Adventures with a Flashforge

[SimonWood]

I printed out some of the Loco Remote track. I am hugely impressed with the design for this - especially the turnout. I can see that if I'm not careful, I will be printing myself a micro layout before I know it...! (In fact I've already dusted off a plan I made when I was playing with RailModeller Express...)

IMG_8447.jpg (13.13 KiB) Viewed 4242 times

However, as with the Lego, the bits that are supposed to clip together, don't... It's not really a problem with the track, as a bit of filing will resolve the issue. But from a diagnostic perspective, I'm starting to think there's a pattern here, that somehow the default print settings are making things slightly larger/thicker than designed...

[FWLR]

Looking through Thingiverse, I can't find people to view. I put people in the search and I have got loads of gamers and other stuff....

[philipy]

But from a diagnostic perspective, I'm starting to think t,here's a pattern here, that somehow the default print settings are making things slightly larger/thicker than designed...

Can't speak for your m/c or custom software, but normally they reckon that prints are around 5% undersized from the drawing and certainly I find that. Printing a 4mm hole, for example, normally needs to be drawn at about 4.25mm diam.
On that basis, since your software is apparently customised to your m/c I guess its possible that somehow they have allowed for the shrinkage by default?

[SimonWood]

Looking through Thingiverse, I can't find people to view. I put people in the search and I have got loads of gamers and other stuff....

I haven't found many people, aside from my War Doctor, which is why MakeHuman is so appealing!

Can't speak for your m/c or custom software, but normally they reckon that prints are around 5% undersized from the drawing and certainly I find that. Printing a 4mm hole, for example, normally needs to be drawn at about 4.25mm diam.
On that basis, since your software is apparently customised to your m/c I guess its possible that somehow they have allowed for the shrinkage by default?

If it was a uniform shrinkage or enlargement, wouldn't the Lego blocks still work with each other even if not with real Lego? And wouldn't my track clip together - the studs being enlarged (or shrunk) by the same amount as the holes for them...? The gauge of the track seems to be spot-on too...

[philipy]

I don't think it is uniform actually, for a start I think it shrinks differently along the grain than across it, and I suspect it will also depend on the printing temps and layer heights as well. Plus, in a wider sense I suspect it will also depend on the source of the filament.

[SimonWood]

I don't think it is uniform actually, for a start I think it shrinks differently along the grain than across it, and I suspect it will also depend on the printing temps and layer heights as well. Plus, in a wider sense I suspect it will also depend on the source of the filament.

If it's not uniform, that makes compensating rather complicated!

[Trevor Thompson]

Wow - this is something I have not played with.

I know that when I print holes they come out undersize - but I cant tell you by how much.

Everything I draw is made to a known scale I actually measure everything in Sketchup. As in add dimensions (its because I was an engineer). So I can measure printouts against designed dimensions.

In fact I might design a box of known size print it and measure it. I will let you know the result!

Trevor

[Trevor Thompson]

PS

That driver does come out well doesn't it - as you point out the fingers are unbelievable.

I wonder how it will come out from a resin printer?

Trevor

[Trevor Thompson]

Some information on shrinkage.

I have just measured the victorian milk churn in sketchup - and the 9 of them I have printed.

Height in the software 45mm. In reality between 45.56 and 45.67mm.

diameter in the software 27.95mm - in the printed versions fairly consistently 26.14mm in on direction and 26.26mm in the other.

So the model is about 10% too high, about 93.5% of the width it should be and 93.4% deep.

So suggesting 5% shrinkage in the plane of the bed is about right.

trevor

[SimonWood]

So suggesting 5% shrinkage in the plane of the bed is about right.

This is certainly tolerable for most things - I certainly wouldn't have noticed it if I hadn't printed things designed to slot together. But now I am wondering why if two parts designed to fit together are 5% smaller than they shouldn't be, why they still don't fit together? It takes me a few seconds with a file to enlarge the holes on each piece of the track so that sections fit together. They don't "clip" as they should, but since I plan to fix them down as part of a micro layout, that's not a problem... really this is not a big issue at all...

