ElectrochemicalMillingDrillingHead < Main

Main.ElectrochemicalMillingDrillingHeadr1.2 - 04 Dec 2008 - 22:58 - EnriquePereztopic end

A RepRap has the potential to be converted to an electrochemical machine by equipping it with an electrochemical machining (ECM) tool head. With this tool head, it could machine any conductive material, regardless of how hard it is or how high its melting point.  In electrochemical machining, the tool head is the cathode, with a negative voltage, and the workpiece is the positive anode. The workpiece is immersed in an electrolyte and the filtered electrolyte flows through or around the tool head.  There is very little tool wear and the objects milled in this way are not distorted. This would allow the RepRap project to produce its own custom metal parts.

It is described at the "Electrochemical Machining" page of the "Manufacturing Engineer on a Disk" at:<br />
http://www.eod.gvsu.edu/eod/manufact/manufact-281.html

and at the Electrochemistry Encylclopedia, at:<br />
http://electrochem.cwru.edu/ed/encycl/art-m03-machining.htm

Do it yourself, home electrochemical machining is described at:<br />
http://www.indoor.flyer.co.uk/ecm.htm

A 24 gauge blunt tip stainless steel dispensing needle coated with high temperature lacquer up to just the tip should make a good machining head. You could use a smaller diameter needle for better accuracy, but smaller diameter needles tend to require higher pressures to push water through them(~20-50 psi).<br />
http://www.zeph.com/applicator_tips.htm

Electrochemical milling uses about three kWhr/in^3.  When machining iron, with a density of 7,870 kg/m^3 (7.87 g/cm^3):<br / >
http://hypertextbook.com/physics/matter/density/

that works out to: 3 kWhr/in^3 / (2.54cm/in)^3 / 7.87g/cm^3 * 1,000g/kg =~ 23 kWhr/kg.  At a high electricity price of 0.3$/kWhr, that works out to: 0.3$/kWhr * 23 kWhr/kg =~ 7$/kg.  Seven $/kg is in the ballpark of plastic filament, assuming that you remove a similar amount of metal as you keep, which would be the case for a sphere for instance.

-- Main.EnriquePerez - 13 Aug 2008

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