Archive for November, 2021

Voron 2.4 Build — Roll-in Spring T Nuts

Sunday, November 21st, 2021

To attach things to T-slot / V-slot aluminum extrusion, one typically puts some kind of nut into the slot of the extrusion; and it’s called a T nut because its cross-section typically has a (potentially abstracted) inverted T shape.

Roll-in spring T nuts

The blank end of this kind of T nut, apparently called roll-in spring T nuts, has a recessed spring and a bearing swaged into place, just protruding from the lower face. The spring pressure on the bearings keeps the nuts from sliding around in the slot on their own, which is really handy during assembly and disassembly.

I was aware of this type but hadn’t used them before and was delighted to find that they can be installed (and with considerably more effort, deinstalled) through the face of the slot. They’re slim enough that they “roll” into the face of the slot, landing slanted on an edge; and then with a downward push, they orient into their final position and the spring pushes them back up to hold their orientation against the slot and retain their position.

Voron 2.4 Build — Frame Assembly

Sunday, November 21st, 2021

I got interested in having a Voron 2.4 3D printer after seeing after seeing Tom Sanladerer’s video review of his completed build. But at the time, the full build cost about $1500 — a little high for my taste — and only a partial kit was available and you had to source some of the parts yourself — not interested — because the Voron is an open-source design, not a product. But not too much later I found a full kit from Fysetc on AliExpress for just under $1000; and after an extensive wait and repeated untruths about the status of the shipment, I have my kit and I’m started to assemble it.

Plenty of others have documented the entire build process; I’ll only share particular items I find noteworthy and different from other printers I’ve assembled.

2020 aluminum extrusion joined by M5 machine screws

The first is the frame joinery. I’m sure the Voron is not the first thing in the world to use the heads of M5 machine screws in the T-track, but I’d not seen it done before. You need an access hole through the aluminum for the hex key to drive the screws; but unlike joints that bolt through the aluminum, the access hole doesn’t have to be precise for you to be able to align the joint.

Voron 2.4 frame

It ends up fairly square and fairly rigid, with the squareness aided by assembling on a discarded scrap of granite countertop.

And yes, that frame is almost as wide as my roll-away dishwasher. I got the kit with 350-mm-cube build volume, which is larger than I need; and I’d probably have picked the 300-mm-cube build volume had there been a full kit for it when I ordered. One of the Voron’s claims to fame is fast printing; and the mass of the larger gantry for the 350-mm printer can be expected to impact the top acceleration I can use without ringing.

Fussing with My Server Power Supply

Saturday, November 13th, 2021

This wretched miserable piece of notworkingness has been causing me a fair bit of grief in the last couple of weeks.

Dell Poweredge 750 server power supply

This is the power supply from the Dell Poweredge 750 (yes, that’s 750, not R750) server from which, if it is still near the year 2021, you are being served this web page. A couple of weeks ago, it developed the new behavior of powering up perfectly well to start booting the server and start running the BIOS tests and then shutting off again.

Being in a bit of a hurry at the time, I grabbed my spare ATX power supply and hooked it up to get the server running again with the lid open and deal with the original power supply later. But with the new power supply connected, the server wouldn’t boot at all, because

Dell Poweredge 750 server power supply motherboard connectors

what is this??? Oh, for a larff, let’s move the purple 5V standby wire from the ATX mother board connector to the PCI power connector, har har! So with the spare power supply connected, the server wasn’t receiving 5V standby [where it wanted it] to run the On button to turn on the power supply and the server.


What Shape Portable USB Powerbank?

Thursday, November 4th, 2021

Cort and I would like to embed lithium cells in portable projects and want power management that:

  1. steps up the lithium cell’s 3.7 V to a well-regulated 5 V
  2. safely charges the lithium cell from some source
  3. powers the load while charging the cell

I knew it’d be easy finding power management modules that met the first two points, but I wasn’t sure whether the third point (power the load while charging) would be a ubiquitous feature, or even clearly called out in documentation. Fortunately, while browsing power management modules, I quickly found that the HT4928S mobile power management chip supports all three, and found cheap modules both with and without USB connectors on them, and ordered a batch of each style.

18650 lithium cell with power management modules

Now I have them and need to test that they work as described, preferably without burning down my house or pocket. The obvious test is to hook one to a secondhand 18650 cell I have lying around. While I’m at it, I may as well 3D-print an enclosure for it and have a spare USB powerbank.