TC: I didn't mean a control loop would take longer to get up to temperature, I had thought rocket_scientist was trying to use the increased resistance of metals at high temperature to auto-regulate the temperature. As for thermocouples/thermistors, I have a bunch of i2c chips lying around so i'd find it easier, but objectively neither approach is particularly difficult. I have to say, i'm curioby james glanville - General
Surely if you're going to all that bother it'd be much easier to use thermocouples/thermistors/i2c temperature sensors? Or even: in series with the heating element. Trying to auto-regulate using a negative feedback loop based on resistance of the element is going to take forever to reach a stable temperature. I'm using pla which is easy to remove, but for anyone with kapton/abs could you leaveby james glanville - General
I'd recommend a direct-drive stepper extruder. The best way to cut the thread if you have a lathe is detailed here: Personally, I took apart my stepper, wrapped the rotor in tape to prevent swarf gnarling it up, then made a wooden jig to attach the bearings to the lathe toolrest. I used an M5 tap, M3-6 is probably best. My extruder is incredibly hackish: but works great, if you're designingby james glanville - General
Yeah, as far as I know anyway. If you're not sure about whether a host setting still works, just set it to a stupidly large/small value and you'll see if its "active"by james glanville - RepRap Host
I meant there are still some settings in the host software that deal with thermistors, even though that's all done in the firmware now, and the host software only deals with real temperatures. As for tweaking the tables, the actual temperature they report doesn't matter, as long as you can find a numeric value that gets the plastic to the correct consistency. Themistors are pretty lousy at beingby james glanville - RepRap Host
Yeah it would be good if some of the useless settings could be pruned from the config box, we don't need thermistor settings either. I don't think anyone is using SNAP any more, but at the very least the snap-only settings should be segregated. When you say the stepping formula is "almost" correct, it /is/ correct, but you must be using the wrong values, or there is backlash in that axis.by james glanville - RepRap Host
The idea has been discussed at length, but no-one has yet managed to come up with a working solution. Problems you may have with that design are that pla has the viscosity of honey when molten, and will probably dribble out of the end constantly, while ignoring attempts to push it. Most people have concluded it would be easier to extrude pellets into filament first, then feed it to a standard extby james glanville - Paste Extrusion Working Group
Ah, if you're using threaded rod to move the axes, you can just calculate the exact number of steps from the pitch of the rod.by james glanville - RepRap Host
I'm pretty sure the step settings in the reprap-host software are remnants from older software/firmware combinations, and the correct place to adjust the settings is in the firmware. Digital calipers are the best tool to get the config right, but you should probably only have to do this once. Remember that the x and y values are probably the same unless you've got some weird machine that uses difby james glanville - RepRap Host
With openscad, are you making sure all the units are in mm? Both skeinforge and the reprap software seem to crash when the model is tiny.by james glanville - RepRap Host
Ah fair enough, I hadn't seen suitable gears sold without a motor attached, so I hadn't made the connection. When I've used small motors, regardless of price, the lifespan is hugely variable. It might be cheaper overall to use the absolute cheapest you can get, and make the design so they can be replaced easily. Also, lifespan is dramatically increased by not running at their maximum speed. Justby james glanville - General
I got that, I meant what job is it doing in your design? If its for cooling, pc fans are cheap,reliable and come with blades already, otherwise I was just curious as to how you were eking out useful torque from them.by james glanville - General
That's a really good idea about the microscope changing thing, I've been thinking about it but I can see some problems that personally I can't see how I'd get around. Firstly, the transition bit between movable barrel and fixed body - It either has to be where the filament is solid, but it then has to crunch/cut the filament and PLA is pretty tough, plus you then need some non-reprappable bladesby james glanville - Plastic Extruder Working Group
I'm afraid I can't help you, but I'm curious at to what the motor is for?by james glanville - General
You need three stepper motors for the x,y and z axes, then either another stepper motor or a dc motor for the extruder. You get the best results with 4 steppers, but they do need to be powerful - are you sure the 95 cent ones have enough torque? Post any information they have on them, or take a picture and someone can give you an idea. For stepper drivers, you /might/ be able to get them from theby james glanville - Controllers
