What did I work on?

…exploration of various methods of constructing structural support for personal digital fabrication machines. objective is to find a method that is:

• self-aligning
• durable
• no fasteners
• inexpensive
• self-replicating
• easy to manufacture
• easy to scale

Prior Art

• Flexures (MTM Snap)
• Plaster cast in acrylic (Plaster Disaster)
• Metal origami
• Traditional fasteners

Initial Ideas

• Modular flexures (snap multiple MTM Snaps to make larger machine)
• Modular molds
• Focus on this
• Make mold and casting material cheap
• Printed/milled molds = expensive, time-intensive
• Metal - very precise, but requires water jet, metal origami, moderately expensive
Foamcore - might not be as precise, but very cheap & easy to work with.

Foamcore Casting

• Box construction
• Finger joints
• hand and laser-cutter scored "flaps"
• Experiments
• Casting in place
• finger-joint foam core & delrin/acrylic
• scoring & cutting by hand
• scoring & cutting on laser cutter
• overlapping flaps add strength
• Casting Material
• hydrostone & Al powder
• hydrostone & Perlite
• around 20 percent weight reduction
• still has good compressive strength (over 2000 lb/in^2

Lessons learned

• Cost
• hydrostone: $18/20lbs, Perlite: $17/50L, Foamcore: less than $4 per 36x24 sheet
• Ease of construction
• laser cutting is accessible & easy, especially with provided templates
• messy and time-consuming to pour

Future Work

• More iteration on large molds
• Strength testing
• Additional weight reduction

Pictures!

This past week:

• Ordered parts to cast single-axis stage in place (lead screw, rods, etc)
• Will cast using foam and acrylic
• Started collecting information on metal perforating/bending

Next week:

• cast concrete
• make bent metal box
• begin design of snap-fit enclosure

Final project will include comparing cost, ease of fabrication/assembly, ease of procuring materials, and material properties (stiffness, torque) of concrete, metal, and snap-fit plastic. Currently working w/ laser cutter team on enclosure, and if small enough, use the enclosure as a test for above materials.

Pictures to come...

Last week focused on building CoreXY stage for laser cutter, ordering necessary materials, and planning the enclosure. Enclosure will be made of concrete and will have a honeycomb stage mounted above acrylic. To do list for next week:

• finish mold design (almost done)
• laser cut foamcore for molds & pour concrete

Questions to be resolved...

• Can we get a smaller fan? Current fan is a little over 9x9".
• Is it ok if we enclose power supply in external enclosure that can be disconnected for portability?
• Currently designing for diode, but should know which laser to use (CO2 vs. diode) by this weekend

This past week:

• Ordered parts to cast single-axis stage in place (lead screw, rods, etc)
• Will cast using foam and acrylic
• Started collecting information on metal perforating/bending

Next week:

• cast concrete
• make bent metal box
• begin design of snap-fit enclosure

Final project will include comparing cost, ease of fabrication/assembly, ease of procuring materials, and material properties (stiffness, torque) of concrete, metal, and snap-fit plastic. Currently working w/ laser cutter team on enclosure, and if small enough, use the enclosure as a test for above materials.

1. What size sheet will final laser cutter cut?  (30" x 18")

2. What are the ventilation needs of the laser cutter?

3. Assuming a transparent material can be used for the top (switch to CO2 laser), which would be better: 
a) a cover to put over the laser cutter        
b)  all integrated - ie no cover, more like normal laser cutters where enclosure & motion control is all together

4.  What are the current specifications for the enclosure regarding safety?  (e.g. aluminum/steel, thickness)

Would be nice to have protective acrylic so no webcam is required:

http://www.lasermet.com/filter-windows-plastic.php

http://www.professionalplastics.com/LASERFILTER

Examples of DIY laser cutter enclosures:

Drawings for open source laser cutter: http://www.buildlog.net/sm_laser/drawings.html

Options for moving forward w/ enclosure:

• use plaster to make structural columns, but include protective acrylic top and sides
• use bent sheet metal (using water jet) for "folded" enclosure
• make self-replicating by using only laser-cut materials

I obtained hydrostone plaster, but didn't have a chance to cast more plaster boxes. I started making "patterns" for modular foamcore molds in Illustrator. I plan on testing these over the weekend/early next week. However, having a specific machine for which to design these molds (anyone in class at the stage of incorporating enclosures?) would be helpful.

This week, I looked into making structures for MTM from a molding process. Using an inexpensive plaster and easy-to-make, modular molds facilitates the machine-replicating process. Ilan & Max proved the rough feasibility of creating a functional single-axis motion stage using laser cut acrylic as a mold. I wanted to see if I could make the mold-making process even easier, using less expensive and more accessible materials.

I first made boxes out of foamcore, cut both by hand and on a laser cutter. Here are a couple:

Unfortunately, my inexperience with plaster made for some messy experiments. Even with tape supplementing the seal of the laser-cut finger joints, the foam core was too leak, and only a thin layer of plaster stayed in my mold. The same can be anticipated of cardboard (unless a very thick, coated mutlti-ply cardboard can be used). I will spend more time experimenting with sealing (more hot glue, tape inside). Another experiment will be to try more "high precision" parts of the machine (e.g. building a single-axis stage) to see if foamcore/cardboard can be lasercut to high precision and used for molding.

This week's exploration of enclosures for MTMs involved thinking about ten different ways to make a box. That is, a box comprised with the following functional requirements:

• made of several parts
• no fasteners
• self (high-precision) alignment

The following are results from class discussions & brainstorming on potential ways to construct box with above requirements:

1. Flexures: HDPE
2. Flexures: Laser-cut and pop-out
3. Mold: foamcore
4. Mold: printed/milled "legos" modular molds
5. Digital Composite Parts
6. Lego construction
7. Adhesive
8. Sheet metal bending
9. Press-fit
10. Dowel connectors
11. Sheet metal: uni-directional scales/hooks
12. Braiding/winding

This week we explored the idea of creating molds, press fits, and scales/hooks:

See Vernelle's page for prior research.