High Precision Homing Switch

Hi,

Looking for a high quality homing switch so that I can get my Lathe's X Axis set correctly and allow my tool changer to be consistent.

When looking at proximity switches, how do you know if its high quality? I did see a test a while ago where a guy on youtube tested a number of them and found a mechanical switch with no arm seemed to be the most reliable.

As I dont have index homing (stepper), what are my options?

Thanks

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Looking for a high quality homing switch so that I can get my Lathe's X Axis set correctly and allow my tool changer to be consistent.

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I don't think the homing accuracy would influence the tool changer as you will have touched off on the part.
The standard proxy switched I find OK

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Originally Posted by Clive S

I don't think the homing accuracy would influence the tool changer as you will have touched off on the part.
The standard proxy switched I find OK

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Thing is, I use Machine home as the starting point / offset.

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Originally Posted by Chaz

Thing is, I use Machine home as the starting point / offset.

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Ok I have not got a turret. But I thought you would have to touch off on the part and that would ref the tool changer position. So sorry can't help further:subdued:

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Originally Posted by Clive S

Ok I have not got a turret. But I thought you would have to touch off on the part and that would ref the tool changer position. So sorry can't help further:subdued:

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Nope. The aim of the machine zero is to be the absolute reference. This means that each tool is offset against that point. So clearly if it moves, then my tools are not referenced correctly anymore.

I used an opto slot sensor on my old lathe, and there was never any measurable variation. I used RS part number 480-5231 however I see that part has now been discontinued. The only problem was I had to make sure a bit swarf hadn't landed in the slot prior to homing, as I never bothered enclosing it.

The new lathe uses proximity combined with servo index homing.

You could combine a proximity or microswitch with a slot sensor on the stepper, provided you can add a suitable slot to the stepper/ballscrew, to essentially give you a poor mans index homing.

Chaz

I have a Balluff mechanical switch which are very good, I don't mind sending it over for you to try.

Just pm me your address if you want to try it. I will post a link to the switch if I can find it on the RS site.

Regards

Andy

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Originally Posted by m_c

I used an opto slot sensor on my old lathe, and there was never any measurable variation. I used RS part number 480-5231 however I see that part has now been discontinued. The only problem was I had to make sure a bit swarf hadn't landed in the slot prior to homing, as I never bothered enclosing it.

The new lathe uses proximity combined with servo index homing.

You could combine a proximity or microswitch with a slot sensor on the stepper, provided you can add a suitable slot to the stepper/ballscrew, to essentially give you a poor mans index homing.

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Thanks, something like this - https://uk.rs-online.com/web/p/photo...nsors/1254515/ ?

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Originally Posted by audioandy

Chaz

I have a Balluff mechanical switch which are very good, I don't mind sending it over for you to try.

Just pm me your address if you want to try it. I will post a link to the switch if I can find it on the RS site.

Regards

Andy

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Thanks, will send you the address. What do they cost?

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Originally Posted by m_c

I used an opto slot sensor on my old lathe, and there was never any measurable variation. I used RS part number 480-5231 however I see that part has now been discontinued. The only problem was I had to make sure a bit swarf hadn't landed in the slot prior to homing, as I never bothered enclosing it.

The new lathe uses proximity combined with servo index homing.

You could combine a proximity or microswitch with a slot sensor on the stepper, provided you can add a suitable slot to the stepper/ballscrew, to essentially give you a poor mans index homing.

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Does this need a 'receiving part' or anything that it can pick up in the slot?

I have a spare one Chaz if it works ok we can sort something out.

We use them at wok and they are built very well.

Andy

Here is a link to the pdf Chaz

http://www.balluff-ua.com/pdf/mechan..._single_EN.pdf

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Originally Posted by Chaz

Does this need a 'receiving part' or anything that it can pick up in the slot?

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You need something that goes through the slot. It doesn't have to be anything fancy, I just used a bit bent bar suitably mounted on the cross slide -
https://farm6.staticflickr.com/5026/...7e86900d_z.jpg

we use these on our machines and linear stages we build.
https://www.zappautomation.co.uk/bes...on-sensor.html
The repeatable accuracy is 1% of the distance of the metallic material used to sense.
other things also need to be taken into account as well to see the accuracy though.
Also very low profile, but not the cheapest.

Chaz, I have made something based on the "touch plate" concept used for mill Z homing.
Attachment 24073
(I hope that works!)
Repeatability seems to be better than 10 microns, and in conjunction with my tool setter on my first trial of homing/applying set tool offset/turning I achieved indicated microm accuracy on diameter. This cost nothing to make, it's essentially a bit of PCB laminated on to 6mm of tufnol superglued to the apron front. Obviously there are issues of wear and tarnishing so I intend to upgrade it with one where the contact surface is beryllium copper.

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Originally Posted by JohnHaine

Chaz, I have made something based on the "touch plate" concept used for mill Z homing.
Attachment 24073
(I hope that works!)
Repeatability seems to be better than 10 microns, and in conjunction with my tool setter on my first trial of homing/applying set tool offset/turning I achieved indicated microm accuracy on diameter. This cost nothing to make, it's essentially a bit of PCB laminated on to 6mm of tufnol superglued to the apron front. Obviously there are issues of wear and tarnishing so I intend to upgrade it with one where the contact surface is beryllium copper.

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Thanks, I had though of similar - this is the way that we deal with milling offsets, so no reason why it wont work on a Lathe. Ill try the switch from audioandy (Thank you) first and go from there.

Thanks for the other suggestion Gary.

Hi Chaz

Switch posted today first class so should be with you tomorrow.

Regards
Andy

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Originally Posted by audioandy

Hi Chaz

Switch posted today first class so should be with you tomorrow.

Regards
Andy

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Thanks, appreciated.

I retested my cheap proximity switch with a 'semi decent' analog DTI and it was surprisingly accurate. My el cheapo electronic DTI seems not to be repeatable. Go figure ...

I also managed to get my spindle speed / encoder setup to work and tweaked my steps for X and Z, explains why I was getting inaccurate cuts, not out my much, but it was out.

Ill still try the mechanical switch - just need to figure how to mount it with my setup.

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Originally Posted by audioandy

Hi Chaz

Switch posted today first class so should be with you tomorrow.

Regards
Andy

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Received, with thanks.

:beer: