Suggestions please Vol3

[Ian S CParticipant @iansc]

MichaelG, the latter ones are the ones I’m thinking of, seems a similar technoligy to the non contact tachometers, I suppose a wireless one would be even better. Ian S C

[Michael GilliganParticipant @michaelgilligan61133]

Ian S C
I may be wrong, but: To my mind, the video ones seem better suited to measuring Displacement than Speed.
… The Slotted Disk Encoders are already “non-contact”.

MichaelG.

But it is certainly possible …

http://www.kronosrobotics.com/Anotes/Athena%20to%20Optical%20Mouse.pdf

Edited By Michael Gilligan on 02/02/2012 09:41:54

[TerrydParticipant @terryd72465]

Quadrature encoder which recognises direction of rotation using ‘Ball’ mouse

 

T

[David LittlewoodParticipant @davidlittlewood51847]

Graham,

 

I have read this thread with some bafflement. I understand you are an experienced machinist and may have good reasons for not wanting to rely on a DRO monitor some way away from the workpiece. If I understand you correctly, you simply want a method of “counting the 3 mms” for you, anf you will use the dial to get the finer divisions.

 

If so, I can’t see why the scale rule on the FB2 will not do this for you. Before I fitted a DRO to my FB2, that’s how I would have done it. As you have already acknowledged, but others less experienced may not know, all measuring scales which use the rotation of the leadscrew for measurement are at best approximate, and at worst downright dangerous; they all ignore backlash, and if not used correctly will cause grief.

 

For others (and maybe for you) it may be helpful to see the DRO I fitted to my FB2 4 years ago. Fitting was a job needing care but no special skills; the monitor can be swung into a place where it is easy to read, and when you learn to trust it you get into the habit of driving the thing on instruments, as it were.

 

The photos were taken before I got round to fitting the Z-axis scale. The only modification to the mill was a small stop block next to the column to stop the carriage crushing the X-axis scale against the column base.

 

Where do you live Graham? If close by (SE London) you would be most welcome to come round and give it a try.

 

To others I would say, don’t think you will get an improvement in accuracy if you fit a leadscrew-driven scale, go for the right solution. I know it’s the biggest improvement I have made to my milling.

 

David

[Ian PParticipant @ianp]

Graham

 

I have followed this thread since the beginning and I do now have a better understanding of what you are trying to achieve. What I am unclear about though is why setting a handwheel index collar to a certain point is any different to turning the handwheel and stopping when a digital display reaches a certain value.

 

I am a total layman in regards to any medical matters and obviously do not know any details of your health problem but I do not see why you have to oscillate to and fro to get to a particular setting. With a normal graduated collar and leadscrew arrangement its usually preferable to approach the target stopping point slowly and in one direction (to account for backlash). There is no reason why the same technique cannot be used with a digital display.

 

I can envisage that the DRO on the Bridgeport you mention has far greater resolution than is required. Can I respectfully suggest that some of the least significant digits are obscured so that the display only shows increments of 0.01mm, I’m sure its worth a try.

 

Ian P

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hello again ,

 

Before electronic DRO there were several good mechanical systems and a small number of good direct observation optical systems in use on machine tools .

 

Amongst the mechanical systems was one which used nested dials . Typically one dial calibrated like a normal index dial in thous and another one geared to the first calibrated in usually whole inches and some sub divisions . Both dials were zero settable .

 

Sometimes there were three dials but only for special purposes .

 

I’ve had hands on one of these and found it remarkable facile and intuitive to use .

 

Given that you find ordinary index dials easy to use adding a second one may not cause you any new usage difficulties at all and yet provide both fine resolution and long distance positional information .

 

Actually doing it should be very easy . You could probably retain existing dial and put extra one behind it . Gearing is is just gearing – no need for epicyclics unless you want absolute minimum space installation .

 

MW

 

 

[Ian S CParticipant @iansc]

MichaelG, I had a look on Google, was quite interested to see that the “mouses without a ball” actually have an 18 x18 camera, and it can be used as a scanner, or a rather crude web cam, and the ones building Robots find uses for them. Ian S C

[Michael GilliganParticipant @michaelgilligan61133]

Ian S C
If I may be philosophical for a moment …

In the small hours of yesterday morning, you professed “I know nothing.”
Now; you have some real understanding of the workings of an astonishing piece of technology … which, thanks to mass production, is available at very low prices, for us to experiment with.

I rejoice that we have the means [through forums like this, and through the democratising power of the Internet], to share the little knowledge that each of us has acquired.

Across the world, there are; creative minds, clever technicians, and people who need things … Never in the history of our civilization has it been so easy to put them together!

It feels a better day already.

MichaelG.

[Ian S CParticipant @iansc]

 MichaelG,If I “know nothing” one day, I try to at least know a little about it as soon as I can, but some of the stuff on the web should be taken with a grain of salt, you just have too filter out the rubbish, ie., the proponants of perpetual motion, or someone who thinks the motor designed by Carnot is the best way to go (actually it can’t work).

