Mill Warped PCB Blanks On An Uneven Bed

Milling a PCB at home is a great way to save some time and money if you are making one-off circuit boards. There is a downside though, it’s a little tough. Sure, just export your Eagle design to CNC-Machine-understandable g-code and fire up your mill…. well, it’s not that easy.

The copper on a PCB blank can be anywhere from about 0.001 to 0.006 inches thick. When milling a board the ideal situation is to mill just deep enough to get through the copper but not cut too deep into the fiberglass backer board. Cutting too deep can weaken the board, break a bit, or in an extreme case, cut through the entire board.

Shallow cuts can result in another problem, inconsistent cut depth over the surface of the board. Check out the left photo above. The traces on the left side of the board appears to have just faded away. This happened because the circuit board was not flat. The side where the traces are missing from is lower than the other so the tool bit is not able to reach that part of the board. Since an ideal depth of cut is about 0.010 inches, even a very small amount of waviness or out of flatness can cause a serious problem in the milling process. If you have a hard time picturing what 0.010 inches is, think the thickness of two pieces of paper, it’s not a lot. There are two main contributors to the flatness problem; the PCB board and/or the machine’s bed. If the bed is not flat, the PCB won’t be. Even if the bed is flat, the PCB may be warped or bent.

PCB fabrication enthusiast [daedelus] had this exact problem, and in true hacker fashion, decided to do something about it. He created a software program called AutoLeveller that takes a g-code file and adds a probing section to the beginning before the milling operation. When the modified g-code file is run on the CNC Machine, it first probes the surface of the PCB in a grid pattern and maps the flatness variation of the PCB’s surface. Then, when running the program, it adjusts the height of the tool bit on the fly so that the actual depth of cut is consistent over the entire board, regardless of how flat or not it is. The result is a clean and usable PCB on the first try.

There is one catch: the Machine Control Software has to be set up to accept a probe. This is easy to do if communicating to the CNC Machine via a computers parallel port. An input pin on the parallel port is pulled high with a resistor and connected electrically to the PCB board. The tool spindle is grounded with a clip lead. When the tool touches the board, the input pin is pulled low and the Machine Control Software records the tool height for that specific XY position.

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Hacklet #4 — PCB Tools and Wristwatches

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The Hackaday Prize is heating up! When we set up the prize, we expected to see some incredible entries, and you guys haven’t let us down. Projects like SatNOGS, which aims to create a global network of satellite ground stations, or OpenMV, a low-cost Python powered vision module, are seriously blowing us away.

We’re starting to give away some prizes through community voting and there’s still plenty of time for you to enter. Check out The Hackaday Prize page for the full details.

Low Cost Printed Circuit Board Tools

Pick and Place

We’ve seen mills, lathes, CNC machines and 3D printers, but if there is any device that gets a hardware hacker’s attention, it’s a pick and place machine. In the PCB industry these machines pick up thousands of parts every hour, perfectly placing them on printed circuit boards. The downside is they’re incredibly expensive. The cheapest Chinese machines without vision start in the $4000 USD price range.

[Neil] aims to break down those price barriers with a $300 Pick and Place Machine that doubles as a 3D printer. He’s using delta 3D printer hardware to do it, and he’s throwing in everything! OpenCV based vision, multiple tool heads, reel and tray pick up, [Neil] has covered all the major points. He can’t do it alone though, so he’s looking for help. Check it out, and give him a hand (or a skull)!
pcbMill

A low-cost pick and place machine will need printed circuit boards to work on. Not to worry, [shlonkin] has you covered with his PCB mill for under $10. Built from recycled printers, an Arduino, and host software written in processing, [shlonkin] has already posted impressive photos of boards his machine has milled. The main problem [shlonkin] has run into is longevity with plastic parts. In his most recent update, he’s looking for ideas. Can you help him?

Digital Watches

Anyone will tell you that digital watches are a pretty neat idea. With the era of smartwatches upon us, more than one hacker has delved into building their own timepiece. We’re happy to report that most of them even tell time.

walltech[Walltech] has gone all out to create the ultimate watch. His OLED Smart Watch 6.0 is the culmination of years of work. The watch features a 1.5” OLED display, an SD card slot, and a vibrator motor. It has Bluetooth 4.0 to connect to the world, and an Atmel ATmega32u4 as its brain. A 500mAh battery will power the watch for 18-24 hours per charge.

[Walltech] plans to make it do everything from SMS and email notifications to music streaming. Don’t see a feature you want? Add it! Smart Watch 6.0 Is completely open source, so you can hop into the code and hack away!

tilttouchtime2On the other side of the spectrum is [askoog89’s] Tilt Touch Time, which utilizes  those awesome bubble LED displays some of us remember from the 70’s. The retro look is only 3D printed skin deep though, as [askoog89] is using an ATtiny2313 processor. Atmel’s Qtouch is providing the capacitive touch sensing, while a tilt sensor helps Tilt Touch Time live up to its name. [Askoog89] has submitted his watch to The Hackaday Prize, so he’s trying to figure out a way to use the touch sensor to sync time with a PC. If that doesn’t work out, we bet those bubble LEDs would make great light sensors for some monitor-blink-sync action.

Fallout fans have seen plenty of PIP boys here on Hackaday, but have you seen [jara’s] PIP Watch? This Personal Information Panel is going big on size but low on power with a 3 inch e-ink display. [Jara] is using an STM32F101 ARM Cortex-M3 CPU, so he’s got plenty of processing power at his disposal. He’s connecting to the world through a Bluetooth serial link. All he needs is a Geiger counter, and he’s good to go!

pipWatch

That’s it for this week’s Hacklet, stay tuned for next week when we bring you more of what’s happening at Hackaday.io!