Rambo with 15v psu blowing fans

[jestah]

Hi guys,

after taking a long breather from trying to get my rostock max running I have returned to make good progress. I have printed my first useable parts (coffee grinder chute to help reduce coffee wasteage in the cafe i work in) and keen to get this thing printing as well as possible.

I have added a 6mm aluminum heat spreader and a 15v psu (dailed up to 18v) that could supply more current to the heater bed. This has helped the bed get to 110 faster but also helpped cope with what is essentially a huge heat sink on the print surface.

This really helped solved some issues but it took a while to work out that these upgrades were also what was killing my peek fan! I burned out quite a few fans before putting a meter across one to relise what was going on.... one palm was applied liberally to face....

Option 1) run two psu.... PITA.....

Option 2) Run two 12v dc fans in series from the 18v supply.....

option 3) connect the 18v supply to a 12v regulator and heat sink


What do you guys think is the best option and any other suggestions to add to the mix?

Thanks!

[Eaglezsoar]

If you do not want to go with two power supplies then option 3 is probably your best bet.
There also is a way to run everything off the one supply and pulse width modulate the fans but I
have never done this.

[bubbasnow]

were you not able to print at lower temps with a surface treatment? i.e. hairspray

[jestah]

were you not able to print at lower temps with a surface treatment? i.e. hairspray

Not too well with ABS as the nozzle would pick up any thing even remotly not stuck down. Lifting the bed temp to 110 has helped with sticking as well as using a 10g to 100g H2o solution (also worked better than hair spray)

[Eric]

I'd go with:

option 4) put a resistor in the fan circuit. The exact value is going to depend on the fan. You may have to experiment to find a value that delivers about 12V to the fan (I'd measure the fan's resistance and try a value about half that as a starting point). The resistor may get warm, but I don't think you'll need a heat sink.

There's also option 5, especially if you haven't replaced your fan yet:

option 5) find a 24V version of the fan. It won't run at full speed at 18V, but it will run and blow some air.

[geneb]

You could also wire in a 7812 voltage regulator. It would take the 18v coming out of the power supply and run it down to 12v for the fan. It's a little part in a TO-220 package and only has three pins.

g.