12 posts tagged with "openpnp"

Three months of placing boards wears a desktop pick and place machine in a few specific places, and all of them are adjustable. Belt tension, the O-rings that seat the nozzle tips, a Z lead screw that shipped dry, and the head offsets somebody nudged while chasing a placement error. Nothing on that list is sealed, and every adjustment moves a number OpenPnP is already using, so maintenance on this class of machine is mostly a measurement job.

A Vertex 4 sells for $1,499 with 50 feeder slots and two JUKI-compatible heads, and it is rated down to 0402 parts. Under IPC-7351 an 0402 gets a total placement budget of 0.1 mm, and an axis that has drifted two tenths of a millimetre is already past it.

Most of the tape on my bench never came on a reel. A hundred 0805 resistors arrive as a foot of tape in an antistatic bag; five thousand of the same part arrive in a sealed foil bag with a desiccant sachet and a card printed with three dots. The two are stored and loaded differently, and getting it wrong costs parts rather than time.

I keep three things next to the Vertex 4 for this: a flush cutter, a roll of splice tape, and a marker. Here is what each one is for.

Four OpenPnP feeder classes cover parts that never came on a reel: tray, tube, loose part and heap. I set all four up on the staging plate of our Vertex 4 to see what each one does with a JST housing, a buck module and the odd 0402 that ends up on the floor mid-run.

The Opulo documentation calls the first board a printer test page, and after running one I think that is the right frame. Before your own design goes on the plate, you run the board the machine shipped with, so that a part landing in the wrong place points at the machine and not at your CAD export. I ran a stopwatch on our first one: 91 minutes from a bare staging plate to five 0603 resistors placed.

The new bench is 30 mm lower and half a metre shorter than the old one, and I did not think that mattered. I carried the Vertex 4 across the room, set it down, homed it, put the same board back on the plate and started the job. Every part landed about 2 mm to the left of its pads, all the way across the panel, and nothing in OpenPnP raised anything I would call an error.

Two millimetres is four 0402 widths. On a 300 mm panel it is also 0.38° of rotation across the whole board, and that second number is the one that eventually told me where to look.

A desktop pick and place machine at $1,499 buys a machine that is already built. The Vertex 4 arrives assembled, wired and calibrated, with a dual JUKI-compatible head, top and bottom vision, a 500 × 400 mm work area, 50 feeder slots and one set of manual tape feeders in the box. Build time runs 5 to 10 days.

That covers the machine and says nothing about your board. On my own bench the questions that have actually stopped an order are part height, part weight, lead pitch and panel size, and none of them appear on a price comparison page.

The first sign is rarely a light. It is a 0603 landing a millimetre behind its pads on the first board of a batch, and the same millimetre on every board after it. By the time anything goes red you have scrapped a few boards.

On a Vertex 4 I have run short feeds, double feeds and a feeder that dropped off the RS-485 bus mid-job, plus one that was fine when I pulled it out and put it back on the shelf. The order below costs a pen and a pair of calipers before it costs a spare feeder.

The first sign was a 0402 that came back from the bottom camera sitting at an angle.

I was halfway through a 20-board batch of a small sensor board: nine 0402 decoupling caps, a dozen 0603s, two SOIC-8s. The machine is a Vertex 4, running OpenPnP. It ships with a 503 and a 505, and the 503 went into N1 for the small end of the BOM, which is the reasonable reading of those two nozzles if you have not thought about it much. I had not thought about it much.

The bottom camera is arguably the most important vision system on your desktop pick-and-place. It's what verifies that the component is correctly oriented on the nozzle before placement. Get the exposure wrong, and you're either blind to misaligned parts or drowning in false detections.

Most OpenPnP guides tell you to "adjust exposure until it looks right." That's not helpful. Here's what's actually happening and how to calibrate it properly.

Photon feeders use UUIDs (Universally Unique Identifiers) to communicate with OpenPnP. This is generally reliable, but it creates a specific class of problems when feeders share IDs, get reassigned, or conflict with each other. If you've ever seen OpenPnP detect the wrong feeder or fail to recognize a feeder that's physically connected, UUID conflicts are the likely culprit.

Here's what's happening under the hood and how to fix it.