Its probably easiest to use a whole separate heater/barrel/nozzle for each plastic, or you'll have to somehow purge the system each time you want to change plastics. As far as I can see, this gives you two main options: Make multiple bowden extruders. The small size of the nozzle apparatus means they could easily be switched mid-build, so support materials would become possible. Make each extruby james glanville - Plastic Extruder Working Group
Are the steppers wired up and working? If the grounds really are isolated, you won't be able to send any commands to the stepper controllers. You're right that MOSFET voltage and current are the things to look out for, its worth getting ones that can handle a much higher current than you need, because they'll get much less hot and may not even need heatsinking. You should pull the MOSFET gate lowby james glanville - Controllers
That stl doesn't work for me either, but I'd be inclined to think it might be the stl itself, as its the first stl that hasn't worked for me. How did you get/make it?by james glanville - Skeinforge
Here's my blog post on the subject, the photos aren't great because I tend to work on my printer at night when the light is terrible.by james glanville - General
I haven't had time to blog about it yet, I will asap. My printer is almost a darwin, at least in terms of dimensions. I got the aluminium from www.aluminiumwarehouse.co.uk but I think there's a pretty large minimum order, and I had to go collect it as their delivery isn't great. I had a free sample MAX6675, and the thermocouple was only a few pounds, and I'd like the flexibility to try reflow solby james glanville - General
My heated bed doesn't differ too much from that one, mine is 2mm aluminum, uses power resistors, a thermocouple and MAX6675, and a STP55NF06 (55A at 60V for only 70p from rapid, I like to massively overspec mosfets so I can forget about overheating them)by james glanville - General
Most people have managed to get it to work just fine, while I have some irks with skeinforge, its a terrific program that we all get to enjoy for free. You say you can't import stl files, nobody is going to help without a more polite and detailed description of the problem.by james glanville - Skeinforge
I think its important to be able to able to maintain working temperature with a small fraction of maximum power input, so you're not waiting for ages. I'm using 12 1ohm resistors in a 3x4 array, 1.33ohms in all. At 12V, the 108W still takes a minute or two to get to 55 degrees, I'd recommend even lower resistances if possible. It will actually save considerable amounts of energy if you have a greby james glanville - General
I think openscad would be a good candidate for an object format, its incredibly quick to make objects, and parametric modelling is very powerful. Thoughts?by james glanville - General Mendel Topics
Although I'm still waiting for my power resistors to arrive, the 2mm piece of aluminium I'm using is very flat, and very strong. Its 30x30cm, but I can't deflect the centre by more than about 1mm, and that takes some force. It sounds like it might be heat treated, as it looks a different colour, and is much much stronger than other sheets I've used. I'm pretty sure its flat enough to use the wholby james glanville - General
Mine get far too hot without a huge fan cooling them down, but my 2.3's are only warm to the touch. I'm also using a stepper controller that does 1/8th stepping which is much smoother. If you're looking to buy a controller, I can't recommend enough. 18 pounds is probably almost as cheap as the parts, and they solder the smd for you.by james glanville - Controllers
The problem I can see with this are that it is an all or nothing approach. What I mean is, unless you get the entire process automated, it will be far less convenient than the laser print then iron then etch method. With this approach, you still have to place all the parts, which is either done painstakingly by hand, or with a hugely complex tool to take parts of varying size and manipulate themby james glanville - Kartik M. Gada Humanitarian Innovation Prize
I got terrible results with silicone with HDPE, I used an ikea flat silicone baking sheet which warped massively with temperature. It also didn't adhere particularly well, though that is probably more HDPE-specific. If ABS or PLA, or a different temperature HDPE could be made to stick to it, and a very thin layer of silicone could be firmly attached to a rigid board, it might work out well. It doby james glanville - General
Hi, I'm not affiliated with the guy in any way, but I thought I'd recommend the following stepper controller: Its not much more than 20 quid shipped anywhere, and I've found it excellent. It manages 1/8th stepping well, which I hope will improve the accuracy of my axes/extruder, and only gets slightly warm to the touch at 2.5A. While it suggests a higher voltage, it works fine at 12V at 10cm/sby james glanville - Controllers
It is, see v-usb (formerly avr-usb) to add usb to various avr chips, but whether there's space for the usb and reprap firmware is another matter. By all means try, I'd certainly prefer a more native usb interface.by james glanville - Controllers