convert rf45 type to belt variable speed and some cnc info?

[ataxy]

can anyone point me to how to convert a rong fu type gear mill to belt drive with variable speed
and what type of stepper would i need to convert it to cnc, not really brand but more like in/oz info and also the same type of info for controller and driver like vdc and amp
one last thing how, if possible, do you calculate the in/oz from a stepper if all you have are voltage, ampering and ohms
i tryed to search for it a BIT i now have a vague idea about the stepper but none about the conversion to belt and variable speed, again if possible

[ataxy]

ok foud this about the gear to belt conversion but i havent read it yet
Belt Drive Spindle Possible?

[ataxy]

about the motor i am not able to find the torque of those motor so does anybody know if they are any good for a small bench mill x2 or x3 type of bench mill or there not worth snit

VEXTA 2-PHASE, 7.4, V 1A STEPPING MOTOR PK266-01A-C23

or this

103-770-0194 Step-Syn - Sanyo Denki Stepping motor
Nominal Voltage 5.1
Current 1
Wires 6
Condition pulled
Steps / Revolution 200
Step Size (degrees) 1.8
NEMA frame size 23

[dcprecision]

I have been doing some preliminary work on a rf 45 and have determined that servos with 600 in/oz. are about the minimum power needed if using ball screws. The problem is due to the table weight and acceleration requirements. If using a 5 tpi ball screw, I would use a 3:1 reduction minimum and possibly a bit more. If the motors can do 3000 rpm, this gives you a 200 ipm table speed. possibly a bit to fast for the motor power limitation. 4:1 gives a respectable 150 ipm. I also would advise lapping all x & y axis ways to minimize friction.

[dcprecision]

Anyone with machinist abilities working with one of these machines quickly realises the need for spindle speed when working with aluminum and small diameter cutters. I have an older RF-45 with the 3 phase / 2 speed motor. This gives a max spindle speed of 3000 rpm. Almost all my work is done using high helix end mills at max speed. This machine is really noisy at high rpm and does it ever generate heat. After a few hours use, you feel like you are standing next to a woodburning stove. Changing to a timing belt drive with an inverter speed controlled 3 phase motor is the way to go. Doing so would reduce noise by probably 75% and cut power consumption and associated heat by a huge amount. Can anyone help with any design info already available???

[ataxy]

thx for those info i would also appreciate plan or info on how to convert one to belt drive for the same reason as you belt also offer the advantage having variable speed wich help when cncing

[dcprecision]

I may desigh a kit in the near future.

[szcharle]

why you change a gear box to belt,i think gear box is good enough ,except the noise a bit loud,gear can given your high torque! belt can not .

[scott wiggins]

I would prefer to see a belt or VFD drive as multiple or step pulleys would be ble to whichever is needed. Current gear on clone seem too limited. Just my 2 cents. I will be following this closely.
Scott

[dcprecision]

When you do a belt conversion on one of these, you remove all gears and oil from the head casting, install a timing belt pulley on the motor, machine another pully to replace the spindle drive gear, then install motor setup with pilleys and belt inside the gear box housing. A friend of mine builds printing equipment transmitting 20 HP with timing belts no problem. I believe the sound may be reduced by 30db, that is a lot. each 3db is a 50% reduction in sound pressure level so we are talking 10X quieter than stock without heat buildup.

[TPPJR]

Only problem is that you can not have both worlds. Either speed or torque. If it is setup for speed and you need to do something slow you may not have the torque to do it. If you set it up for torque then you will not have the speed. The reason Tormach has a two speed belt drive. If I absolutely had to I think that I could set it up for speed and deal with the low end torque since 90%+ of my work is at speed. Been thinking about belt drive. You would also have to figure out a way to lock the spindle for tool change out. Now I just select the lowest gear and all is well.

I have done a couple of things to fight the heat build up. They are on my photopage at: RF-45 info and ideas To include a lower spindle bearing cooler and a gear head cooler.

Thomas

[dcprecision]

I agree that you can't have both worlds. The best power solution I can think of is to install a 3 phase 2 speed motor that is inverter rated and run with a 1:1 or lower belt ratio. This gives a spindle rpm of lets say 300 to 2500 low speed and 600 to 5000 high speed. So far as torque is concerned. By reducing the ratio to 1 : .75 you can still get around 4000 rpm high with improved torque. Even when using a 3/4" end mill you still want at least 1500 in aluminum and 750 in steel for optimum material removal. The only application I can think of requiring high torque / very low speed is when drilling very large diameter holes ( 5/8" + ) with a drill bit. If its CNC, you can mill them. My RF-45 came with a 2 speed motor from the factory so I am set to experiment when I get around to it.