But a little part of me wants to spend far more time than that "fixing" the problem, either by messing with the STL files to compensate the drawing, or to fiddle with the slicer settings to find out why holes come out too small... And because I know these pieces have been designed to be printed - and other people have printed them successfully - it seems to me that the issue must be one with the slicer/printer, albeit not just with a particular one as we know from this thread that people with different machines have experienced it. But, at least as far as FlashPrint goes, I cannot see any setting that would obviously be connected with the print encroaching on a hole... except maybe for "Shells" and even then I assume that these are all printed within the boundaries of any given solid...?

[SimonWood]

I wonder how it will come out from a resin printer?

I look forward to finding out when you try it!

[philipy]

But a little part of me wants to spend far more time than that "fixing" the problem, either by messing with the STL files to compensate the drawing, or to fiddle with the slicer settings to find out why holes come out too small..

I don't know anything about your Flashprint, but I'm not at all sure that a slicer can do the sort of editing that you need, to fiddle with adjusting things like Lego studs and holes. Certainly Cura can flip, multiply, move, etc and the scale function allows scaling by different amounts in the three planes, but I doubt that adjusting one small element of an stl file is possible. I think you need to go back to a CAD file to do that. I know it is possible to import stl's into Sketchup but don't know if Tinkercad can accept them.

[ge_rik]

......I know it is possible to import stl's into Sketchup but don't know if Tinkercad can accept them.

You can import .STL, .OBJ and .SVG files into TinkerCAD

Rik

[SimonWood]

I don't know anything about your Flashprint, but I'm not at all sure that a slicer can do the sort of editing that you need, to fiddle with adjusting things like Lego studs and holes. Certainly Cura can flip, multiply, move, etc and the scale function allows scaling by different amounts in the three planes, but I doubt that adjusting one small element of an stl file is possible. I think you need to go back to a CAD file to do that. I know it is possible to import stl's into Sketchup but don't know if Tinkercad can accept them.

I have already augmented an STL file in TinkerCAD - adding to a Lego block. (This is one reason making Lego appeals to me - the ability to create new pieces, or converters - a bit like this Duplo to Brio adapter.)

I can definitely scale in FlashPrint, and duplicate and (I think) mirror. Maybe scaling differently in the 3 planes will resolve it? But I'm hoping there's some universal setting I can find... I've discovered "elephants footing" this morning, and read up on solutions, but on examining the prints I'm doubtful that's the problem. Think I need to keep looking...

[Trevor Thompson]

Simon

The Flashforge slicing software will allow all of the general manipulations like scaling, duplicating and so on. But you will have to go into the CAD package to adjust specific parts such as the pip size.

I have been looking more carefully at shrinkage and I think it is a lot less than I said last night - I think I got my math wrong. More on that in the place I posted it last night.

Trevor

[Trevor Thompson]

Some information on shrinkage.

I have just measured the victorian milk churn in sketchup - and the 9 of them I have printed.

Height in the software 45mm. In reality between 45.56 and 45.67mm.

diameter in the software 27.95mm - in the printed versions fairly consistently 26.14mm in on direction and 26.26mm in the other.

So the model is about 10% too high, about 93.5% of the width it should be and 93.4% deep.

So suggesting 5% shrinkage in the plane of the bed is about right.

trevor

I have thought about this again.

I did the maths in a hurry and made stupid errors.
The error in the height of the milkchurn - 0.5mm out in 45 mm - so 1mm out in 90 mm - that is something near 1.5% not 5%.
the error in the diameter 0.8mm out in 28mm - so 2.4mm out in 86mm - that is in the order of 3%. I have to admit that measuring the diameter accurately was difficult.

