It will be one of your life's great joys to design and build your own machine and I hope that you decide to do it. One fun thing is getting to decide which parts you'll focus your attention on. Since there are existing designs which work well, you can even decide to focus your attention on nothing in particular except following someone else's instructions, like I did when I built my Mendel90, anby golfwolf - General
QuoteMechaBits @ golfwolf Not sure if old bones are as good as new ones for making glue maybe still good as a filler, perhaps strong & light cross members could be carved, but after people have had allotted time in the ground they get "moved" dumped at sea? I suppose one could argue they become the property of the collective, for the benefit of the group. Would recycled concrete work? By strby golfwolf - General
If you are so lucky to live in a post-holocaust state like America, there are plenty of bones under your feetby golfwolf - General
Another interesting question along those lines, why aren't more people casting their frames with vibration damping epoxy+granite composites, in 3D printed molds?by golfwolf - General
Is anybody speaking from experience ITT, defending lone inventor patents?by golfwolf - General
I'm deadly serious actually. Our technical work is political whether we like it or not. This has been true for centuries now. The options are to support it actively, support it passively, or to deprive it of our support actively, but there is no way to deprive it of our support passively, except by making things which physically serve little useful purpose for warmaking. You'd be fool to not consby golfwolf - General
I have a specific patent question. I discovered (have not published) an extension of exact constraint theory, and I've used it to make an extremely hi-precision, cheap, low-friction linear rail. My question is, would a patent slow down whitey from using it to make weapons? I've studied the history of amerikan whites, the massive holocaust they carried out in North America, how they keep the worldby golfwolf - General
I think it depends what you want to do. The underlying concept of a lot of CAD is that, the process of building models simulates the act of machining. So you can cut extrude to simulate milling, rotate helical extrude for threadcutting, or rotate extrude for turning. I think that's kind of the spirit of it, so in Solidworks for instance you end up with something approximating an ordered list of aby golfwolf - General
I don't have any advice except in the future to consider stockpiling + sealing rare filaments. This is an unfortunate consequence of being market dependent. Someday if Reprap is able to make its entire supply chain, you won't need to worry about the market cutting off supplyby golfwolf - General
Definitely do a CNC lathe... the lathe can make nearly everything a mill can, plus items like your leadscrews, bearings, and smooth rods. A lathe with a boring bar, chucked along the XY plane, can also manufacture flat planes for your build surface. For other things, access to a mill might be more convenient. I think there is more overlap in usefulness between a mill and a 3D printer, than perhapby golfwolf - General
Something like a rack and pinion?by golfwolf - General
Quoteleadinglights Any attempt to download any of the books on this are met wit the message:- ACCESS TO THE WEBSITES LISTED ON THIS PAGE HAS BEEN BLOCKED PURSUANT TO ORDERS OF THE HIGH COURT I am not sure that I would like to steal a copy of the book but equally I am disappointed that the author does not make the book available freely for non-commercial use. If I get some time I may visit a uniby golfwolf - General
the book is available on your local internet technical libraryby golfwolf - General
Very cool design -- in terms of constraint, leadscrew nuts operate on the same principle as motor shaft couplings, so the designs should be similar. Have you considered using V-ways instead of square slots to house the balls? Right now the ball constraints flip from one side of the square slot to the other, creating backlash, but with a V, the balls will always stay nested. Blanding has a numbeby golfwolf - Mechanics
FireLine is kevlar, right?by golfwolf - Mechanics
There are applications where this mechanism would not be appropriate, such as milling machines. The (single) strings work as constraints because the carriage, reliably, has got stable forces. Bed weight and nesting force. Small forces from pulling plastic off the nozzle. Vibration from the X/Y gantry. So a plucked constraint string would raise and rotate the bed, it's true, but there's not much iby golfwolf - General
