Hi RepRap Community,

first of all a little Introduction to my 3D-Printer Story.
I've started with 3D-Printing 3 Weeks ago with a Prusa i3 Hephestos from BQ. It didn't take long till I ordered a HeatBed and, just because of good Product Description, a Carbon-Plate (absolute worth). Because I was a bit skeptical about Power consumption and the default Prusa PSU I changed it to a "dirty-ATX-PSU" solution. Next "Upgrade" was a PI with Octoprint. After playing around with Slic3r and Cura I also gave Simplify a try and IMHO it's definitively better. Right know I'm testing different settings and Filaments.
But there are some things I can't figure out, pls. excuse if a Q was already asked and answered, I couldn't find anything on the net.

1. Power Consumption
   Right now I use a "China-Firecracker-PSU". A good PSU is ordered and will arrive next week, but I'm not sure if only a good PSU will help. ATM the two Power Inputs on the RAMPS Board are bridged - shall I change this and Power the 2 Inputs with separate PSU-Power Outputs? The China-PSU has definitively a hard work, as soon as the HeatBed is powered the Fans spin slower, but I'm not sure if it's only the PSU or if its the Power Input Bridge.
   
   
2. Prusa detailed XYZ TechSpecs
   Found a lot of Tech Specs but what I'm missing are the maximum XYZ Speeds (mm/s) (not for Printing, max that HW can deliver)
   
   
3. Extruder & Fan
   Because of the HeatBed I turn off the Fan for the first Layers, but as soon as the Fan begins to Spin the Extruder-Temp drops. Sometimes that much that the Filament isn't melting anymore. Its possible that this Problem is directly related with Power Consumption (HeatBed + fast HotEnd heating which is cooled by the fan), but maybe someone here has already experience with that.

That's it for the beginning,
Greetings & THX,
OGrue

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3d-Print Newbie
prusa i3 Hephestos with 12V AluHeatBed, CarbonPlate and OctoPI // Simplify3D

1. Most ATX power supplies won't play nicely if you hook up two separate supplies and share a ground, which RAMPS boards have. Use one power supply. If your power supply provides separate 12V power rails for different sets of wires, you can split those. It would be expected for voltage to drop a little when one or more large current draws turn on, such as the heated bed and/or hot end. You may notice fans running slightly slower or leds dim slightly. Neither should affect performance considerably. Your Arduino regulates the 12V supply down to 5V so if your voltage dips to say 11.5V, it's not going to notice. All this presumes your power supply can deliver the power that's needed. Many cheap supplies over state their capabilities, or there wattage is there total combined wattage for all rails and not just the 12V rail. Check the specs at minimum.

2. I don't think I've seen any published specs for any printer. Testing your self is the only reliable way to find out for YOUR printer.

3. Don't direct your fan right at the extruder. Or get a fan shroud that directs the air down and not right at the heat block. For example: [www.thingiverse.com]

Have a read of the 'How to Choose a Reprap PSU' on the Reprap wiki.

I'd shy away from anything less than 400W, just to be sure. PSU is not somewhere you want problems to stem from

Hi again,
sry for the late response, the "quiet" time of the year was very stressful....
First of all THX for the Answers, the "How to Choose a PSU" was an interesting reading, however it just describes my guideline in building PC's - never choose a cheap PSU. Today I finally received the new PSU and I just finished a quick test print. Temps are stable now (also when the Cooling-Fan spins up - btw. Fan is heading just to the Filament, standard-Setting on the Hephestos) and all temps are raising much faster.
Next Step will be a little Addon-Board with 5vStandby for Powering the Raspberry, PSU-ON from Raspberry, 12V outputs with Poti for Fans/LED Stripes and of course the 12V supply for the Printer - I'll post it when everything is tested and working.
Oh, and if anyone's interested in the PSU - I've chosen the Silverstone ST45SF-G, 450W Gold / SFX / full CableMGMT to get rid of extra-cables.

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3d-Print Newbie
prusa i3 Hephestos with 12V AluHeatBed, CarbonPlate and OctoPI // Simplify3D