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 (http://www.talkshopbot.com/forum/search.php?searchid=1662598).

-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 (http://www.talkshopbot.com/forum/search.php?searchid=1662598).

-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

[Kromet International]

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

Brady, that is kind of the answer I expected to hear. Thanks for answering my question. I am worried about getting coolant in the spindle rather than burning out the bearings I know its not a sealed unit and built for a wet environment. Time will tell I guess, it doesn't appear that many of you use these machines for aggressive machining. That being said we are getting positive results.

[Kyle Stapleton]

Can you post some pictures of your setup and what you make?

[Brady Watson]

....it doesn't appear that many of you use these machines for aggressive machining.

Au contraire mon frere! Many of us do...just not in aluminum :D

It is after all a light CNC router, and not a milling machine. It simply lacks the mass and rigidity of a milling machine. This is why my Bridgeport CNC weighs 4000 pounds with a 16x12" machinable area.

Something like a Haas Mini Mill or gantry mill would be the proper tool for aluminum milling billet parts. Even a Tormach. Unless you are cutting sheets under 1/4", the SB isn't the right choice for production in my opinion. It's fine for one-offs. Yes it can be used in production this way...but for how long? If your profit margins are wide enough...you can just buy a new one every year :D

-B

[Kromet International]

Au contraire mon frere! Many of us do...just not in aluminum :D

It is after all a light CNC router, and not a milling machine. It simply lacks the mass and rigidity of a milling machine. This is why my Bridgeport CNC weighs 4000 pounds with a 16x12" machinable area.

Something like a Haas Mini Mill or gantry mill would be the proper tool for aluminum milling billet parts. Even a Tormach. Unless you are cutting sheets under 1/4", the SB isn't the right choice for production in my opinion. It's fine for one-offs. Yes it can be used in production this way...but for how long? If your profit margins are wide enough...you can just buy a new one every year :D

-B

At the end of the day I don't pay the bills so it really doesn't make much of a difference to me. I just want to see the machine running as fast and as hard as possible right to the limits.

[Kromet International]

Can you post some pictures of your setup and what you make?

If you want to see what we do here just go to www.kromet.com.

Our setups are a shunk pin type system where we drop custom fixtures into place.

We have a custom machined 1" table which our shopbot machined. We have installed a 21 gallon coolant tank with custom troughs and a filtration system to separate the aluminum from the coolant. We have installed guarding and light curtains for safety. We are turning the shopbot from a hobby toy into a state of the art machining operation.

When I do get sometime out in the shop I will post pictures of our set up.

[Kyle Stapleton]

Sounds cool.