Gantry Support Howto

How to add highly effective yet easily removed support structures to your objects.

The Object

The Object

The Problem

Definitely needs support!

The Solution

1. Add some bridges. Bridges print beautifully, and when they're only 1-2 layers thick/wide are very easy to cut through.
   Added Bridges
2. Build a gantry up to the bridges. Add some superstructure, thin walls will likely deform when we bridge if built this high by themselves!
   Gantry w/ superstructure
3. Add a foot to the gantry so it doesn't fall over while being printed
   Added Foot. Note cut-out around object itself.
4. Gantry Support ready to go!
   Gantry Support
5. Print!

Post-Print Removal

Success! Cutting Bridge Gantry Separated Cleaning Bridge Remnants

Result

Cleaned Supported Section Gantry Now Do The Other Side Even Cleaner No evidence of support on resulting surface

Closing Thoughts

Gantry support is a highly effective method of adding support.

• It can effectively support sections where llamella support might blemish a surface.
• It can support larger sections high up an object using little material where llamella support would use a large volume of material
• It can be stacked to get support into particular sections - simply make an intermediate bridge, and build another gantry on your bridge!
• For irregular shapes (eg belly of venetian lion), one could try using openscad's projection(), minkowski() and extrude() to create a profile-fitting bridge

This method is not suitable for:

• Irregular or organic supported surfaces where a bridge won't support everything, eg underneath mushrooms.
• Areas that have no space around them for gantries and bridges, or which would be inaccessible with a blade post-print
• Probably several other circumstances that I haven't thought of yet!

  I look forward to seeing your gantry supports on thingiverse!

Volumetric Stage Two

This seemingly innocuous calibration part was produced with a rather interesting set of numbers.

When extruding, the volume extruded (V) in mm³ is equal to πR²E, where R is radius of the filament, and E is distance passed from skeinforge/sfact via gcode.

For gcode to be printer-agnostic, we need a universal unit for filament extruded.

If we choose mm³ units, then we must solve D for D=2R, V=E, V=πR²E and feed this to skeinforge/sfact. The result is D=2.√(1/π), or about 1.128mm. Filament of this diameter would have the curious property that 1mm (length) has a volume of exactly 1mm³.

We must then alter our firmware to accept E in units of mm³, and adjust all the corresponding speeds appropriately. I had my sfact tuned for a filament diameter of 3.0mm. π(3/2)² is almost exactly 7, so all speeds must be multiplied by 7, and retract distance must also be multiplied by 7.

So, with diameter = 1.128 (orig. 3.0), E_steps=90 (orig. 635), retract distance = 12 (orig. 1.7) and retract speed=400 I produced the pictured calibration part.

Next step: move retraction into firmware! It's unlikely that we're all going to have printers that need to suck back 12mm³ of filament!

ps: my extrusion width is set to 0.5mm rather than the default 0.6, so the pictured reading shows a fairly well calibrated set of numbers :)

And the Printing continues

I've printed, broken and adjusted lots of things since my last post. I've taken my frankenmendel to a science expo and had a lot of people very interested. I've submitted a few things to thingiverse. I've snapped my Z belt a few times, I've had pulleys spinning on motor shafts despite set screws on all four axes at different times. I've added springs under my bed, reshaped the bed clamps, replaced parts with ones I've printed, ripped up my tape with the nozzle countless times, had wires falling out of my electronics... It all seems to be settling down though, anything that comes loose gets blasted with the hot glue these days!

Here's a quick photo tour:

Herringbone Extruder Gears Cube Gears Lash Maze modified Y bracket Heart Crown Spool Holders Butterfly, two colour Frame Vertex Frame Vertex Complete Electronics Mechanics

My things are on thingiverse if you're wondering.

First Print!

Just finished my first print!

Material: 3mm Orange PLA
Layer height: 0.35mm
Nozzle diam: 0.5mm

Something happened here, printer randomly decided to slow down to about 10 steps per second and start driving out into space. I paused it, cut off the blob with my dremel and hit resume. It seemed to go okay from there, but there's a noticeably bad layer through the middle of the object. I hope it won't affect it too much.

Here's the object still stuck to the bed

And here's the other side so you can see the bridges. They're a bit stringy, but good enough to print over the top of. Not bad for a first print :D

I calculated my E_steps_per_mm instead of measuring it, seems like my calculations were good! :D

Calculation was 3200 [steps/rev] * 39/11 [wade gear ratio] / 6.75 [hob effective diameter] / 3.1415926535 [pi] = 535.0

For those curious, that's cheap cloth tape on the bed, probably PVC or something. I just couldn't get this PLA to stick to the bare glass.

Extruder failure!

After my success with MakerGear's new SS barrels and thoroughly enjoying my heatsink mounting system, I tried printing some PLA. This involved switching barrels for a brass one with a 3mm bore that I had lying around. I decided to try reusing my heatsink mount to see how it would go with the brass barrel, and also because I didn't want to have to take my entire wade's apart again to put on the groovemount that came with this barrel. A few short minutes after getting it all warmed up and squirting hot PLA at 200°C, I noticed the following:

Extruder failure Extruder failure Extruder failure

Considering that this same wade's and carriage had been perfectly fine printing nylon at 290°C, it becomes evident that the stainless steel barrel and its thermal break had far more to do with that success than my heatsink!

The heat really likes travelling up that brass:

How am I gonna clean this?

Now I know why everyone's adding fans!

One of Greg's Accessible Wade's has been earmarked as the first thing to print for quite a long time due to how much of a hassle it is getting around this classic wade's. It seems my hand is being forced.

I think this is salvageable...

And It Begins!

Here's my first print!

Something happened to the comms after that little bit, and I was so excited that I pulled it off the bed and ran off to show people before taking photos which is why you can see that it's not stuck to the bed.

First Print

First Print

First Print

That's the 1.65mm nylon weed trimmer line I showed yesterday at 290°C nozzle, 110°C bed- printing nylon apparently requires an excellent hot end!

Calibration, here we come!

Hot end mounted
Mounting detail

With a new X carriage that actually has room for the heatsink (courtesy of Auzze), it's now time to start calibration!

It's been a long road getting here, and would have been quite a bit longer without the generosity of the reprap community. My first post in this blog was November 3, 2009! So, almost 21 months later, I'm just about to start :D