The Original Rroofl

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The Original Rroofl

Rroofl first light.jpg
This is how it started at Massey University's FabLab during Fab8nz. Note the lasercut cardboard mockup on the left, which was great for scribbling changes on.

Rroofl axes complete.jpg
Rroofl mechanical assy1.jpg
Rroofl awaiting x axis.jpg
The Rroofl design was produced as alpha kits with extended Sells/Prusa-style vertex pieces. These allowed more room for an extruder to rise, giving more headroom and higher builds. They also allowed the X carriage to return in a sane manner to the X stop without hitting the framework on tall builds!

X Axis uses the carriage from the Kiwified Mendel, which went on to become the Prusa. This supports a NEMA17 and 3 x 608Z bearings as corner pulleys; T5 belt does not like corners under tension. Tension in the belt will draw under-constrained Z sliders onto Z guide rods. The X carriage has 4 clip-like printed PLA bearings which give adequate performance on both extruded 9-10mm dia. aluminium tube and drawn steel rod ("piano wire") as narrow as 1/4" and probably narrower under tension. Ideally, these are fitted into the X carriage snugly (use heater and mallet technology) before being slipped on over the ends of the X rails

The X motor and Idler Mounts have slots to allow the X rails to be pinned in place. End stop microswitch is held in place by a single 2mm zip tie or hot-melt glue etc.

Y axis

2mm zip tie used to hold end stop switch in place. Uses 5mm zip ties in the frame to hold both NEMA17 drive motor and the idler. Needs to be measured and the cutting files updated.

Z axis

Gears now working even if not well printed. Sockets hold 6 x 608 bearings to support the Z axis drive rods and each end of the Z drive trans-axle. The waterjet cut holes in the frame to support Z brackets need to be +0.5mm diameter and more widely spaced as per the new Z bracket spacings. The gears mesh best with one washer under each of the gears fixed to the Z drive rods. Experiment, and be prepared to grind a few bits of plastic off in pursuit of perfection.

The Z endstop was built into the design by Hamish User:BouncyMonkey, who added a microswitch holder to the Z motor bracket. A length of M8 screw thread to the underside of the X motor bracket pokes the former when the X carriage descends too far. He is also doing pioneering work in creating a sturdy, low-cost, sheetboard frame that local artisans can cut by hand with a scroll saw if necessary.

The deposition bed is a simple piece of 8mm MDF stuck down with double-sided foam, so it needs no fancy holes. Y carriage is in 2 identical parts joined with M8 rod. Y belt secured to carriage with zip ties, which also tension it. It is important to clean the bed's underside before sticking it down.

It looks like we can drop all the holes in the lower part of the frame (and the top edge of both short ends) by about 15mm to increase our build height a bit. If we take another 5mm off the top edges we can claim that back for build height by dropping the height of the Y carriage a bit.

The circuit holding panel needs to move up and away from the build area (printed version does this by using extended length vertex parts), and needs a hole matrix for mounting Arduinos etc. on. If this part is made from MDF or plywood, it is much easier to screw boards into place in while prototyping. It does need to be strong and securely placed, however, as it does actually add considerable structural integrity to the build.


Prototype rroofl electronics.jpg
Electronics are assembled and working well. Stepper motors are Sparkfun NEMA17's and some beefier ones scrounged from Massey University, Wellington. Drivers are a mix of EasyDriver V4's and Makerbot V3.3's and connect to an Arduino 1280 Mega using mostly commercial jumper leads. Connectors and lead lengths are a nightmare, so we need to rationalise this into something that suits the inventory. It is important that we use screw terminals instead of proprietary plugs wherever we can, so pin spacing on stepper motor board through holes ideally needs to be 5.08mm (0.2") all-in-a-row.

There are no fixed or special electronics, though they must be designed to run of car batteries and donkey-powered generators etc. Not only does this make the printer capable of running on homebrew power, it ensures that they will continue to run in the event of natural disasters. Just put an automotive electrical lighter plug on the power lead and you can run it in the car. Do remember that the spring goes under the fuse in those things, not on top of it (otherwise the spring melts).

