Messages

31

General Mach Discussion / Re: Switching on/off large DC Motor

« on: November 05, 2009, 11:21:31 AM »

Thanks Nosmo, I did notice that and was a little confused.  I guess it has to do with the polarity of the permanent magnet blowout, this is new territory to me. 

Dustin

32

General Mach Discussion / Re: Switching on/off large DC Motor

« on: November 04, 2009, 06:00:08 PM »

I will keep it in mind, good suggestion.  For now I have ordered P&B part number PRD-11DH0-24 (mouser 655-PRD-11DH0-24) for $34.  They are 1/3 HP rated at 125VDC with magnetic blowouts and DPDT contacts.  24VDC coil on the one I ordered, but there are lots and lots of options. 

As for the braking, I am going to have a 2-ohm resistor in series with the braking circuit to limit the current to 30A max.  I am seriously considering adding a 2ohm resistor in series with the motor all the time also to limit the inrush to something reasonable (30A) as I can handle the voltage drop and power consumption, and this is an intermittent application.

Thanks for the suggestion, I will let you know how my relay stands up.

Dustin

33

Show"N"Tell ( Your Machines) / Re: 1979 Takisawa DTX-1 Turret Lathe

« on: November 04, 2009, 10:16:35 AM »

Hi John,

So far the Vipers have been behaving well.  It is a little tricky to get everything hooked up properly, like the phase of the encoder and motor polarity, etc, but once it is all figured out they seem to work very well.  The motors are Gettys Fanuc, and have 2000 line differential encoders. 

If your drives, or "amplifiers" are working well, you may consider some sort of out-of-Mach motion control board.  I've heard there are some that just get commands from Mach and close the encoder loop etc all in hardware.  Not an expert here, and I knew Mach works pretty well at motion control so I went the digital drive route.

Dustin

34

Show"N"Tell ( Your Machines) / Re: 1979 Takisawa DTX-1 Turret Lathe

« on: November 03, 2009, 10:33:07 AM »

John, THanks for the comments, they are the original motors with Viper drives.  I did not want to get into making the old Fanuc stuff work.  It all ran off of 460VAC and looked kind of old and scary :-)  It also took up about 2 cubic feet of panel...

The vipers are working great so far, but I have yet to cut metal with them.  I would've replaced the motors with AC systems, but they have really special tapered shafts for the zero-backlash drive gears, I didn't want to figure out how to connect them.

DUstin

35

Show"N"Tell ( Your Machines) / Re: 1979 Takisawa DTX-1 Turret Lathe

« on: November 03, 2009, 10:28:06 AM »

Yes, they are Viper 200's.  So far so good, the motors were way too big for Geckos, I've had problems with those faulting all the time on larger systems ( I run the knee with one on my mill, and I've done a few other projects).  The vipers seem like nice drives so far, very configurable and I found them to be not too bad to setup.  But I've had a lot of experience with PID servo stuff.  Hope they work well in the long run!


Dustin

36

General Mach Discussion / Re: Switching on/off large DC Motor

« on: November 01, 2009, 10:43:57 PM »

Thanks Nosmo,  I know normal relays cannot do the trick, I am looking at some contactors that are inductive DC rated that run ~$35 per pole, that is sounding better than rigging up another supply.

Dustin

37

General Mach Discussion / Re: Switching on/off large DC Motor

« on: November 01, 2009, 04:10:22 PM »

Hi Ray, Thanks for the thought.  It does draw a huge current at start, about 100A based on measuring a current sense resistor in series with the load with my digital o-scope.  I am going to be using a 5ohm resistor for braking, maybe I can somehow get that in series to start and still use it for braking?  Will need to draw that up...

Dustin

38

General Mach Discussion / Re: Switching on/off large DC Motor

« on: November 01, 2009, 03:33:09 PM »

Hi Hood,

Thanks for the post, I searched for "DC contactors" and found a place in no-time, http://www.dccontactors.com/contact.html.  I will give them a call tomorrow and place an order, hopefully I can get my money back for the fried semiconductors....  For some reason Automation Direct does not do DC contactors, I called and talked to their support and everything, they sent me down the solid state relay path..

Anyway, thanks,
Dustin

39

General Mach Discussion / Switching on/off large DC Motor

« on: November 01, 2009, 02:18:22 PM »

Hi All,

This is not exactly a Mach question, but thought someone might be able to help.  I am having trouble with switching my DC turret motor on/off without killing whatever is doing the switching.  I cannot find any mechanical relays that are rated for DC at the current/voltage I want to switch, and the super-expensive DC solid state relay I bought from http://www.power-io.com turned it on about 3 times before failing on.  The guy I talked to there said it would work fine, and I installed the inductance-spike diode as required, etc...

The motor draws 5 amps @60V while running, and a whole lot more when starting up.  The DC supply is 60V 1500VA with a 40,000mfd cap, and also runs a Viper 200.

Thanks for any suggestions,
Dustin

40

Show"N"Tell ( Your Machines) / Re: 1979 Takisawa DTX-1 Turret Lathe

« on: November 01, 2009, 02:09:08 PM »

Hi Hood,

Yea, they just move the quill, I figured you meant you wanted to move the whole thing after I thought about it awhile, getting a long enough ball screw for the quill would probably not be a problem :-)

Sounds like your spindle has a big thru-hole! That would be nice for lots of stuff.  This guy is mostly going to be making pulleys for my other company www.altmount.com, we make serpentine belt kits for boat engine alternators.  I am really looking forward to having a nice lathe!

Your turret expansion project sounds cool!

Dustin