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Open Rapid Unlimited Geometry Destroyable mold molding and casting



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Description

video: https://drive.google.com/open?id=1VGlquEBo5x0yyUD2698-msUQTolf16_l
More details: https://drive.google.com/open?id=1Pyen9GwdQuxgJ7-u9vSK6CIJEq8jVhNI
OpenRUGDMMAC,  pronounced "open rugged-mac", is essentially a successor to 3d printing.  It uses additive combined with subtractive manufacturing techniques to overcome the fundamental weaknesses of both.  The system produces highly accurate, disintegratable molds of almost any desired shape, with none of the geometrical or accuracy limits imposed by machining, or 3d printing in their usual form.  These molds are then filled in sort of premium molding or casting process.  The part, still surrounded by the mold, is submersed in a water bath, subject to ultrasound to disintegrate the mold, even from the smallest cracks, and you have your part.

Features include:
-Inherently capable of higher accuracy than 3d printing.  This is very important for many applications, where parts must have bearing surfaces, seal against fluid leakage, snap together, or otherwise fit effectively.  This also means smooth surface finishes.  There is none of the stair step effect seen in conventional layer by layer additive manufacturing. The distortions caused in sintering and heat treatment can also be greatly reduced through techniques that include the use of a custom shaped, highly accurate, temperature resistant mold.

- It is inherently far faster for large objects. Things like engine parts, agricultural power tools, even a whole automotive chassis can be produced relatively quickly, because the milling process speed increases greatly with the size of the tool used, and larger objects allow for larger tools.  Unlike 3d printing, there is no need to compromise on accuracy or feature size to achieve high build speeds.  Although there are many techniques that involve larger and smaller nozzles used in the same print, 3d printing is still fundamentally quite slow due to cooling times, and the very small layer heights needed to achieve the accuracy required of real parts.

- Leverages the well proven process of 3d rest milling.  This utilizes successively smaller tools to reach where the larger ones cannot.  It's fast, yet highly accurate and provides high detail.

- Capable of realizing parts with almost any feature size, aspect ratio, and sharpness, through the use of a sufficiently small layer height and sufficiently small diameter tools.  This is an essential enabling and distinguishing factor.  We can make objects as thin as a water bottle wall, and as small as micro gears, or as large as a car chassis, or features like this all present in a single part.

-  Capable of producing stress free parts.  This is also a core empowering factor, which allows us to reach further than conventional layer by layer manufacturing can, and yet with a very wide range of materials.  Stress is a concept that is not commonly understood in the maker community, but it is a critical factor in any manufactured part.  In conventional layered manufacturing, the layers contract upon deposition, and this leads to the so called elephant foot phenomenon, in which the part curls upward off the build plate.  This occurs with essentially all additive manufacturing, and adds up with each layer becoming crippling for larger objects.  Although there are many methods to try to mitigate this, they always have and always will be far from perfect, and will be specific to the materials used.  Rugdmmac avoids this by printing a cast out of specialized, low shrinkage materials, and then producing the final part from a very wide selection of materials, without the complications of layer bonding, or layer by layer shrinkage.

- Capable of using a very wide range of materials relatively easily, with little additional development effort.  Metals of any kind through casting or sintering, the toughest ceramics through gel casting and sintering, unreinforced or fiber reinforced plastics of nearly any kind - including polycarbonate, peek, nylon, specialized plastics for chemical engineering or medical uses.  Even glass is commonly injection molded.   Elastomers such as natural rubber or silicone rubbers.  Foams, for the soles of shoes or garments.  This is the third core enabling factor.

- Unpatentable.   This process has been publicly known since 1992.  It is based on readily available, basic technology.  We merely need to combine a straightforwards material addition process with conventional rest milling technology, and write some software to harness existing cad/cam tools for the creation of the final Gcode the material will run.  There is no new science needed. 


See more in the 
short version doc, dig deeper in the long version doc. 

Goals : Develop the hardware (robot, including an auto tool change high accuracy router and the deposition apparatus) and the software. A plugin for fusion 360 will get us a long way.

Background: This project is the direct outgrowth of two years of experience in fablabs and makerspaces around the world, full time.  Including 4 months at open source ecology. Humanity currently has no way to economically make accurate objects, especially of a size larger than your fist, especially of high complexity or with certain features, especially of metals or other tough materials.  This technique will provide major progress on all those fronts practically overnight.


OpenRUGDMMAC_CAS
OpenRUGDMMAC_Path_to_market

Applications 

  • digital fabrication
  • add more...   

