# Are the default Z offsets wildly wrong? **URL:** \ **Category:** Uncategorized\ **Created:** [July 29, 2025, 4:51am UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628 "2025-07-29T04:51:02Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![dlang](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/dlang/32/859_2.png) [@dlang](https://forums.maslowcnc.com/u/dlang)\ **Post date:** [July 29, 2025, 4:51am UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/1 "2025-07-29T04:51:02Z")
I was measuring my maslow today, and I think the default Z offsets are wildly wrong. I measure 36mm from the bottom of the sled to the bottom of the first arm. The anchor is just over a mm higher. but the lowest default Z offset is 34mm, which is not only slightly short (but it could have been my measurements) but it also leaves no room for a wasteboard or workpiece. with the thinking being that the wasteboard is 3/4" and the workpiece is 3/4" that’s another 36mm to add, so the lower arm should be 72-75mm which would put the top arm pretty close to 140mm, not 100. am I missing something obvious? or have we been strugling with bad offsets all along? ---
**Author:** ![MontanaEthicalHacker](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/montanaethicalhacker/32/28357_2.png) [@MontanaEthicalHacker](https://forums.maslowcnc.com/u/MontanaEthicalHacker)\ **Post date:** [July 29, 2025, 7:30am UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/2 "2025-07-29T07:30:16Z")
I don’t know. I think the offsets are inconsistent. I’ve been keeping track of my Z offsets because they seem to cause tertiary problems. I’m doing a test run of an 8" Yggdrasil relief with the router turned off and the z-stop set WAY above the project board. I’m 62.5mm between the bottom of the first router clamp and the top of a z-axis motor. My cut will move the z-axis down to 52.0mm(same measurement). I haven’t cut anything with my M4 yet. However, I’ve done some dry runs. I noticed that if I don’t have my zhome/zstop set at a fair height, I can run into a 15mm error. [15mm Position Error While Moving Investigation - #19 by bar](https://forums.maslowcnc.com/t/15mm-position-error-while-moving-investigation/21218/19) So I loosened my router chuck and dropped the bit a cm. But yes. I have to be careful to set the Z-axis carefully. Unrelated, Thank you for all of your development work! I’ve been lurking for a long time. I might actually have some small PRs in an age or two. Perhaps something to send telemetry and errors to a central log server for QA? It would have to be secure and not an invasion of privacy, so it could be better that this take a longer time to develop. CISSP with 3yrs of Criminal Justice, hackspace owner for 15yrs. Coding since 90’s. I’ve changed legislation to support privacy. If I do this… I’ll probably still screw it up… So I welcome advice. ---
**Author:** ![bar](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/bar/32/10_2.png) [@bar](https://forums.maslowcnc.com/u/bar)\ **Post date:** [July 29, 2025, 5:04pm UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/3 "2025-07-29T17:04:05Z")
> [@dlang](#): > > leaves no room for a wasteboard or workpiece. It’s true we aren’t accounting for the thickness of the wood currently. I think that we should do some testing to see how big of a difference it makes but it’s a great point. ---
**Author:** ![dlang](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/dlang/32/859_2.png) [@dlang](https://forums.maslowcnc.com/u/dlang)\ **Post date:** [July 29, 2025, 7:13pm UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/4 "2025-07-29T19:13:52Z")
Bar wrote: > It’s true we aren’t accounting for the thickness of the wood currently. I > think that we should do some testing to see how big of a difference it makes > but it’s a great point. I knew that we didn’t account for the workpiece size, but I thought we accounted for a wasteboard size. we have had some people post that raising the anchors and setting the Z offsets to zero make a huge difference, it could be that just the Z offsets being correct could account for the huge difference. for the top left arm, the 40mm error results in a difference of ~8mm in the effective length of the arm when it’s near the top left corner (I use 600mm of belt length for checking this sort of thing as a nice round number) I would say that the best fix for this will be to add in separate wasteboard and workpiece thickness variables rather than changing the offset numbers (set them through the popup that does the retract/extend/tension/etc) David Lang ---