The day you stop learning, is the day they put you in your wooden box (no ones come back to say they keep learning, maybe they learned enough to keep away). Ian S C

Edited By Ian S C on 03/02/2012 10:55:25

[Sub MandrelParticipant @submandrel]

On Today this morning there was a discussion with an engineer of his company’s liquid air energy storage system. They said so it’s like a steam engine, he said well it’s like a steam turbine in a power station. They kept saying it’s like a steam engine and in the end he said it’s actually a Rankine Cycle* and they shut up

 

Neil

 

* as we all know this menas a turbine in a closed loop of vapour and liquid between a boiler and a condenser.

[Michael HornerParticipant @michaelhorner54327]

Hi Gray

I note from a different post that you have retired now, did you get your counter built?

This looks like a good idea for the cross slide of a minilathe. On big jobs I lose count of where I am upto then go oversize/undersize.

For the Z axis I have fitted a digital caliper and it works great because it's out of the way, to fit the same thing on the cross would get all the debris on it and it would get in the way. I envisage one of the cheap rotary encoders fitting on the end of the lead screw at the back of the cross slide. The one I am thinking of using has 24 pulse output which would give me a resolution of 0.0833333 mm which is close enough for me, I would then use the dial on the handle to finish off.

I am at the moment writing the algorythem because I will be using a PicChip to pull the thing together. My head is hurting working out the how to work out the direction of travel but I suppose that's what keeps they grey matter alive!

Cheers Michael

[Grizzly bearParticipant @grizzlybear]

May I just say, having put a PC mouse to to sleep, removed the encoder bits. Don't forget the steel ball, it's easily drilled and makes a useful knob. You all knew this of course.

Regards Bear..

[Les Jones 1Participant @lesjones1]

Hi Michael,
If you want some sample code to get you started with writing code for a PIC I can send you versions for a PIC16F628 and a PIC16F690. If you PM me with an email address I wil send you copies of the code.

Les.

[Michael HornerParticipant @michaelhorner54327]

Hi Les

Thanks for the copy of the code, it is well annotated. Just got to find the old rev counter I made so I can recode it for it's new purpose and hope I didn't use all of portb to drive the 7-segment displays!

Cheers Michael

[Les Jones 1Participant @lesjones1]

Hi Michael,
I think you will have problems using a PIC16F628 as you have to use some port B pins to drive the segment displays. (I am assuming multiplexed 7 segment LED's) There will be lot of writes to port B for the multiplexing which will probably cause the PIC to miss some interrupts (Hence loosing position.) With the LCD display I used there is only a couple of writes to update the display and these would happen just after an interrupt had occured. I think you would be better off using a PIC with enough I/O pins to only use port B for the quadrature inputs. Another option would be to use an Atmel micro as these do not have the same problem of missing interrupt on change events.

Les.

[John Stevenson 1Participant @johnstevenson1]

Gray,

If this is something to just give you a guide as opposed to being a readout working to 18 decimal places.

What about one of the ARC cross slide units with a pulley on it , pulled along by a Bowden cable. Adjustments could be made for travel by the size of the pulleys ?

This way the pitch of the screws doesn't matter.

John S.

[blowlampParticipant @blowlamp]

Posted by John Stevenson on 11/11/2012 11:48:25:

Gray,

If this is something to just give you a guide as opposed to being a readout working to 18 decimal places.

What about one of the ARC cross slide units with a pulley on it , pulled along by a Bowden cable. Adjustments could be made for travel by the size of the pulleys ?

This way the pitch of the screws doesn't matter.

John S.

These units work well enough, but I'm finding battery life to be abysmal – a couple of months at the most.

Martin.

[John Stevenson 1Participant @johnstevenson1]

Good heavens man, 2 months ?

That works out to sixpence a week, you need to take the old pop bottles back and use the refund money to get a new battery.

John S.

[Sub MandrelParticipant @submandrel]

MichaelG, I had a look on Google, was quite interested to see that the "mouses without a ball" actually have an 18 x18 camera, and it can be used as a scanner, or a rather crude web cam, and the ones building Robots find uses for them. Ian S C

Excellent! I've been on the lookout for something like that for years!

Neil

[blowlampParticipant @blowlamp]

Posted by John Stevenson on 11/11/2012 12:41:00:

Good heavens man, 2 months ?

That works out to sixpence a week, you need to take the old pop bottles back and use the refund money to get a new battery.

John S.

Well yes, but that's while they're turned off

The first couple of times they went flat, I was going to call the Police, 'cos I thought I'd been mugged.

I kind of expected around six months – maybe a year, similar to what I get from my cheapo calipers.

Martin.

[Michael HornerParticipant @michaelhorner54327]

Hi Gray

I came across this whilst looking for something else! Couldn't find the price of this particular unit but units in the range were in the region of £38.

DA08 Digital Position Indicator by SIKO

Food for thought.

Cheers Michael.

[Author]

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