QuoteDale Dunn The first interesting thing is that ABS has the reputation for being stronger, but PLA tested with both higher tensile strength and elastic modulus. My guess is the heat resistance of ABS makes is seem stronger when building printers and other things that get warm. Characterizing strength is tricky thing. In a complex part, the kind we love to print on 3D printers, there are typiby LoboCNC - General
Quotekarabas BTW there are many steppers with already integrated encoder on ebay. Are they suitable? For simplicity, my closed-loop stepper controller needs the number of encoder counts per rev. to be equal to the number of microsteps per rev. (or otherwise some integer multiple). Right now, I'm using 16x microstepping which gives 3200 microsteps per rev. I'm then using an AMT103 encoder set fby LoboCNC - General
I actually tried this and it didn't work very well. By the time I got enough compression force to drive the filament effectively, the rolling friction of the highly compressed rubber took a huge amount of torque. It takes a lot less torque to effectively cut teeth into the filament, which allow for a much higher driving force. It could be that playing around with different durometer rubber myby LoboCNC - General
Quoteohioplastics This may be a dumb question, but does metric acme rod exist? I've only ever seen imperial McMaster-Carr sells metric ACME rod.by LoboCNC - General
Acme rod does tend to be straighter, but I've certainly seen some crooked ACME rod, too. The main advantage of an ACME thread over a standard thread for power transmission applications is that the more square thread (29 deg. v. 60 deg. as Ralf points out) reduces the friction in the axial direction (the direction you are pushing). The down side of that is if there is any side loading of the nutby LoboCNC - General
Quotekarabas So what have you decide about kit/chip selling? I've been pulled off on another project, but I'm hoping to get back to the closed-loop stepper controller soon. I am leaning towards selling a kit (board + enclosure) and putting together a list of compatible dual shaft motors. Hopefully in the next 2 months.by LoboCNC - General
Your steppers sound pretty normal to me for a screw drive mechanism. Screw drives are much stiffer and transmit much more noise. I'm guessing that the axes with the intermediate belt drive reductions are less noisy. You can often quiet things down by lowering the current limit setting on the drivers. You can lower the current so that you have enough torque when operating at low speeds. At hiby LoboCNC - General
Thanks for the isopropyl alcohol tip. The rest of the board looks pretty cleanly built, and the current sense resistors do look to be real 0.1 ohm resistors.by LoboCNC - General
I recently got 3 Printrboard clones (GEEE Tech) on ebay. Only $60 ea with free shipping from China. (I still don't see how that works.) The boards looked good except they weren't cleaned well - a uniform resin film over them. I figure their cleaning vat solvent was long over due for changing. Not being hugely familiar with Arduino stuff (I had managed to wrestle a Brainwave board into submisby LoboCNC - General
Any non-linear printer is going to have non-uniform accuracy over the build area. This is because any irregularities (play in joints, unequal length arms, unequal spacing of the towers, parallelness errors in the towers or arms) will manifest themselves to different degrees at different points in the workspace because the kinematics are highly non-linear. e.g, say one arm is a little longer thby LoboCNC - General
I suspect the zero backlash has more to do with the fact that all axes are gravity loaded, which takes the play out of the joints. You could take a standard Cartesian printer with sloppy joints, tilt it at 45 degrees and get the same effect. (Of course, you'd have some pretty weird overhang issues)by LoboCNC - General
The motors you're looking at are mid-range. The shorter motors (34mm) are typically have ~30 oz-in holding torque, the 40mm ones (like yours) are ~50 oz-in and the longer 47mm ones are ~70 oz-in. The separable cable is a nice feature which makes assembly and disassembly of your printer easier. The current of 1.2A doesn't mean anything by itself - other than that's the max. current your driverby LoboCNC - General
Quotejamesdanielv LoboCNC, provide that feedback to the page author. Now here's a stupid question: I've looked over the Slic3r manual web pages and haven't seen any obvious place where I can provide feedback (presumably to the author, Gary Hodgson). I must be missing something obvious.by LoboCNC - General
QuoteOhmarinus But seriously, the web is not kindergarten anymore. In 2014 you would expect people to google for stuff, this is very easy to find out! Please tell me if I'm too rude, but I really feel like this needs to be said sometimes. And I know that even I can post the most rediculous stuff, however I do look for my information through google before I start asking. It is a fine line to walkby LoboCNC - General
I fully understand the motivation for the original post. It's nice that there is a Slic3r manual, but as I've found with much of the wikis and other documentation for open-source 3D printing, it seems to be written for people who already have a good idea of how things work. If you read over the Slic3r manual after having done a bunch of prints, it is is a pretty good resource. If you are justby LoboCNC - General