**Author:** ![bar](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/bar/32/10_2.png) [@bar](https://forums.maslowcnc.com/u/bar)\ **Post date:** [July 29, 2025, 7:16pm UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/5 "2025-07-29T19:16:05Z")
> [@dlang](#): > > thickness variables rather than changing the offset numbers (set them > through the popup that does the retract/extend/tension/etc) I agree, I think that won’t be hard to do. I would like to see some testing to see that it matters before we add things to the UI just because of how confusing folks already find the settings that we have ---
**Author:** ![dlang](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/dlang/32/859_2.png) [@dlang](https://forums.maslowcnc.com/u/dlang)\ **Post date:** [July 29, 2025, 7:36pm UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/6 "2025-07-29T19:36:51Z")
Bar wrote: > I would like to see some testing to see that it matters before we add things > to the UI just because of how confusing folks already find the settings that > we have I cam come up with tests that will show it’s a huge problem (using a 2" foam board for your wasteboard, and a thick workpiece) 🙂 but what sort of testing are you thinking of? do we want to talk someone who is struggling with calibration through changing the offsets and see if it helps? do we want to have someone who’s machine is working well change their offsets to introduce deliberate errors? do we want someone who’s machine is working well to save their yaml file and re-do their offsets and do a new calibration? something else? David Lang ---
**Author:** ![dlang](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/dlang/32/859_2.png) [@dlang](https://forums.maslowcnc.com/u/dlang)\ **Post date:** [July 29, 2025, 7:39pm UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/7 "2025-07-29T19:39:11Z")
Bar wrote: > I would like to see some testing to see that it matters before we add things > to the UI just because of how confusing folks already find the settings that > we have how about adding the variables to the code, but not add them to the UI yet (and have them default to 0 if not set in the yaml). we could direct people to the fluidnc advanced config tab to set them while we are testing to see how much of a difference they make. (it would be easier and safer than changing the 4 z offset values in that same tab) David Lang ---
**Author:** ![bar](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/bar/32/10_2.png) [@bar](https://forums.maslowcnc.com/u/bar)\ **Post date:** [July 29, 2025, 8:02pm UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/8 "2025-07-29T20:02:04Z")
> [@dlang](#): > > how about adding the variables to the code, but not add them to the UI yet (and > have them default to 0 if not set in the yaml). we could direct people to the > fluidnc advanced config tab to set them while we are testing to see how much of > a difference they make This is a fantastic idea ---
**Author:** ![MontanaEthicalHacker](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/montanaethicalhacker/32/28357_2.png) [@MontanaEthicalHacker](https://forums.maslowcnc.com/u/MontanaEthicalHacker)\ **Post date:** [July 29, 2025, 9:00pm UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/9 "2025-07-29T21:00:20Z")
I like how you two discuss these ideas in an open forum so others get a feel for the evolution of dev to prod features. ---
**Author:** ![dlang](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/dlang/32/859_2.png) [@dlang](https://forums.maslowcnc.com/u/dlang)\ **Post date:** [July 29, 2025, 10:51pm UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/10 "2025-07-29T22:51:18Z")
I would make it two variables, not one. While one can work (tell people to add the wassteboard and the workpiece thicknesses), I think people will be more likely to make mistakes if it is one variable rather than two. also, I measure the arms at 21mm thick, so if the lowest one is 34mm, the next should be 55mm (current 56), the next 76mm (current 78), and the final one 97mm (current100). I don’t think being off single digit mm in height matters much, but being the ocd type, if we make any changes to the defaults, we should make them correct. ---
**Author:** ![Betalombo](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/betalombo/32/26664_2.png) [@Betalombo](https://forums.maslowcnc.com/u/Betalombo)\ **Post date:** [August 5, 2025, 1:07am UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/11 "2025-08-05T01:07:43Z")
I have noticed a big difference by changing my work piece from 15mm to 9mm thick, the difference is noticeable in the clearance of the lower belts on my vertical frame, in my case it is useful to be able to adjust the height of each arm independently, since the anchors are not at the same level between them, when I change those few millimeters in height the clearance is corrected and the precision increases ---
