I think extruding a cement paste mixed to set quite fast should be quite useful on small scale as well. There's been some discussion about printing out wax for lost wax casting, but the parts are not reuseable. Cement possibly could be, you could use sand casting sand with casting sand binder to make shells, and then pour sand around to contain any outflow pressure, and so long as you design inby grael - General
I think it's still a feasible solution if you are on a budget and prepared to do some component assembly to make the finished building. So long as you can group the parts separately prior to printing, then you should be able to deal with overhangs. I would also look at it as promoting modular assembly of the final product, for if your design principals work well on the model, then they should wby grael - General
I get your humour, but practically, some convection ovens have very fast air flow. Some air flow is good, but not if it's blowing components around the PCB.by grael - Reprappers
That all looks a lot easier than I had anticipated !by grael - Controllers
I've just been doing some preliminary research into g-codes and then that led me to gerber files, which if you've been involved in PCB design, you will know are an industry standard PCB layer definition format. Although I haven't delved very deeply yet, it seems that the gerber files shouldn't be very difficult to handle, and if that is the case, (they have a good degree of similarity to g-code,by grael - Controllers
Some success, notes added to my new blog (below) Almost time to start on G-code processing and file transfer protocols, I have a little more I/O that I'd like to get running first though, ADC, keypad, axis limit testing, and at some stage I want to have the USB operational. I have Linux and Windows, I'll see what the python support is like for USB on the front end, else I might even dabble in Cby grael - RepRap Host
Hi Vic, I see your activity on the threads tonight... I'm still expecting to be asking you for some PLA and/or ABS in due course, My machine's still coming together though. Some beastly problems with the default linker file for my 32 bit micro, but I'm working around them for now. I think Catalyst are a wellington Co, might be interesting to compare machines at some stage later. Graham Danielby grael - New Zealand RepRap User Group
Not much progress at all for the last week. I've been having issues that I think are related to the default Raisonance Linker, and trying to figure out what I need for a link file that will work reliably for me. Some discussion on my problem in this thread: It's a bit discouraging to development when you know that despite your best efforts, something is likely to go wrong beyond one's own contrby grael - RepRap Host
Still early days, but I'm hoping to have this circuit board able to do useful work in another couple of months: It's too early to release at the moment, to all but the most avid software developersby grael - Wanted
pcbmotor.com are pioneering (and patented) this field I believe. I think you are confusing SMD capacitors with SMD piezo electric elements.by grael - Plastic Extruder Working Group
I don't think writing a CAD program in Python necessarily makes it slow. These days, the rendering ought to be able to be done with a seperate tool set that can interface where required for moulding and connection options. Years ago, I wrote some simple maths code to show cross sections through an engine I'd invented, and I used to play at creating interesting 3D pictures using some simple 3D fuby grael - RepRap Host
Hi JBB, I'm using a very small array structure already for the PWM for each axis, so that's very easy to extend. At the moment though, I'm irked that serial bootloader boot mode is leaving the chip in a different condition than a full reset. I can boot load, and have the chip seemingly dead, or only doing part of my set functions, or boot in flash, and it works. I have quite a bit of work to dby grael - RepRap Host
You will probably find you don't have time to control the coil current by doing analogue to digital conversions on the feedback voltage, It's almost certainly too fast a voltage rise, especially when your processor is busy doing other things too. If you want to take an approach like that, see if you can set up those input pins to do a comparator function against internal voltage references, andby grael - Controllers
The brushless motors used today for radio control don't typically have sensors. This is done by sensing the voltage of the one out of three windings not being driven. Brushless motors can be easily designed for true multi pole operation, where as small electric motors (RC industry size), have only two poles at any particular time, but distributed over one or more winding hub. Because the brushlby grael - Controllers
I have now "blogified":by grael - RepRap Host
After some frustration with inconsistent startup behaviour with the PWM timer settings, that seems to change depending on whether I do a clean reset to flash code, or a bootloader reset to the same flash code, I decided I needed to work on another important step, which happens to be useful for diagnostics the LCD ! I found a demo LCD project on the net, that was for another ARM micontroller, aby grael - RepRap Host
