# WC - Extend Chains Initial and Final Gear Positions **URL:** \ **Category:** Troubleshooting\ **Created:** [February 2, 2021, 3:43pm UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993 "2021-02-02T15:43:25Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![jonatpridesleap](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/jonatpridesleap/32/6639_2.png) [@jonatpridesleap](https://forums.maslowcnc.com/u/jonatpridesleap)\ **Post date:** [February 2, 2021, 3:43pm UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/1 "2021-02-02T15:43:25Z")
Currently using Web Control with Holey calibration and I have begun the set up and calibration process. I am on the extend chains step. I’ve noticed that after setting the sprockets to the 12 oclock position and extending chains, the sprocket teeth do not return to the 12 oclock position after the chains are extended. The are both off by 2 to 5 degrees. Are they supposed to stop at the 12 oclock position after the chains are extended? I am using the the stock motors, gears and chains originaly shipped by Bar/Maslow. ---
**Author:** ![PaulMek](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/paulmek/32/19215_2.png) [@PaulMek](https://forums.maslowcnc.com/u/PaulMek)\ **Post date:** [February 3, 2021, 1:16am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/2 "2021-02-03T01:16:23Z")
I dont think they are supposed to be at the 12 oclock position after setting the chains and sprockets’. The purpose of setting the chains and sprockets is to send the chain out a specific length so the control board knows where the sled is. ---
**Author:** ![kayaker37](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/kayaker37/32/12681_2.png) [@kayaker37](https://forums.maslowcnc.com/u/kayaker37)\ **Post date:** [February 3, 2021, 1:31am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/3 "2021-02-03T01:31:18Z")
They were supposed to as they were making a multiple of complete turns, and I remember someone more recently figured out how to correct it, not sure if the fix made its way in to newer code, I haven’t updated in a long time now, and so much has changed. Web Control seemed to know it was not exactly where it should have been, so it didn’t really matter. Didn’t hurt cuts any. ---
**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:** [February 3, 2021, 1:54am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/4 "2021-02-03T01:54:29Z")
with a trival calibration, yes they should however with the more advanced calibration, it is not going to be exactly at 12 o’clock This means that when you reset the chains and put them at 12 o’clock, you are introducing error. fixing this is going to require a fairly significant revamp of the internals. Currently the firmware just tracks the length of chain fed out, adn has various correction factors what will need to happen is to track the gear position, and then calculate the chain length from that (and as part of this, left and right chain lengths for the 0,0 positions will probably differ, at least a little bit) David Lang ---
**Author:** ![jonatpridesleap](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/jonatpridesleap/32/6639_2.png) [@jonatpridesleap](https://forums.maslowcnc.com/u/jonatpridesleap)\ **Post date:** [February 3, 2021, 2:13am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/5 "2021-02-03T02:13:30Z")
[dlang](https://forums.maslowcnc.com/u/dlang), so it sounds like I shouldn’t really worry about the position mismatch then because there is really nothing I can do about it. ---
**Author:** ![PaulMek](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/paulmek/32/19215_2.png) [@PaulMek](https://forums.maslowcnc.com/u/PaulMek)\ **Post date:** [February 3, 2021, 2:19am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/6 "2021-02-03T02:19:48Z")
Interesting. Mine never were after setting the gears and chains…, but like said above, it didnt affect the cuts - for me either. ---
**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:** [February 3, 2021, 2:51am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/7 "2021-02-03T02:51:29Z")
unfortunantly yes. ---
**Author:** ![jonatpridesleap](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/jonatpridesleap/32/6639_2.png) [@jonatpridesleap](https://forums.maslowcnc.com/u/jonatpridesleap)\ **Post date:** [February 3, 2021, 5:10am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/8 "2021-02-03T05:10:01Z")
Problems I cant fix and that don’t really cause too many other problems for me are best kind of problems to 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:** [February 3, 2021, 5:50am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/9 "2021-02-03T05:50:09Z")
itwill decrease your accuracy a smidge when you reset the chains compared to feeding them out from 9. but you may or may not notice the difference. David Lang ---
**Author:** ![Orob](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/orob/32/16344_2.png) [@Orob](https://forums.maslowcnc.com/u/Orob)\ **Post date:** [February 3, 2021, 1:06pm UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/10 "2021-02-03T13:06:57Z")
change the chain extension from 1650 to 1651. it should be a multiple of 6.35 for 1/4’ chain. ---
**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:** [February 3, 2021, 8:20pm UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/11 "2021-02-03T20:20:31Z")
the problem is that once you change the calibration correction values, 1651mm of chain is not an integer number of teeth. ---
**Author:** ![Orob](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/orob/32/16344_2.png) [@Orob](https://forums.maslowcnc.com/u/Orob)\ **Post date:** [February 3, 2021, 11:36pm UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/12 "2021-02-03T23:36:39Z")
But it needs to be… ---
