Assembly V: Turning it On

Powering up the printer ended up being quite boring (which is good), so to fill out this post I'll go into a some more detail about how everything is wired.

Power enters the printer through a fused and filtered IEC power inlet.  I decided to go a little heavy on the fuses for this build since they are low cost and I'd like this printer to be well protected.

I also included two additional fuses to protect the bed heater (8A) and the hotend heaters (5A).  Both of these fuses are fast acting so if any of my heaters short power will be cut immediately.  Astute readers might notice I'm using 5mm glass fuses which are not rated to break DC arcs, however they will never have to stop more than 16A as the AC inlet and DC supply are fused and current limited.

Since the majority of wiring in the printer is completely untested, I powered only a few circuits at a time and monitored their current consumption to ensure they were running properly.  I started by testing the main Smoothieboard power and the e-stop indicator light.

Powering the Smoothieboard let me test the SSRs, which turned on successfully.  The indicator lights on the SSRs are quite dim as I'm only putting ~4.8V across the input.  The MOSFET SSR is particularly dim due to its 3.5V minimum switching voltage, but it functions normally and maintains a very low voltage drop under load.

I tested the heated bed circuit next.  This is the section of the wiring that is most likely to have problems since it is carrying up to 8 amps of current.  I started by powering the bed with only a few watts of power to double check that electricity was going where it should.

The bed warmed by 0.5c, which isn't much, but provides confidence that power is going to the right place.

I then connected it to the full 24V supply and switched it on.

I am using an exceptionally powerful bed for such a small printer and it is also insulated to ensure as much heat as possible ends up the the aluminium plate.  It can reach 70c in two minutes which is quite impressive.

I also took the liberty of measuring temperature under the bed to ensure that it is not overheating the linear stage.  Everything seems fine for now, but I'll see how it turns out with prolonged use.

The printer is frame itself is grounded quite well, however there is still some resistance across the linear stages (likely from the anodizing or roller bearings) which is one of the reasons why I chose not to use an AC powered bed.

Since most of the assembly is behind us I took the liberty of cleaning up and repositioning the printer in a more convenient spot.

I finally connected everything to the power supply after testing the remaining 24V circuits,

The 72V supply has already been tested with the servos so I hooked it up as well.

I finished with a few configuration tweaks, since the final build is wired slightly differently from my bench tests.

There is still ten or twenty hours of work before the printer is finished, but the most challenging parts of this project are now complete.  I've actually quite impressed by how well everything has gone so far - normally first time builds from CAD have hiccups.

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