Need help holding and cutting thin Al sheet on router

[glenneaux]

Hey everyone

Looking for some advice/help in trying to improve some things at my work..

currently, we have a vacuum pump on our router, running 3mm mdf spoilboard. we are cutting for example .050" aluminium sheet. the operators generally run it at 500mm/min wth a 2.4mm 2flute upcut end mill.

What im looking to do is run something a bit bigger, say 4mm 2flute upcut endmill and wanting to bump the speed up considerably say 1000mm/min but im finding the sheets lifting up and vibrating a lot.

we're running mist sprayers?

So how do i do it? downcut cutters? bigger? smaller?? Better vacuum? Who's doing it? how?

[MadMax]

Is your spoilboard gasketed to the part edge? If you've got a lot of spill around the part, you might not be getting as much pull as you could if you have leakage where the part isn't sitting. If you've already covered up the area around the part there might not be much more you can do except pull a stronger vacuum but there may not be much room for improvement if you're already close to 0psi. You can't get any more hold down than 15psi unless you caulk up your doors and pressurize the room to greater than one atmosphere.

[hoghead]

One of the things you’re not telling us is the RPM you are running, is your RPM controllable or are you stuck with a set RPM? You need to understand "chip load" (Google “chip load”). If you increase your feed-rate you need to increase the RPM of the tool in order to maintain the correct chip load, increasing tool diameter does not help and might hurt. Besides understanding chip load you need to look at the surface speed of the tool, increasing the diameter of the tool will increase the surface speed of the tool and might not be helping. In short the spindle speed of your machine and the tool in use along with the feed-rate will determine the chip load. If you want to increase feed rate you need to increase RPM.

[warrenb]

Try a straight flute cutter before a down cut. Aluminum gets tricky by gumming up on you. You're just going to have to experiment. You definately need to look at your vacuum system and make sure as little leakage as possible is occuring. It's a tough project. It may come down to you running at full speed (as fast as you want) and leaving tabs every 6 - 12 inches or so that get cleaned up after everything is cut.

Good Luck