[LeeWay]

I would check the switch first just to see what kind of shape it's in.
I am totally satisfied with the repeatability I get with X on mine. Maybe .001" or very close to that. It has stayed that way since I first started production runs a few months ago. I haven't reset anything and all my parts are still sized within that tolerance.
Honestly .005" would be good enough for our parts. Now for someone like John Grimsmo that machines very tiny titanium parts, I can certainly see the need for much better accuracy.
Just because I get acceptable accuracy now does not mean that if you guys find a good replacement switch, that I won't swap it out. I will be watching.

[MichaelHenry]

I would check the switch first just to see what kind of shape it's in.
I am totally satisfied with the repeatability I get with X on mine. Maybe .001" or very close to that. It has stayed that way since I first started production runs a few months ago. I haven't reset anything and all my parts are still sized within that tolerance.
Honestly .005" would be good enough for our parts. Now for someone like John Grimsmo that machines very tiny titanium parts, I can certainly see the need for much better accuracy.
Just because I get acceptable accuracy now does not mean that if you guys find a good replacement switch, that I won't swap it out. I will be watching.

I'll check my switches before making any changes. The switches on my mill seem to be very repeatable but maybe that was just luck of the draw when I checked the mill switches.

[MichaelHenry]

There have been complaints about X axis homing, me included. When I checked the switch the roller was *very* wobbly and the plunger kind of sticky ( and this was after a bit of gun lube ) . so no wonder from one reset to another the X axis homes sometimes with a .010 variance.

OK, I'm not a switch guru, but I some internet research got to some Honeywell sealed roller switch for not much ( ~$35. ). This just has to be better! How's the action on your Omron switch? Is it sealed? That might be a plus.

Very cool what your doing .. disassemble to get it installed, should inspire some other people, who also have a space challenge. The only thing I'd worry about is getting the headstock back into true, tho I assume it's pinned. When you get it running, it you have a larger ( 3-4" ) piece of aluminum tube ( or bar ), take a light cut and check for taper.

I still haven't dug the Omrons out to look, but they were around $75 each from McMaster-Carr, not that that means much,

I ran the two collar test with 3-in OD 6061 on the lathe over about 8-in of length in the garage when the lathe was still in as received condition and plan to repeat that test when the lathe is all setup in the basement. As you guess the headstock is pinned, but I'm not sure how precise that makes it. It will be fun to find out.

[MichaelHenry]

The Omrons I have are not of the same form factor as the Tormach switches so they probably won't work on the lathe unless I figure out an innovative way to mount them. In a 10-test trial of reference repeatability the difference between the maximum and minimum off set on a standard was 0.0162 inches on my X and 0.0410 inches on my Z. The slop in my Z switch is very noticeable by touch. I'm not sure, but thought that the repeatability on my 1100 mill was more like 0.001-0.002". I think that I will be looking for some better switches for the lathe. Has anyone found anything?

Tomorrow I plan to run some simple tests with the Omron switches to see how repeatable they are.

[LeeWay]

Have you contacted Tormach about them? I don't get any noticeable movement with mine. The roller rolls, but it should. Maybe just a bad batch of switches?

[adamvs]

I have one of the first lathes .. I think number 46. I get about what Michael gets. I dunno. Is it worth it to replace the switches? I mean, Z .. who cares. X is more of an issue, but it'll never be as good as doing a test cut with a master tool and adjusting work offsets ( you essentially do this on the mill ).

[LeeWay]

I have done that procedure several times over the past few weeks and you are right. It is dead simple. That said, it is nice to know I can get our parts turned well within our tolerances just using the homing switch.
Maybe you guys don't have bad switches. I may have an exceptionally good one.

[adamvs]

I may have an exceptionally good one.

I was thinking the same thing . you got the lucky end of the curve.

[MichaelHenry]

My predilection to accidentally bumping E-stop buttons has me considering ways to avoid the time needed to reference the master tool. I'm probably being too anal, but using a piece of paper between tool and work as a presetting aid doesn't strike me as all that accurate, especially in X. I've played around with using a Haimer as a toolsetting aid but suspect that will be just as fiddly or time consuming.

I'll be testing an Omron limit switch gripped in the vise for repeatability on my 1100 tonight, but suspect that will only be repeatable to a couple thousandths of an inch. The roller is a lot tighter than the ones on my 15L lathe so there's a little ray of hope.

[adamvs]

I, for one, am very interested is how your switches behave. The piece of paper method is really not that bad, specially on Z. Once you get a feel for it you're usually within a thou. Still the best is doing a test cut. After I started doing these ( test cuts ), it's certainly fast enough, faster than the piece of paper method.

[LeeWay]

Faster rapids would certainly help with setup. When you do the test cut, you really need to move the carriage pretty far back to be able to manipulate and read the Mic.
Once my warranty is up, I will be testing that out, though I am sure others with have it figured out by then. I did order the extended warranty.

[MichaelHenry]

I, for one, am very interested is how your switches behave.

