Building a 3D Printer, RepRap Mendel Prusa2 by craynerd

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raynerd:
I`ve just purchased RAMPS 1.4 and I`m going to use an ATX supply for power....however, I`m not sure if an ATX will cope with both the motor current and that pulled by the heated bed as well! I believe my ATX is rated 24A on the 12V line but I`m not sure....think I might run the heatbed on a second ATX or purchase a dedicated unit. Just seems a shame with the ATX available.

I`ve got a little issue at present with the misalignment of the x axis belt over from the motor end, over the carriage and to the bearing on the idler end. It seems to be no where near in line with the belt clamps!!

Chris

ChrisC:
12 Volts 24 Amps should be just about ok. Hot end resistor is normally 6.8 Ohms = 1.7Amps. The motor current draw is unlikely to be greater than 8 amps, but best to measure it. So that leaves 14 Amps for the hot bed. I assume you are using one of the PCB hot beds, the guy I bought mine from says they have a resistance when cold of 1 ohm (resistance increases as it heats up of course), but I have seen reports of resistances around 0.8 ohms. A 1 ohm bed will draw a maximum of 11 amps, but a 0.8 ohm bed will draw 15 amps.

Chinese 12Volt 30amp power supplies sell on ebay for just over £20.

I initially used a Gen 6 board, which is not ideal: it is acoustically very noisy, has a design fault with the thermistor input circuit and doesn't support a hot bed. I'm in the process of building a Sanguinololu; I'd be interested to hear how you find the Ramps 1.4 shield.

Chris

ChrisC:
Oops hit Post too soon!

Sorry to hear you're having problems with the X belt alignment. There are a lot of variations to the designs of the X carriage and the motor and idler ends. In the end you sometimes just have to come up with a compromise... once you get it running you can re-print a better part! One problem I found was with the X idler. The design shows a 8mm bearing with two fixed penny washers. The belt running on these fixed washers caused too much friction on my system and caused missed steps (worked ok on the Y axis though). I turned up an aluminium pulley which I glued onto the bearing using loctite. The flanges now rotate with the pulley, it does mean that the diameter of the idler is too large, so the belt runs up hill on one side. I'll replace it with a smaller pulley in due course. There are designs for printed parts to fit onto the bearing to achieve the same result.

Chris

ParCan:
Hi

Your build is coming on really well. I like your Z Couplings. They are very similar to what I have.
See how you get on with them.

The X Belt can be a real pain.
See if you can find a couple or 3 washers that fit inside the penny washer either side, thus allowing the penny washer to rotate.

I have run with LM6UU's on my Huxley on silver steel with no ill effects. I'd see how you get on. Just give them 1 or 2 drops of thin oil every 10 or so hours to keep it all free and nice.

24 Amps is enough for a Heat Bed and the machine.
You may need to put a load on the 5V rail to keep tthe 12 V up.
My advice for the heated bed is also to run it through a relay or somethign to keep all that current away from your RAMPS.

It's all looking rather good I have to say :)

Alex.

Noitoen:
A good source for guide rods is on old Xerox machines or printers.

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