Just to be super clear here, this is a very small error, A cut part measurement is never to be trusted. Too many ways that measurement can be off. Remember, I am only seeing 1.7mm(0.07") over 1220mm (4’).
Only a few people have ever even noticed in several years. I just need to be super clear this is not for correcting cut sizes 99.95% of the time that is going to be a cam issue.
I have a 200mm set of calipers and the deviation is so small it can still get lost in the measurement.
The test is poking holes with a V bit or making dots with a pen.
You should not have to. The only measurement that is going to be very far off is the extruder, as I talked about earlier. Over a 200mm 3d printer the error would be 0.114mm short. Most people can not measure that distance accurately.
1m metal ruler with a 30° vbit would be better. You can place it, use some masking tape for securing it to the table move the z axis really close and jod the machine a couple of times. Then just move the ruler to the other axis.
Wouldn’t surprise me if the average steel ruler might be slightly more accurate than a tape measure, but that’s also a major loss in distance, checking 1m vs 2.4m. It’s probably reasonable to just check the longest dimension and assume the error is the same.
Now I’m considering being a complete nutter and taking my reference measurement ruler to the hardware store and checking it against all the brands…
I was pretty shocked at how accurate, or at least consistent all my tapes are. I have a Sterrett metric, two different $3 adhesive sticker tapes, and an old Stanley. They are all closer than I can see a difference.
But,
This just adds to the point, this is a very small number, take your measurement with a grain of salt if it is under 4’.
I do not own one, I can not imagine many people do.
That is why I have not made any new docs pages. I can not come up with a way to suggest how accurate we can get this. The error is so tiny it is easily within the ballpark of tape measure standards.
I would also venture to say of the people that own calipers, probably only have a 6" /150mm set and those typically only do two decimal places accurately, third is always rounded. That is not enough to get a good measurement.
The ruler is not the issue. You can buy one small tape measure( a 3m is just fine) and always use it for checking square or this measurements. Different tape measures can have small errors between each other. (Never start measuring at the tapes zero. I always start measuring at 10cms .)
There is nothing wrong with the endstops. The belt is the issue, the error is very consistent and mechanical microswitches are ridiculously accurate. Inductive switches are large and require power, and correct polarity. It just adds to the size and complexity for no gain. Plus you need to tune them.
Just to be clear, no endstop issues. They are accurate to far above the error I am getting.
Can confirm the mechanical end stops are solid, they stuck within +/- .001" when I was getting them setup for squaring over 12".
The most economical way I can think of to measure over a machines travel accurately would be a linear scale encoder with .005mm resolution and a DRO screen (up to 1.5m is what I can find easily), can even do a .001mm scale if you want to really pull your hair out.
I would bet that has more to do with the firmware and stepper actions microsteps homing speed than the switch. I bet the switch could add another zero (at least the Omron’s).
Just trying to get a reasonable number for most peoples uses. That is going to have to be a tape measure on a LR, and an MPCNC the error is probably to small to easily measure. Just going to have to show good practice like was mentioned above not to use the hook and start at another mark like 1" or 10mm/10cm.
If someone in any country needs to be more precise than a tape measure than I would expect them to have the ability to measure it.
Just need to gear an instruction page to larger machines and a tape measure. If that is how they calibrate, then those parts should come out matching the best tool they have.
I had actually ran into this on my LR3 last week when I was cutting the struts for the LR4. I noticed the bolt holes werent exactly lining up with the prints, and overall length was off by a few mm’s.
I triple measured stuff and ended up adjusting my steps on the X axis, and slightly on the Y axis. thought it was just something I had done wrong and only just now noticed. adjusting the steps sovled it… after calibrating the steps it cut fine.
Then I dismantled the lr3 for the parts to upgrade it, will see if i have the same thing with the 4 (though, it’ll be new belts…so yeh).
I HIGHLY recommend not judging anything off of a cut part.
You need to do a dot or poke test. Cut parts can be off for any number of reasons. The distance between the screw holes would be insignificant with the current error.
1.75mm its a lot in my field. Thats why i always work with 3mm oversize everything. So nothing gets out of alignment, i’d better shim the sheets when installing
It is a simple test and calibration that takes 2 minutes, and it is extremely accurate.
Two dots or pokes, measure, input the new values and save. No big deal.
If it is a lot for you do the test, simple. For some people I am sure they will not even bother.
You do need to always quantify numbers like that though. 1.75/1220mm. That is not the same as 1.75/20mm
More than a mm shows up into mu work and borders dont align, i do work 2-3mm oversized depending on the job, but some architects do touches the acm on the joints, (vertical jointed edges )
Thats why i always work with 3mm oversize everything. So nothing gets out of alignment, i’d better shim the sheets when installing