Show all posts by user
Discuss any sort of mechanical stuff here: positioning systems, gears, extruding methods, etc.
Re: Isn't welding already FDM metal printing without the messy powder? - 11 years ago
@Have Blue, Yes, I know that Sciaky is doing that, but two-stage machining is, so far, not accepted in the 3d printing world, so it bears pointing out.by Annirak - General
Re: Precision Movement at a Distance - 11 years ago
Wissing Wrote: ------------------------------------------------------- > I got a servo to work off an Arduino... it didn't > seem that complicated, and it was pretty cheap. > Now, the higher-torque ones will probably be more > expensive. Driving the servo isn't the problem... it's controlling the servo that's the problem. > Would it be feasible to use a regular 1-RPM DC > gearby Annirak - Mechanics
Re: Current limiting factors for plastruder performance - 11 years ago
Thanks for taking the time to lay it out for me. 1. Not really my specialty. Unfortunately, I'm not a materials person. But I'll keep my eyes open for a material that has a. A high melt point, b. low friction, c. is easy to work. Do you know if anyone has tried enamelled ceramics? 2. I have a few ideas for dumping heat into the hot end much faster, but I still need to do some experimentationby Annirak - Plastic Extruder Working Group
Re: New arm design for Simpson style printer. - 11 years ago
@LShearer: That's actually, roughly, the design we started with. There are a number of optimizations that we did to get where we are now. Proportionality was a big consideration, so was zero-backlash. We managed to get rid of the belt drive by switching to the (seriously, I'm not being narcissistic; someone else named it) Annirak drive. But it had a problem with non-constant length of the drby Annirak - Delta Machines
Re: How many extruders do you need? - 11 years ago
2 points: 1) Temperature moves slowly. Fast ADCs are not a requirement for temperature control. You can calculate the speed needed from the load variability and the thermal mass heat capacity of the hot end. The load variability is just the power needed at maximum extrusion rate minus the power needed at minimum extrusion rate, multiplied by the maximum rate of change of extrusion rate. 2) I'by Annirak - Controllers
Re: Precision Movement at a Distance - 11 years ago
Servos are a bad idea unless you're buying (expensive) industrial ones. Stepper motors are used for a few very good reasons. Stepper motors can be run "open loop." This means you don't need feedback. Microstepping allows you to divide the precision down to very small increments. With 1/32 microstepping, you can get 0.06 degree resolution. To get something equivalent from a servo, you need a shaby Annirak - Mechanics
Re: Isn't welding already FDM metal printing without the messy powder? - 11 years ago
I think the problem is resolution. If you're willing to accept a two-stage manufacturing process, with additive machining (MIG welding in electron beam mode) followed by subtractive machining (CNC milling), there's a lot of possibility to this.by Annirak - General
Re: New arm design for Simpson style printer. - 11 years ago
@A2: it took me a bit to figure out what was bothering me about your suggestions of additional or asymmetric pulleys. Here it is: the simplicity of the Simpson geometry comes from symmetry. As soon as you break the symmetry, the math falls apart and gets really complex. Your latest suggestion is asymmetric. Because of this, it's much more complex to work out the kinematics. If you think n*(2*pi*rby Annirak - Delta Machines
Re: New arm design for Simpson style printer. - 11 years ago
A2 Wrote: ------------------------------------------------------- > I'm not understanding how a loop corrects for > non-linearity. Please point me to a scholarly > paper that will help me understand the magic of > loops The magic of loops: But seriously, it's a geometry question. As long as you perform complete loops, the total engagement of the cable on any pulley remains equalby Annirak - Delta Machines
Re: New arm design for Simpson style printer. - 11 years ago
@A2, How hard is it, in software, to compensate for the behaviour you are trying to eliminate? If it's easy to compensate, just roll it into the inverse kinematics. The overriding principle of designing new geometries of 3D printer is: pick the best geometry to fit . If this doesn't match cartesian geometry, compensate in software. This is no different. While the solution you propose looks gby Annirak - Delta Machines
Re: Coil-Threaded Rods - 11 years ago
All the official RepRaps seem to have threaded rod for the Z stage, so this is well known and well accepted. What's the tolerance on the threads? If the electronics are replaced with PID controlled servos or gearmotors, threaded rod has lower power consumption because it requires lower holding torque. So, the Z stage would only consume power during the z-adjustments. I'm not sure you could poby Annirak - Mechanics
Re: Sourcing dc, ac, and bldc motors - 11 years ago
Also, it seems that a 2-phase bldc and a stepper are functionally equivalent. The stepper just has more steps and is intended to run open loop, where bldc is intended to run closed loop. Perhaps I should focus on dc motors with printed gear boxes.by Annirak - Stepper Motors, Servo Motors, DC Motors
Re: Sourcing dc, ac, and bldc motors - 11 years ago
I know that bldc is complex to drive. That's not my concern; I'm trying to find low cost, light weight, high torque motors. A team order, I know. But ACIM, BLDC, and DC motors are supposed to be simpler and lower cost than steppers, so I'm hoping that I'm just looking in the wrong place.by Annirak - Stepper Motors, Servo Motors, DC Motors
Sourcing dc, ac, and bldc motors - 11 years ago
I've heard countless claims that DC motors are less expensive than stepper motors, likewise that bldc are cheaper still. What I haven't been able to find is a source for these rumoured cheap motors. I'm looking for a DC, AC, or BLDC motor with a torque/speed product equivalent to our favourite steppers. Say, 4000g.cm at 60rpm. The problem I've found is that all the cheap, hobby BLDC motors areby Annirak - Stepper Motors, Servo Motors, DC Motors