I ran 10 sample trials on the 15L X & Z axes, the 1100 (S3 upgraded) X, Y, & Z axes, and ran a test on an Omron DC4-1602 switch. The Omron was held in the vise on my 1100 and and I used the spindle nose to trip the switch along the X-axis on the mill, using a DVM to watch for low resitance when the switch closed. This Omron is probably not a good candidate for the 15L lathe, but it's the only name brand limit switch I have on hand. The other tests were run by running a Haimer probe up to the zero point at a preselected location. On the lathe, the Haimer was mounted in one of the gang tool holders and zero points were measured against a ~1-in test bar held in a 5C collet in the spindle. The probe was zeroed against the side of the bar for the X tests and the end of the bar for the Z tests. Runout on the bar was a couple tenth or less on the OD and the face of the bar, but the spindle was not rotated between tests so the runout should have no significant effect..

The mill tests were run with the Haimer in the spindle and zeroed against locations on the fixed jaw of my 5-in Tormach vise, as appropriate for the X, Y, and Z axes. Each axis was tested with fixed coordinates for the other two axes. That is, when X was tested, the table and spindle were first moved to a pre-selected fixed Y and Z coordinate and the Haimer probe was then zeroed against the vise along X. Data was collected for each test after first powering down the system, starting it back up and referencing each of the axes (3 for the mill and Omron, two for the lathe).

I then tabulated the DRO values for the tested axis, took an arithmetic average, calculated max and min deviations from that average and expressed the result as the sum of the minimum and maximum. That gives me an approximate indication of the maximum error I could expect if work or part coordinates were only established by referencing the 2 or 3 axes and not by touching off on the work. I realize that those calculations are somewhat redundant, so don't bang me up too bad.

The results, as maximum error in ten tests, follows:

Lathe X: 0.0162"
Z: 0.0410"

Mill X: 0.0005"
Y: 0.0033"
Z: 0.0012"**

Omron: 0.0004"

It seems clear to me that the switches in my lathe are far worse than the ones in my mill, even though the lathe is essentially new and the mill has seen 8 years of "ridden hard and put away wet" use. I'll be contacting Tormach to see what they have to say about it. Replacement switches from them are around $20 each, but I will probably opt to buy something from Honeywell that fits the same form factor, probably around $40-50 each. I will probably find that touching off on a piece of paper or taking a test kit works well enough but for the moment I'd like to make a significant improvement in the lathe switch repeatability.




*The mill Z results might have been skewed slightly by after effects from two odd control errors during tests on that axis. In both cases, I got an alert during X-reference about the enclosure door switch but I don't have the enclosure. I ignored the 1st instance and instead of homing, the X axis was sent hard against the left side and I had to Stop and cycle power. Probably nothing and only mentioned for completeness.

[David C. Allen]

I purchased 3 Honeywell MircoSwitch BZ-2RQ18-A2 which have a 0.0004" to 0.0020" differential travel, and they were no better than the stock Series 3 PCNC 1100 switches. The BM-1RQ18-A2 has a differential travel of 0.0005 to 0.0010" which may be a better switch. Honeywell MircoSwitch states "Differential Travel = Plunger or actuator travel from point where contacts “snap-over” to point where they “snap-back.”

David

[LeeWay]

You know, I have two extra switches on my machine that I really have hardly noticed.
The two that go on the chip guard.
They appear to be the same.
I will check the play in those when I get a chance.

We really only need one good switch, so cost will not be too great that way. I face all my parts each time, so the Z switch is no problem. We at least want our switches to be more accurate than the backlash on that axis. Let the meager backlash be the weak link. I think mine is about the same right now. I'll add a bit more later about that.

MY switch though is getting .0002" repeatability variance after homing on the diameter each day in X. Well that is what it was when we started out with it.
I have to check that again now to see what it is.
I'll let you know.

[MichaelHenry]

Thanks David - that BM-1RQ18-A2 looks like a good match but it looks like most vendors don't stock them and their is a qty 5 minimum to order.

Lee - I called Tormach today to see what they suggested but tech support was busy and no one has called back yet, though I called at 3 pm so that's not surprising. Hopefully they will call back tomorrow and I'll see what they say. I also wanted to ask them about the 0.003" backlash I see in Z.

[LeeWay]

I'll be interested in what they have to say.

[David C. Allen]

Thanks David - that BM-1RQ18-A2 looks like a good match but it looks like most vendors don't stock them and their is a qty 5 minimum to order.

Michael
Digi-Key Part Number 480-4543-ND Digi-Key Stock: 2 Can ship immediately $45.82 Manufacturer Part Number BM-1RQ18-A2

David

[MichaelHenry]

I'll be interested in what they have to say.

No call back yesterday or today. Have others had a problem getting a tech support call back? I'm not batting too well on that score lately.

[LeeWay]

I have always had fast replies. I have seen where it can take a while though by posts on the forum.

[MichaelHenry]

Thanks David. I found them there too and just ordered a pair.