paper tape trays

On Wed, Apr 25, 2012 at 1:24 PM, Richard <legalize at xmission.com> wrote: I have built several printers and organize activities and lecture on the topic. I am not a doomsayer - I think 3D printing is really cool and I am especially excited about under-$2K-USD models to get the technology into the hands of people like the members of this list. That said, it's not a magic bullet, it's not cheap as chips, but for the situations where it's a good fit, it's cheaper than many traditional manufacturing techniques including bypassing the mold-making costs of injection molding, the labor costs of traditional machining, and since shapes are freely shared on sites like Thingiverse, even sometimes bypassing the expense of skilled labor to design the parts in the first place. It fits a niche between one-off hand-made prototypes and true mass production. If you need exactly 1 or if you need thousands/millions, there are other ways to accomplish your task. If you want dozens or if you want minor customizations that don't map well to economies of scale, it can be a less expensive choice than endless engineering revisions. As for straight dollar cost per item, it depends entirely on the size of the object and the printing technology. Hobby-grade FDM (filament deposition modelling) printers are coarse but inexpensive. The filament is typically plastic welding rod in 3mm or 1.75mm diameters and can be purchased for as little as $12USD/lb. A toggle switch is indeed cheap, but because the output nozzle is about 0.3mm-0.5mm, it will have a coarse texture. Sintered powder printers produce smoother results for a higher cost (don't have exact numbers, but not $12/lb). Stereolithography produces very nice high-res results, but the resin costs $200 per *liter*. I just did some calculations for someone, and a solid badge 50mm x 50mm x 6mm (2"x2"x1/4") is about $3.50 USD just in resin. Hobby grade printers are also smaller than professional printers. I have some DEC papertape trays - they are about 8"x10" and hold several sets of papertape in partitioned bays. Mine are cast acrylic, though I think I may have seen some once made of vacuformed ABS with an acrylic lid. A hollow box with sidewalls at least 1mm thick and a floor at least 3mm thick (so that you have several layers of filaments to bond together for strength) that's 8"x10"x1" is going to weigh several ounces and won't fit on most hobby-grade printers. The MakerBot CupCake (somewhat common with several thousand made) has a 100mm^2 (4"x4") bed... too small. Various RepRap models can print up to about 200mm^2 (8"x8") - a bit smaller than the trays I've seen, but you might be able to make something work. I don't have a shape to run through my calculation tools, but based on the badge price, printing a tray with Stereolithography would run at least $30 in resin alone, and probably closer to $50. These are open-topped designs, BTW, a base, sides, and partition walls - it skips the problem of support material, etc., to allow printing a lid. Vacuforming a tray should cost no more than a few dollars each, once you have a tool large enough to pull a form around 8"x10". Oh... and I forgot slow... a medium-sized item, something that fits in the palm of your hand, can take 2 hrs to print on a hobby-grade FDM printer. Stereolithography often is rated as to how many millimeters per hour the part can "grow" (one entire layer is done as one action, so it matters little for printing time how extensive each layer is and matters greatly for how many total layers there are). I would budget several hours to print something 8"x10" on a RepRap. Each. It would be faster (but probably not cheaper) to CNC mill a tray out of a single block of plastic - HDPE (high density polyethylene) for example. Unfortunately, unless you are buying scrap, it's going to be many dollars for a slab of plastic that thick. Time-Cost-Quality - pick two. -ethan