Height Map - Substantial z-offset after setting z-offset

TimsWorkshop

@fcwilt hey mate, so what do you reckon is going on here? I did a print last night and this morning started a new one, but noticed I had to make some large baby step corrections.... so I stopped and re-ran a G29 and a huge difference in my mesh...

Mesh done two nights ago:

Mesh done just 5 minutes ago:

I can probably run a G32 and will have to adjust the springs... but what a shocking difference in just two days.

fcwilt

@infidelprops

You are still doing the single G30 at bed center to set the Z=0 Datum before doing G29 to create the height map?

Frederick

TimsWorkshop

@fcwilt said in Height Map - Substantial z-offset after setting z-offset:

@infidelprops

You are still doing the single G30 at bed center to set the Z=0 Datum before doing G29 to create the height map?

Frederick

Yeah it is

fcwilt

@infidelprops said in Height Map - Substantial z-offset after setting z-offset:

@fcwilt said in Height Map - Substantial z-offset after setting z-offset:

@infidelprops

You are still doing the single G30 at bed center to set the Z=0 Datum before doing G29 to create the height map?

Frederick

Yeah it is

Well I don't know what is happening.

In theory if the height map is created after setting the Z=0 Datum at bed center, then a few points of the height map which are near bed center, ought to have an Z offset close to zero, as indicated by the green color in the upper height map image.

Are there any commands between the G30 and the G29 that might be causing the problem?

Frederick

TimsWorkshop

@fcwilt A few, but it's just doing a double probe before G29 starts:

M558 F900              ; Home EZABL Fast 15mm/s
G30                    ; home Z by probing the bed
M558 F450              ; Home EZABL Slow 7.5mm/s
G30                    ; home Z by probing the bed

fcwilt

@infidelprops said in Height Map - Substantial z-offset after setting z-offset:

@fcwilt A few, but it's just doing a double probe before G29 starts:

M558 F900              ; Home EZABL Fast 15mm/s
G30                    ; home Z by probing the bed
M558 F450              ; Home EZABL Slow 7.5mm/s
G30                    ; home Z by probing the bed

If you are in fact using a EZABL probe you may need to slow down the probing speed.

Unless they have some tech trick up their sleeve (which they may) their probe is described as a capacitive device with 100 Hz switching frequency.

I've tested a number of different inductive and capacitive probes and found the capacitive probes needed a much slower probing speed than the better inductive ones. Generally the higher the switching frequency the shorter the response time. I have some inductive probes with a 3000 Hz switching frequency.

So, just as a test, probe just once at F100, rather than twice at 900/450, and see if that makes any difference.

Frederick

TimsWorkshop

@fcwilt Thanks mate - I'll give it a go

TimsWorkshop

@fcwilt so I did a G32 and had to adjust the knobs again, and then ran a G29 with one probe and F100... it took a while, but mesh looks much better. We'll see how it looks tomorrow after a 20hr print.

zapta

@fcwilt said in Height Map - Substantial z-offset after setting z-offset:

I was a programmer for 30+ years but now given the limited number of files I put them in one place and I always know where they are - the System folder.
71 year old brains crave simplicity

@fcwilt, software engineering is a relatively new profession. Did you transition from another discipline?

Software engineering is unique because people from other disciplines can easily transition to it and do well just by applying common sense. This is not the case with other branches of engineering and STEM (imagine a software engineer designing a bridge ;)).

fcwilt

@zapta said in Height Map - Substantial z-offset after setting z-offset:

@fcwilt said in Height Map - Substantial z-offset after setting z-offset:

I was a programmer for 30+ years but now given the limited number of files I put them in one place and I always know where they are - the System folder.
71 year old brains crave simplicity

@fcwilt, software engineering is a relatively new profession. Did you transition from another discipline?

Actually I studied digital circuit design and did that for a couple of years but when microprocessors began to take off my company needed someone to learn how to code for them.

From that I learned that I liked programming and had the skills. So I branched out into application programming.

Frederick

TimsWorkshop

@infidelprops said in Height Map - Substantial z-offset after setting z-offset:

@fcwilt so I did a G32 and had to adjust the knobs again, and then ran a G29 with one probe and F100... it took a while, but mesh looks much better. We'll see how it looks tomorrow after a 20hr print.

So finished the print and ran another G29... this time it was still a good mesh and worked well. Not sure but thinking I may want to tune my stepper motors to help reduce them falling, one side or the other.

fcwilt

@infidelprops said in Height Map - Substantial z-offset after setting z-offset:

@infidelprops said in Height Map - Substantial z-offset after setting z-offset:

@fcwilt so I did a G32 and had to adjust the knobs again, and then ran a G29 with one probe and F100... it took a while, but mesh looks much better. We'll see how it looks tomorrow after a 20hr print.

Sounds promising.

So finished the print and ran another G29... this time it was still a good mesh and worked well. Not sure but thinking I may want to tune my stepper motors to help reduce them falling, one side or the other.

One of the benefits of auto bed leveling is getting the Z steppers back in sync.

On my 3 Z printer when removing the magnetic print surface a stepper sometimes moves due to the reduced current levels.

Frederick

TimsWorkshop

@fcwilt Thanks mate - I've just got BL Touches delivered and am going to put those in versus the EZABL probe.. that will be todays task.

zapta

@fcwilt said in Height Map - Substantial z-offset after setting z-offset:

One of the benefits of auto bed leveling is getting the Z steppers back in sync.

Stumbled today upon this unboxing video. The printer has two Z motors as well as a belt that keeps them sync'ed. It's an interesting idea.

https://youtu.be/CkTgm4AQjhY?t=397

fcwilt

@zapta said in Height Map - Substantial z-offset after setting z-offset:

Stumbled today upon this unboxing video. The printer has two Z motors as well as a belt that keeps them sync'ed. It's an interesting idea.

https://youtu.be/CkTgm4AQjhY?t=397

Thanks.

I've got one of the earlier, smaller Sapphire Core XY unit

It was a pretty nice unit of the box.

But I cannot help myself and had to mod it (Duet, PanelDue, better hotend, Zesty Nimble, better bed).

Happy with the unit.

Here is a quick-and-dirty video of my 3 Z Stepper Belt Drive printer showing the ability to deal with a badly out of level bed:

3 Z Stepper Printer

Frederick

TimsWorkshop

@fcwilt Just wanted to post a quick update... I ditched the EZABL and put new BLT's in and haven't had a problem since. Prints are coming out beautiful and I haven't had to adjust the baby steps since the first MBL/ABL.

Thanks again for all the insight and help!

fcwilt

@infidelprops said in Height Map - Substantial z-offset after setting z-offset:

@fcwilt Just wanted to post a quick update... I ditched the EZABL and put new BLT's in and haven't had a problem since. Prints are coming out beautiful and I haven't had to adjust the baby steps since the first MBL/ABL.

Thanks again for all the insight and help!

I love a happy ending.

I had doubts about the EZABL when I found out it was capacitive. Before you removed it did you ever try a very slow probing speed?

Frederick