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Good evening All
I have just bought a chipmaster to convert to cnc. The first challenge is the 1.5 hp 440v motor. I know I can rewire it for 240 and run off a vfd but I'm not sure it is worth the hassle and I'm looking for other options.
My goal is to cut accurate threads so I have been looking at a closed loop vector VFD for the spindle. Is this the best option or am I OTT?
Ive been out of it for a while so not sure of the latest tech. any suggestions welcome.
Thanks in advance
If the motor is dual voltage and can be rewired 240 then that and a drive would be the quickest option, vector drives do a good job of stabilising motor speed.
- Nick
Accurate threading is far more dependant on what motion controller you'll be using, than how the spindle is powered.
A basic VFD will drive the spindle good enough to thread.
For the most accurate threading, a motion controller that will accept a spindle encoder signal is the best option. Something that uses a single pulse can produce acceptable threads, but it'll depend on the level of accuracy you're aiming for.
Hi Ross,
Long time no hear! Have a look at these -
Setting up Mach3 for lathes:
https://www.youtube.com/watch?v=ZSbljHlBgaY
Fitting an index ring to give pulses to Mach:
https://www.youtube.com/watch?v=yY_4HwmZEaQ
Thread cutting:
https://www.youtube.com/watch?v=6yzrMNjGVDA
And my favourite manual thread cut video:
https://www.youtube.com/watch?v=Lb_BURLuI70
My understanding is you don't necessarily need a special VFD / motor combo for CNC thread cutting, just a good pulse feedback to Mach3 (through an interface card I believe) so that the feeds are synchronised to start at the same point on each pass.
Thanks Guys.
I have been going back and forth on the open loop vs closed loop vfds. some say that a closed loop vfd will keep perfect time and then mach only needs the 1 pulse per revolution.
The existing motor is the original 1.5hp so would be looking to switch up to a 3hp, its the vector vfds that jump up in price.
I'll have a look at the cards. as I want to do fine threads. I have just got two pci card encoder controllers but they are absolute and not incremental so probably no good. any motion controllers you can recommend?
Thanks for all the Links Rcnc, I will have a look later.
Unless you're going to replace the v-belts with a toothed belt, a closed loop motor isn't going to be much benefit, as the belt will cause slight speed fluctuations as load changes.
You also need to consider gearing, and how much torque you're likely to need at the spindle. Are you going to continue to use the gears, if so you need to factor that in, at which point you need to use a spindle encoder, as you'll struggle to get threading to work in multiple gears without a spindle encoder.
Off the top of my head, the following motion controllers spring to mind-
PoKeys 57CNC something or other (I think it supports encoders)
PMDX have a couple motion controllers, but they're Mach 4 only, and you'd need to check they support lathe (I think they do, but not 100% sure)
CS-Labs CSMIO/IP-A or S along with their threading module.
Dynomotion KFlop either on it's own, or with any of their add-on boards (Mach 3 only, or use their own KMotionCNC software)
SmoothSteppper, however I'm not sure if they have implemented full encoder for the spindle yet.
There are also the UC100 and 300, however I'm not sure if they support turn/threading.
A key thing to consider, is if the boards support turn/threading. Not all boards do.
Without getting a load of flack. Linuxcnc with a mesa card is what I use on the lathe with a 60 slot encoder disc on the spindle.
Get the pitch forks sharpened! ;-)Quote:
Originally Posted by Clive S
I've got a Mesa card sat on my desk just now, which is on my list of things to try, as I want to have a play with PathPilot. Got no intention of fitting it any machine, as I like my KFlops.
I take it then you have read the posts from cncbasher on the other channel.:apologetic:Quote:
Originally Posted by m_c
Wow, information overload. Going to take a while to look over all those options.
The pokeys looked quite good but is a bit pricey and not sure it dose threading. Thanks for the heads up, seems a lots has changed since I last dabbled with cnc.
Might have to go over to the driver section and catch up.
Really tempted with EMC2, mesa boards and path pilot. I was looking at Tormach in the first place so now that they have moved to Linux and pathpilot in beta for non TM machines then that will be good enough for me.
Just put off by learning Linux.