I'm not claiming perfection. This is only a prototype run and in the electronics industry, chips are always being superceeded, and becoming obsolete. However I did go to some lengths to make the design versatile, and competent. The fantastic thing about that approach, is that you find after production, that there are masses of other applications it can handle also. I have friends talking about uby grael - General
OK, just had a quick look at the chip you are talking about: -Dead simple to use. -Has some basic current control in-built. -Micro stepping difficult to implement with this chip, the external logic you would need, would eliminate any benefits of using it. If you want some ideas, have a look at my image at the bottom of this page: , where I have an L298 direct connected to a 3.3 volt STM32 ARMby grael - Controllers
I don't think those boards are designed for direct driving of an L298 like chip, too many pins on the driver side. I think all the boards Zack designed used an L297 to convert step and direction requests into motor coil control. I don't like designing in more chips than are required, so on my machine I designed in a bigger microcontroller from the start. If you want ardwino compatibility, and mby grael - Controllers
Nothing like exposing your code to the world to make you aware of it's short comings... Have just edited smiley faces out " B ) " (without the space), tidied up my SteppinOut routine, and then converted a * 4 operation to a << 2 operation !by grael - RepRap Host
I see there's been some activity while I slept, and went to work ! My main effort over the weekend went to shifting as much calculation into the interrupt as possible, removing case statements, and if..else statements, converting them all to boolean and linear maths. ST7 user (company rep?) on STM32 forums put me right on "extern", and sharing of variables across multiple files. I did quite aby grael - RepRap Host
thanks annodomini2, That certainly reduces the number of calls made within the interrupt, although I'm not sure there's a savings on portC, which still would only make one of the 4 possible phase settings. I had a look at my list code before, and it did seem to compile to something a bit unwieldy. I couldn't see any evidence of the switch case statement utilising a jump table, so I'm guessingby grael - RepRap Host
I pulled apart a pixma printer a while back, I think it had DC motors and an encoder tape, disc inside it.by grael - Mechanics
Nophead, I shortened it to running 4 switch case statements, each with 4 options. If I knew C better, I'd try to to a 32 bit load of the BRR and BSRR registers concatenated(they are two parts of a 32 bit register), but instead I'm using the GPIO_WriteBit routines. If I shorten it like the fowlowing code, it almost chokes on a systick reload of 0x100, or 256 dec. void SysTickHandler(void) {by grael - RepRap Host
Thanks nophead ! I figured out the extern command yesterday, and started using it, but had some strange side effects using a variable in and out of interrupts, and wondered if there was an issue with the interrupt fiddling at the wrong time, the "volatile" command explains what I was missing ! I was using a u16 [5] variable for the step selections, and two motors wouldn't count, changed it to uby grael - RepRap Host
nophead Wrote: ------------------------------------------------------- > I am playing with Allegro drivers with built in > diodes and synchronous rectification. > Unfortunately that makes the sense current flows > through the resistor in both directions, so it > swings +- 0.5V maximum for 2A drive and 0.25R > resistors. I will probably just offset it with a > pair of resistorby grael - Mechanics
nophead Wrote: ------------------------------------------------------- > I am playing with Allegro drivers with built in > diodes and synchronous rectification. > Unfortunately that makes the sense current flows > through the resistor in both directions, so it > swings +- 0.5V maximum for 2A drive and 0.25R > resistors. I will probably just offset it with a > pair of resistorby grael - Mechanics
Thanks for the info Bodge it. I have quite a variety of stepper motors I've salvaged from old printers over the years. No idea what the rated current is on most of them ! I have from 0.9 degree per step, up to 7.5 degrees per step. Have you found the lower step size useful in any of your work ? Regarding your Z axis hysteresis, I suggest in the mean time, before upgrading to optical interrupby grael - Controllers
Thanks Nick, yes, I have that setting here too. It's a bit different from assembler, when you specify EVERYTHING, and you have your finger on the pulse of everything too... I am enjoying learning C though. Apart from the irritations... Like at the moment, I'd really like to know how to chose scope of variables, and I can't figure out the correct syntax yet, I don't want my interrupts to be doinby grael - RepRap Host
ASD, Thank you for your interest. That very same solution has just been posted right here, and is completely free:by grael - Controllers