Hello Guest it is July 19, 2019, 11:09:56 AM

Author Topic: Spindle RPM  (Read 14805 times)

0 Members and 1 Guest are viewing this topic.

Offline jimpinder

*
  •  1,233 1,233
  • Wakefield, West Yorks, UK
    • View Profile
Re: Spindle RPM
« Reply #10 on: July 19, 2008, 10:59:13 AM »
I do not think that the speed of a single phase motor is variable. You will need to change your motor to a three phase one. Once you do this you can get several makes of single phase to three phase inverters to control it. Mine is an Omron (quite old) but very servicable. I changed my motor from a 1hp single to a 1 3/4 hp three phase motor - and controlled it with the Omron manually. The Omron gives full speed and direction control. The torque of the motor falls off if you try and use it below about 50% speed (30 hz), so I will be putting in some gearbox/pulley arrangements to turn some of my larger pieces.

Unlike Hood, who uses a slot detector, I use a reflective detector - same principle - ir.led shining and reflects onto a detector - mounted 5mm from my chuck mounting plate (painted matt black). A small reflector, made from my granddaughters "sticky" bits and pieces, stuck to the edge of the mounting plate, reflects the IR back once per rev.

As I put in the original post, it works well, but seems to over read. I put this down to a 12 volt supply to the Omron instead of 10. I will work on that.
By the way - one inverter (providing it is large enough for your largest machine, can supply all your machines, you do not need an inverter for them all. (You can only use one at once, though)

Not me driving the engine - I'm better looking.

Offline Hood

*
  •  25,849 25,849
  • Carnoustie, Scotland
    • View Profile
Re: Spindle RPM
« Reply #11 on: July 19, 2008, 11:02:25 AM »
VFD are normally  for 3 phase motors but you do get ones for single phase motors. Never used one or even seen one for that matter  but a quick google brought up this one.
http://www.minarik.com/cgi-bin/ECA_Software/ECA_Search/ECA_Search.pl?TID=minarikcorp%20-%20ProductDisplay%20-%20AC_DRIVES&TERMS_PARTS_CUSTOM.PART_ID=AC211S-1.1&TERMS_PRICING.DISCOUNT_CODE=USER&TERMS_PRICING.DBASE=DIST&TERMS_PARTS_CUSTOM.minarikcorp=1&TERMS_INVENTORY.dbase=DIST

Seems from a quick look it can be controlled by 0-10V so you would need a speed controller similar to the type Peter Homann (and others) sell. www.homanndesigns.com
Hood
« Last Edit: July 19, 2008, 11:04:55 AM by Hood »

Offline Hood

*
  •  25,849 25,849
  • Carnoustie, Scotland
    • View Profile
Re: Spindle RPM
« Reply #12 on: July 19, 2008, 11:11:55 AM »
OOPS,
Forget that link for the VFD, further reading makes me think its only for a 3 phase motor.
Will do a bit more searching .

Hood

Offline Hood

*
  •  25,849 25,849
  • Carnoustie, Scotland
    • View Profile
Re: Spindle RPM
« Reply #13 on: July 19, 2008, 11:17:24 AM »
http://www.anaconsystems.com/text/opti_e2.html  This one looks more like it.
Hood

Offline Perfo

*
  •  143 143
    • View Profile
Re: Spindle RPM
« Reply #14 on: July 19, 2008, 11:36:40 AM »
As far as I know the common single phase motor runs at a speed slightly behind the circulating stator field, as you apply load the 'slip' or difference between the applied field and rotor field increases and draws more current trying to catch up. so in essence all you have to do is provide it with a sort of sin wave at whatever frequency you want (within reason) and the motor will try and match it ( I may be completely wrong of course). Problem being it is a lot harder to produce a good variable frequency controller than some sort of chopper controller that basically turns the power off for part of the cycle and thus gives you poor low speed torque . Handy you only need one converter and just switch it to one machine or the other but it would mean swapping the motors on the lathe and miller which I suppose isn't a huge problem as they have the same foot print and shaft size but is extra hassle and extra cost as well as the cost of the converter. So I may have to leave it as it is for now unless I come up with a cheap set up for either. Hood if the VFD thing requires 0 to 10v to set the speed, what does Mach3 give out to try and control it? Is a frequency control or a pulse width controller? either one is fairly easy to get 0 to 10v out of especially if it can be set up as part of a feed back loop and thus any inaccuracies in the drive circuit get noticed by the once per rev and will auto compensate. The sticky reflective pad is also a good idea as I could mount this in the pulley housing on the spindle pulley and thus keep it out of the way of danger though I suppose I could also mount a slot plate up there so both are possible.
« Last Edit: July 19, 2008, 11:40:21 AM by Perfo »

