[DonFrambach]

Got an idea last night that I thought best to run by you experts.

I want to precisely home my small router so I can do complicated projects over several days with my machine turned off between sessions. This will require precisely resetting my X, Y, and Z axis. Z is no problem because I can rezero to an uncut part of my project. Resetting X and Y will be much more difficult.

Currently I'm using mechanical switches as my limits and I home to X- and to Y-. These are clearly not going to be precise enough. For one, the X switches are mounted with velcro so I'm sure that they are shifting a bit.

I purchased these proximity switches from CNCRouterParts thinking that these would allow precise homing. http://www.cncrouterparts.com/proxim...kit-p-215.html

Before installing these new switches, I got to thinking about how to confirm that they were working properly and figured that I could mount a dial indicator to the X and Y axis to see how repeatable my homing was. In then occurred to me that these dial indicators could be left permanently in place if I figured out a way to mount them in a way to protect them from dust and injury as I used my machine. I would then use the indicators to set zero (to a very high precision) without changing out my mechanical limit switches.

Thought I'd use two of these relatively inexpensive 1" travel dial indicators from LittleMachineShop: http://littlemachineshop.com/product...4112&category=


Comments?

[LeeWay]

HF has some about half that price. I have one that I use for general knocking around. It works fine. Had a nice old Starrett that got smashed. I have another that stays in the box and is only pulled out for those special occasions.

1" Travel Machinist's Dial Indicator

[underthetire]

Wonder if you could use an electronic one to signal the control. Similar to how super high precision machines use LVDT's for homing. Those will home to less than 2 millionths of an inch.

[DonFrambach]

HF has some about half that price. I have one that I use for general knocking around. It works fine. Had a nice old Starrett that got smashed. I have another that stays in the box and is only pulled out for those special occasions.

1" Travel Machinist's Dial Indicator

Appreciate that.

LittleMachineShop also sells a 1" indicator for $12.95 but it only has a lug back while the "professional" model has both a lug and a flat back which should make for more mounting options. I also thought that the "professional" model would likely be of higher quality and, at $29.95, was still within budget.

But what do you think of permanently mounting dial indicators to a router?

[DonFrambach]

Wonder if you could use an electronic one to signal the control. Similar to how super high precision machines use LVDT's for homing. Those will home to less than 2 millionths of an inch.

Yikes!! I think .001" will be fine. Though I think I can do better than that with a dial indicator.

[LeeWay]

I think it sounds like a good idea. I am not sure how well it will stand up to vibration, but worth a try with these cheapies.

[harryn]

I have a friend that mounted a DRO on his mini lathe - really likes it. Same concept I guess.

If the travel is 1 inch, then that gives + / - 0.5 inch of useful distance to center it in.

Personally, I would try to use a digital read out if you can swing it, because it is so much easier to avoid errors.

Harry

[LeeWay]

I think the issue with a digital indicator or a DRO is that you have to turn it off. Then you have to re calibrate it. With a dial indicator, it will stay in the relaxed state until touched.

[robedney]

Well, if you're asking if it's a good idea or not -- I think it's good enough to steal, so I'm going to.

[neilw20]

Want it really accurate? Put a reed switch on stepper shaft, in series with the home switch. This will get it much closer.
Switch is only enabled once stepper is at a correct rotational position.
Some variation can still occur with microstepping, but it will sure be better. This depends where driver was when powered up, I think.
Once referenced, turn it all off, and do it again. Might get a more consistent position that way. My SX3 with optical switches is within 0.002" (and no switch on shaft either)
Nice precise signals from opto to BOB are needed to achieve this. With an old LPT port on another computer its was quite poor.
A very low approach speed makes it quite good.
It takes forever to get there, so I have rough marks near the limits, and rapid almost to the marks first.

[Al_The_Man]

Have you seen this gadget, you possibly could use them and some re-reference the zero point on power up?

Portable magnetic digital read out for lathe cross slide and carriage travel - $10 - YouTube


Micro Digital Read Out
Ebay 370641402894
They would be nice if there was an output on them!
Al.

[Dylwad]

I use Omron optical home switches on my router, repeatability better than a single step, and would be lost without them.

Most of what I do requires at least 2 tool changes, 1/8" shank bits with depth collars, er20 chuck. I bolt the stock on to the fixture plate (corian with brass threaded inserts) load the first tool, home the machine, jog to the X and Y zero on the part, hit print screen and paste that image to paint shop pro, crop the image to just show the x and y offset and zero the machines x and y. Jog to the middle of the stock and touch off on the z with a piece of paper, hit print screen again and crop to just show the z offset. Zero the z on the machine and now I have my offsets from home saved if I need them for some reason.