I have measured the first part of the Goods shed - a section of the side of the building, That should be 139.95 x 105.57 but when printed is 139.45 x 105.66mm. So on the long side (across the printer) it is 0.5mm too short - in 140mm - so even in my head I can see that is about 0.3%. The short side (front to back on the printer) it is 0.09mm too long in about 100mm so that is about 1% too long. So the error in this component is negligible.

I have also measured the Ashbury Coach. The drawing says it should be 151.97mm long over the body, it is actually 150.71 long. It should be 73.5mm wide over the body, and it is actually 74.13mm. So that is 0.75mm too wide in 74mm so about 1%. I also measured the wheel diameter - should be 24mm diameter and is 23.86mm - that is about 0.6mm too small. That is about 2.4%.

So as a conclusion I am convinced that in practical terms when just creating a scale model the dimensions of components are mostly within 1% of the design size. There is a bigger error on tall objects - it is probably around 1.5%

I wonder what the manufacturing tolerance on a Lego brick is!

Trevor

[FWLR]

That is very interesting to know Trevor thank you. Shrinkage is not worth bothering about is it, when there are such small differences in the finished part.
But then I guess the rivet counters would still find something to say don't you think....

[ge_rik]

I've been pondering about the discussion about shrinkage etc. Doesn't it depend on how your printer has been calibrated?

There are so many variables at play between drawing and printing - but at the end of the day, isn't what comes out on the printbed dependent on how each printer has been set-up? I'd imagine that, for example, over time, the belts controlling the position of the print head will stretch. I've already had to tighten them on my newer printer. And on my old printer, those who cloned its design from the original on which it's based, replaced the fancy screw threaded rods for the Z axis with ordinary (cheaper) M8 threaded rod and so must have recalibrated the software to compensate.

I found this about calibration. I've not tried it out yet, but it looks interesting
https://all3dp.com/2/how-to-calibrate-a ... explained/

Rik

[FWLR]

I have tried to open the site Rik, but it wants me to allow adds. So I did but it still wants me to allow adds again. I have allowed the site on my ad-blocker so it should allow them for that site....

Anyway my thinking is, with screw threads they are more likely to keep calibration than belts. When I was setting CNC machines, the old belted one's had to be calibrated on a regular basis and the screwed ones not that much, although they too had to be calibrated also. Don't these machines have a calibration program that will do it automatically, especially if they are screw threaded ones.

[SimonWood]

So as a conclusion I am convinced that in practical terms when just creating a scale model the dimensions of components are mostly within 1% of the design size. There is a bigger error on tall objects - it is probably around 1.5%

I wonder what the manufacturing tolerance on a Lego brick is!

Whilst I guess Lego bricks have to be precise enough to clip together reliably 99.9% of the time, the tolerances there are fine for our kind of work, I think!

That is very interesting to know Trevor thank you. Shrinkage is not worth bothering about is it, when there are such small differences in the finished part.
But then I guess the rivet counters would still find something to say don't you think....

It's not so much the modelling (and rivet counting) that interested me but the functional aspects - e.g. my prints of the Loco Remote track not clipping together as designed. It's not so much a problem in the sense of being an issue for my purposes as being a puzzle...

I've been pondering about the discussion about shrinkage etc. Doesn't it depend on how your printer has been calibrated?

I'm sure it does - and the page you link to looks fascinating, but I must confess it's going to take me some time to get my head around it, as all I've done it hoik this machine out of its box and plug it in. Really all I'm doing right now is exploring where I seem to be bumping up against its limitations - but these are a long way from affecting what I really want to do with it... the same curiosity will, I'm sure, lead me to explore the calibration more fully. In particular, I wonder if providing the filament diameter (and fiddling with the temperature settings) might make the pips fit the holes...

In the meantime, on the Lego wagon I used tabs. There I noticed that for a tab drawn at 64mm I needed a slot drawn at 64.8mm for it to fit into. Tab and slot were both drawn and printed in the same plane...