I agree complete, CidVilas. I just have a lot more experience programming the AVRs, and from what I have seen so far, the architecture is more flexible, especially PWM which I use extensively for DC motor control in the under water robot I am still working on. But the basic concept off more processing power, more memory, more I/O ports setup for step/direction stepper motor controller input, addiby rocket_scientist - Next Wave Electronics Working Group
An 8 bit ADC with a pre-amplifier designed to amplify the signal at the top end to just under 5 volts has a resolution of 0.39% per LSB. That means that under ideal conditions, the full range of signal change would be 2 LSBs. With a 10 bit ADC, that would be 8 LSBs. The other option is to subtract a set level, such 100C or even 20C, and further amplify the signel. The bigger problem I see is tby rocket_scientist - General
Or go to a higher voltage. A standard PC switching power supply will provide up to 20Amps of +12V power. The 12v pushes more current through, and the power is the product of voltage times current, so you get over 5 times more power from the same resistors going from a 5v supply to a 12v. And the MOSFETs should typically handle at least 30v. And with higher voltage, you could increase the resistanby rocket_scientist - General
Mccoyn has also designed and had fabricated a single board solution that he calls Gen2onaBoard. It includes 4 Polulu drivers on the mother board, plus the extruder and heated bed heater controls. I bought 2 of the first batch, but have not stuffed the boards yet. It is an ATMega644P/Sangruino 40 pin DIP based system with all through-hole parts for easy hand assembly on a 100mmx100mm board. Sweetby rocket_scientist - General
Driving it with DC on nichrome is basically what we are doing now. If I could get the wire embedded in the inside of the glass tube, I would be happily promoting that. It would be a great way to do it with glass. But I have not yet figured out how to embed the nichrome wire in the glass without burning up the nichrome in the torch flame, let alone putting it on the inside without adding ridges toby rocket_scientist - General
Yes, if the software only kept track of full steps, you should never lose a full step. However, if you 8 micros steps into a step change at 16 microstepping level and suddenly jumped all the way up to full stepping, it would not be well defined whether it would roll back to the previous whole step, or roll forward to the next full step. If the software kept track of steps and microsteps usingby rocket_scientist - Controllers
Good point nophead! I remember most of the diagrams should copper tubing, not copper wire, to make up the 20 turn primary. Since the same frequency occurs there, it would also need as much skin as it can get without being heavy. I still think that what ever conductor is deposited on the inside of the glass must be thick to carry the thermal load, even if the skin effect makes the effective electby rocket_scientist - General
dissidence, According to the functional block diagram, there is no latching or memory of the microstepping inputs, so the stepper driver should instantly change the microstepping when you change one of the inputs. No need to power down or reset at all. This means that if your main control board can control the 3 microstepping input lines, you can dynamically switch from 16th steps for fine conby rocket_scientist - Controllers
Good points. I had also suggested somewhere that a two processor system would be good. A pentium class single board computer handling the user interface and file storage, probably running some Linux version for the human side. On the other side a real time, interrupt driven, 16 bit timer controlled micro. However, I think that the bigger 32bit micros may be a better choice. Even if we don't use tby rocket_scientist - Controllers
I like the general idea, but suggest instead the Atmel 32bit micro AT91SAM7XC256B. It DOES have a built in boot loader, and can be loaded through either the serial port (2 USAURTs) or the USB 12.0Mbit port. Further, it has an ehternet MAC built in that will run 10/100. All you need to add is a phy chip, transformers and connector. Looks like an extra $15 for hardware adds an ethernet interface. Aby rocket_scientist - Next Wave Electronics Working Group
QuoteTraumflug I fear we're pretty limited here, as all ATmega processors are 8 bit, running at 20 MHz max. The Mega 2560 gives a lot of room for firmware, but it can't make steppers running faster. Moving to an entirely different processor like the AVR32 or AMD Cortex should be postponed until this PCB replicating thing works, IMHO. I have been looking at the Atmel 32 microcontrollers, and I tby rocket_scientist - Next Wave Electronics Working Group
I suspect that even with the high quality and heavy weight rating, they will still not have the desired stability for a large reprap. But as traumflug said, they would be great for a repstrap. I do not know where they are being dumped locally to give them a try, but if I did it sounds like a better solution then the drawer slides I could by at Home Depot. Mikeby rocket_scientist - General
Anthong, Have you measured the resistance of your heater? And what supply voltage is the MOSFET switching? Most common is to use the 12V supply to run the bed heater. If your heater resistance is too low, then when you start out to warm it up to operating temp, the current will be too high and the MOSFET will over heat. Try connecting the heater directly to 12V through a multimeter set for 20 Aby rocket_scientist - General
I had not thought of chemically plating silver on the inside of the glass. That would maintain the efficient shape of the glass. And once a good layer of silver has been deposited, you can switch to electroplating copper onto the silver to get a less expensive thick layer to carry all the heating current. That would make the inductive heating approach work well for everything accept monitoring thby rocket_scientist - General
