[cbucner]

Thanks Al.
My ball screws are enclosed so I turned the shaft to see what res i have.
It looks like it takes 5 turns of the shaft for the table to move 1" same with Y axis and Z too.So my screws are .20".
So I will get me something around 512-1024 sould do just fine.
Now I took some time today and parted the bandit control.
Nothing to use in there, the transformer has only 104v , 220v, 208v outputs.
I will go with gecko drives and 60-70V power supply.
I was looking on ebay for these toroidal trnasformers, and I will get a 52-56V one 1.5kv , after the bridge and filtration should have around 70v.
I turned the servos today at 36v and they do just fine, around 2" sec
From my calculations, if the servos are 1800rpm at 110v then they should turn at 900 rpm at 55v.
900rpm will give me 15rpm/sec = 3inch movement of the table / sec. at 55v.
I guess if my calculations are right.
I will fit the encoders on the shaft of the servos.
I took one servo apart and put it on the lathe .
I will drill a 5/16hole, then use a 5/16 rod and then I will tun it down to 1/4 for minimal runout.
Any better ideeas on how to install a 1/4 shaft on a 5/8 servo shaft??
Then I will use the glue on encoders like Vince did.
Thanks again Al For all your time.
Any input is much appreciated.

[Barry_ward]

Here's my choice:

Even thought I have not looked inside my motors yet (the tach is enclosed on the end of the shaft) I'll replace them with encoders. (Drilling, shafting, etc as reqd) I'll try running them on my geckos at 60V as I have this supply (60 V 50A)

I've run all of the axis on 24V and they are pretty fast. 60V should work fairly well.

What I really want, is to replace the spindle DRIVE motor with a DC servo so that I can drive a tap in sync with the Z.


Barry

[cbucner]

Still waiting on the things I ordered.
I went for 3 320 gecko drivers, one toroid 52V 1.5kva around 22A output
Should give me 60V after the bridge and capacitors, 3 US digital encoders
and a cnc4pc breakout board.
I did not recieve anything yet and waiting for a week already!!!
I ran out of stuff to do so I'm working on my band saw , and other stuff in the garage , have them ready for when I'm gonna need them.

[Barry_ward]

CB,

Did you dismantle you motor(s) and look at the condition of the communtator?

I've found that it's beneficial on about 50% of the motors that I've seen that have any mileage on them.

You can tell if the communitator segments need cleaning between them when you spin the motor by hand - it should turn without having any non-linear resistance to turning. If the segments begin to get fouled with brush carbon or communitator copper the motor efficiency drops radically.

Another test is to run the motor at very low voltage, if it turns but changes speed with an IRREGULAR pattern you should probably clean andor resurface the communitator.

It also gives you a chance to blow the old brush carbon dust out..

I'll be doing mine and cutting the tach portion off of my motors before putting them back on the machine.

regards,

Barry

[KTP]

It is quite possible your machine is 2.5mm per rev instead of 2.54mm (5 turns per inch). This is what my Shizuoka B-3V ballscrews are. Just a heads up, but you will probably figure it out when you start machining with it

I originally went with Gecko drives but because of problems with the very high resolution encoders and the fact that I wanted to run the motors at a higher voltage, I designed a step/direction to analog converter board (the Pixie P100 at www.skyko.com). This allows me to use practically any brush or brushless motor and matching amplifier with the common step/dir signals from programs such as Mach 3.

Good luck with your conversion. Shizuoka mills are damn nice iron!

[cbucner]

I got all the parts I was waiting for so I started working on mounting the encoders on the shaft of the servos.
I started by drilling the servo shaft on the lathe with a smaller bit for a pilot hole than I used a 10/32 drill bit .
I than turned down an 6061 aluminum 3/8 to 10/32 and press fitted in the servo shaft.
My encoder shaft is 1/4 and I'm glad I did the 10/32" on the servo because if you think that you will get minimum runout after the press fit you're wrong
I Used the lathe after that and turned the servo shaft to 1/4" for minimal runout.After this I had almost 0 runout on the 1/4 shaft that was coming out of the servo.Forgot to take a pic.
Next the hole on the bottom of the servo was way bigger than the encoder case, so I made an adapter plate which was 2 3/4" in dia and 1/4" thick with a 1 1/4" shoulder machined on it so it will fit on the servo hole and drilled a 5/16" hole in it so the 1/4" servo shaft will go thru it.
Check the picture and you will see the adaptor plate.
I did this so the encoder will sit perfect on a flat plate around the 1/4" shaft.
I didn't like the ideea having my encoder enclosed on an electrical box with a cap plate on it because it looks like so I came up with the ideea of making a nice cap for it.
I didn't have a 4" round stock so I used an 1" plate that I cut square and than turn it on a 4" round.Than I bored out the inside so it will enclose the whole end of the servo.Check picture.
I used 1/4 -20 screws to secure the cap to the end of the servo.
I drilled and tapped two mounting holes right underneath the brushes where the cast was thick to hold such screws.
It turned out :cheers:
You can see how the whole servo turned out at the end.
Now I'm done with one of them and have 2 more to go.
I will post some more when I'm done with all 3 and I will try to take some pictures when I do the next one.
Any comments or sugestions will be much appreciated
Thanks guys!!