**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:** [February 3, 2021, 11:55pm UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/13 "2021-02-03T23:55:05Z")
if one chain is 6.35mm per link and the other is 6.3501mm per link, they can’t both extend to 1651mm with an integer number of tooth moves. add in chain sag, which varies based on the amount of chain fed, and the tension on the chain and it’s even uglier. This is why I say that fixing this would require some deep changes in the firmware. IMHO, this would be 1. track position by encoder steps, not mm 1b. this requires a lot of conversion from mm to encoder position 1. add B commands that move by encoder steps (the current ones move by mm) 2. change the ‘home’/‘chain reset’ position to allow for different lengths of chain on each side 3. change the initial ‘extend chains’ step in calibration to instead be ‘feed/retract 1 tooth from each side’ (with the option to just feed/retract 1 tooth from one side) repeatedly, even if this means that the resulting sled position is not exactly in the center) David Lang ---
**Author:** ![kayaker37](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/kayaker37/32/12681_2.png) [@kayaker37](https://forums.maslowcnc.com/u/kayaker37)\ **Post date:** [February 4, 2021, 1:10am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/14 "2021-02-04T01:10:08Z")
Here is a link to the post I mentioned before: > [@Encoder steps.. Issue with returning sprocket to 12 o'clock after precise number of links fed out... again](https://forums.maslowcnc.com/t/encoder-steps-issue-with-returning-sprocket-to-12-oclock-after-precise-number-of-links-fed-out-again/6578/34): > > I just ran into this myself today. Surprised this has been an issue for two years. It was very disturbing when I saw it, I was concerned that our encoder counts could have gotten messed up again. But I was relieved to find this thread. The issue wasn’t really software, but more of a controls issue. The difference between B02 and B09 is that B02 directly called axis.detach() when it was done. This is a no-no. The PID controls should handle detaching the axes directly, and nothing else exce… ---
**Author:** ![Orob](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/orob/32/16344_2.png) [@Orob](https://forums.maslowcnc.com/u/Orob)\ **Post date:** [February 4, 2021, 1:23am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/15 "2021-02-04T01:23:28Z")
That makes sense. Gcode is in mm though, so it must be converted whether it is done at the chain or at the encoder. I guess my point is that the conversion location in firmware can be moved, but it still has to take place. It remains unclear to me if that conversion would be more accurate if it were moved. ---
**Author:** ![jonatpridesleap](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/jonatpridesleap/32/6639_2.png) [@jonatpridesleap](https://forums.maslowcnc.com/u/jonatpridesleap)\ **Post date:** [February 4, 2021, 2:33am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/16 "2021-02-04T02:33:45Z")
Ok, so my takeaway here is that this is a known problem but everyone has this problem and apparently has had it from the very beginning. The root cause has been determined but implementing the fix is the next hurdle. In the meantime, it doesn’t appear to cause any noticeable accuracy issues possibly owing to a relatively sophisticated calibration routine. It does present a problem when resetting chains however. ---
**Author:** ![Orob](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/orob/32/16344_2.png) [@Orob](https://forums.maslowcnc.com/u/Orob)\ **Post date:** [February 4, 2021, 2:37am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/17 "2021-02-04T02:37:42Z")
So reset your chains before you calibrate ---
**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:** [February 4, 2021, 5:31am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/18 "2021-02-04T05:31:07Z")
The trick is that for positioning the ‘reset chains’ point, we want to move/define the location in terms of encoder steps and then record the mm position that this ends up in. with the current system, we move in mm and don’t know where we will end up in encoder steps (and therefor sprocket position) I could be having tunnel vision here and be missing something, but at the very least, the default 1651mm clain length will have to be broken up into separate left and right chain lengths to ccount for differences in the chains 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:** [February 4, 2021, 5:34am UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/19 "2021-02-04T05:34:06Z")
the process of calibration will change the effective chain lengths for the same sprocket location. in practice, this is something people just live with and ignore. an error of 5 degrees in the sprocket translates to 0.88mm in chain length, which can be up to 2mm of position (worst cases) David Lang ---
**Author:** ![Orob](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/orob/32/16344_2.png) [@Orob](https://forums.maslowcnc.com/u/Orob)\ **Post date:** [February 4, 2021, 12:29pm UTC](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993/20 "2021-02-04T12:29:40Z")
Ok this makes more sense. The makerverse calibration routine gets more attractive to me now because it addresses these or attempts to works around them. Does the cain length extension take into account that we use the second to the last pin on the chain to attach rather than the last one? [Next page](https://forums.maslowcnc.com/t/wc-extend-chains-initial-and-final-gear-positions/15993.md?page=2)