Low Profile Tool Height Setter. - Oldal 2

Dátum/Date: Vasárnap, 2012-05-13, 17:53 | Üzenet/Post # 22

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Thanks guys.

Tweakie.

Success consists of going from failure to failure without loss of enthusiasm.

Dátum/Date: Vasárnap, 2012-05-13, 18:03 | Üzenet/Post # 23

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tweakie, perfect results! Seems so smooth and easy, I ordered this thing into my future plans smile

Dátum/Date: Péntek, 2012-05-18, 09:09 | Üzenet/Post # 24

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This text is 0.5mm high and engraved 0.05mm deep.

OK, it is not that good and would probably make a watchmaker cry if he saw it but the purpose of this was to test the accuracy of the prototype tool setter and so far, I am extremely pleased with the results.

I have taken on a suggestion of incorporating an over-travel switch (just in case the G31 command or it’s associated ‘Cypress Basic’ script goes wild) to operate a ‘limit’ input. This will involve a re-design of the PCB and the connecting cable, plug and socket will then need 4 wires instead of 3.

Something to keep me off the streets for a while. biggrin

Tweakie.

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Dátum/Date: Péntek, 2012-05-18, 20:17 | Üzenet/Post # 25

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tweakie, nice results, much smaller than readable with naked eyes, I suppose the machine is very accurate and able to give fine results. What is wring with G31 command? Does not stop the tool?

Dátum/Date: Szombat, 2012-05-19, 06:20 | Üzenet/Post # 26

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Quote (Amatőr)

What is wring with G31 command? Does not stop the tool?

Hi Amator,

I have used the G31 command for many years now and never had a problem but issues related to the CB script have been reported on the Mach forum from time to time where the probing move does not stop. So it is perhaps better to be safe than sorry and an over-travel switch may be a worthwhile addition.

It is my opinion that the reported problems relating to G31 stem from a basically unstable set-up and there are usually other problems with the system reported by the same user.

Tweakie.

Success consists of going from failure to failure without loss of enthusiasm.

Dátum/Date: Szombat, 2012-05-19, 19:06 | Üzenet/Post # 27

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Quote (tweakie)

better to be safe than sorry

That's the point.
A little more work costs less than a damaged setter and tool.

Dátum/Date: Vasárnap, 2012-06-17, 11:03 | Üzenet/Post # 28

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By way of an update, I have now managed to make a measurement relating to the operation of this probe which was as follows;

My Z axis only moves in steps of 0.001875mm and the accuracy of these micro-steps is open to discussion but jogging downwards (in single steps) until electrical contact is made between the tool tip and the top of probe plate then setting the Z Axis DRO to zero it takes a further 2 steps to operate the probe with the Z Axis DRO now reading -0.0037mm. This measurement could, I suppose, be incorporated into the G31 probing script but the overall accuracy has proved to be more than sufficient for my needs as it stands at present.

I have now devised a way in which an ‘over travel switch’ (to operate a limit switch input) can be incorporated whilst still using the existing 3 core connection cable but some more machining will be necessary to the inside of the aluminium case to allow for an additional PCB.

I will post some more details and pictures as I proceed.

Tweakie.

Success consists of going from failure to failure without loss of enthusiasm.

Dátum/Date: Kedd, 2012-06-19, 12:56 | Üzenet/Post # 29

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A little more progress - This is the over-travel limit switch, well 3 switches actually but they are connected in parallel and operate on the 'first home' principle.

The total thickness, including the PCB, is 2mm and this assembly fits beneath the the contact plate (in the base of the probe) and will activate a limit input if the G31 probing routine failed.

The probe will continue to use the 3 wire connection to the machine and additional circuitry has now been fitted, at the breakout board end, to detect probe circuit continuity. This effectively signals a 'Probe Already Grounded' condition to the probing routine if either the positive or GND connecting wires are disconnected or if the probe is not actually connected to the machine. This added 'fail safe' feature was considered necessary because I am signalling the over-travel limit through the two supply wires.

Hopefully, I have now covered every eventuality but life always seems to punish the complacent and so 'time will tell'. biggrin

Tweakie.

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Dátum/Date: Csütörtök, 2012-06-21, 19:57 | Üzenet/Post # 30

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tweakie, nice work! What signal did You use to send it through the supply line? I suppose that can be some vaweform that sitting on the power wires, am I wrong?

Dátum/Date: Péntek, 2012-06-22, 07:01 | Üzenet/Post # 31

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Hi Amator,

In operation the probe draws very little current so the overtravel switch is used to short the supply lines via a series resistance which changes the state of the limit from High to Low.
It is a bit more complicated in the actual circuit but this diagram shows the principle.

Tweakie.

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Dátum/Date: Péntek, 2012-06-22, 14:16 | Üzenet/Post # 32

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tweakie, I see! That's so brainy idea! Very useful design.