[Barry_ward]

Well, sort of - I don't have much time and I still want to build some kind of DC Spindle drive too.

I can't believe how close we really are. Checkout http://www.barryfish.com/TheShizServos. The only difference so far is that I needed to remove the tach armature and I am going to mount the Gecko in end of the servo. That's so that the servo will just need DC and the step/dir pulses. I'm going to make my end plate a cylindrical heatsink that sticks out the end of the motor - The motor with gecko and encoder will still be shorter than the original drive.


Barry

[cbucner]

Hey Barry what's your CPR on your encoder and did you get to the point of moving the servo??
I'm going to get some 3/8 flex on monday so I can run my wires for the servo and for the encoder to the control box.
I will try tomorrow to see if I can run the servo!!
I will run into a lot ofnew things but I hope I will figure it out.
Any sugestions huh?? I hear adjusting the gecko can be a dificult.
Let me know if you ran into any troubles and what was the trick!!
Thanks man hope will be done in the same time.

[Barry_ward]

In my photos the motor is hooked up to the gecko and to a 0-80V lab supply. For the step source I have a "function generator" so I can run at 0.1 to 1,000,000 steps / second.

The encoders I have are 1200 PPR and fit on a 1/2 (exactly) shaft - (see broken one in photo....)

Increasing the encoder resolution count decreases the amount of hunting the servo does at rest. Since the servo is always trying to have an exact position, but the encoder has descrete steps the motor must turn 1/4 of the PPR to try to stay in the same place. This is not really a problem since the 1/4800 of a rev is a very small movement and the motor shaft can move that much and not move the machine at all. The drawback from using high resolution encoders is that you need a control system that can drive them fast. I'm going to use DESKCNC which can run 4 axis at 125,000 steps per second.

125,000 / 4800 = 26 RPM
0.2" per rev = 5.2 IPS or 312 IPM
but my machine has a 2:1 belt ratio so my max speed is about 150 IPM with DESKCNC.

On the bench the motor easily runs at 100,000 SPS at 60V - faster than that an I need more that the 1 amp my little bench supplies will give.

Read the gecko instruction sheet (2 or 3 times) if your servos don't work with the setting as shipped. (My buddy installed his without adjustment and does not have any problem and he has a falrly badass homebuilt gantry machine with 1.25" ball screws)

If you are going to tweak them for best performance, try one with no load first - best with a limited current supply, like 1 amp. The motors can oscillate with high gain settings so it's nice to see that behaviour on the bench before it's on the machine. Increasing the gain settin increases the power that the servo system uses to hold the system at position - and to get it into position so higer gain is better to a point. Increase the damping to reduce the voracity of the stationary position.

Borrow a scope if you dont have one and do the GAIN and DAMPING setting after the motor is in it's final position on the machine. When you first start, turn the LIMIT control down to where the fault light (just) stays off, that way you have less chance to hurt anything.

Don't be scared by anything in the above blab, The Geckos rock!. You will be amazed when you start one up. A gecko and an encoder turn DC motors into really cool motion systems.

Barry

[cbucner]

Thanks Barry!
My encoders are 1250ppr and I hope I will not have any problems.
I will try today to see what's going on.
I'm using cnc4pc interface board so I got to figure that one out too.
I'll let you know
Was your servo shaft long like in the picture or you shaft it?
I'm using a 52V 1.5kw power supply.
After the bridge and the condenser I have 67V which goes down to about 60v with all 3 servos running.
The table flies at that voltage.It's moving from one end to the other in 3-4 secs.

[cbucner]

Hey Barry I remember you said you're looking for a dc motor for your spindle.
I got over 100 motors for sale .
The best I've seen was a 1hp at 180dc.
Check my listings
http://search.ebay.com/_W0QQfgtpZ1QQ...Zcatalinbucner
Let me know if you're looking for some motor.
I will try too see if I have it.
good luck to you.

