CNC RC Motor Spindle

[jjr2001]

Here is a model airplane motor powered, belt driven, CNC Mill spindle. Right now the high rpm is 2000. Other pulleys are in the works for higher ranges. The Motor is a typical RC motor of 400kv. That is 400 rpm per volt.
With my 12 volt power supply that comes out to 4800 rpm for the motor at the high speed end. The pulley reduction is 2.4 to 1. Without any cutting load the spindle was measured with a tach right at 2000 rpm. Power supply is capable of 70 amps at 12 vdc and this setup is running about 16 amps under cutting load so I have plenty of head room on the power supply.

The speed controller is a standard RC motor 100 amp simple controller. I added a fan to cool the speed controller and then it blows toward the motor to help it out a bit also. Extra capacitors are added inside the white box to protect the speed controller from transients. Heating of the motor does not seem to be a problem at all. I think the generous amounts of aluminum are making a great heatsink.


(see post 9 to see how much of a "good value" this turned out to be!)

The actual spindle shaft is an off shore ER-20 collet setup. It was $15.00 with the collet nut which was a good value. The shaft itself when installed in the bearings and housing had about 5 tenths run out. Plenty good for me. However the collet did not seem to fit properly when the nut was installed. The off shore collet nut had a ring of steel that was preventing the collet from registering inside the shaft on the ER-20 taper. I had to bore out at least .030" deep for about .125" inside the nut to keep the extra metal from interfering with the seating of the collet. Now with a 3/8" collet and a dowel rod in the collet the run out is about .002". Not as good as I would like but it will work for now.

The spindle shaft housing was a chunk of mystery metal from my metal supplier. It was tubing and required just a small amount of machining to fit the bearings and then just clean up the outside. The bearings are an easy press fit. Half inch aluminum T-6061 was used for all the other mounting pieces. The pulleys are more mystery metal. The CNC machine was used for spotting and counter boring the holes in the mounting plate. The final diameter for the spindle housing mounting holes in the aluminum was done on the mill with a boring head. I pinned both the top and bottom mounting plates together to bore the holes so they would be lined up.

So far it looks pretty good. One of the pics shows the finish on the side of a band sawn chunk of aluminum.
Next part is to make a tooling plate of 3/4" aluminum plate. The CNC machine will make it's own and we will see if it can earn its keep!

Here is a link to the CNC machine the spindle will be used with:
http://www.homemadetools.net/forum/c...6078#post65886


Cheers,
JR

[Paul Jones]

JR,

Great information and the 70A, 12VDC power supply and the heatsink capabilities of the motor mount. You could always add more fins to the surrounding housing.

I think many milling tool manufacturers say that each tenth of runout reduces tool life by 10% in CNC work. It may not be exactly correct but that is why I buy some of the more expensive ER collets with 0.0002" TIR because the solid carbide cutters are pretty expensive, and the longer the tool life, the better for my wallet.

Your photos proves your machine can machine a beautiful finish on the rough-sawn aluminum. Nice to be a a point where your machine can generate even better parts for itself.

Thanks for the photos and progress report.

Paul

[jjr2001]

Wow, that is a lot of lost life due to run out. I will buy at least two new ER-20 collets. One for 1/8 and one for 3/8 since they will be my most used cutters. It makes sense that tool life would be reduced since the run out is going to put more tool load on the flutes that come closest to the metal (or plastic) you are cutting. I did add a heat sink to one of my power feed motors since it was never designed for continuous use and I was putting a very heavy duty cycle on it. Worked like a champ. Now the motor is warm not hot.

Here is link for that heat sink. Just made it on the lathe and mill out of some aluminum plate.
http://www.homemadetools.net/forum/s...9982#post71647
It is on post 8.

Cheers, JR

[Jon]

Congratulations jjr2001 - your CNC Mill Spindle is the Tool of the Week!

Lots of nice entries this week, including a Tilting Table for Jig Welding by Frank S, a Basic Dividing Head from Metaler, your Banjos, and a Grinding Rest from DonRecardo, from a Metaler design.

Since this is your second win, you'll be receiving a $25 prize, from your choice of PayPal, Amazon, or bitcoin. Please PM me your award preference, plus a current email address, and I'll get it sent out immediately.

This one hasn't been inserted into the encyclopedia yet, but it made it in before the weekly deadline. Here's your previous Tool of the Week winning build:

Grinder Fine Feed Adjuster by jjr2001

tags: grinder, adjustable

Previous winners can be viewed here: 100 Homemade Tool of the Week winning tools

Congrats again!

[jjr2001]

Thank You Jon, First we get an idea or see an idea for a tool we need, that is good. Then we decide to make the tool and that is a certain amount of fun. Then we make the tool and that is just plain fun. Then sometimes we get an award for the tool and that is just plain awesome. Thanks again, John R. aka JR.

[PJs]

Congrats JR...Great tool and a winner for sure. Adding to your already impressive Bling! ~PJ

[jjr2001]

Thanks PJ, so many great ideas on this site the building will never stop!

[DIYer]

Thanks jjr2001! We've added your CNC Motor Spindle to our CNC category,
as well as to your builder page: jjr2001's Homemade Tools. Your receipt:

CNC Motor Spindle by jjr2001

tags: CNC, spindle, motor

[jjr2001]

The point here is if you buy an inexpensive import ER-20 or any other type of shafting make sure it is true by chucking it up in the lathe and checking it for runout. It may just save you a tear down!!!

In the first post I noted the .002 runout and have since found that I was lucky to get that low. I had a poor collet and in addition the shaft was defective from the overseas factory. The luck was in angular placement of the collet in the shaft. I measured .003 for the runout of the shaft and about the same for the bad collet. When put together at the real lucky position run out was better than .001.......At worst it was.006....Yikes.

Could not live with that. Destroyed the bad collet. Disassembled the shaft from the bearings and housing. I had found that the shaft OD was better than .0004. However the taper for the collet was .003.... Ok, lathe time.

Chucked up the shaft in my lathe and indicated it to better than .0005". Then I used a dial test indicator to set the compound to the taper of the shaft collet socket. When I had the angle right for the ER-20 taper I put my dremel on the tool post with a small grinding wheel and took very light passes on that ugly taper. You could hear the runout as it was turning. Eventually after about 12 passes the sound became quite steady and I knew it was done.

Testing on the lathe with a dial test indicator showed no movement in the indicator.

Result after putting the spindle back together was better than .0005 runout. Now that I can live with.

Cheers, JR

[L98fiero]

Nice looking mount and good warnings about the collets and chucks