That is badddd asssss! With the fishing line tensioned with rubber bands it must let it have adjustable 'zeroes', avoiding the problem of overconstraint in the 4/17 post. Out of curiosity, without the rubber bands, are there hard 'zeroes', and does it fall down freely w/o the bands? I'm definitely gonna build this mechanism now. It's climbing up the project roster, faster than an over-counterweiby golfwolf - General
Quoteo_lampe QuoteAnother way is to use ground cylindrical rods as guide surfaces, with flat wheels. That's not the same. When the flat wheel rotates around Z-axis ( center of bed ) and the cylindric rod is fixed, the contact point wouldn't be tangential to the z-axis. That's another constraint. I hope, I made my point clear. I think I see. I'm imagining that, because of the forces from the nesby golfwolf - General
This is a minor note about the 3 constraint wheels. Although in the diagram, the wheels are cylinders, they actually need to be rounded so as to only contact the guide surfaces at one point, instead of a line. A single point of contact, with a rounded wheel, draws a line up the guide surface, of length Z. A flat wheel will draw a plane, of area Z*(wheel thickness). Plane constraints aren't equivby golfwolf - General
I like magnets too I'm picturing a magnetic knife block for the contactless guide surface. Like ICP though, I'm kind of rusty on magnets. If you have a permanent magnet, where the spring-loaded nesting wheel is now, oriented to push against the knife block -- does it still have a straight-line force vector? If it does, does it run into the same instability problem like the nesting wheel? Perhapsby golfwolf - General
Sorry I gave your post a couple days to process but I still don't understand... the nesting wheel maintains a force vector, in the normal plane of the pivot axis. Bumps change the direction of the force vector, spinning around that plane, but we're talking <1deg in practice. Like even moldy pallet wood can maintain that. Changes in force magnitude are not so important, so long as it's >0, oby golfwolf - General
Quoteo_lampe You could do that, but it's against the rules of exact constraint theory. Tilting the axis of the wheel could introduce banding. You could also use linear bearings running on a smooth rod to replace the nesting wheel, but it's the same rule breaker. Let's face it: You'd need two sets of anti-roll cables on X and Y-plane to obey the rules. I'm a newbie with kinematic design, but, noby golfwolf - General
Quoteo_lampe e.g. the spring loaded nesting wheel ist at it's highest load when the bed is horizontal, the spring will always try to push the corner up/down if possible. Oh, true that. I think this could be solved by setting the nesting force vector at a slight Z angle (no longer parallel to the bed plane), with the wheel's pivot hole drilled not straight down along Z, but with a small X/Y compoby golfwolf - General
QuoteMelty Instead of being fixed in place, could the anti-rotation cables be auto-tensioned with suitably strong springs to eliminate some of that risk? That's a good idea -- could I locate the spring beneath the carriage? Forgive me, I'm going to write out the mechanism as I understand it: The anti-rotation cables have a 'stop' position (they're in stop position in the pic). At 'stop' positioby golfwolf - General
Quoteo_lampe Quote Looking at the top diagram, if the bed rotates about +Y or -Y, the vertical cables will attempt to pull in towards the center of the carriage. Since the cables are under tension, this will be resisted and there is no rotation. To rephrase, any rotation should increase cable tension. The cables at the side only increase their tension when the rotation force is in CCW directionby golfwolf - General
Quotethe_digital_dentist I wasn't trying to s**t all over it, just pointing out some of the places where I think there are likely to be problems. The counterweight doesn't have anything to do with the "bed" flexing. The problem is trying to lift the bed from one corner. The edges/corners away from the lifted corner are going to lag the motion at the lifted corner, moving both up and down, evenby golfwolf - General
Quotethe_digital_dentist Interesting. My first impression is that it looks like too many moving parts with too many critical relationships. In a 3D printer, the allowable error is very small because the error shows up in the print surface. I've seen a couple printers made with cantilevered beds and arrangements of crossed cables at the far end of the bed to try to keep it from bouncing. I havby golfwolf - General
Hey yall. Came across this design for a carriage in Blanding's Exact Constraint. There are no leadscrews, and all but the bed, motor, and maybe pulley axles, can be made from plastic. So it's highly reprappable . For background, Exact Constraint Analysis is a new-ish kinematic science used for very, very precise devices. By analyzing all constraints acting on a moving device, and subtracting theby golfwolf - General