[cbucner]

I was looking today for a 25pin male to male cable to connect my computer to the breakout board.
Now here's the fun, What kind of cable is this.
There are a lot of 25 male to male cables.
What's the pinout, is it pin to pin , I mean pin 1 computer to pin 1 at the other end and so on , beacuse I got a 25 pin male to male cable from best buy and it's not pin to pin , it's a dif layout.
Please let me know so I can take care of this matter.
Thanks

[Stevie]

I always make my own interconnects from Printer ext cables

The PC end is ok; use a multimeter to figure out the wire color codes from the PC end 25pin; then buy another 25pin from Radio Shack and simply solder to pins in the order you need; i end up cutting a few off as they are not needed

[cbucner]

Thanks Steve , I figured it out , and I found a cable that was pin to pin .
What kind of cable do you use for your encoders Steve??
I got some security cable they call it at homedepot with 4 + ground shielded 22awg wire for 27c/foot.I has the foil type shield not the wire type shield, should that be a problem??
Thanks

[Stevie]

I'll be using an old 7 wire plotter interconnect; about 15ft long

As for foil shield; should be great; thats whats inside stepper wire

[cbucner]

Thanks Steve.
I got the first servo running , kinda tricky but it did work now I'm lost into the motor tuning in mach3 . Gotta figure that out.
Are your motors making the same noise when stopped, kinda like a buzz from time to time.And when they run they are like singing , kinda funny.
I'm not into electronics , more the mechanic , machinist guy.
Hey Barry where did you get with your project.
I'm done with my second servo today, I'll try to have the last one done tomorrow and then starting to take care of the electrical panel.
I'll post some pics tomorrow.

[Barry_ward]

CB

The "singing" that you sometimes hear is the servo moving between two encoder positions. The reasons that it is random is that your encoder is not perfectly centered (some positions require more or less than 1/resolution of a turn)

and the motor is sometimes sitting at a torque-ier position (armature to magnet and communitator to brush).

Bottom line: Don't worry about the noise.

Status of my Shiz is it's cleaner and I started on the 2nd motor - I've got the tach off, but have not cleaned the motor or cut the shaft.

I looked at the spindle drive mechanics. I need to build a different housing for the pulley / bearing assembly to accomidate my DC drive motors and the provision for a low profile spindle tightener.

Barry

[cbucner]

Ok, I'm done with all three motors and I already mounted them back on the mill.
I cut down the portion with the resolver and tach from the mounting plates and caped them nice with 1/4 " plate.
I have some pics during the shafting of the last motor as well some of the mill with all motors mounted back.
I was looking for a nice way to run the wires from the motors to the box and come up with a nice way to do it, I used 1/4 npt to 3/8 hose brass connector that threads into the motor cap and I will run black 3/8 pvc hose from the motors to the box .I have some pics of the connectors mounted on the end of the motors.i had to buy an 1/4 npt tap from the hardware store.
I already started today the elctrical wiring and I'm using the same original panel box. I have a layout and check the heatsink for the gecko's.
I hope there is no problem mounting them so close one to another.
I'll have a fan cooling the heatsink.

[Barry_ward]

CB,

What are you going to do with the front panel? I'm going to build a control system for monitoring the utilities of my mill. I'm going to eliminate the Z mechanical indicators as the Z will be indicated on the screen and I can look at the tool anyway. Here's what I'm trying to cram on there. What do you think? (the jpg is the beginning of the layout)

Machine
Main Power Button / Light
Servo Power Button / Light
Computer Power Button / Light
Oiler
Motor Power
Low Oil Indicator
DrawBar
Clamp Button / Light
Unclamp Button / Light
Spindle
Speed Readout
Low Gear Button / Light
High Gear Button / Light
Speed – triple button / light
Auto
Override w / mpg
Off
Direction Buttons / Lights
CW
CCW
Torque LED Bargraph
Home Light
MPG
Spindle Speed Button / Light
X Button / Light
Y Button / Light
Z Button / Light
A Button / Light
Status
X Axis
Home Light
Left Limit Light
Right Limit Light
Load LED Bargraph
Y Axis
Home Light
Distal Limit Light
Proximal Limit Light
Load LED Bargraph
Z Axis
Home Light
Up Limit Light
Down Limit Light
Load LED Bargraph
A Axis
Home Light
Load LED Bargraph
E-STOPS
Feeds & Spindle Halt / Restart Button
Mandatory Stop

[Barry_ward]

Oh, yeah forgot coolant control