Saturday, May 15, 2010
Quick hot bed temperature controller...
I received some aluminum plates (one for my rapman and other for my mendel) and some 50W resistors (still waiting for the 100W ones) tied it all together and it worked just like Chris shown on his super cool blog :), anyhow using the max power (~12A ~500W) I can push to the bed it can overshoot the max temperature those resistors are specified to handle so I needed some way to control it. Initially I used the simple thermal switch (like you can see in TA oven) but as I want to be able to change the temperature from the motherboard I decided to replace it with small electronics.
I do not have a SSR lying around but I have bunch of "no name / no marking" 25A 600V triac's that are perfect for the job, I used the MOC3043 (optocoupler with triak output and zero crossing detection) to separate the electronics from the AC going in to heat bed (I'm using 41VAC), the microchip PIC16F819 is used to drive the LCD, read NTC and work as I2C slave. NTC is connected with 10K resistor to maximize reading range between 20 and 180C. NTC used is same one from BFB hot end's (GT-204).
I do not have a SSR lying around but I have bunch of "no name / no marking" 25A 600V triac's that are perfect for the job, I used the MOC3043 (optocoupler with triak output and zero crossing detection) to separate the electronics from the AC going in to heat bed (I'm using 41VAC), the microchip PIC16F819 is used to drive the LCD, read NTC and work as I2C slave. NTC is connected with 10K resistor to maximize reading range between 20 and 180C. NTC used is same one from BFB hot end's (GT-204).
"firmware" is written in PICC C, it takes ~70% ROM and ~40% RAM so there's room for more functionality if needed. I2C slave address is 0xAB but it can be changed, first 2 addresses (0 and 1) are read/write and contain target temperature for the heat bed while second 2 (2 and 3) are read only and here you can read current temperature of the heat bed. To avoid float math, the temperature is stored as *100 value. When turned on - the controller reads last stored temperature from the EEPROM (locatio 0 and 1), when both key's are pressed the current target temperature is stored in EEPROM. You can both change the target temp via i2c or using key's (whatever happens last).
Source (PICC C file) is available here.
Source (PICC C file) is available here.
Labels: controller, heated bed, I2C, Mendel, PIC, RapMan
Wednesday, May 12, 2010
A Heated Bed for Mendel
A little while ago, Nophead made a Dibond heated bed. Dibond is a sandwich of LDPE between two aluminium sheets, and is very flat.
I thought I'd have a go too. Instead of the TO220 resistors he used, I used nichrome wire taped down with Kapton on the back.
Then I insulated that with crack-filler foam, cut down to about 10mm thick with a bread knife.
It seems to work well. Here are the larger Mendel parts printed on it in PLA with it set to 50oC. Their bottoms are f. as pancakes.
I used a piece of ordinary aluminium sheet clipped on the top with bulldog clips to give me a removable tray with good thermal conductivity. That is what has the blue tape on here. The tray is flexible, but the Dibond holds it flat.
I thought it'd be clever to use the 5v supply out of my PC PSU, as that's not being used for anything else. But the current (16A) is a bit silly - connectors and so on get warmish. For the next one I'll run it at 12v and about 7A.
Dibond is rated up to 80oC, which means it's fine for PLA, but might not get hot enough for ABS.
I've integrated it into the host software, the G Codes, and the firmware and updated the copies in the repository. I have to go to Cardiff tomorrow to give a RepRap talk to the British Computer Society, but I hope to put all the details on the wiki over the weekend.
I thought I'd have a go too. Instead of the TO220 resistors he used, I used nichrome wire taped down with Kapton on the back.
Then I insulated that with crack-filler foam, cut down to about 10mm thick with a bread knife.
It seems to work well. Here are the larger Mendel parts printed on it in PLA with it set to 50oC. Their bottoms are f. as pancakes.
I used a piece of ordinary aluminium sheet clipped on the top with bulldog clips to give me a removable tray with good thermal conductivity. That is what has the blue tape on here. The tray is flexible, but the Dibond holds it flat.
