Drill and Profile cut aluminum

[dcribbs]

Our school just got a 48x48 PRSAlpha with a 2.2HP Spindle. We are interested in cutting a bunch of gusset plates out of .09 thick Aluminum sheet. We would like to drill the holes and cut the profile with the CNCrouter.

Any suggestions on:
1. Drilling? The holes are designed to fit a #8-32 screw. Do I just purchase the right size drill and have at it? Speed/plunge rate for drilling through aluminum?

2. Profile cut? Spiral flute upcut probably, but at what speed/feed?

This is our first cutting with Aluminum so I don't want to screw it up. As a newbie any advice is appreciated!

Thanks,

Dave

[Brady Watson]

Drilling AL on a CNC router is a no-no. Instead, use an inside profile cutting strategy using a spiral ramp is preferred. The RPM is just too high for drilling. Your spindle's min RPM is about 5,000.

A single flute spiral-O bit (Onsrud is a good source) is the preferred tool for cutting AL on your ShopBot.

There is a lot of information that has been posted. Please use the search function & try "Cutting Aluminum", or something like this.

-B

[donek]

holes that small are going to be very difficult to profile. I'm guessing the reason you wish to drill is for the accuracy. The simplest approach here is to spot drill. Meaning you are basically providing a small mark similar to what a punch produces. You can use one of these
http://www.mscdirect.com/product/details/63769335
put it in your 1/4in collet and drill to a depth of about .060. Then you can go back and drill the hole on a drill press and know the holes are placed where you want them.
The cutter I always use on aluminum is
http://www.mscdirect.com/product/details/71177190
they are big enough that they are not really easy to break. Feed speed is 1.2ips, max cut depth is 0.05in. Always climb cut.

[Kromet International]

Drilling AL on a CNC router is a no-no. Instead, use an inside profile cutting strategy using a spiral ramp is preferred. The RPM is just too high for drilling. Your spindle's min RPM is about 5,000.

A single flute spiral-O bit (Onsrud is a good source) is the preferred tool for cutting AL on your ShopBot.

There is a lot of information that has been posted. Please use the search function & try "Cutting Aluminum", or something like this.

-B

I'm curious to know the reasoning behind not drilling with the shopbot? What could happen? We drill on our machine and plunge cut with endmills (1/8-1/4" thick aluminum) and it looks and sounds great while performing. We aren't misting we are flood cooling.

[Brady Watson]

I'm curious to know the reasoning behind not drilling with the shopbot? What could happen? We drill on our machine and plunge cut with endmills (1/8-1/4" thick aluminum) and it looks and sounds great while performing. We aren't misting we are flood cooling.

Flood cooling on what machine exactly? A milling machine or ShopBot router?

-B

[Kromet International]

Flood cooling on what machine exactly? A milling machine or ShopBot router?

-B

We flood on our shopbots.

[Brady Watson]

We flood on our shopbots.

Then drilling is no problem because you have flood coolant. However, most do not & may be holding their parts down on a porous vacuum table without a coolant trap.

The reason you never drill is you cannot get the spindle RPM down low enough for the proper drilling chipload when cutting dry. It will load up the end of the bit with aluminum in a split second. There are a few HSS drill geometries out there (in fractional diameters to match a fractional collet) that can work without loading up. Dry.

Additionally, those spindles are not designed for drilling dense materials like aluminum. It's a great way to wipe the bearings out of it prematurely. You also really have to watch shock loads. These spindles and routers are designed to route - which means XY movement. There's been lots of discussion regarding this in the past. HSD spindles are more expensive to rebuild than it is to replace, so plan on buying a spare if drilling is something you do every day.

Bottom line...Your machine...your spindle...do what you want.

-B