I’ve noticed that homing is not perfectly accurate. I can home, zero the machine work coordinates, cut, then re-home, and cut the same thing and it will be in a slightly different location.
In one case, I was cutting dog holes with a roughing pass and a finishing pass. The holes that I cut the finishing pass after re-homing were slightly loose. Too lose for use in registering workpieces.
Is this common or is this a defect? Is there a more accurate way to produce consistent homing results?
Adam
I only zero Z between roughing and finishing passes. I don’t think you can rely on consistent homing.
Sounds like a product of the infrared sensors. Proximity would have been more accurate imo.
A beam of light being interrupted is not as accurate as distance from a piece of metal
My experience with homing precision:
This is about what I’ve seen. It’s a bummer, but something I can work around.
Hey Adam,
I have no experience with photoelectric homing sensors as used on Elite Series. I propagate retrofitting inductive proximity sensors on the Original Series since the stock machines only have stall homing. The excellent accuracy and repeatability of inductive proximity sensors is known (one example are these ones) and was also confirmed here.
But, in practice, why would you re-home during machine uptime? Homing is only necessary once after startup.
What you would do is re-zero workpiece coordinates. That should always have a good repeatability. But you would only need to re-zero workpiece coordinates (with a touch probe or plate) if you moved your workpiece or fixed a new one.
By the way, if you just want to move the carriages to the home position, and you say it lacks some repeatability accuracy when you home with the limit sensors, I would avoid using it. What you can do is simply G53 G0 X0 Y0 Z0 in the MDI command entry field. G53 means “Move in machine coordinates”. This should not make problems with repeatability and accuracy, as you don’t rehome then. You may also program a target for G30 (“Go to predefined position”) and use this instead.
Hey Adam,
In addition to what @Aiph5u mentioned above, I have to ask if the the finish cut on the registration holes perhaps cut oversize, regardless of positioning accuracy? If you left, say, 0.010" [0.25mm] finish stock, then the combined X-Y error would have to be in access of 0.005" [0.013mm] to create the ‘winking’ effect shown.
Could you visibly see or hear that the cutter was not cutting a complete circle on the finish pass?
Masso advertises 10 micron accuracy of their optical homing sensors, if you are having repeatability issues on the Elite I’d look for an external source - debris in the sensor or outside sources of IR light (such as sunlight at different levels/times of the day) that might be affecting the trigger.
If you are reading through the forums there’s a vast difference between the Elite and the classic X50/X35 with stall homing and repeatability. Take note of which machine is being referenced in the information provided.
Hey Espressomatic, hey Adam, hey all,
yes, therefore, if the homing is obviously not reliable enough, I would say, there is much that speaks for providing an opportunity for zeroing (with a touch probe or plate) even when drilling holes in the table, in order to override the inaccuracy of homing. Fences have been presented in the forum, or blocks that remain permanently clamped to the wasteboard, to which you can apply your touch plate.
I only had this problem because the machine froze in Y. That’s a separate issue that I’ll have to get to the bottom of it it repeats.
I was cutting the wasteboard, so zeroing to the home position.
My finishing pass was perfectly sized. The holes that I cut fully on one side of the re-homing were perfect. The others were slightly oblong.
My Elite homes to near perfect repeatability checked with dial indicators on X and Y, I did have to slow my homing speed down a bit from me speeding it up from factory settings but it repeats very, very close.
Pat
Is it the Masso sensors on the Elite?
Hey Adam,
yes, but what I tried to explain is, moving to home position and homing is not the same. While with the first (with G53 G0 X0 Y0 Z0, or with G30, or the park position button) your machine stays within your “good” established coordinates, homing will delete your home coordinates and establish new ones based on driving all carriages to their limit sensors. You see the difference?
And that’s also why when you probe with a touch probe or touch plate – and be it on your wasteboard with a permanently clamped block or fence to which you apply your touch plate – you get good repeatability over shutdowns and reboots, while with homing, you maybe get not.
Hey Adam,
yes, the Elite Homing Sensors use photoelectric sensors as limit switches, not inductive proximity sensors as seen here.
microns of what? µm or µinches?
Has someone reproduced this accuracy?
Hey Adam,
by the way, as Bill @Machinist brought into the discussion above, not accurate dog holes, especially after second pass, and even oval dog holes, were already a frequent topic in this forum.
The stock Masso homing sensor is not on the Elite, the package is far different than what Onefinity has on the elite. It’s possible they partnered with Masso to produce it, I was referencing it as an example of an advertised accuracy of a photoelectric sensor on the market.
I’ve always thought the generally accepted definition of a micron was a micrometer, or in this case I suppose whatever unit of measurement they use in Australia…
Hey Derek,
Ah, okay, I did not know that.
But do you think that photoelectric sensors can be less accurate than inductive proximity ones?
Just had a look at this, seems you are right!
It’s just that the word “microns” is completely unusual in the region where I live, so I did not know where to put it.
Here we say “Mü” for µm (in IPA: [my:]), exactly as we pronounce the greek letter “µ” (that is the official unit prefix for “Micro-”) (Unicode: U+03BC, legacy symbol: U+00B5). Seems that Americans pronounce this greek letter “/ˈm(j)uː/”
I think a lot of these, maybe even Masso’s, are using the Panasonic sensors.
They all seem to have the stated 0.01mm repeatability.
From my earlier research more money will often get better repeatability/quality, regardless of sensor type. Sometimes I think it comes down to form factor (ease/cost of installation), or best type based on application (inductive may not be best when ferrous chips are produced).
One other question is what accuracy/repeatability is needed or beneficial for your application, or when other factors like backlash, machine construction, quality of linear motion components, etc are considered.
Good to know, I don’t own the elite and I referenced the pictures online that looked like a larger molded plastic part than the Masso sensor.
If you watch the homing process, the carriage moves until the light is broken. By the time it notice that, it has moved a little bit farther, but you see the carriage back up just a bit to stop where the light was broken. I have noticed that the repeatability is less than .001, because my reading never change form one home to another.