I thought it'd be clever to use the 5v supply out of my PC PSU, as that's not being used for anything else. But the current (16A) is a bit silly - connectors and so on get warmish. For the next one I'll run it at 12v and about 7A.
Dibond is rated up to 80oC, which means it's fine for PLA, but might not get hot enough for ABS.
I've integrated it into the host software, the G Codes, and the firmware and updated the copies in the repository. I have to go to Cardiff tomorrow to give a RepRap talk to the British Computer Society, but I hope to put all the details on the wiki over the weekend.
Labels: dibond, heated bed, Mendel
Saturday, April 03, 2010
Hot copper and PLA
Acting on a suggestion from Vik, I have found that PLA can be extruded onto copper clad board and, if it is hot enough, it sticks very well. I have to flex the board to remove it. 55°C is too cold but 130°C works well. I haven't tried anything in between yet.
Assuming PLA will resist PCB etchant, this could be a way of making PCB's without a laser printer, albeit quite low resolution. With 0.3mm filament squashed to 0.24mm a single line would be 0.36mm wide, which is 14 thou.
It also seems like a good bed material for making PLA objects on.
More details here: hydraraptor.blogspot.com/2010/04/cu-pla
Assuming PLA will resist PCB etchant, this could be a way of making PCB's without a laser printer, albeit quite low resolution. With 0.3mm filament squashed to 0.24mm a single line would be 0.36mm wide, which is 14 thou.
It also seems like a good bed material for making PLA objects on.
More details here: hydraraptor.blogspot.com/2010/04/cu-pla
Labels: copper, heated bed, pcb, pla
Monday, March 08, 2010
Heated Bed and post-McWire Design Sprints! (Marathons?)
Are you designing your own heated bed? Do you have a perfect one already?
Or have you simply eliminated several blind alleys? ("Wow, that magnesium really didn't want to stop burning, did it?")
Please come check out the Heated Bed Forum Thread and the associated Heated Bed wiki page.
Similarly, we're about to drop the McWire RepStrap like a slowly moving and generally unsatisfactory hot potato. And we want to hear what you are building instead as a bootstrap RepRap machine.
Discussion: McWire Successor Forum Thread
By the way - we're nearly done with the server stuff to really open up the RepRap project to user contribution*, in part by actually making use of the mediawiki that we're moving into.
In the meantime, let me remind you that you're already very welcome to go to http://objects.reprap.org, poke around, log in and click "edit", or create a new page for your RepStrap, post-mendel RepRap, RepRap-related or RepRappable project. Or simply your version of the ideal heated bed, RepStrap, and so on.
If you're not working on the Heated Bed or the RepStrap to beat all RepStraps, but you have a good project, try starting a new working group in the Forum, (and a new wiki page).
* While at the same time, making sure that the Mendel docs still work and are somewhat stable. (That's the tricky part - I've always heard stability is supposed to be a good thing for documentation.)
Or have you simply eliminated several blind alleys? ("Wow, that magnesium really didn't want to stop burning, did it?")
Please come check out the Heated Bed Forum Thread and the associated Heated Bed wiki page.
Similarly, we're about to drop the McWire RepStrap like a slowly moving and generally unsatisfactory hot potato. And we want to hear what you are building instead as a bootstrap RepRap machine.
Discussion: McWire Successor Forum Thread
By the way - we're nearly done with the server stuff to really open up the RepRap project to user contribution*, in part by actually making use of the mediawiki that we're moving into.
In the meantime, let me remind you that you're already very welcome to go to http://objects.reprap.org, poke around, log in and click "edit", or create a new page for your RepStrap, post-mendel RepRap, RepRap-related or RepRappable project. Or simply your version of the ideal heated bed, RepStrap, and so on.
If you're not working on the Heated Bed or the RepStrap to beat all RepStraps, but you have a good project, try starting a new working group in the Forum, (and a new wiki page).
* While at the same time, making sure that the Mendel docs still work and are somewhat stable. (That's the tricky part - I've always heard stability is supposed to be a good thing for documentation.)
Labels: heated bed, mcwire, wiki