Which Mesa cards do you use?
You won't need to learn Linux, you'll end up with a desktop and mouse like a windows machine, you'll only need to go "deep" if you want to.Quote:
Originally Posted by Ross77
If you can run win and mach you can run LinuxCNC, allot of people get spooked by the word Linux :).
.Me
Thanks Lee.
Ive been on the linuxcnc page and the cnczone tormach section and it seems you have to tinker with the settings quite a bit for non tormach machines.
If I could pick up a disc and cheap mesa card in the Uk then Id probably have a crack at it.
I use the mesa 5i25 + 7i76 which from the manual gives:-
The 7I76 is daughtercard/breakout board for use with MESA's 25 pin I/O FPGA
cards like the 5I25. The 7I76 is designed for interfacing up to 5 Axis of step &dir step
motor or servo motor drives and also provides a spindle encoder interface, isolated analog
spindle speed control and 48 isolated I/O points for general purpose field I/O use.
All step and direction outputs are buffered 5V signals that can drive 24 mA. All
outputs support differential mode to reduce susceptibility to noise. An isolated analog
spindle voltage with direction and enable outputs is provided for spindle control as is a
single spindle encoder channel with TTL or differential inputs.
48 points of isolated field I/O are provided for general control use including limit
switch and control panel inputs, coolant enable and tool changer control outputs. Isolated
I/O includes 32 sinking inputs and 16 sourcing outputs. Inputs can sense 5V to 32V signals
and the outputs can switch 5V through 32V signals. Maximum output load is 300 mA.
Outputs are short circuit protected. Field I/O is powered by an isolated 8-32V field power
source.
The 7I76 provides a one channel encoder interface with index. This is intended as a spindle encoder but can be used for other purposes. The encoder input can be programmed for differential or single ended encoders. The encoder interface also provides short circuit protected 5V power to the encoder. When used with single ended encoders, the ENCA+, ENCB+ and IDX+ signals are wired to the encoder and the ENCA-,ENCB-, and IDX- terminal left unconnected.
Mesa cards can be purchased in Europe.
Do you use Pathpilot with that? how difficult was it implement the spindle encoder?
Lee it is a leaning curve but so is a cad or cam program. Linuxcnc is very easy to install from the live CD. and there is a wizard for setting up the drives and motors but after that you have to edit the ini and hal files to tweak it. One problem is homing with a slaved axis but it has been addressed but still not easy to do. (For me anyway)Quote:
Originally Posted by Lee Roberts
No I don't use PathPilot but do use the spindle encoder for the lathe and that is very easy to setup I have also setup jog wheels for X and Z on the lathe.Quote:
Originally Posted by Ross77
There is a tutorial on the other channel by cncbasher to set up PP. https://forum.linuxcnc.org/forum/pat...tutorial-part1
I used the same control box for the Mill and the Lathe and just use two different profiles.
Hi Clive
Could you elaborate on using PP without a mesa card? all the posts I read say that PP wont install without a mesa card.
Do you not need the control card to take some processing power off the main pc?
Ross I think I might have mislead you. When I said using the PP I meant parallel port You can use LInuxcnc with the parallel port and a simple BOB to do threading on the lathe with an encoder on the spindle.Quote:
Originally Posted by Ross77
I am at this time using just Linuxcnc with the axis front end. But I might have a go with PathPilot
But I am pretty sure you can setup PathPilot also with the parallel port and a simple BOB. Did you have a read at the link by cncbasher on the tutorials to set it up. Tutorial three mention setting up PathPilot with the PP.
Ah that make sense. yes I have been al over the place trying to get up to speed with it all. I've been watching the Path pilot demos and it look really good. so quick and easy for R&D as well as production. it looks like it can be fussy on the PC used so the costs are slowly creeping up. Might just try Linixcnc and shift to Pathpilot later.
Thanks
Making progress with the electrical side and think I know which route to take.
So the next major challenge is whether to use the existing cross slide lead screw or fit a ball screw! theses not much room for a ballscrew so would have to mount it to the side for the carriage.
Options seem pretty limited. any pros and cons of mounting the ballscrew off axis vs. using the leadscrew?