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Author Topic: Dial Gauges  (Read 2160 times)

Faceting Frank

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Dial Gauges
« on: July 02, 2023, 07:52:02 PM »
Bit of interesting info on dial gauges.
My dial gauge is operated by an aluminium lever attached to the bar the quill pivots on. The gauge seemed to be sticking at one point, but found it was the groove worn into the bar by the gauge pin. Not a straight groove, but a slightly curved one, so the pin had a bit of an uphill travel at one point.
So, for a quick fix put some Vaseline on the bar, only to find it had dampened the gauge flutter. Just did this today, so still not sure why it did this. Still works accurately and consistent.

RoughCreations

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Re: Dial Gauges
« Reply #1 on: July 03, 2023, 09:23:24 AM »
Good that you have the issue under control.
I like the look and promise of analog-style dial indicators in faceting machines, however I am of the firm opinion that they are really not the best choice for use in providing depth of cut information whilst faceting, and in fact are probably a poor choice.
Due to the very principle of operation and construction of these things, I think they are much better suited to a more stationary, sedentary use such as checking tolerances etc on an engineering workbench. The internal workings typically consist of a gear train, rack and hair spring. The gear train usually has several gears, maybe 6. This inherent design is not helpful in managing gauge flutter due to uneven laps, and may even amplify the problem. Gear lash and spring bounce, which should be dampened in an ideal world, are all factors contributing to the problem in analog dial indicators.
Sometimes the gauge spindle can be depressed a few extra revolutions inwards, as indicated by the revolution counter sub-dial. More revolutions loads up the hair spring more, creating extra spring force to the bar you mention Frank. Maybe the Vaseline acts to dampen the dial gauge mechanism a little externally.
The solution? You guessed it.... optical encoders  :) The LED sources, code wheels and photo detectors in these units mean that there is no part-to-part contact to cause wear with use. Any errors that may be present in the encoder movement occur at the quantum-level by photons. That's good enough for my faceting accuracy!
The electronic signals from an encoder can be processed and programmatically smoothed on the fly by the micro-controller, only presenting user-friendly information to the faceting display screen. The occasional aired complaints of screen-flicker with encoders and digital displays is really related to the programming of the micro-controller, not the technology itself. Crikey, you can even display the encoder information back as a dial for a warm fuzzy feeling if you want. Below is a prototype setup for my new encoder box (the Video mS gauge on the RHS of the colour screen is the selected dial smoothing).

RC
« Last Edit: July 03, 2023, 11:39:50 AM by RoughCreations »
Rough Creations - Beauty from rough beginnings

Faceting Frank

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Re: Dial Gauges
« Reply #2 on: July 03, 2023, 08:34:30 PM »
Impressive looking encoder you have there. Have looked at digital protractor encoders a few times in the past and not confident in being able to fit one to my machine.
Would need to build a new quill assembly and support designed to have an encoder fitted, rather than trying to fit one to my current setup.
Need to fit a brass shim to the lever where it contacts the dial gauge pin to stop the wear. But also experiment with a damper of some sort. I know its not the laps, as the needle doesn’t move much at very slow speed.

Dihusky

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Re: Dial Gauges
« Reply #3 on: September 18, 2023, 01:25:37 PM »
Maybe I'm just getting old, but reliance on electronics I find a worry, eyes, ears and touch and a good 10X never lie, electronics need to be zeroed on a regular basis and one actually doesn't know if the reading is out until it is too late.

I just rebuilt a GFE3 for a client, it didn't have a dial gauge and the indicator system had been partially removed, it did have a rather clunky electronic angle reader which got in the way of everything on the quill head, looking at the latest AFG photos of the Narrabri meeting this gadget was not being used, I think the student will become a better facetor using her eyes and ears until she is ready to upgrade to additional gadgetry.

The dial gauge on my Hall is probably 30 years old and still going strong, that and my personal senses give me everything I need.

Not a fan of electronics unless it's speed control.

MakkyBrown

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Re: Dial Gauges
« Reply #4 on: September 19, 2023, 12:10:52 AM »
The high resolution optical encoders with an index are pretty good. You set them up so they calibrate every time the hand piece is lifted above 90 degrees. Once you fit one you discover just how far out your machines protractor and 45 degree dop are.

MB

Dihusky

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Re: Dial Gauges
« Reply #5 on: September 19, 2023, 08:58:08 AM »
Have to agree with machine protractors MB, I think I'm a bit spoilt with my old beast, dial in repeatability to 0.1 degree every time. Can come back to any facet on a cut to within around 0.001 degrees, a simple wipe to confirm. Only know of two Hall 2000E's but there maybe a few more. 

MakkyBrown

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Re: Dial Gauges
« Reply #6 on: September 23, 2023, 05:17:09 PM »
Have to agree with machine protractors MB, I think I'm a bit spoilt with my old beast, dial in repeatability to 0.1 degree every time. Can come back to any facet on a cut to within around 0.001 degrees, a simple wipe to confirm. Only know of two Hall 2000E's but there maybe a few more.
I'd love to see a pic of it. A lot of work to get your machine accurate as I'm finding out on my build. Hand-piece runout is bugging me atm. Might have to give up on using a stainless colect clamp and go with the steel cnc ones. I've made multiple quills. Trying to battle weight as well that comes with having a stepper motor on the index. One more try using titanium, which will be fun as I've never worked with it before. Happy with my lap, 1/2 thou runout on the platen outer face, protractor encoder will be easy, just the handpiece grr atm.
MB

Faceting Frank

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Re: Dial Gauges
« Reply #7 on: September 23, 2023, 06:43:15 PM »
Have you thought about adding a weight to the quill assembly MB, to put the centre of gravity at the pivot point. 

FlashGP

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Re: Dial Gauges
« Reply #8 on: October 27, 2023, 08:47:31 PM »

Hi Frank,


How would that change the reading of an angle sensor?


Wouldn’t the angle be the same regardless of where the centre of gravity is?
Yours Sincerely
Flash (Gordon)

Faceting Frank

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Re: Dial Gauges
« Reply #9 on: October 28, 2023, 08:05:26 AM »
Hi Gordon.
The “Trying to battle weight” comment made me think there was some leverage applied by the quill that the stepper motor did not like.

MakkyBrown

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Re: Dial Gauges
« Reply #10 on: November 02, 2023, 10:54:46 PM »
Have you thought about adding a weight to the quill assembly MB, to put the centre of gravity at the pivot point.
It's tricky as I need the shaft and the ideal pivot point goes through the motor. I will get back to it at some stage but being distracted by other things atm.
MB

 

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