Alignment for both top and bottom prints

[DavidYon47]

Ended up needing a quickie Pi Hat, extremely simple, but a combination of surface-mount, through-hole, and vias. I'm in the process of following the YouTube demo for ink-filled vias. You may remember I had to fall back to eyelets on milled copper, but I have higher hopes for an all-Voltera board.

One thing that would make my life easier is using the mill for the holes and final outline. Unfortunately the V1 has extremely coarse alignment for the first side. As in, yup, this won't attempt to print on the bracket instead of the FR4. So I'm stuck having to use calipers to compute the X and Y offsets of where the circuit ended up on the board, that way the mill knows where the holes are supposed to be. Calipers have their limits, plus I'm stuck using a feature nearest (0,0) and computing an additional offset. So even being very careful in measuring, the holes hit the vias, but there's noticeable skew.

I will probably get this to work, but it's a fairly clumsy workflow, even with practice. I also just realized that there can't be any skew in the V1 clamping, as I can tell the mill an X/Y offset, but not a rotational offset.

So I don't have any specific ideas on how to solve this, but it sure would be nice to be able to combine the two tools for what each does best. It's tantalizingly close.

[mewertow]

Hi @DavidYon47,

If you would like better alignment between the mill and the V-One, I would suggest doing all the milling operations first, and printing afterwards.

1) Drill fiducial marks, through-holes, and vias into the substrate and mill the outline before printing anything with the V-One. Make sure that the fiducials are spaced out (near the edges of the substrate).

2) Now, head over to the V-One and select 'Aligned Printing' for the first layer. Since the fiducials/holes are already included in the PCB design, you can align to these.

3) Proceed as usual.

This way, you won't have to worry about aligning the circuit with the mill - you can use the V-One's built-in aligned printing feature to align with the drills, which should give you pretty good alignment, without having to use calipers. The order of printing first layer before drilling is what we typically suggest for double-sided printing, since most users don't have a mill available, and need to align with the printed features manually.

Hopefully that helps! I'm not intimately familiar with the workflow of the mill you are using, but I think that this procedure should work fine. Also, the general procedure for aligned printing can be found in our user guides section.

• Matt

[DavidYon47]

Aha, I see. I was put off by the fact that the GUI was so insistent that Aligned Printing is for the bottom layer that I didn't consider it for both sides (thought maybe there was some mirroring done by the V1 software or something).

I'm baking filled-in vias on a second try now, where I put a + mark inside a mounting hole and lined up the first print closer to the bottom edge to help make alignment easier. Alas I still have crescenting on the pads and vias, but it may be close enough to work and I'm a little pressed for time.

Next time I'll try the mill first per your suggestion, that makes sense to me now.

Quick question: on Aligned Printing, does it assume that pads and vias are drilled already, therefore it will attempt to avoid dropping ink into the pad/via hole? As opposed to normal printing where it treats them as filled in polygons just like SMD pads.

Thanks again...

[mewertow]

No problem, and good luck with your print! To answer your questions:

1) Mirroring is only applied by default to .gbl files, since these are exclusively for the bottom layer. You should be fine to use aligned printing any time you want to align with an existing feature on the board.

2) Any time there is a drill .txt file loaded during a print procedure, the V-One will exclude the drill area from printing. You should see that your through-hole pads and vias have an excluded region in the center, where the V-One expects a drill.

[DavidYon47]

Thanks, I tried the mill-it-first workflow with Aligned Prints on both passes. That cured the alignment problem completely.

[troy]

did you load the holes file or not? I ask because I've wanted to try not loading it so that the vias print as pads -- potentially ensuring a good contact between surface and filling. It should work, but I don't want to recommend it until i try it or see it done.

[troy]

note that if you try my idea. you need to bake the filled board otherwise you'll probe the centers of the vias and have a bad time. it means 3 bakes total, which is not great. but you get all the higher risk stuff done up front.

[DavidYon47]

I use the holes file for both sides. I've tried filling the via holes after the first bake, and tried filling them before the first print and baking them with the first side. No matter what I do I always end up with cupping in the via holes, leading to continuity failures with at least one via.

I've tried touching up the via holes after the first bake in hopes the second one will top up the cup and get better contact. I've yet to have consistent results, and the futzing gets time-consuming after awhile.

I'm not sure that having the machine drop a full pad over a pre-drilled hole is going to help much. As I've said, I've pre-filled them, then topped them off (which is way more ink than just a single layer), and still I get one or two vias that don't connect.