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Tolerance test

by whitemousegary, published

Tolerance test by whitemousegary Nov 8, 2012
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Summary

A simple test for testing whether your 3D printer can print parts to fit.

2013-05-07: I have my TOM well calibrated already. Pair#0 always fits now. See http://www.thingiverse.com/thing:52946 .

Instructions

2013-05-07: I have my TOM well calibrated already. Pair#0 always fits now. See http://www.thingiverse.com/thing:52946 .

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My Makerbot is having problem to print parts to fit. I'm wondering whether I am the only one having such problem. So, I designed a simple test to test it.

In this page, there is a .stl file test.stl. test.stl has six pairs of plug and slot. The pairs are labeled with number 0 to 5 with decreasing tolerance. Pair#0 is the ideal case where its plug and its slot are edge to edge touching each other. If you printed Pair#0 and its a tight fit, your 3D printer is perfectly calibrated. With respect to the ideal case, Pair#1 has a plug radius 0.05mm smaller and a slot radius 0.05mm bigger, Pair#2~0.10mm, Pair#3~0.15mm, etc...

Please do me a favour. Print test.stl and reply to this page which pair is the first tight fit. The calibration of my Makerbot is probably way off, the first tight fit is Pair#2.

Thanks a lot.

PS: the six pairs for testing are also available individually, i.e. test00.stl to test05.stl. If you want to save some material, you may want to use them instead. All pairs are drew with Google Sketchup, and the source file is test.skp.

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Printed #5 and #2. First one's ok but the second doesn't fit. Not sure about the exact diameters but the #5 plug is 7.18 - 7.33 mm, the hole is 7.53 - 7.63 mm. .The #2 plug is 7.44 - 7.58 mm, the hole is 7.22 - 7.27 mm. All pieces have an outer diameter between 14.84 and 14.96 mm. Can't really say if it's the inner or outer (or both) diameters being off. Could you please post the exact measurements from where the offsets originate, please?

The diff on the plug/hole diameters are due to the little bump where extrusion starts on the outer/innermost perimeter.

The diff on the plug/hole diameters are due to the little bump where extrusion starts on the outer/innermost perimeter.

"the little bump" should not be tolerated with a properly calibrated 3D printer with a properly designed extruder.

In most cases, "the little bump" is there because you have a lousy extruder (e.g. the extruder designs with emphasis "minimalistic")

Ok, so which extruder/hot end combo do you recommend? I'm currently running a Wade/J-head 0.5 mm setup with 3 mm PLA. I've been looking at both the E3Dv6 and the Prometheus v2 but can't decide if it's worth the $. Epecially with the tons of negative comments I've seen about the E3Dv6.

Could the bump be due to too warm hot end? Not that I think I'm way off. Printing at 190/185 degrees.

^^", maybe I'm not specific enough. When I said "a lousy extruder", I'm referring to the driver block. The hotend is unlikely to have problem if the design have a PTFE tube inside (e.g. a J-head).

Thanks for your replies! Could be. This is what I've got: http://v2.pxl.se/i/l2.jpg . The hole for feeding the filament to the hotend is a tight fit. Apart from that I don't know. Been trying to get the right amount of tension on the idler (had it too tight before). Can't say if the J-head I've got has a PTFE tube or not. It's about two years old and I don't know if the design has changed since.

Sep 22, 2015 - Modified Sep 22, 2015
whitemousegary - in reply to HSBallina

This is what I've got: http://v2.pxl.se/i/l2.jpg .

An ad-hoc design like this is extremely error prone to the mechanical precision of parts, while the printed gears are almost certainly couldn't offer an acceptable mechanical precision. These kind of ad-hoc designs are just intended for "ad-hoc" usages. If quality is important, ad-hoc no more please.

For instances, if you want a gear box, you should buy a gear box or a stepper motor with gear box; the mount on the stepper motor for pushing filaments towards the driver gear should be mechanically sound; the driver gear must be in good quality, which cost you just a few bucks on the market. ... ...

Yayaya, print quality comes with parts precision requirements, which translates to prices. The rumors, that said ad-hoc driver blocks are fine, are just one-big-scam (or... some remote goals that haven't been achieved).

