for M3 screw
2 M3 nut Fastener
NOTE: The only current tested hotend mount is the j-head style mount reflected in the SCAD/STL files for the extruder block.
Stepper Motor Mount
00str00der - 14.jpg
2 M3×12 bolts Fastener M3x10mm is OK without lock washers
2 M3 Fender washers Fastener std. washers will work
2 M3 lock washers Fastener optional - resists vibration
Stepper Motor
1 NEMA 17 bipolar stepper motors Stepper 0.49 Nm (69 ozf*in) works well. We've been using the Stepper Motors from Terawatt Industries and it appears to be more force than necessary. Should be capable of creating a holding torque of at least 0.4Nm (56.6 ozf*in), at the very least.
Extruder Mount
00str00der-11.jpg
2 M4×20 socket cap screw Fastener The Sheliak X-Carriage has a three-point mounting system for this extruder.
1 M4×20 button head cap screw Fastener Required. We're discussing a revision so a regular screw can be used.
3 M4 nuts Fastener x-carriage mount - nylock nuts are better, then skip the lock washers
3 M4 washers Fastener x-carriage mount
3 M4 lock washers Fastener optional if using nylock nuts

3D CAD Files

STL and OpenSCAD source files for the latest version can be found on Github at https://github.com/Terawatt-Industries/00str00der and https://github.com/iquizzle/00str00der.

IMPORTANT: STL files are not organized by version number - they are organized by GT2 pulley and belt sizes. Read the file at https://github.com/Terawatt-Industries/00str00der/dist/stl/README.md for more.

Assembly instructions

A few people have put an 00str00der kit together with only assembly guides based on earlier ancestors:

How to make the hobbed bolt

We've been using Terawatt Industries hobbed and knurled bolts with this component, which is a M8x60mm bolt hobbed at 30mm from the head. 65mm+ works slightly better with the current (Rev. B) extruder block design. We're considering a few options around revising this, including using a non-threaded M8 rod or other machined options; but currently the 'traditional' hobbed bolt works great.

If you don't want to purchase a hobbed bolt then Wade's_Geared_Extruder describes how to make your own.

Upgrade/Retrofit

Direct-Drive Configuration

Direct-drive configuration is where the 00str00der sits on a moving platform attached to the print-head (hot end), such as an X-carriage, as is popular on many Mendel-type designs.

There are two ways to upgrade or retro-fit an existing direct-drive machine to an 00str00der:

  1. Use the 00str00der Adapter Plate to attach to a compatible X-carriage. This is the fastest way. The plate is designed to work with hole spacing used on many popular open-source x-carriages found on the interwebs. (TODO: cite hole-spacing spec).
    1. Assemble the extruder on the adapter plate.
    2. Attach 00str00der+plate to an existing x-carriage.
  2. Use the Sheliak X-Carriage to replace the entire x-carriage. The Sheliak X-Carriage is designed specifically for the 00str00der and is compatible with many Mendel-type machines that use 50mm linear rail spacing. The best reason to replace the whole X-carriage is to take advantage of the press-fit bearing mounts on the Sheliak X-carriage. CAD files for the Sheliak X-carriage are in the PrismX 3D Printer Github repository.
    1. Assemble the x-carriage
    2. Assemble the 00str00der tower
    3. Attach the 00str00der to the x-carriage
    4. Replace an existing x-carriage with the new one.

Bowden Configuration

Bowden configuration is where the 00str00der sits stationary, attached to a printer frame or externally, such as on many Delta 3D Printers and the UConduit H-Bot 3D printer.

For Bowden configurations upgrading or retrofitting an existing 3D printer with an 00str00der extruder should be straightforward. You will need to mount the 00str00der to the frame. The UConduit H-bot 3D printer has an example mount, but this is to attach to 3/4" tubing. Somebody needs to design a mount for other types of frame materials...

Version History

NOTE: The photos above apply to version 0.9.

Version 0.9

  • Rev. A: for use with h-bot in Bowden configuration
  • Rev. B: for use with Prism/MendelMax machine; 3-point attachment to Sheliak x-carriage
  • Rev. C: converges rev.A + B; testing started: for use with M4x50mm bolts on idler

Version 1.0

Based on 0.9 Rev. C. Considered stable. Vitamin BOM refined for nylock nuts and M4 screws for j-head groove-mount.

The complete version 1.0 BOM can be found on KitBom at http://kitbom.com/terawattindustries/00str00der-extruder-v10.

Version 1.1

Considered stable. Same as version 1.0 but with 60T big pulley, 16T small pulley. 16T pulleys easier to source; 1:3.25 ratio reduces torque on tower; 60T pulley allows access to groove mount set-screws.

The complete version 1.1 BOM can be found on KitBom at http://kitbom.com/terawattindustries/00str00der-extruder-v11.

Extruder Calibration

Configurator

Terawatt Industries has created the 00str00der Configurator which calculates the steps-per-mm for you. To use the 00str00der Configurator open a web browser to http://store.terawattindustries.com/00config.

Manual Procedure

The procedure to calibrate the 00str00der is as follows:

  • Measure the O.D. of the knurled (hobbed) area of the M8 hobbed bolt, preferably with digital calipers. The exact OD will depend on things like manufacturer and batch.
  • Calculate the gear ratio between small and larger gear.
  • Find the step angle for the motor - most common NEMA17 motors are 200 steps per revolution.
  • Find the microstepping value supported by your stepper drivers. This usually depends on brand of driver and type of control electronics.
  • Use the following formula:
steps_per_mm = (gear_ratio / (hobbed_bolt_OD * Pi)) * ((360 / motor_step_size) * (1 / driver_microstepping))

For example:

  • A hobbed bolt where the knurled bolt measures 7.52mm in outer-diameter (O.D.)
  • The gear ratio for a 17-to-65-tooth gear system is ~3.8235. In other words, ~3.8235 revolutions of the smaller gear equal one revolution of the larger gear.
  • NEMA17 motors are common with 1.8 step angle and RAMPS 1.4 with pololu drivers supports 1/16 microstepping.

steps_per_mm = (3.8235 / (7.52 * 3.1416)) * ((360 / 1.8) * (1 / 1/16)) = 517.8957 ~= 517.9

Stepper Driver

You can use community-tested electronics to drive this extruder. Newer electronics like Smoothieboard will work fine too.