Short-term goals

  • Design considerations
  • Design
  • Prototyping

Long-term goals

Milestones

  • Build team
  • Structure project
  • Design
  • Find a lab for prototyping
  • Product design

Announcements

  • Public domaining of ideas I got a bit worried over the last couple of days that there might be patent encumberances on some of the ideas here, because it has become clear that there ...
    Posted May 24, 2019, 7:18 AM by Anthony Douglas
  • work continues, very slowly Things are continuing.  My current focus is to try to create a plugin in fusion 360 which will allow the automation or semi automation of the CAM programming process to ...
    Posted May 16, 2019, 4:17 PM by Anthony Douglas
  • work continues, very slowly Things are continuing.  My current focus is to try to create a plugin in fusion 360 which will allow the automation or semi automation of the CAM programming process to ...
    Posted May 16, 2019, 4:16 PM by Anthony Douglas
  • work continues, very slowly Things are continuing.  My current focus is to try to create a plugin in fusion 360 which will allow the automation or semi automation of the CAM programming process to ...
    Posted May 16, 2019, 4:15 PM by Anthony Douglas
  • Progress report I have made some substantial progress in the last month and a half, mostly because I have had a vague semblance of a workspace, a section of a shared two ...
    Posted Apr 9, 2019, 10:39 AM by Anthony Douglas
Showing posts 1 - 5 of 6. View more »

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Tools, activities, and processes

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Skills and resources needed

  • Software engineering: Python.  Probably the fastest, most effective approach is to write an add in for fusion 360 to do the gcode generation.  We can simply use EMC2 or grbl to interpret the gcode all the way to the relevant stepper motor signals, and accept input from sensors to run custom python programs.  Major progress has been made on this already.
  • We require above all a stable, reasonable quality room to work in.  It may be a shared room, but we need about two hundred square feet as a bare minimum.  This is by far the largest barrier in any of this, and the first hurdle, only after the resolution of which can anything else proceed.  A benefactor is currently allowing me the use of his garage. We have the funding to pay rent.  However the market is very poor in this regard; this sort of thing is extremely rare on the rental market.
A good micrometer, digital calipers, and hole gauge, a small selection of small end mills from quarter inch to 1/32, carbide.  Some v/conical end mills of the types commonly used in pcb manufacture. Oscilloscope, good Vom, good soldering iron. 
Powders of graphite from ten to 100 microns diameter, ideally a selection.  

-Calcium aluminate cement, of good quality and high purity.  Lithium chloride is the best accelerator, and can cause setting in about thirty seconds at a concentration of 1.5 percent, so we need some of that.  Fine ball milling also can help. Addition of already hydrated material in powdered form may also help

-Some low expansion calcium sulfate, such as so called dental stone such as Zero Stone, there are a couple other brands.  They are not the same as plaster of paris, but are much more highly refined, and set much faster to much stronger materials.  The proprietary mixes also contain setting accelerators such as potassium sulfate or less ideally zinc sulfate to cause setting in roughly six minutes, compared with fifty minutes for plaster of paris.  Fine milling of the particles also helps.  We may want to subject it to more ball milling to further reduce setting time.  Addition of already hydrated calcium sulfate dihydrate crystals as a powdered form also helps a lot, and in addition.

-Some graphite powder to use as a filler.  Bonded powders are generally adviseable, as they have good properties after deposition, and tend to shrink or expand little.  The dental stone and CAC are primarily binders.  We can use a high fraction of filler without worrying about flow properties, because the material can be packed with a plate into the desired areas.  Indeed, to use only sparing amounts of binder, allowing what it is ultimately a micro porous solid to be produced, has many advantages. It solves the problem of entrapped bubbles, and it also good during casting, because you may dispense perhaps with a vacuum.  It would cause some compromise on surface finish as the porosity is transferred to the finished part.  The strength will also go down with reduced binder ratio. However, we do not need it to be very strong.

- We will need an accurate, auto tool change 3d milling machine using emc2 as the controller.  This is a critical requirement. This is quite expensive. It may be about four thousand bucks. The spindles used on pcb milling machines, which directly grab eigth inch end mills without tool holders, are about five hundred bucks each on ebay, and may be a good bet.  The next closest will be 1800 bucks, it would be one of the hard to find auto change adapters for a conventional china spindle.  The synchronous motor ittself is only a hundred bucks or so. Unfortunately, no one has laid the foundation here, although it should have been done; such tools should be available off the shelf, but they are not.  

- We will need to fabricate an apparatus that mixes and pours the plaster like material, and removes bubbles through some means, perhaps vibration.  For this we can use openbeam, some connectors, and belt and toothed pulley stepper motors with whatever linear bearings.  Emc2 can probably control the stepper motors, the same controller as the main cnc machine can probably be used.  Otherwise we can use an arduino that accepts data from the main gcode program, completes the deposition, and tells the main gcode program to resume when it is done.  Most of the custom parts can probably be produced through 3d printing, including the powder and liquid dispensing, mixing and rinsing provisions. RC servos can be used as basic actuators where steppers would be more complicated, such as valve actuation and small, repeatable actuations.

We need above all, peace, stability, time, and some collaborators to draw upon when needed.



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