Need Help!- Pittman 14203 series servo options query

[Stewey]

edited- I made a mistake with the number, but I'll leave the rest of the info here...

HI,
I have checked 'all over' the web, and can't find any websites with info on an old servo I'm tempted to replace.

It's a Pittman 19203 D173, DC 24 volt brush servo, 500 cpr encoder, 1/4" shaft, 54mm OD of case, 112 mm long overall inc the encoder.
Sorry I misread that- it's a 14203, but it was smudged & faded on the label so the 4 looked like a 9.

As well as I can see, it is very similar to the newer Pittman 14204 S006 in every way, but I can't find out what torque ours is, or was supposed to have.
OK I have now found the torque- 21 oz-inch.

I cannot find any internet references to 19000 series servos at all- they stop at 14000. Ours is 1995 vintage, I think.
That's irrelevant now.


There's a multitude of 14000 series servos on ebay, but most are much less in torque, or have a smaller shaft, or a different encoder and lesser or much greater torque, but some could be close if I knew what torque ours was.

(it drives the Z axis of a router, with a 3 hp Perske spindle, via a toothed belt and 1:2 reduction & an acme screw.)

Any info would be appreciated, thanks!

[Stewey]

P.S. I forgot to say that formerly, the router used to do as lot of basically 2D cutting- drop the Z axis to a depth and stay there for a while, then lift, travel and lower again- nothing strenuous.

I'm now doing a bit of 3D stuff where the Z axis is constantly changing, (or rather, trying to do 3D stuff) and the servo gets/got agonisingly hot- so I'm guessing it's underpowered. If I know what torque the Pittman 19203 D173 was, then I can guess what we might need in the way of a new one.

(Thanks!)

[Stewey]

OK, I have figured it out.
I got the number wrong originally.

[Stewey]

Different question- I had an option on ebay of a Pittman 14204 servo, rated for 30 Vdc, or a 14206 rated for 48 vdc.
Both have more torque than the underpowered one we have (14203, 24Vdc).

The suppply voltage to the controller board is about 36 Vdc.

Which would be better- the bigger one with half the max volts, or the smaller one nearer to the ideal voltage?

Much of the time, it runs at a much lower voltage anyhow- in the 10-17 volts range, as it doesn't need to change too fast.

Many thanks for any opinions.

[Al_The_Man]

There is no direct connection between the motor and the supply, there is a drive in between.
A-M-C recommend from 110% to 150% P.S. above the motor voltage (servo's).
http://electronicdesign.com/Articles...leID=7635&pg=1
Al.

[Stewey]

Thank you for that link, Al.

I was basing my figures on the multimeter measurement of the DC output of the rectifier, which then gets divided between what I have been calling (out of ignorance, I guess) the three controller boards, which you are calling drives.
Thanks.

[Al_The_Man]

Drives, Amplifiers, controllers, are pretty much used interchangeably, although controllers can imply motor control where the loop is closed back to the drive, rather than closed back to a separate CNC controller.
But all are used loosely.
Al.

[Stewey]

I have a different query now...

a new bigger servo will be coming. I'tll still have the 500 cpr encoder.

Am I likely to need to alter any of the PID settings for the new servo in the driver software for the router- or should I just be able to plug the new servo in place & go?

The existing Z axis servo became incredibly hot, and I changed bearings thinking that was the possible problem.
When I retried it, the shaft spun readily enough by hand- not too easily- the magnetism in the stator made things a bit difficult.

When I reconnected it, it would no longer turn slowly at low current/voltage settings where it did before. It took a higher % to make it rotate. I figured that'd be OK, and I reconnected it. Then I managed to blow a Mosfet transistor.
I've just replaced that, but I'm thinking the original Z servo was underpowered for constant 3D height changes, while beforehand it was OK just moving to a set height/depth & staying there while a perimeter was routed.

So back to my original question of a sort- how will I know how if if I need to alter the PID settings in the driver- driver being the software in the PC which the router communicates with?

Many thanks (& sorry I'm so ignorant!)

[epineh]

Hi Stewey, I would definitely think you will have to alter the PID settings, I have found this to be the case on my machine swapping almost identical looking servo's and more so with larger than existing servo's.

I can't for the life of me remember if you have mentioned the drives you are using on this machine or not...either way I have forgotten the make/model anyway you should make sure the drive can handle the current rating of the new servo just to be sure, if the encoder count is the same then that will be handy.

What is the controlling software ? ...as in where is the PID done, on the PC or on the servo drives.

Cheers.

Russell.

[Stewey]

HI Russell,
thanks for the reply.

The whole machine is/was an Esab, converted to become a K-series Tekcel (an Aussie brand of router, not unlike the Gerbers, I believe).

The servos have an encoder "interpretation & feedback board" attached to them (as it's about 3 or 4 metres back to the drive/controller board.)

The drive, or controller card for the servo is a proprietory one, "T10D" made by Tekcel. (I'm awaiting a price.) The drive card has a socket for DC power in (comes from the rectifier), a socket for DC power out to the servo, and a 4-pin socket for control of the servo supply voltage & pulses I guess. It uses PWM (pulse width modulation).

The 4-pin lead from that drive (and the other two axes' drives) goes back to another PC board, which costs about $2000 to replace- a proprietory Tekcel TT11B board which has sockets for limit-switch feedback signals, sockets for servo encoder feedback signals,, and a couple of EPROMS which tell it all what to do & how to do it.

The Software we use is Enroute- for design, and also for toolpath creation.

The Router is then controlled by Tekmove on your PC. It is driver software in which you set the resolution of each axis servo (in counts per mm), the bed size, the postion of the tool length sensor, the position of the various origins you might choose to save, the PID figures, acceleration & jogging speeds etc etc.

When you turn the router on, it boots up, (via the application in the EPROM) then looks for the PC it's supposed to be attached to, and downloads all the plot files in the appropriate folder on the PC to the 'pendant' (permanently mounted on the router gantry). You use the joystick to select the various options & set feed speeds, pick the file you want etc.

[Stewey]

P.S. The PID figures in the Tekmove driver software are currently in order as follows:

Idle PID
Kp, Ki, Kd, I_lim

Y: 150, 45, 2000, 45
X: ditto
Z: 150, 1000, 6000, 100

Move PID
Kp, Ki, Kd, I_lim

Y: 200, 50, 5000, 55
X: 150, 45, 2000, 45
Z: 150, 45, 2000, 45

(Thanks!)

[Stewey]

Here are some photos which may clarify some bits of my inadequate explanations:

The main computer on the router frame itself, containing the power supply for the servos, the drives for the servos, and the other boards that make it run & let it interpret the encoder signals etc:



The T10D 'drive' board which is now fried. It formerly worked the Zaxis servo:



The Pittman 14203 D173 servo which now operates in jerks of 180 degrees at low power, and stalls at higher power. I'm going to replace it. You can see the small board on top into which the encoder lead connects. A lead from that then goes back to the TT11F board, then from there to the T10D which drives each servo.



(I hope they came through)