Cura model height question

[burtoogle 513]

Personally, I only ever use the middle slicing tolerance as I expect (hope) the slicer to create a gcode file that is dimensionally faithful WRT the model.  Of course, the printer may not actually print what I want (dimensionally) because 3d printers that squirt plastic never do. So then I may need to adjust my model just like designers/manufacturers have been doing for hundreds of years to compensate for dimensional errors that are introduced by whatever material and process has been used. Nothing new about that.

[GregValiant 1,251]

Dimensionally I'm impressed with the accuracy of the machine on everything but the diameter of small holes.  Rather than fudging with Horizontal Hole Expansion I rely on the absolute accuracy of the hole location and drill them to size when necessary.  Slowly but surely the mechanical calibration will go away as the machine continues to wear in and as a result dimensional accuracy will go with it.  When it's freshly dialed in it's amazingly accurate (for a Chinese POS built to a price point).

 

I won't be switching away from Middle any time soon since my CRS disease keeps me from remembering to switch it back.  I'm gonna whine about that until I empty the trash and can't see my scrap anymore.

[paxpring 4]

14 hours ago, GregValiant said:

Ghostkeeper's Usage description of "Slicing Tolerance" - "This setting is named after its intended use rather than its functional effect. If you have multiple pieces that need to slide past each other, the theoretical shape of the layers may physically prevent exact fits. In such a case, you can set this setting to Exclusive so that the layers are guaranteed to stay within the bounds of the original volume. Barring warping, sagging and similar deformation effects, this would guarantee that the parts fit within each other and are able to slide past each other.

In reality there are always other effects going on that prevent this. In practice, this setting can be used to get slightly more or less tolerance between two sloped surfaces, as can be seen in the above images."

     I am an ME with 50 years experience scribbling special machines, fixtures, dies, automation, whatever.  It was always a basic tenet that any part be fully described within the borders of the drawing.  Didn't matter who made detail 1 or who made detail 2 - they need to fit together.  Tolerances, location of features, etc., needs to be part of the drawing - which is now the 3d model.

So I have a  philosophical problem with the idea of generating "tolerance" via a software setting.  It is akin to allowing the technician to determine tolerances.  That indicates ad-libbing by the technician and should never be allowed.  Now that the designer and the technician are often the same person doesn't change my view of that.  If two parts need to fit together, they should be designed to fit together.

    Being aware of what type of machine was going to be used to make a metal part was necessary to design a part that could actually be made (as opposed to what we referred to as Optical Illusions).  Being aware of the 3d printer/slicer/firmware capabilities is just as necessary.  An eye must be kept on those capabilities when designing parts of an assembly.

Paxpring - in one of your initial posts you mentioned problems between the PrusaSlicer / Prusa combination and then using Cura with (I must assume) the same Prusa printer.  If the parts slice differently in Cura than they did in PrusaSlicer causing dimensional anomalies within the Gcode this would seem to be an elemental problem between the slicers that needs to be addressed (somehow).  Using the Exclusive setting (with it's side-effects) to make adjustments in dimensions just doesn't sit well with me.  Again, it has the effect of allowing a technician to unilaterally alter a design.

 

And after all of that - the old guy forgot to change Exclusive back to Middle, sliced and printed a model that turned out two layers too short.

 

 

I use Cura solely for the UM5S and PrusaSlicer solely for the MK3S.

The fact that I have to dive into (UM labeled as) "experiemental" parameters in Cura and tinker with them in order to achieve dimensional accuracy, just feels wrong to me. Like I said before, I feel that dimensional accuracy should be one of Cura's top priority defaults. The only reason I brought up that I use PrusaSlicer is because there I get dimensional accuracy from the start. I have to agree with you that, designing with the slicer's bad dimensional accuracy is something I refuse doing, I would rather switch slicers. 

 

 

[GregValiant 1,251]

Paxpring - I came across this thread which seems to be relevant to the dimensional issue and the UMS5.  Maybe there is something in there you can use.

 

[paxpring 4]

9 hours ago, GregValiant said:

Paxpring - I came across this thread which seems to be relevant to the dimensional issue and the UMS5.  Maybe there is something in there you can use.

 

 

Thank you for the link, I scanned through it and it contains a lot of useful information! 

 

Nonetheless, the origin of my issue still bothers me. The fact that UM advertises their machines to be used in business environments together with the absence of out-of-the-box dimensional accuracy just does not rhyme for me. Especially with regards to the machines' price tags. If anyone could enlighten me on the reasoning of UM for the latter, that would be awesome!

[nallath 1,120]

2 hours ago, paxpring said:

 

Thank you for the link, I scanned through it and it contains a lot of useful information! 

 

Nonetheless, the origin of my issue still bothers me. The fact that UM advertises their machines to be used in business environments together with the absence of out-of-the-box dimensional accuracy just does not rhyme for me. Especially with regards to the machines' price tags. If anyone could enlighten me on the reasoning of UM for the latter, that would be awesome!

Lots of reasons, really. One of them being is that not everyone is printing parts that need to fit well. Some settings have a positive influence on accuracy, but a very negative influence on how the part looks (which is a big thing for a lot of visual prototyping / architectural business). So as with all things, it's a balancing act. This balancing act is also the main reason that we added the "intent" profiles; those make it easier to select settings for what you want to achieve.

 

The experimental settings are primarily because they are simply not quite as stable as the rest of the features. So we basicly have two choices to make here; Don't release those features at all, or provide them with a bit of a warning that it might not quite work as it should. We chose for the second option, since we believe that it's better to at least provide the tools. In that sense, it's also nice that people need / use them, since it indicates that we need to put more effort into improving them so that they can move out of experimental.

