My New RF45 clone CNC conversio finished!

[GMitchell]

Hi guys, I have just finished making my RF45 clone into a CNC mill.

I have turned this into my first ever website. Please have a look and tell me what you think, any comments, dead links or questions, please contact me.

My website email is CNC@graetech.com

Thankyou

Graeme

http://www.graetech.com
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[hesham morsy]

the website will be a reference for cnc conversion it seems like u did your home work
excellent job

[Kipper]

I'll take a pinch of salt with all that..

[knowell2]

Graeme, my RF 45 is experiencing the same problem. It is leaking oil in the spindle. Do you by have the specs for the oil seals? I want to be ready when I take the whole assembly apart. Thanks.

[GMitchell]

Hi, I went looking for the receipt from the bearing shop, but couldn't find it. I did however keep the actual seals, bearings etc that I replaced last year, just in case anything strange ever happened again in the mill gearbox.

I found 4 oil seals in my plastic bag, three were actually from the machine, and the last one I was trying to addapt to the top spline cover to stop swarf getting in during tool changes. The two smaller seals that are actually on the spline drive shaft are most likely the offending items. The third oil seal is from the motor input shaft. (i'm telling you this so that the photo doesn't confuse you)

There is also two little shaft seals where the gear change levers go through the front of the gearbox, behind the sheet metal cover. Just check to see if they are weeping, it may be an easier fix for you?

Spline drive shaft seals: They are double lip seals, I measured approx 45mm OD x 35mm ID x 10mm depth, but I can clearly remember at the bearing / oil seal shop they could not get 45x35x10, I had to use 45x35x7 or something similar, but it worked anyway.

Go to the American "grizzly" machine tool website and get their workshop manual for a model G0484

http://www.grizzly.com/images/partslists/g0484_pl.pdf

Their machine is similar, not identical, but all of the gearbox's main features are exactly the same as mine (but the chinese factory that made my mill may be different to who made yours?), anyway the diagram will be a very good starting point for you.

The lip seals are part 237 in the exploded view diagram.

Have a look where they are on my web page, third photo from the top.
http://www.graetech.com/index_files/Page975.htm

I have attached some pics for your reference.

Good luck,

Graeme

[stevespo]

Graeme, just a quick thank you for all the effort you put into documenting your conversion. This should be required reading for anyone thinking about building a machine or performing a conversion. Most of us learn these things through research, trial and error. You'll certainly save some people a lot of time and money, and make for a more enjoyable learning process. Thanks again.

Steve

[LUCKY13]

Thank you for your right up.

The machine looks like its very nice and doing a good job for you. Its always good when information is made available for other to see and use, great job. And again thanks for your efforts, it helps.



I have a question though. Am I understanding right that you are using servo's with no gearing/timing belt setup (dirrect drive to the ballscrews) ?


I didnt think this was possible with servos and that they had to be geared down. Or do you simple have such strong servo's that they can drive the ball screws anyway ?



Jess

[GMitchell]

Hi Jess, You are right, I have used a the servo motor to drive the ballscrew directly (with a good quality shaft coupling.) on my X and Y axes.

It all comes down to doing the calculations, and seeing what will work practically.

To start with, I had an idea what I wanted to achieve, a pushing force in the order of 4000 Newtons give or take a bit (900 pounds of pushing force in your scale) and I wanted to have rapids of at least 200 inches per minute. These were just figures that I thought were about right, not any special reason for them.

There is a simple calculation that can be done to calculate pushing force from torque on a thread if you know the thread pitch and torque. I did the numbers and with a large enough servo motor, It was definitely possible to go direct drive, it works really well.

I just used the standard "kelinginc" servo motors from their website, nothing special.

There are reasons to gear down if you need to, for example you may have a weak motor (by that I mean low shaft torque) , and are not worried about speed. I think that the Industrial hobbies people gear down 4:1 to gain more pushing force, but they have lost their top end speed 4:1 too.

It is all about trade offs.

Graeme.

[Runner4404spd]

IH gears down 4:1 to get more torque into the cut. i've got a 3hp spindle motor on mine and now that its tuned and setup right i can plow right through material and will break a cutter before i stall a motor. also having the extra torque allows the gibbs to run really tight so you get very little backlash and axial motion.

[knowell2]

Thanks Graeme for taking the time to post the pictures of the oil seals. I'll check my local bearing supply store and bring the pictures for reference.