If I need to go back to that offset I home the machine and put the coordinates into the mdi box. I don't use g code offsets, and have shortcuts saved on the F keys for various things, like going to x0 y0 z5 to change bits, or x5 y5 to zero on my main fixture plate, and have a G20 set up to check for missed steps(which you can only do with accurate home switches) I don't use Mach3 though so ymmv

Why put a mechanical measuring device on the machine when you can use the machine itself, you just need precise home switches. I still have limit switches, but they are only used as limits. The omron opticals are around $20 each and take about as much work to mount as dial indicators.

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[LeeWay]

When you think about what type of switches you use, you need to consider what type machine it is. I cut lots of polycarbonate with my router. It makes lots of light weigh large size chips that go everywhere. Opticals would not be my first choice. I do have some on my 3D printer though and they are very precise.
My router no longer has limits or homes. I installed good hard stops instead and removed the switches I did have there. I have no trouble zeroing Z and X is fairly easy by eye, but can't get a line of sight on the Y for the eyeball calibration routine.
I think Mechanical dial calipers are in the cards for the future.

[Dylwad]

When you think about what type of switches you use, you need to consider what type machine it is. I cut lots of polycarbonate with my router. It makes lots of light weigh large size chips that go everywhere. Opticals would not be my first choice. I do have some on my 3D printer though and they are very precise.
My router no longer has limits or homes. I installed good hard stops instead and removed the switches I did have there. I have no trouble zeroing Z and X is fairly easy by eye, but can't get a line of sight on the Y for the eyeball calibration routine.
I think Mechanical dial calipers are in the cards for the future.

So tell me what the difference is between making sure optical switches are clear of debris before homing and making sure the surface the dial indicator hits is also clear of debris?

Swarf in the switches doesnt effect anything while cutting, only during homing. A small blast of compressed air takes care of that, or a decent dust collection system and placing the switches out of the way if the chips works too.

I would be more worried about dust inside of the indicators, which are full of tiny precision gears and axles covered in lubricant.

Seems silly to me to take an automated machine with the capability of homing itself with a press of a button and put analog devices on it that require you to manually tell it where home is.

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[LeeWay]

Well, nothing will hang on the point of a dial indicator.

My truck has a computer, but I still drive it using eyesight. Get this though, I still have to use a mechanical pneumatic gauge for checking the tire pressure. I know, I know. Back in the stone age.

There are many many different degrees of automation. I have 5 different cnc machines and they are all automated to varying degrees. Just as much as I need actually. I had switches on my router, but they were not accurate enough, so removed them when I redid the control box and upgraded the drives and motors. No need for limits with good hard stops. There is a need to crank up at exactly home or get there with at least the precision of a dial indicator. I use jig plates for all my parts on that machine and have holes located in those plate. They are a specific number away from Home. I have to travel there and get the bit to go into that hole to know I am at least that close.
A dial indicator would save all the travel and time doing that. I just don't need that much automation on my router.

[mcarvey]

I've mounted dial indicators to the X and Y axis to do exactly this, and it works great. Very fast and easy way to accurately reference home, calibrate steps/inch, check backlash, and check to see if you've lost any steps. Accurate home switches are great and all, but it always takes more time than you think to wire them, and in the end, you'll have to put an indicator on the axis anyway so you can verify that they are working properly. FWIW I used the low cost indicators and haven't had an issue with them. If you are cutting wood you may want to make some sort of covering/cap so dust doesn't get in the bearing surface.

Hope this helps,
-Matt

[ger21]

Seems silly to me to take an automated machine with the capability of homing itself with a press of a button and put analog devices on it that require you to manually tell it where home is.

+1

Buy or build yourself some magnetic hall home switches, and push a button to home. Cheaper than buying dial indicators, and much faster.

[Dylwad]

Simple easy and reliable.

The home script is about as easy as it gets too
g30 z-.05 f40
g30 x.05 y.05 f50
g30 x0 y0 z0 f2

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[neilw20]

If the homing switch is somewhere not at the limit of travel, having the blocking strip continue all the way to the end of travel means you get an error if homing is attempted when past the homing point. It never heads off past that point and crashes the stops when homing.
I've done that on my machine and it never crashes the stops while homing anymore.
Sometimes annoying to move off the red zone but, never goes bang anymore.

[Dylwad]

Got that covered, the limits trip while the flags are still blocking the home switches. Good point though if you set home in the middle of the travel for some reason.