Edited August 20, 2020 by nallath

[paxpring 4]

1 minute ago, nallath said:

Lots of reasons, really. One of them being is that not everyone is printing parts that need to fit well. Some settings have a positive influence on accuracy, but a very negative influence on how the part looks (which is a big thing for a lot of visual prototyping / architectural business). So as with all things, it's a balancing act. This balancing act is also the main reason that we added the "intent" profiles; those make it easier to select settings for what you want to achieve.

 

The experimental settings are primarily because they are simply not quite as stable as the rest of the features. So we basicly have two choices to make here; Don't release those features at all, or provide them with a bit of a warning that it might not quite work as it should. We chose for the second option, since we believe that it's better to at least provide the tools. In that sense, it's also nice that people need / use them, since it indicates that we need to put more effort into improving them so that they can move out of experimental.

 

Okay, so I owe Ultimaker an apology. I've missed the "engineering profile" completely and I was under the impression Cura had no such thing. That believe was the fuel for my previous post. I have now tested the (unedited) default engineering 0.15 profile and am very pleased with the outcome. Thanks everyone for all help, case closed! 😅

 

 

[nallath 1,120]

Just now, paxpring said:

 

Okay, so I owe Ultimaker an apology. I've missed the "engineering profile" completely and I was under the impression Cura had no such thing. That believe was the fuel for my previous post. I have now tested the (unedited) default engineering 0.15 profile and am very pleased with the outcome. Thanks everyone for all help, case closed! 😅

 

 

The engineering profile mostly improves the accuracy in the XY direction.

For the next sprint, we're going to be working on material shrinkage compensation, so I expect that to be in the 4.8 release.

[DivingDuck 104]

4 minutes ago, paxpring said:

Okay, so I owe Ultimaker an apology.

Up to the point that you have to print a part with different levels in Z that are not following an divisor of a layer hight 😉

[paxpring 4]

7 minutes ago, nallath said:

The engineering profile mostly improves the accuracy in the XY direction.

 

I've noticed that indeed. The only thing still worth mentioning is is the corner handling. It looks like it cannot accurately lay down my 90 degree angles. Some ghosting is visible and it swings outside of the coner, creating a .1mm thickness increase (should be 2mm) on the corners.  Is this simply a matter of decreasing the speeds? Or is there some other parameter we can tweak to tackle the bulge on the corners and the ghosting and at the same time maintain the speeds?

 

4 minutes ago, DivingDuck said:

Up to the point that you have to print a part with different levels in Z that are not following an divisor of a layer hight 😉

 

In that case I need a tutorial from you on how to do that! 😆

[DivingDuck 104]

Well, I thought the solution is variable layer hight, but I was wrong.

[nallath 1,120]

You actually found the reason why the settings that produce more accurate prints are not the same as the visual ones.

 

The engineering profiles have a very, very high jerk setting. This means that they are forced through the corner as fast as possible (instead of slowing down for the corner). This means that it doesn't pause as much in the corner, which means you have less of a blob in the corner. The downside of this is that you get these wobble vibrations. They do cause a slight inaccuracy, but that is way less than the blob you would normally get. Unfortunately, these wobbles are really easily noticeable to the human eye (which is why we can't enable this setting by default, since the "visual crowd" would get pretty upset...)

 

 

[GregValiant 1,251]

There is no correct place to put this, but since accuracy and finish are involved I stuck it in this thread.

 

I've started work on my own 3d printer design.  It will:

1a.  Produce 3d Prints with a finish like 12 coats of hand-rubbed lacquer.

1b.  Provide an accuracy of +/- 1 nanometer.

2.  Come with slicing software that knows what the user wants and never forgets to move the Z seam.

3.  Have a Single Button-Single Function virtual "Start Print" control.

4.  Provide a printing speed of 1,000,000 mm/sec.

5.  Print any material from chocolate to tungsten.

6.  Be powered by an on-board flux capacitor.

7.  Be absolutely silent.

8.  Be easily up-gradable.

9.  Have a price tag of $19.95 and a 100 year warranty.

10.  Remember birthdays and anniversaries and automatically print a nice gift.

 

It's called the Harry Potter 3d Platinum Pro XL Extended v1 Cabriolet.

It is available for pre-order now.

I hope Ultimaker doesn't take exception to this blatant advertising blurb on their forum.

 

 

Edited August 22, 2020 by GregValiant

[paxpring 4]

On 8/22/2020 at 3:51 PM, GregValiant said:

There is no correct place to put this, but since accuracy and finish are involved I stuck it in this thread.

 

I've started work on my own 3d printer design.  It will:

1a.  Produce 3d Prints with a finish like 12 coats of hand-rubbed lacquer.

1b.  Provide an accuracy of +/- 1 nanometer.

2.  Come with slicing software that knows what the user wants and never forgets to move the Z seam.

3.  Have a Single Button-Single Function virtual "Start Print" control.

4.  Provide a printing speed of 1,000,000 mm/sec.

5.  Print any material from chocolate to tungsten.

6.  Be powered by an on-board flux capacitor.

7.  Be absolutely silent.

8.  Be easily up-gradable.

9.  Have a price tag of $19.95 and a 100 year warranty.

10.  Remember birthdays and anniversaries and automatically print a nice gift.

 

It's called the Harry Potter 3d Platinum Pro XL Extended v1 Cabriolet.

It is available for pre-order now.

I hope Ultimaker doesn't take exception to this blatant advertising blurb on their forum.

 

 

 

Would fund this solid 5/7