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Author Topic: Can RPM be Controlled by Mach?  (Read 2696 times)

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Offline Katoh

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Can RPM be Controlled by Mach?
« on: July 16, 2013, 08:04:56 PM »
G'Day Friends
Sorry its being a long time between drinks, Still playing around with the new lathe and believe it or not still have not cut anything yet.
Well I have had a request to make something which has got me of my "behined" and into work mode on it again. A short introduction, its VFD run with a homman didgy speed control . RPM feed back to mach for true rpm. Well it all works fine that way, today I was just playing around and setting up my pulley's when I noticed I could not get my true rpm to match my programed rpm?
With some fine tuning on the trimpot I can get all six pulley,s to run true rpm as the original motor just hard wired, but if you go less  than that rpm it will read slower and more than that rpm will read higher?
Now I'm looking at things like threading or even just turning, spindle speed input should match actual speed rpm, but doesn't.

Question Say if I input 200 rpm on pulley 1, standard for the 50hrz motor is 125 rpm, well I get 125rpm feedback but if I enter 200rpm I get 220 rpm feedback, Will mach correct this? drop speed till it gets to 200 or increase depending if higher or lower.
In general turning I don't see much of a problem but threading it could lead to all sorts of disasters.

Thanks
Cheers
Katoh

Offline Hood

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Re: Can RPM be Controlled by Mach?
« Reply #1 on: July 17, 2013, 01:44:59 AM »
The RPM being different does not matter at all for threading, what is important is the true spindle speed is read correctly by Mach. Mach will match the axis to the actual rather than the commanded, that is why you can thread on a machine that has manual spindle speed control as long as you have feedback to Mach.

Hood

Offline Katoh

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Re: Can RPM be Controlled by Mach?
« Reply #2 on: July 17, 2013, 02:05:53 AM »
Thanks Hood
I understand exactly what you said. Just when your new to a game some of the rules are different. I checked the rpm feedback to Mach and it is what it says it is. Wasn't the best way to check bet it said 50RPM and I sat there with a stopwatch and just counted, spot on 50.
Well I  should really post a couple of pics of this beast. I should really have a separate thread about the build altogether, I will when time permits. but for now. this is how its come out so far.
Cheers
Katoh

Offline Hood

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Re: Can RPM be Controlled by Mach?
« Reply #3 on: July 17, 2013, 02:50:36 AM »
Looks great, presume you made the enclosure? Are you going to have it totally enclosed? Sliding door or lifting lid?

Hood

Offline Katoh

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Re: Can RPM be Controlled by Mach?
« Reply #4 on: July 17, 2013, 03:11:29 AM »
I have a piece of plate steel bent to match that profile as the door/opening, will cut some perspex into it as a viewing window. I would love to make it slide, but finding runner's to hold out a door 1.1 meters is not an task. My next option is to fit an aluminum u rail to the front section and just put on two handles on the lid so you simply lift on and off.
To hinge it from the top will work OK (original Idea) but gets in the way of the screen and requires struts to keep it up. Either way I have to figure out something.
The last part of the lathe that needs to be wired in is the coolant pump, its there underneath with its own stainless bin from an old dairy cabinet, pays not to throw anything away at times, but the downside to that is my yard looks like it belongs to Steptoe. The coolant plumbing is all copper from old sinks 1" and it drains into a large stainless tea strainer from Ebay $5Au. I have some left over leds from the boat that built that I will install in the lid and that should be it.
I estimate total build with the lathe (new) to be about 2.5 to 2.8 Thou Au and that includes tooling, not to bad I think. a lot of work, way more than what I expected but not to bad.

Cheers
Katoh
Cheers
Katoh
Re: Can RPM be Controlled by Mach?
« Reply #5 on: July 17, 2013, 09:47:06 AM »
Looks great Katoh!  Looking forward to your build thread.  I can't seem get enough of other peoples' CNC lathe project pictures.

...a lot of work, way more than what I expected but not to bad.
So true!  Lathe's have only 2 axes and should be 2/3 as much work as mills.  NOT!
Milton from Tennessee ya'll.

Offline Katoh

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Re: Can RPM be Controlled by Mach?
« Reply #6 on: July 17, 2013, 10:12:38 AM »
Thanks for the kind words.
I built from scratch, a 3.2m x 1.8m flat bed router with a 1.2m 4th axis built around a rotary table and a home made bed that fits my wood lathe end and live center. That was a lot of work but that darn lathe for some reason was more.
The funny thing is the lathe is a built unit, how hard is it to build a stand replace the the lead screws with ball screws, scrap the gearbox and most other parts to fit 2 motors. A little wiring and your done. "What a load of Crap" Its not easy!
I have a Bridgeport knee mill sitting and begging me to be retrofitted, need to get this lathe out of the garage first so I can bring in the mill, very soon now. But I'm going to cheat, there are numerous company's that make a kit for them both X, Y and the quill for the Z. I am simply going to spend the coin and get the Kit. Motors and Wiring isn't a hassle just time consuming, once that ones done I'm calling it quits and going fishing, or play more with my Jag.

Cheers
Katoh
Cheers
Katoh

Offline Hood

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Re: Can RPM be Controlled by Mach?
« Reply #7 on: July 17, 2013, 10:24:58 AM »
Ha ha yes lathes are different beasts all together, my big lathe was already a CNC and even the wee one was but ot was rather poor on the bearings etc so I totally redid that side of things and it was a fair bit of work.

Hood

Offline Chaoticone

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Re: Can RPM be Controlled by Mach?
« Reply #8 on: July 17, 2013, 12:39:48 PM »
Looks good Katoh, looks good.  :)

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

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