lonepine31 Wrote: ------------------------------------------------------- > Hi Mike, > > Are you organizing another meeting? When is it? > Still at the TechShop? > > Thanks! I was referring to the next South Bay Metalworkers meeting -- on the new schedule of first Tues. of each month, it will be tomorrow night at 7:30 PM, Menlo Park TechShop. You're certainly welcome to atby mikew67 - California, San Francisco Bay Area RUG
Hello, again. Just wanted to mention that I'm working on a "RepStrap" (I guess you would call it that) -- a manually machined (lathe and mill) 3D printer, borrowing RepRap community ideas liberally >< Have just completed a variation on Wade's geared head, machined from aluminum. Showed it to some folks at Maker Faire (e.g., the MakerBot team) who want me to publish the implementation.by mikew67 - California, San Francisco Bay Area RUG
In Palo Alto. Was at the Menlo Park TechShop last night for a South Bay Metal Workers meeting (see our Yahoo group: SBMetal Meets 2nd Tues. of each month, 7 PM, MP TechShop). We didn't have a quorum, but this group was meeting next door, so we merged meetings :-) Interesting session. Thanks, JR, et al. I joined here over a year ago, but haven't been active. Other projects (embedded systeby mikew67 - California, San Francisco Bay Area RUG
Will definitely be at the Faire and will drop by the RepRap booth to make connections with everyone and share stories on experiments with extruder technology. Currently I'm diving into the professional engineering literature on plastic extrusion. Field is clearly very arcane, with lots of patents and trade secrets, and a focus on high volume continuous production. Hope to extract some usefulby mikew67 - General
nophead, Thanks. Great stuff. Seems like the world of RepRap could well benefit from a topic index into your blogs. (Does that exist already? Am I missing something? :-) Mike (another experimenter)by mikew67 - Plastic Extruder Working Group
As a partial answer to my own question -- Take a look at Wade's geared extruder: In his final test, he's able to exert 16 kg force on a 1.5 mm filament. Converting units, that's 3,200 psi!!!! (By my unit conversion, 1 kg force/(9/4 π mm^2) ~ 200 psi. Let me know if that's in error.) That's an amazing number for the little mechanical assemblies used here. I suspect something will leakby mikew67 - Plastic Extruder Working Group
Re smokeless oil -- I do some metalcasting with oil-bonded sand molds, i.e., much higher temperatures than thermoforming plastics. Smoke can be a problem there. Kent State Univ. developed a smokeless alternative to the commercial Petrobond formula, called K-Bond. The trick was to use a synthetic oil which is the common base of 2-cycle smokeless oil. So go to your local motorcycle or outboardby mikew67 - Plastic Extruder Working Group
Folks, If you want to experiment with a couple different thermoplastics, you can get a set of 50 pieces, roughly 1/3 each of PVC, PP and ABS, "roughly" (slightly out of round) 3 mm (1/8") dia. and 1 ft. long. They're sold as plastic welding rods by Harbor Freight: Item 41602, $5.99 or less on sale. HF also sells "plastic welders" of varying complexity (electrical heater, externally-supby mikew67 - Polymer Working Group
Bob M, Thanks for the response -- nophead's blog does indeed contain lots of interesting stuff. A great source and thoughtful author. But could you perhaps point me at some specific posting there that might answer my question? I'm looking for a concise summary. (One of the failings of blogs, wikis, etc., is that unless someone takes the time to summarize the "good stuff", it's hard to find iby mikew67 - Plastic Extruder Working Group
Folks, I'm building a version of the geared extruder to do some experiments on extruder design. Has anyone put together a table of heater power for various plastics vs. extrusion rate? (with a column for extrusion temperature, too :-) How about pressure (or force on the filament) vs temp and nozzle size? Thanks, Mikeby mikew67 - Plastic Extruder Working Group