Re: Grounded Experimental Delta Printer - 11 years ago
Quotepjoyce42 Actually my original thought would be to use some of the aluminum extrusions from 80/20 or rexroth. I don't know the exact numbers, but I would expect that the torsional stiffness is, at a minimum, comparable to the 3d printed plastic arms of the same cross-sectional area. I was trying to avoid round rods because then you would have to find a way to fix the rod. With the aluminum exby Annirak - Delta Machines
Current limiting factors for plastruder performance - 11 years ago
While I've been working on electronics and delta bots, I haven't paid much attention to extruders. I have heard that the extruder is currently a limitation in how fast printing can go. Is this a fluid dynamics problem (increased resistance in the filament at higher speeds) or is it a thermodynamics problem (the plastic is not being heated fast enough)? Or, is it something else entirely?by Annirak - Plastic Extruder Working Group
Re: Grounded Experimental Delta Printer - 11 years ago
That print looks pretty good! I have to have a black-hat moment: Can you ramp it up any more? Or did you hit a step-rate limit?by Annirak - Delta Machines
Re: Grounded Experimental Delta Printer - 11 years ago
Yeah, I had one force triangle flipped, which mixed up my whole batch of math and complicated things.by Annirak - Delta Machines
Re: Idea: A blacksmith bot based on Simpson - 11 years ago
If you're going that route, you could to fine-gauge MIG welding. If you can get the right mode of welding, the arc actually transports the metal to the work surface. Not sure what kind of resolution you'd get, though.by Annirak - Delta Machines
Re: Grounded Experimental Delta Printer - 11 years ago
Please correct me if I'm wrong. EDIT: Turns out I'm wrong. I've still got to get some decent geometry software together so that you can see what I'm talking about, but here's my attempt at a description. For simplicity, I've ignored block/tackle setups. All they do is change the tension anyway. There are two lengths that are important: d1 is the distance from the center of a gear to the stby Annirak - Delta Machines
Re: New arm design for Simpson style printer. - 11 years ago
Have you run any Finite Element Modelling on the arms to check for stress points or model the wear?by Annirak - Delta Machines
Re: Grounded Experimental Delta Printer - 11 years ago
There's one thing that's been bugging me since the start of the gear-based design. I'm not sure we can fix it without breaking the simplicity of the math. The two pairs of mounts have an asymmetric range of motion. The outer bolts get much closer together than the inner bolts. The inner bolts get much further apart than the outer bolts. Unless my physics are horrendously wrong, what this worby Annirak - Delta Machines
Re: Grounded Experimental Delta Printer - 11 years ago
QuoteBuytaert I don't know programing, but there's a thing called Parallella that look interesting : I have a couple of those ordered. They certainly have the processing power, but the other part of the question is whether they can handle the latency. How fast do you have to respond, and is that even possible?by Annirak - Delta Machines
Re: Grounded Experimental Delta Printer - 11 years ago
I'm being pedantic. Quotenicholas.seward The Annirak Drive or the Proportional Gear Joint Drive both make the relative rotation of one of the steppers proportional to la, lb, or lc. Not quite. I mean, it's close enough to make little difference, but I think it's an important distinction. The PGJD has an additional term: La = gc + lw * ka / kp where La is the total arm length, gc is the consby Annirak - Delta Machines
Re: Level shifter issues - 11 years ago
After looking into it some more, these are the options I've come up with: L6743 FAN3100 They're both in a similar price range and they are real MOSFET drivers, not just high speed current amplifiers.by Annirak - Controllers
Re: Grounded Experimental Delta Printer - 11 years ago
I thought I doodled the inverse kinematics up at the start of this thread. They need a little updating for the new design. Nicholas.Seward used essentially the same math, but with some simplifications. I don't think that some of those simplifications still apply (e.g. shoulder joints are no longer cosited in the x-y plane. QuoteAnnirak You have three input variables: the three angles of the eby Annirak - Delta Machines
Re: Level shifter issues - 11 years ago
So I had to do some sim to get a decent answer; thankfully, Diodes Inc. provides SPICE models for these devices. It turns out that the reason there's no VIH or VIL is that there isn't one. It's a pure current amplifier. The output voltage is (roughly) the input voltage. I guess these aren't really effective for level translation.by Annirak - Controllers
Re: Level shifter issues - 11 years ago
QuoteNoobman Just imho, this context is not ideal, especially not when talking about fast switch times and precise control What, 46ns is too slow for you? at 100kHz, tr=46ns, tf=35ns changes the output duty cycles less than 1%. Those times are with a 10nF load, which is far higher than you'll get with a MOSFET. Aren't these MOSFETs used inside a PID loop? Well, PID is what guarantees precisioby Annirak - Controllers
Re: New arm design for Simpson style printer. - 11 years ago
MattMoses Wrote: ------------------------------------------------------- > A2: If you would like help setting up a > wiki page, I'd be happy to give you pointers. The > easiest thing to do is to pick a page you like, > and use it's source as inspiration. You can create > and call your page pretty much whatever you > want... something like > "A2_Variant_Simpson_Build_log" woulby Annirak - Delta Machines
Re: Level shifter issues - 11 years ago
Have a look at ZXGD3005E6TA. It's pretty low cost and has a peak output current of 10A. That's the absolute maximum of course, but it's still not bad.by Annirak - Controllers