Offline Perfo

*
  •  143 143
    • View Profile
Re: Spindle RPM
« Reply #15 on: July 19, 2008, 01:02:38 PM »
I looked at that one Hood yep it looks like it would do the job but $525 plus tax plus shipping...hmmm it may just end up a would like for the future.
Jim I've had a thought about your over speed problem and I'm thinking it would be unlikely to be the supply voltage to the box as it's a digital signal it's not easy to see how supply fluctuations can give you a multiplier effect.  I would tend to think you are getting multi pulses from somewhere these things are quite fast enough to trigger a couple or more times on the same target. Is the target as small as possible and completely flat i.e. no bent corners ?If you use reflective material such as the reflective strips on clothing they contain a number of miniscule reflective surfaces to maximise the chance of getting a reflection no matter where the light source is and thus something like this could give you multiple triggers. The other thing that can effect IR receivers is back ground light. I know it's not meant to but there is a fair bit of IR in normal light so maybe something is being reflected off something else? I would think a small blob of Tipex would give you a good enough target to try in case the multi trigger is your problem. I'm thinking aloud here so please feel free to ignore me if (no doubted) you've already thought of all this. The only other thing I suppose is noise pick up on the cable it it’s long enough or goes near enough to an electrically noisy thing.

Offline Hood

*
  •  25,849 25,849
  • Carnoustie, Scotland
    • View Profile
Re: Spindle RPM
« Reply #16 on: July 19, 2008, 03:07:32 PM »
I think Mach can either use PWM or Step/Direction for the spindle.

One thing might be worth looking at is getting 3 phase motors for your machines, single to 3 phase VFDs can be got often quite cheaply on eBay, think the most I paid for any of the ones I got was £45 and £60  for my 5HP ones for the Bridgeport. I have 3 phase so the ones I have are 3 in 3 out but some can be used single in 3 out with a bit of derating, a quick check of the manual of any you see will let you know if thats the case. Also eBay is a good place to pick up 3 phase motors as they go fairly cheap and once you have them you will get more for your single phase motors ;)
Hood

Offline budman68

*
  • *
  •  2,360 2,360
    • View Profile
Re: Spindle RPM
« Reply #17 on: July 19, 2008, 03:51:16 PM »


http://www.alliedelec.com/Search/SearchResults.aspx?N=0&Ntt=slotted+optical+switch+917b&Ntk=Primary&sid=11B3A79D9029&i=0
This is the closest I could see on the US site.

The switch doesn't do anything particularly clever it's a light source (often infrared LED) and a photodetector often a photo transistor either mounted in an IR transparent package or has small lenses to stop cross talk etc. As long as it will run on the voltage you need and will provide a sink for the data pin (usual to put a pull up resistor on the output) you may also need to put a current limiter resistor on the feed to the LED depending on what one you get. Oh and ensure it will run at the max frequency you intend but this is unlikely to be a problem.
The thing I worried about is would the parallel port read it quick enough to get an accurate reading or would there need to be some electronic scaling but Hood has answered this one and fortunately it'll bolt straight on. I'll be trying to connect mine to the smoothstepper board (on order) which has a dedicated input for spindle speed (I think).

Thanks for that, no wonder I couldn't find anything on it, Hood speelled it ending with a "C", not a "K", lol!

Thanks again-  :)
----------------------------------------------------------------------
Just because I'm a Global Moderator, don't assume that I know anything !

Dave->    ;)

Offline Hood

*
  •  25,849 25,849
  • Carnoustie, Scotland
    • View Profile
Re: Spindle RPM
« Reply #18 on: July 19, 2008, 04:11:09 PM »
spelling is not my strong point ;) Come to think of it I dont think I have any strong points :D

Hood

Offline budman68

*
  • *
  •  2,360 2,360
    • View Profile
Re: Spindle RPM
« Reply #19 on: July 19, 2008, 04:33:48 PM »
No sweat, my friend, thank you for the future help on this when I need it  ;)
----------------------------------------------------------------------
Just because I'm a Global Moderator, don't assume that I know anything !

Dave->    ;)