3D Printing Problem.

[Gina]

I have a question for 3D printing experts here :-  The escape wheel for my pendulum clock has a serious defect!  In spite of extreme care, the axle hole is not in the centre of the points circle!!  Or indeed of the pinion.  How this has happened I don't know!!!  Has anyone any suggestions or ideas.  The error seems to be nearly a mm!!!  The axle is 3mm.

[Dr_Ju_ju]

Post the STL file & I'll check it out ....

[PeterW]

3D tool free... I always go measure my STL in case I’ve botched my openSCAD.... saves embarrassment.

Peter

[Gina]

10 hours ago, Dr_Ju_ju said:

Post the STL file & I'll check it out ....

Thank you.  EscapeWheelDB.stl

[Dr_Ju_ju]

Dropping the STL into Tinkercad & PrusaSlicer, shows the wheel size to be 141 x 141 mm is that correct ?, and even though the central hole appears central, the sizing, depending on the slicer you're using, can sometimes 'offset' holes... 

[teoria_del_big_bang]

Gina,

The STL looks right to me checking it in 3D-Tool

Above checks the 3mm hole (which is actually 3.4 mm), the inner diameter at R15 and the outer diameter at R57 and the center of those are all in the same place.

Below shows the inner gear at R13,5 and again its center is exactly in same place as above.

And finally the outer diameter of the escape mechanism at R70.5 again shows the center to be in same place as all other dimensions.

Steve

[teoria_del_big_bang]

And a zoom in to show all points are same center

Steve

[teoria_del_big_bang]

What makes you think it is wrong, have you printed it and then can measure the hole is 1 mm out ?

Steve

[Gina]

33 minutes ago, Dr_Ju_ju said:

Dropping the STL into Tinkercad & PrusaSlicer, shows the wheel size to be 141 x 141 mm is that correct ?, and even though the central hole appears central, the sizing, depending on the slicer you're using, can sometimes 'offset' holes... 

Thanks for your reply.  Yes, 141mm is correct.  Didn't know a slicer could offset a hole!  My slicer is Simplify3D.  I wondered if using a larger axle and hence hole would help.

[teoria_del_big_bang]

5 minutes ago, Gina said:

Thanks for your reply.  Yes, 141mm is correct.  Didn't know a slicer could offset a hole!  My slicer is Simplify3D.  I wondered if using a larger axle and hence hole would help.

I can see the slicers may have quite a large possible offset due to the extrusion width but that would not account for 1mm surely.
 

Even then I would of thought something made up from concentric circles should still come out pretty accurate regarding the concentricity, maybe out a bit size wise ??? Wouldn't it ??

Steve

Edited January 26, 2021 by teoria_del_big_bang

[Gina]

4 minutes ago, teoria_del_big_bang said:

What makes you think it is wrong, have you printed it and then can measure the hole is 1 mm out ?

Steve

When the escape wheel is on it axle and spun the teeth are not centred on the axle.  The designed hole size is 3.4mm to allow for the thickness of the extruded filament which is 0.4mm from nozzle of that size.  This makes for a good fit.

[teoria_del_big_bang]

Is there any chance the STL could have gone onto the plate of the slicer at a slight angle that you did not notice, I have had this before, that might cause something like this to happen ?

[Gina]

2 minutes ago, teoria_del_big_bang said:

I can see the slicers may have quite a large possible offset due to the extrusion width but that would not account for 1mm surely.
 

Even then I would of thought something made up from concentric circles should still come out pretty accurate ??? Wouldn't it ??

Steve

I would have thought so.  I should say, I don't usually have this problem.  For this application I need an accurate print.  The teeth need to be the same distance from the centre for the escapement to work properly.

[Dr_Ju_ju]

I'm confused, as I work under the impression that the extrusion thickness is taken into consideration by the slicer, which will adjust the amount of material extruded, to cater appropriately, such that parts end up the correct size etc...

[Gina]

1 minute ago, teoria_del_big_bang said:

Is there any chance the STL could have gone onto the plate of the slicer at a slight angle that you did not notice, I have had this before, that might cause something like this to happen ?

I wouldn't have thought so.

[Gina]

1 minute ago, Dr_Ju_ju said:

I'm confused, as I work under the impression that the extrusion thickness is taken into consideration by the slicer, which will adjust the amount of material extruded, to cater appropriately, such that parts end up the correct size etc...

I would have thought the slicer could have taken the nozzle size and adjusted the dimensions to suit but that is not my experience.  I've had the same with several different slicers.  I could understand that the free ones might not be as clever as a paid for one.  I was recommended S3D and have found it very good with a number of good features and although it automatically alters print speed and extrusion rate to suit the what its printing at the time, as the print proceeds, it doesn't allow for the thickness of the extruded filament.  I have printed with various size nozzles and have found I need to allow half the nozzle size on all faces to get really accurate dimensions.

[teoria_del_big_bang]

I must admit I had not noticed this before and withing say 0.1 mm always seemed to get correct sizes without taking into account the extrusion width so assumed the slicer took care of it, Normally apart from the elephants foot on the first layer the dimensions seem pretty good using PrusaSlicer which is based on Slic3r.

I have just dropped the STL into my slicer and seems fine.

I can try and print one this afternoon if it helps and see what happens ?

Steve

[Gina]

That would be interesting - thank you.  I'm pretty sure it is more likely to be my printer that isn't right though I have checked everything I can think of.

[teoria_del_big_bang]

Okay I can give it a go.

Do you want me to try a specific filament (PLA, PETG) and colour in case it is good I can post it ?

 

[Gina]

White PLA is what I've been using.  Thank you very much.

[Gina]

Just printed a new escape wheel with fresh filament and it has printed fine.  So If you haven't already done it Steve you can leave it.  If you have then I apologise and thank you for your efforts.

[teoria_del_big_bang]

Just started but no worries I am glad it is sorted. 

I made a clock (not my design) a while aut not really got it working correctly, I think too much friction so the weight had to be really heavy.
I might get all the bits back out and have another go now 🙂 

Steve

[Gina]

That's interesting.  Good luck with it if you decide to have another go.  I shall be very interested if you do.