Aka47, I have heard several people suggest wire wrap as an easier alternative to etching or isolation milling the PC board. I agree that it sounds like it is worth a try for through hole device only boards, or at least when any surface mount device is mounted on a chip header so it can be plugged into a socket. The wire wrap should work well for signals up to 20Mhz or higher, but I think they staby rocket_scientist - Controllers
Tramflug, I agree that what I was laying out for a future machine is more expansive. But the machine I was talking about would also have multiple extruder heads, possibly multiple orifice sizes per head, some degree of subtractive process, some possible re-orienting of plastic pieces to avoid gravity and support material problems, support material, 3D scanning of unknown pieces to build an editabby rocket_scientist - Controllers
I searched for sleeving and STILL missed that one! Yes, it looks like it should work quite well. Hopefully we can stretch or flare it at the top end to keep if from being pushed through along with the PLA. Let me wait until I get a few other things to order from them to spread out the shipping cost and I will give it a try. I now have my own supply of PLA, so I can make a comparison test. Possiblby rocket_scientist - General
Greg, it might be best to use the 1/8" /ID, 1/4"OD PTFE tubing from mcmaster-carr to provide the sleeving. It will require a larger diameter glass. When I get a chance, I will try to build one. The next problem is that the inside diameter will transition from 3.2mm PTFE to 6 or 7 mm glass interior diameter. That will make it hard to heat the plastic until it hits the tip and widens out. I am notby rocket_scientist - General
Some good points there, NooBMan. I have not read all the text in the last three pages, it is all ancient history by now, at least in reprap terms . However, I have been looking at what it would take to go beyond the current designs. For the first few requirements, I agree with NooBMan: 1) More than 3 stepper axes. 7 should be a minimum Whether controlling a milling head (three extra axes plusby rocket_scientist - Controllers
Aluminum for one. Copper is too high. But pretty much all solders and lead. Of course, we could step up to quartz glass, which has a higher melting point than borosilicate! Mikeby rocket_scientist - General
You could also research the various 3D graphic file formats to find something better than STL that can handle multiple material types, or colors, or handle adding embedded wires for making conductive circuits, or specifically angled fiberglass threads to reinforce the plastic. There are many existing file formats, some open, some proprietary but well know, some closed. If you examined many of theby rocket_scientist - General
Viktor, actually, we are going in the opposite direction. We are not trying to melt the Stainless Steel, but simply heat it to a constant temperature to melt the plastic. ABS is what is setting the limits. And a conventional temperature measurement in an induction heater is likely to be self heated more than contact heated, rendering it useless. Thus IR non-contact thermometers working from a dby rocket_scientist - General
Glad to hear that you have the higher quality thermocouple wire that includes the shielding. So that knocks out 2/3 fo my suggestions. Hopefully the power supply filtering will take care of the problem. edit: removed Mikeby rocket_scientist - General
Koko, when you said you grounded the thermocouple shield, exactly what did you do? The standard thermocouple (or at least the ones I have made from thermocouple extension wire and Harbor Freight freebies) does NOT have an outershield of braided or foil conductor wrapped around it like a coax cable. They do have a plus wire (yellow IIRC) and a negative wire, but neither one is a shield and even grby rocket_scientist - General
I have been looking for an IR sensor chip that could be directly connected to the controlling micro. The few that I found did not go up to 250C. And the prices were looking kind of high. I also looked for a complete digital thermometer that had a USB connection. Hundreds of dollars! It looks like the cheapest way to go is to buy a Harbor Freight digital IR thermometer and take it apart and find tby rocket_scientist - General
Sorry to double post, but I just realized I have a question. When inductively heating a piece of stainless steel tubing in the end of the glass nozzle, won't it be difficult to measure the temperature? Whether we use a thermistor or a thermocouple, the device and it's wiring will still be within the magnetic field of the inductive heater, and that may swamp the measurement values. The thermistorby rocket_scientist - General
Jacob, great work! Getting inductive coupling to work at this kind of frequency probably means a variable frequency switching power supply, rather like the switching supply inside our computers. I believe that the power MOSFETS we use for heater control can be switched at these frequencies. By finding the most efficient coupling frequency, you then control the temperature by increasing (or dby rocket_scientist - General
New results. I fired up the glass wrapped nozzle and just for fun, I tried to hold a piece of perf-board underneath and move it back and forth to build up a small block. Nothing stuck, but I also saw that the blunt tip was rubbing against the fresh, soft plastic against the bottom of the glass and causing it to stick more to the ground glass tip than to the perf-board. I think that the drawn tipby rocket_scientist - General
Sounds like they are using a vapor degreaser setup. A stainless steel tank with a thin layer of liquid on the bottom, heating coils on the bottom and possibly part way up the sides, then cooling coils all around the top walls. As long as the solvent vapor is significantly heavier than air, it remains inside the tank, with a visible demarcation where the cold section makes a lid of cold air over tby rocket_scientist - General
Ryanp, the arduino duemilanova IS an ATMega168, so the choice is more one of packaging and programming. The arduino duemilanova is already on a board, with voltage regulator, I/O pins on connectors, and a built in boot loader. The ATMega needs a board to mount it on, connectors for I/O, voltage regulator, crystal, etc. I have been researching a bit the gap between the Arduinos and ATMegas and tby rocket_scientist - General