Birch Plywood Cutting Stratagies

[gavztheouch]

I am building some prototype chairs out of Birch plywood. My router x and y axis are solid, the weak link is my router a 2hp hand held router and my z axis which deflects under heavy/mid loading.

I have a 1/4" spiral upcut bit which has enough cutting depth to cut the whole 18mm of my plywood boards in one pass.

On my first run I cut out each profile in three passes @ 2000mm/min or 80 inch/min. I know this is slow I have been reading as many threads on the topic and I know 10000mm/min is more common and achievable with 10hp spindles.

The first complete chair took me 1hour 45 mins to cut out. This to me will do however I am worried my router will not cope with the load. I would also like to preserve my tooling however im not sure how best to do this as I can't run at the recommended speeds?

The noise coming off of the router bit was piercing and I had to wear a set of ear muffs to make being near the router tolerable, is this normal?

I reckon the next thing to do would be to just dismount the router and make some passes at differing depths and speeds by hand and just feel the resistance, to see whether all the noise is justified.

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[ger21]

The noise coming off of the router bit was piercing and I had to wear a set of ear muffs to make being near the router tolerable, is this normal?

1/4" bits can really scream at higher rpm's
What rpm are you running at? Do you have a variable speed router? How fast is your machine capable of moving?

If you can, I'd try using about 15,000-18,000 rpm, increase the feedrate to 4000-5000mm/min, and make 4-5 passes instead. You don't need 10HP to cut that fast with a 1/4" bit. If you make 5-6 passes, you're 2HP router should be more than able to cut at 10,000mm/min

Lower rpm and faster feedrate are what's needed for longer tool life.

[louieatienza]

I will echo Gerry's comments about your spindle running too fast. I've been touting the use of single-edge spiral compression tools for routers with lower horsepower, since they usually have more "oomph" at higher RPMs. They also have a very large flute which evacuates chips better and faster.

That said, you could be better off using a 3/8" diameter bit, which is far stiffer than 1/4" and might alleviate some of the noise. Use a bit with no more than 1" of flute, and get the shaft all the way in the collet so that the flute just sticks out past the collet. The closer the work is to the collet the stiffer overall the bit will be.

You can find what's optimal for your machine by testing different feeds, speeds, and cut depths. You'd test feed first by making a few slots, going faster with each, seeing where cut starts to suffer, then back off about 5-10%. You would do the same for the spindle speed and depth of cut.

I posted a thread in the DIY woodworking machines section on different bits and endmills, and go over briefly how to calculate feedrates for a given bit. I also have a 2HP router as spindle, and cut 3/4" through in 2 passes, with a 1/2" single flute compression spiral at about 120ipm... and I don't have a powerful drive system or superstiff frame...