Seems like there are two camps - those with extruder issues and those with occasional skipped steps. Sounds like additional sensing and feedback control is needed all the way around to make 3D printing completely reliable.by LoboCNC - General
Quotekarabas QuoteLoboCNC The driver boards you mention are really nothing more than a driver chip on a carrier board. Yes I know. I mean the breadboard approach is reasonable here for lower cost when DIY kit. Honestly saying I am a bit sceptical about selling this as a product for low demand. Oh, I see. And thanks for your opinion - that's what I'm looking for - to see if this is worth doingby LoboCNC - General
The driver boards you mention are really nothing more than a driver chip on a carrier board. For closed loop control, you need a micro reading the encoder and then executing a fair amount of code to perform the closed loop control. You also need to be able to control the REF input for the driver chip with a high resolution PWM output. The data sheet describes all the gory details.by LoboCNC - General
The data sheet I put together (ps3.pdf) has a schematic.by LoboCNC - General
Right now, I'm trying to decide if I want to make the boards available as a product or not. There is also the possibility of just selling the pre-programmed PIC-SERVO S3 controller chip. (Unfortunately, I can't open-source the controller chip firmware because it is based on proprietary code not owned by me.) Hopefully, I'll have my plans sorted out early next year and will make an announcementby LoboCNC - General
In the original post, I think I mentioned that the incremental cost of the closed-loop control over an open-loop system would be more like $60 per axis, or $240 more for a whole machine. But it might make sense to just use closed-loop control on the extruder, or maybe just on the X & Y axes. Some kind of machine vision would be cool, though, if you could discern a position errors of a few sby LoboCNC - General
Yes, the closed-loop servo controller can correct for pretty much any size of position error. With an open loop stepper, if the motor gets out of position by more than 1 full step, the motor is actually locks onto the adjacent detent position which is 4 full steps off from the desired position. With the closed-loop servo controller, the motor is constantly pushed back to the correct goal positiby LoboCNC - General
Yes, closed-loop control of the motor will allow it to move past minor nozzle collisions with curled edges. The motor may get pushed out of position a little, but it will spring back into position after it has moved past the obstruction, and the rest of the print will not be affected. With a really major obstruction, though, the closed-loop servo will eventually give up. I usually set the maby LoboCNC - General
Quotealj_rprp However, did you look in the DIY CNC milling crowd like shapeoko ? Here, the higher loads on axis make a closed loop system highly desirable. Actually, I'm already selling a 3-axis closed-loop controller board for the Lobo CNC milling machine.by LoboCNC - General
Quotejamesdanielv there was something interesting mentioned in this post. extrude issues and stalling could be detected. if it could then reliability of the machine would improve, however the feedstock usually stops feeding, and the motor shaft rarely stops. the place to control the extruder feedback should be somewhere else other than the motor. The way you could handle the filament stripping wby LoboCNC - General
Oh, I see what you are saying - why move the axes faster when extruders are already close to maxing out. I suppose if you are printing really thin layers, then you do want to move fast but the extrude rate is fairly low. For some of the all-metal hot ends that don't like extruding at low rates, you may actually want to move the axes faster to keep the extruder happy. What I've gleaned from allby LoboCNC - General
QuoteRobin2 @lobocnc, it looks like "nobody knows or cares". I suspect you are right - that most people are happy enough with open-loop steppers to not bother thinking about the issue. But then, most people are happy with their computers until they are shown a faster one. I'm trying to figure out if closed-loop control would improve performance for the average printer. QuoteRobin2 On the othby LoboCNC - General
Quoteiquizzle Quoteoutput power requirements - masses, speeds, accelerations Unfortunately, a lot of power is going to go into friction and that's not consistent between printers -- nor is it necessarily constant along the linear rod or consistent in time as bearings age, lose lubrication, even between two different LM8UUs due to sloppy manufacturing tolerances, etc. You probably can't operateby LoboCNC - General
Perhaps some background might help clarify what I'm after. I'm working on a closed-loop stepper controller (see previous post) that I think will most useful for CNC machines and higher performance printers, but I'm trying to figure out if it would also be useful for more middle-of-the-road printers. I'm trying to sort out whether or not typical printers are bumping up against any motor performaby LoboCNC - General
QuoteDorian Power is simply current times voltage. What I'm actually talking about is the required mechanical output power of the motor, which is equal to force x speed. The output power (Pout) is equal to the input power (Pin = voltage x current) multiplied by some efficiency factor. For systems with little friction and no gravity or spring loading etc. (like most printer mechanisms), the foby LoboCNC - General