**Author:** ![dlang](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/dlang/32/859_2.png) [@dlang](https://forums.maslowcnc.com/u/dlang)\ **Post date:** [August 5, 2025, 1:54am UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/12 "2025-08-05T01:54:00Z")
Javier Betancourt wrote: > I have noticed a big difference by changing my work piece from 15mm to 9mm > thick, the difference is noticeable in the clearance of the lower belts on my > vertical frame, in my case it is useful to be able to adjust the height of > each arm independently, since the anchors are not at the same level between > them, when I change those few millimeters in height the clearance is corrected > and the precision increases the Z offset is the way to adjust an individual arm, the proposal to add a workpiece and wasteboard offset should help accuracy, but I don’t understand how clearance would change (are you changing the anchor locations???) could you show us pictures of what you mean? David Lang ---
**Author:** ![Betalombo](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/betalombo/32/26664_2.png) [@Betalombo](https://forums.maslowcnc.com/u/Betalombo)\ **Post date:** [August 5, 2025, 3:22am UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/13 "2025-08-05T03:22:25Z")
I may not be understanding correctly, due to the translator. My anchor points aren’t aligned with each other or with the waste table. Some are lower than others, so I have to individually change their programmed height. Later, when I change my work material, I increase or decrease them all equally according to their thickness. My point was that those millimeters of error are reflected in the clearance and precision. ---
**Author:** ![dlang](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/dlang/32/859_2.png) [@dlang](https://forums.maslowcnc.com/u/dlang)\ **Post date:** [August 5, 2025, 3:45am UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/14 "2025-08-05T03:45:13Z")
Javier Betancourt wrote: > I may not be understanding correctly, due to the translator. My anchor points > aren’t aligned with each other or with the waste table. Some are lower than > others, so I have to individually change their programmed height. Later, when > I change my work material, I increase or decrease them all equally according > to their thickness. My point was that those millimeters of error are reflected > in the clearance and precision. the idea of the proposed change is that you won’t have to change each of the four individually, you will set them once for what’s correct with one wasteboard and then as you change your workpiece, there will only be one setting to change. but I’m still not understanding how those changes affect clearance (precision I understand, but not clearance) David Lang ---
**Author:** ![Betalombo](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/betalombo/32/26664_2.png) [@Betalombo](https://forums.maslowcnc.com/u/Betalombo)\ **Post date:** [August 6, 2025, 12:12am UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/15 "2025-08-06T00:12:51Z")
> [@dlang](#): > > but I’m still not understanding how those changes affect clearance (precision I > understand, but not clearance) Oh, I’m so sorry, it’s definitely a translation issue. The term “clearance” referred to “loose belts”. And I do agree that it would be wonderful to adjust a single measurement without having to always go back to the yamln file. ---
**Author:** ![RandomDave](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/randomdave/32/28146_2.png) [@RandomDave](https://forums.maslowcnc.com/u/RandomDave)\ **Post date:** [August 10, 2025, 10:36am UTC](https://forums.maslowcnc.com/t/are-the-default-z-offsets-wildly-wrong/24628/16 "2025-08-10T10:36:45Z")
A couple of thoughts on this and shims from while i’ve been pondering other stuff. - It might be the bits i’ve been using, but I have to raise the Z-assembly 30+mm from z-stop to Z-home. Given I really only need a range of about 20mm (cutting 12mm ply most of the time, a few mm cut clearance and 5mm travel clearance), I could alter Z-stop by shimming the z-motors 10mm+ (if that makes sense). It’s relevant because that would mean you could/should raise the anchor points 10mm to minimise belt angles in normal use. - I set my anchor points based on the spoil board, and then shim them with the depth of the material i’m going to cut. Depending on the users setup that’s either pretty easy, or a pain, but it again is a good way of minimising belt angle without a software value (though I do thing a software value is useful).