[celephicus]

I have an option to buy an old PCB Pick & Place machine. For those not in the electronics industry, these are a very solid flat bed about 1500mm square with an X-Y gantry above it holding tooling for placing parts on circuit boards. The drive is several 1" leadscrews, with AC servomotors and associated drive electronics.

It has been out in the rain, and has been ratted every time another machine broke, so everything apart from the basic mechanics is probably broken or missing. The X-Y motions still turn by hand though, so I could replace the motors with steppers no problem.

It looks ideal for conversion to a wood router, has anyone ever done anything similar? I would love to see some pictures.

Celephicus

[diecutter]

I would go for it if you could get it cheap (that is, for a little above scrap value) . then you can sell it for scrap if it does not work out and only lose a little. Sounds like it would be more solid and precise than most routers, and capable of fast moves since those are the characteristics that pick and place machines excelled at.

I built my cnc router by modifying a machine that was used for interpreting the film shot by U.S. spy planes. It has worked out great. 32" x 32" actual cutting area with a Hitachi 2 1/4 hp variable speed router. Total including all parts was $600.

[Nails]

I'd make sure the X Y gantry is beefy enough for using a router with it. It is common for one of the axes to be driven by a ballscrew only on one end. That won't be good when your router is cutting on the far end, flexing the gantry because of the forces resisting the cutting. For a pick and place, there are no lateral forces except acceleration and decelleration.

Small routers typically have a ballscrew through the center on the longest axis, and bigger routers would be driven on each end with two gear racks, and two drive gears connected to a common driveshaft spun by a single motor, or dual motors syncronized and each spinning a ballscrew on each end, or a single motor that spins both ballscrews, synchronized by a timing belt/chain.

Yes, pick and place machines are solid and precise. But only for what they were designed to do. You also have to consider that these machines are designed only carry tiny lightweight parts. To keep the speeds fast as possible, the moving part of the gantry frame will be built as light as possible. The moving cross-member on the gantry might not be as rigid as you need for the forces required for the router to cut into the wood, leading to end-part dimensional inaccuracies (unless you cut really slow to allow it to "unflex"). It just matters what kind of accuracy you are looking for. This may all be acceptable if the accuracy and cutting speeds you desire are modest.

In general, the design goals for a CNC router, and PCB pick and place machine are quite different. You can't expect a PCB pick and place machine to make a great, accurate CNC router without some modifications.

For sure, it will have a nice base/frame, ballscrews, thrust-bearings, bearing end-blocks, proximity/home sensors, motors, linear rails, etc. Given the right price, it certainly is a good start at obtaining the fundamental building blocks for building a CNC router, if you can't use it as-is.