Can't say if the J-head I've got has a PTFE tube or not

If it's a J-head (or a modified J-head), it's almost certainly have a PTFE tube inside. Let's put it in another way. If you can print with PLA for more than 30 minutes without blockages, the hotend MUST have a PTFE tube inside. ^^

Sep 16, 2015 - Modified Sep 16, 2015
whitemousegary - in reply to HSBallina

"Pair#0 is the ideal case where its plug and its slot are edge to edge touching each other. ... With respect to the ideal case, Pair#1 has a plug radius 0.05mm smaller and a slot radius 0.05mm bigger, Pair#2~0.10mm, Pair#3~0.15mm, etc..."

For Pair#0, the diameter of the plug is 7.5mm, and the diameter of the hole is also 7.5mm.

For Pair#1, the diameter of the plug is 7.4mm, and the diameter of the hole is 7.6mm.

For Pair#2, ... 7.3mm, and ... 7.7mm.

For Pair#3, ... 7.2mm, and ... 7.8mm.

For Pair#4, ... 7.1mm, and ... 7.9mm.

For Pair#5, ... 7.0mm, and ... 8.0mm.

Can't really say if it's the inner or outer (or both) diameters being off.

Both are off (of course). It's just simply doesn't make sense to separate the inner and outer diameters to do calibration.

the exact diameters but the #5 plug is 7.18 - 7.33 mm, the hole is 7.53 - 7.63 mm. .The #2 plug is 7.44 - 7.58 mm, the hole is 7.22 - 7.27 mm.

The calibration of your 3D printer is simply way off. With a properly calibrated 3D printer, Pair#0 should always fit.
In the instruction, I left a notice.... "2013-05-07: I have my TOM well calibrated already. Pair#0 always fits now. See http://www.thingiverse.com/thing:52946 ."

Calibrate your 3D printer to print parts to fit

Thank you for the measurements. And a great guide. Though I'm slicing with Slic3r so I'm not well versed in the Skeinforge lingo.

Machine: Replicator 2X
Printed on Standard Resolution (infill 10% and layer/bead height .2mm)
All models printed (0-5) were printed and every one fit together, except for #0. #1 fit tight enough that I only got about 15 degrees of play when I put the pieces together and turned them in opposite directions from one another. #2 gave me about 35-40 degrees of play when I turned them in opposite directions from one another. All of the others were loose enough that, while they go together, they do not effectively "hold together".
Hopefully this information is helpful.

... All models printed (0-5) were printed and every one fit together, except for #0. ...

If your 3D printer is well calibrated, Pair#0 should always fits (it's a discussion ended long long time ago). There is no reason to settle for less. See http://www.thingiverse.com/thing:52946 for detail.

Calibrate your 3D printer to print parts to fit

Agreed in that my printer probably should be able to print #0 and the pieces should be able to fit. However, again, your instructions asked people to submit results for your records, so I did. Essentially, I had to start somewhere in order to figure out where my printer stands on the issue of tolerance, which is why I found this print of your so useful.

these files wont slice in slic3r 9.9 for some reason but 9.8 does after repairing in netfabb

I'm having #1 fit really nice with my Rep2. #0 is just not going to fit. #2 is a bit loose. Thanks for the files, a great idea!

Mar 22, 2013 - Modified Dec 18, 2014
whitemousegary - in reply to Altimus

I have solved my tolerance problem . Check this out http://www.thingiverse.com/thing:52946 . REP2 should be doing a better than TOM. You are wasting the potential of your machine.

Calibrate your 3D printer to print parts to fit

My makerbot replicator also the first pair that is a tight fit is #2

 Mmm... interesting, thanks.

Great Idea, I did somthing similar for my own use.  The real problem is that when you scale parts, the tolerances change in the model, but not in real life.  So after scaling, parts that were perfect before become too tight or too loose.   If you have a 3D program that utilizes constraints then the tolerances wont change, but you still have to re-export it to a new STL. 

Another great design aid is to print different wall thickness,  even one that tapers to nothing,  that way you can see how your printer manages different walls thickness.   at some point it will fail to print, and if you add a printed scale to it, you can see exactly at what thickness.

Actually,  I have done something a bit aggressive.  I modified the Skeinforge inset plugin to add an extra inset.  In this way, tolerances stay the same even after scaling.

By the way, infill density will also affect tolerances.  For instance, printing 100% infill will make the object bigger by 0.05mm, which is subtle for appearance by devastating for tolerances.

Anyway, I really want to know how the other 3D printers doing.  Can you print it and tell me about the first pair that fit?

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