Brother TC-211

I found milling on my machine has to be extremely light. I actually had the table move pit of the way on a.030 side cuti cut .250 deep in aluminum with a .375 carbide endmill. I think the table is set up like a Jig bore. Precise positioning but very little side loading support

JohnW wrote:

I still have the motors. They need a good clean but turn smoothly (ie bearings are OK at least). X and Y are 100w 3.25kg/cm servo motors, Z is 200w 6.5kg/cm according to the original sales brochures for the machine. One thing I have noticed is that the ball spindle pitch on the machine seems more coarse that I would have expected.

that is to achieve the desired feedrates without incurring whip of the ballscrews.

It all looks standard, and I wondered how they manage to meet the original precision spec of 0.01mm. What sort of angular positioning accuracy are the original (Toshiba?) resolvers likely to achieve?

Well, my resolver converters get 4096 quadrature counts/rev, but they might have had a higher res converter originally.
Fanuc uses 1 million count/rev encoders on some machines for this reason. .01mm is not really all that fine, it works out to .0003937"

Yes, the Z axis is quite heavy! It has the original a 1.5KW servo spindle motor on it. I was thinking of a counter weight if I converted the machine to manual only.

With regard to side loads, I was more concerned with the actual vertical ways not being rigid enough for milling, or getting damaged from side loads. From pictures on the web the spindle tube appears about 6 or 7 inches long, with 4 ball bearing races, two at each end... The spec says the spindle motor is a 1.5KW Servo motor. Is it a servo because for the tapping operations, you need to synchronise the exact number of rotations with plunge depth for thread cutting?

At least with LinuxCNC, the Z axis syncs to the spindle rotation, so it doesn't need a precise spindle control. But, there is a video of one of these machines doing tapping, and the spindle is reversing REALLY rapidly to do a peck tapping cycle.
They may also need spindle orient to transfer tools from the carousel.

Jon

mblaszkiewicz wrote:

I found milling on my machine has to be extremely light. I actually had the table move pit of the way on a.030 side cuti cut .250 deep in aluminum with a .375 carbide endmill. I think the table is set up like a Jig bore. Precise positioning but very little side loading support

Was this because the side forces from milling were rotating the servo motors? Adding a brake is no good if you want to mill a circle or curve, with X and Y smoothly changing. I wonder was that some sort of motor drive issue that could be corrected? Or is it these Toshiba servo motors by nature of their design (assuming you have the standard motors)?

No it was actually the table lifting and moving. The machine was designed as a high speed drill tap. All forces down.

mblaszkiewicz wrote:

No it was actually the table lifting and moving. The machine was designed as a high speed drill tap. All forces down.

Very useful to know! So it is not going to be my general purpose milling machine! My revised plan now then, to just get going, is to use a Closed Loop 12nm NEMA 34 Stepper for the Z, and two open loop NEMA 23 Stepper motors I have already to move X and Y, and a parallel card. This should get me in to Linux CNC, at least engraving perspex, hopefully without getting crushed by the Z axis.

Is there any way I can get the original spindle motor, a Toshiba RA10M AC Servo motor, 1.5KW, 3K rpm 6K max running off 3 phase without a VFD? Can I just wire it up to the 3 phases and run it open loop at least for a short time, say 10 minutes? Will it be going at 6K then?

JohnW wrote:

mblaszkiewicz wrote:

Is there any way I can get the original spindle motor, a Toshiba RA10M AC Servo motor, 1.5KW, 3K rpm 6K max running off 3 phase without a VFD? Can I just wire it up to the 3 phases and run it open loop at least for a short time, say 10 minutes? Will it be going at 6K then?

If it is a permanent magnet motor, it will not start when abruptly connected to 3-phase mains. Unless the volts/Hz curve simultaneously matches the applied voltage AND the frequency, then even if started, it will not run with reasonable current. IE. it will burn up or blow a breaker.

Jon

mblaszkiewicz wrote:

No it was actually the table lifting and moving. The machine was designed as a high speed drill tap. All forces down.

thats not right. if its moving, freely, in any direction, its got worn out ways and / or ball screws / supports or possibly something loose.

if its moving under side force the error should be detected in linuxcnc on the encoder/resolver. you only have 100w servos on the x and y, they are not going to hold up to much heavy milling, BUT, its still a good 200lbs peak linear force. so if it being pushed off course during cutting, either the cut is very heavy, or youve got something very wrong mechanically.

JohnW wrote:

mblaszkiewicz wrote:

No it was actually the table lifting and moving. The machine was designed as a high speed drill tap. All forces down.

Very useful to know! So it is not going to be my general purpose milling machine! My revised plan now then, to just get going, is to use a Closed Loop 12nm NEMA 34 Stepper for the Z, and two open loop NEMA 23 Stepper motors I have already to move X and Y, and a parallel card. This should get me in to Linux CNC, at least engraving perspex, hopefully without getting crushed by the Z axis.

Is there any way I can get the original spindle motor, a Toshiba RA10M AC Servo motor, 1.5KW, 3K rpm 6K max running off 3 phase without a VFD? Can I just wire it up to the 3 phases and run it open loop at least for a short time, say 10 minutes? Will it be going at 6K then?

no, you can only run the spindle motor with a dedicated servo drive.

the machine is very much a heavy duty milling machine with very good spindle bearings that handle side loads well - the machine has milling cycles and is very much intended for face milling and slotting. when people call it light drill tap, they are comparing it to things like a huge mori or mazak 40 taper etc (which people who run 50 tape call light duty). the tc211 will be at least as much above things like tormachs and other hobby mills in rigidity as the 40 tapers are above it.

on my tc 225, with 410w xy servos and 3.1kw spindle i can plow through aluminium with a 1/2" zrn coated cutter at 196ipm 1/2" deep, 1/8" step over 6000rpm and it doesnt make a peep. the tc 211 wont do that, but it wont be that far off, the rigidity will be similar, just not the power.

if you have the drives, use the original motors. if you dont have the drives, try to find them on ebay for cheap. if you cant find them, buy new xyz servos from delta (asd-b2) for $1500 if you can afford it. steppers would be not ideal on this machine for a number of reasons besides just performance. 1st; physical size. the servos on the brother are somewhat odd metric sizes, not nema 23/34, and their shafts are also somewhat unusual diamtres. youd need to make adapters, and get couplings and hope they fit under the way covers. you also need a brake on the Z, which is inside the servo. otherwise the axis will fall when the power is cut. on a machine as heavy as the brother, with linear guides, the steppers internal detent torque will not hold up the head.

my brothers have 86mm (looks like nema34 but isnt) and 120mm servos with 16mm shafts.delta does make a 750w 86mm motor to fit. it think on your machine that would be the Z. i think your xy might be 60mm "standard" japanese spec, which delta (and everyone else) makes in 200w and 400w.


for the spindle motor, you can do 2 things (i am assuming your spindle has an encoder, not a resolver).
1: get a drive like the delta c2000. this will run a 3 phase servo like a regular analogue spindle. the drives cost alot. probably $600-$800.
2: get a drive that runs "any" servo. delta makes the asd-a2r for this, but its impossible to find. some people have used surplus allan bradley 3000 drives off ebay. they work just fine, and in the wattage you need, arent too expensive.


thinking about it, we should check if the AB 3000 drives run resolvers. if they do, you might be able to replace all 4 drives and use the stock motors for less than 1k. these drives are not ultra high performance, but they should work pretty good for the price and be a hell of alot better than any steppers. they have been used on a TC229 conversion with reasonable success (the machine got slower than its original 1400ipm).