Home |
Search |
Today's Posts |
|
Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
Reply |
|
|
LinkBack | Thread Tools | Display Modes |
#41
Posted to rec.crafts.metalworking
|
|||
|
|||
Duplicate Boring
On 4/11/2011 5:26 PM, Ed Huntress wrote:
wrote in message ... On 4/11/2011 2:40 PM, Ed Huntress wrote: Molding polystyrene beads.g (Styrofoam is a trademark name for EPF -- expanded polystyrene foam, You may be looking for the word "Extruded". Kevin Gallimore Styrofoam is indeed extruded, but the generic definition for EPF is "expanded." Extruded foam was expanded in the process of making it. You'll see both definitions for EPF in the industry literature. Dow uses the acronym "XPS" for "Styrofoam" brand extruded polystyrene foam. http://building.dow.com/media/news/2011/20110112a.htm Kevin Gallimore |
#42
Posted to rec.crafts.metalworking
|
|||
|
|||
Duplicate Boring
On Apr 11, 2:26*pm, Tim Wescott wrote:
On 04/11/2011 10:14 AM, Spehro Pefhany wrote: On Mon, 11 Apr 2011 09:53:05 -0700, Tim wrote: On 04/10/2011 03:19 PM, Brian Lawson wrote: On Sat, 09 Apr 2011 13:47:57 -0700, Tim wrote: SNIP Because the process is to put a flat piece of foam in the mold, clamp it, then chuck it in an oven to heat. *The foam* softens and expands to meet the edges of the mold. *Then you take it out of the oven and let it cool, and voile! *A part (or a mess -- it's best to enter any sort of casting process with your eyes open). SNIP I've never done it, but it reads like what you want to do would be achieved with blow molding. *You could even put "tread" on the tire then. Interesting thought. *Probably beyond the sophistication I was aiming for (mostly hand tools, with bits& *bobs turned on the lathe). And I think blow molding is for styrofoam beads, which isn't what Depron is. *I'm not sure that I've seen styrofoam beads that are small enough for a wheel that's 3/16" thick and 3/4" diameter. Blow molding is what is used to make plastic bottles. Basically a thick plastic goober* is extruded vertically (the plastic has to be of a type that has a viscosity high enough that it doesn't drool off the nozzle). The mold clamps around the parison (sealing off the bottom end) and then it's inflated with compressed air through the top. After it cools a bit, a nice sharp knife called a moil** slices off a bit at the top (usually the top of the neck where the closure goes), the mold opens and the bottle falls out. The tab at the bottom is stripped off automatically or manually. I don't know how you'd do this without a rather complex machine- but the molds are relatively easy because the pressures are very low by molding standards. * It's called a "parison", a term borrowed from a French term "paraison", relating to glass blowing. ** not joking, that's what it's called-- at least it's not spelled "mohel". Ah -- that wouldn't work, and once again I'm confused in my terminology. * The application is very weight-sensitive: indoor rubber power competition rules call out a seven gram minimum weight for this sort of plane*, and that minimum is _very_ hard to build down to. *I've got a pair of wheels that look injection molded, but have about the same wall width as most of the blow molded things I've seen. *They weigh in at 600mg for the pair, while my wheels weigh in at less than 100mg each. So what do you call molding with styrofoam beads? * AFAIK, just about anything with wheels and a minimum weight calls out 7 grams -- 14 grams for outdoor. -- Tim Wescott Wescott Design Serviceshttp://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details athttp://www.wescottdesign.com/actfes/actfes.html- Hide quoted text - - Show quoted text - I seem to remember seeing something about expanded polystyrene molding in a microwave oven. If that's possible, then you could make your molds out of wood, which would be a whole lot easier. Another option might be vacuum formed plastic over a wood pattern.Shouldn't be too hard to cobble up a small vacuum forming rig. You could even buy a Mattel Vacuform - There are plenty of people still selling sheets for it. |
Reply |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Duplicate Census Forms | Home Repair | |||
Suitable boring bar for use in sideways hole in boring head? | Metalworking | |||
Duplicate an antique finish | Woodworking | |||
Duplicate Spindle Nose | Metalworking | |||
best way to duplicate hole in bronze? | Metalworking |