If you mean twisting in order to have the flat belt back go over flat pulleys, that's great except where you attempt to twist a length of belt that varies in span, e.g. between motor and carriage. The twist could end up very tight. Or if you're twisting so that the crossed belts don't collide, you would still need some vertical separation in order to prevent abrasion. If you have a look in myby polyglot - Mechanics
50um positioning repeatability seems reasonable considering the generally oozy nature of extruded plastic coming out of a 250um+ nozzle. Your typical belt-drive has about 25-100um of repeatability and a nominal resolution of maybe 10um but that last number/"specifiction" is based on micro stepping and is entirely in the imagination as soon as there is non-zero load on the stepper motor. An acmeby polyglot - Mechanics
I've got a dimensioning question/problem. I'm trying to build a corexy out of all off-the-shelf aluminium bits, which means using bearing pillows like SC12UU etc. I'm using 12mm rods because I also want to do a bit of light milling on this machine. Anyway, the problem is that the SC12UU are 28mm deep which means that the gap in the middle of my X carriage is 56mm smaller than the total Y-widthby polyglot - CoreXY Machines
Might be easier to mill from solid dry foam. The cutting forces are pretty low even with a big cutter so a reprap-style build is probably rigid enough.by polyglot - Let's design something! (I've got an idea ...)
QuoteOhmarinusthe only thing that didn't work were the small 8mm posts. They were too thick, but only by a few micron. I had no tools to grind them down, so I decided to find another solution. They're probably expecting you to press them into bearings using a bearing press. It's meant to be an interference fit.by polyglot - CoreXY Machines
There are a lot of $2 pulleys on eBay but the quality seems uniformly horrible. I just laid down cash for a Bulldog XL extruder and Hexagon J-head, so I better get cracking on the rest now.by polyglot - CoreXY Machines
Thanks for the robotdigg link, it looks like they're the upstream supplier from our local shop and half the price on everything I also hadn't thought of twisting belts. Taking rcengr's diagram on the right and putting a twist in the belts where they cross would mean all idlers running on the back of the belt and no extra idlers required. Twisting the belt next to the motor worries me a bit thby polyglot - CoreXY Machines
Oooh, 2 of 604ZZ flanged bearings stacked ought to make a nice flat idler. And a stack of three or so MR84ZZ inside a toothed pulley with 8mm bore ought to make a passable toothed idler. Still seeking opinions on the inverted belt configuration and the relative merits of moving knot vs torsion bar for keeping the bed straight.by polyglot - CoreXY Machines
I'm pondering building a CoreXY+Z system and have a couple questions that I'm hoping you can help with. Does anyone know of an affordable source of GT2 idler pulleys? With shipping to Australia? The only ones I see on eBay are $15 each shipped and I need lots of them. If not, does anyone know of an easy way to hack up an idler with flanges (to stop the belt wandering off the sides), e.g. fromby polyglot - CoreXY Machines
The advantage is higher speed traversals, especially on stepper drivers and/or firmware where the step rate is limited. For example, those Toshiba drivers can do only 30kHz or something like that, and some of the Arduino-based firmware is limited in its step rate. Consider the case where people are using screw drives, e.g. 4mm pitch on a 200-step motor would be typical, for a step size of 0.02mby polyglot - Developers
Current boards (RAMPS, RUMBA etc) seem to have microstepping enabled via dip switches/jumpers on the board. Would it not be better if these were GPIO pins and could therefore be set via firmware? That would allow a firmware to enable microstepping when extruding shells and then disable it when performing fast traverses and maybe on infills if you have a powerful hot-end. Even a simple full-steby polyglot - Developers
Hi all, I'm considering building a MendelMax 1.5 (my first 3D printer build) and looking for a direct-drive extruder and hot-end. I stumbled on these things or their myriad variations on eBay and was wondering if anyone had tried them. The lack of any gear ratio between the tiny stepper and the filament seems to me like it's asking for trouble. If doing direct-drive, should I get one of the gby polyglot - General Mendel Topics