One option being explored here is the use of an inexpensive breadboarding panel as a universal parts interface and bodging board. No soldering required, it encourages tinkering, and simplifies things when you blow a pin on your Arduino - just move the connector and recompile. OTHO a cat can wreak havoc with it. The Du Pont jumper/connectors seem resistant to normal vibrations and movement.

Zero endstops are all implemented with microswitches. a 10K resistor pulls the relevant input low (Arduino Mega 2560's have these built-in but the 1280 needs them), closing the switch makes it go high. There are no max limit switches.

The stepper motor driver's STEP & DIR leads must not be longer than about 200mm. Otherwise they start to pick up weird signals from outer space and use your nozzle as a kind of Ouija board.

When cable paths are established, we need mounting holes for cable ties so we can tidy them up.

A stepper motor module capable of driving 2A and made from FabLab inventory is being designed. Hopefully with sane connectors!

Spiral cable tidy is one option for constraining the cabling, and it is at least reusable.


Please link or add your files here, folks.

Guide to the filenames and intended arrangement of the Z-axis

Note that the Y axis brackets are replaced with zip ties in the prototype. If it works, why not? It looks likely that we will need to brace the frame across the top. In the prototype this is done with M8 threaded rod.

File:Rroofl Z-axis The archive included here contains the assembly model for checking gear meshes and interference. This model has been used to create the STLs listed on the image. Stand-in geometry for switches, motors, and gears have also been used to help in the design process. - updated 28th October 2012 by User:BouncyMonkey

File:Rroofl Z-axis The image above will guide you to the appropriate model contained within this archive. - updated 28th October 2012 by User:BouncyMonkey

Note that the tops of the M8 Z drive screws should not be overly constrained, so the bearings allowed for there will seldom be necessary.

Rroofl x idler end.jpg
The X Idler & Motor Assemblies. The slots in the sockets for the X rails allow for final tensioning and/or clamping, so the rails do not have to be cut with a precision of higher than 6-7mm. Ensure one end of each rail is pushed as far as it'll go into a socket. After assembly, take up the slack with one of these:

Proper Method: The outside of the socket is tapered. Using an approx 16mm M3 screw, 2 M3 washers and a nut, tighten immediately behind the end of the rail, right through the slot in the rail's socket.

Ghetto: Loop a zip tie round the front of the socket and through the aforementioned slot. Tighten zip tie so that it is snug behind the end of the rail.

Other Printed Parts

Rroofl y carriage complete.jpg
File:Y bed runners.scad The Y runners. It would be great if someone could vector this to cut on a laser. Print two of these and join with a couple of 140mm lengths of M8 studding, nuts and washers. Ease the frame into shape on the rails before fully tightening. Y Slider legs can be compressed with a bolt or zip ties if it is necessary to level the bed. The actual deposition bed is attached by using small double-sided foam adhesive pads. Clean the bed before sticking pads to it.

Rroofl y carriage belt.jpg
The Y belt is attached with zip ties; Make loops in the belt ends and secure with zip ties. Thread another zip tie through the small holes in one side of the leg of the Y carriage, pass it through the loop in the belt and then use to tension the belt to your requirements. Note that if you leave a large loop of zip tie this introduces unwanted springyness, so you'll have to cinch it with a zip tie or two.

Another good trick we've tried is to use a cable tie to hold one end loosely in place, but tension up the belt and clip it against one of the central supports with a medium bulldog clip from the stationery cupboard. Either way it pays to do that before you stick the bed in place with the foam tabs. Common measurements. Based on Simpleton's include file so lots of crap in it.

File:X axis bits.scad OpenSCAD file for the x-axis parts. Needs Contains the X Axis Idler and Motor Traveller Ends, which are also the Z axis sliders. Yes, we know the belt goes right over the top of the Z stop adjuster screw hole. We're moving it and the microswitch a bit. You can still make it work.

File:Printed rroofl Contains historical printable STLs used in the prototype X, Y & Z axis.

Rroofl mendel prusa adaptor.jpg
File:Rroofl mendel adap.scad Printing 4 simple blocks (dark green parts in the accompanying image) with M8 holes at right angles allows the entire Z axis mechanism to be ported onto old Mendel and Prusa frames. The Y Sliders are also perforated in several places to make the attachment of a belt easier in such retrofits.

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