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Re: 3D printer "smarts"

Posted: Sun Apr 27, 2014 11:01 pm
by andrew
drphilgood wrote: John, any comments?
No, personally I don't use 3D printing.
cef had similar thoughts a while ago re: available power:

Re: 3D printer "smarts"

Posted: Mon Apr 28, 2014 2:52 am
by cef
There's a few issues here.

1. RAMPS and Ethernet connector:
Ramps itself is so very close to colliding with the Arduino Mega USB connector, and a bad soldering job on a RAMPS board can lead to shorts. The Ethernet connector on the EtherMega is larger, so you'd need to either replace all the headers with taller ones, or use longer pins on the RAMPS to avoid a collision and short.

2. Firmware:
Marlin already uses a large portion of the room available on a Mega if you include all the bells and whistles (eg: LCD display). Physically adding in Ethernet code as well may blow it over the storage space available on the EtherMega.

3. Speed:
If you were to try using Ethernet, you may find that you'd need to reduce the max speeds and microstepping so that there is extra processing time available for processing the data from Ethernet. If you're using DRV8825's with 1/32 microsteps, then I think you'd be out of luck. These already can perform slower than 1/16th microsteps (depends on the mechanics of how many steps = how many mm's of course), simply due to the number of step pulses that need to be generated.

I was involved with RAMPS-FD, which I was hoping to try on an EtherDue (coming soon!), but bobc has pulled out of that (and has disappeared off the RepRap forum). Your best bet might however be to use an EtherDue with something like RADDS, and see how it goes. That said, there are also other Due-variant boards out there with Wifi and/or Bluetooth that could work in a similar way. The extra processing power in the Due core would definitely make an improvement to the situation, especially when it comes to the maths translations used in say a Delta.

PS: The reason I haven't tried picking up the RAMPS-FD project and taking it further is because I simply don't have the extra time to do so. RAMPS-FD had more protection on it than RADDS does, and it also had a different form-factor that made it more suitable for use with certain Due-variants (like the UDOO, which has an ARM based PC as well as the SAM3x core all on the one board).

Re: 3D printer "smarts"

Posted: Tue Apr 29, 2014 1:38 am
by cef
I would either use an extra set of stacking headers to raise the board up, or use longer header pins on the RAMPS. The Ethernet connector is taller than a USB is on a standard Mega (about 2-3mm taller), so you can't simply put RAMPS on top and insulate it with some Kapton.The Ethernet jack sits higher than the shield.

I've not used the EtherMega with such a large firmware, but uploading the standard Marlin (without then adding Ethernet support) does work fine.

Regarding 24V. The EtherMega should handle 28V, but this is specced pretty much with nothing on top. 24V should be fine, but if it is an issue you should consider using a step-down converter or a cheap 3 pin reg to get 5V to run the RAMPS/Mega directly, or going down to say 9V to feed the VIN on the Mega. Note that if you do this, you STILL want a diode before the regulator. This is partially for protection, but partially to stop the Mega powering the whole board if you plug it in via USB (the regulator will allow voltage to flow through it backwards).

FWIW: I also use 24V completely, but I run my (standard) Mega off an adjustable 24V down-converter (adjustable between 15V and 3.3V output). I set it to about 10V and use that to run the Mega (via it's VIN) and also use it to run some fans.