Tap or inserts for 3D printed material

[CraigT82]

On a 3D printed focuser base (newt), for the holes to mount the focuser to the base, would it be better to drill/tap the four M5 holes? Or would it be better to use threaded inserts? 
 

Base material is PLA.
 

cheers

[qisback]

If 3d printed it’s always better to plan the holes rather than drilling.

During the print it will layer a 100% infill wall around the area which is almost always solid rather than infilled. You can then put brass threaded inserts secured with a small dab of glue/plastic weld, this means the force from tightening the screw will be spread through the brass threaded insert through the 3d printed part.
If you secured directly by drilling and tapping the 3d part, the hole is would almost certainly be drilled through an infilled area (normally 15-25% infill unless changed) which is almost impossible to tap, you would need to design the holes into the print to be smaller than you needed so a wall is printed and thus is able to be tapped, however the force would be applied directly to the PLA which is soft (also changes with temperature) and is easier to strip.

 

[CraigT82]

Thanks for that very useful info.

So if I design the holes into the drawing of the part, would the slicer software add the infill wall around the hole?  Or would I need to design that hole wall into the initial model?

If I planned the holes for tapping, how much smaller does the designed hole need to be?  Say for a M5 tap would the initial hole want to be 3mm? 4mm?

Cheers 

[Chriske]

1 hour ago, qisback said:

If 3d printed it’s always better to plan the holes rather than drilling.

During the print it will layer a 100% infill wall around the area which is almost always solid rather than infilled. You can then put brass threaded inserts secured with a small dab of glue/plastic weld, this means the force from tightening the screw will be spread through the brass threaded insert through the 3d printed part.
If you secured directly by drilling and tapping the 3d part, the hole is would almost certainly be drilled through an infilled area (normally 15-25% infill unless changed) which is almost impossible to tap, you would need to design the holes into the print to be smaller than you needed so a wall is printed and thus is able to be tapped, however the force would be applied directly to the PLA which is soft (also changes with temperature) and is easier to strip.

 

+1

I'll add : if the parts does not come apart I'll always tap in the PLA itself. Drawing a hole in advance, so the position of the holes are perfectly in line. The upper part is always drilled a bit bigger, so no tapping in that part at all, Only the lower part needs tapping.
If the parts do come apart very often for some reason you absolutely need to apply inserts...!!

[Chriske]

3 minutes ago, CraigT82 said:

Thanks for that very useful info.

So if I design the holes into the drawing of the part, would the slicer software add the infill wall around the hole?  Or would I need to design that hole wall into the initial model?

If I planned the holes for tapping, how much smaller does the designed hole need to be?  Say for a M5 tap would the initial hole want to be 3mm? 4mm?

Cheers 

[CraigT82]

Just now, Chriske said:

Thanks, are these dimensions specific to PLA?

[Chriske]

So for a thread M5 you need to draw a 4.2mm hole. After a part is printed I always clean these holes with the correct drill..

[Chriske]

1 minute ago, CraigT82 said:

Thanks, are these dimensions specific to PLA?

For any filament type...
The figures in that list are for any material as a matter of fact, even (any)metal.

[Chriske]

One more important issue about tapping in printed parts... GO S*L*O*W... very slow...!
It is a soft material indeed and you might think tapping fast just because it is very soft.
Well, the problem is that the material will not release by itself from the tap, while your tapping in printed parts. The trick, like tapping in metal, turning the tap once in a while counterclock a little bit does not work in printed parts at all.
Blind holes (depending on how deep you need to go) are done in 4 'sessions'. Tap a few mm and remove the tap completely, clean the tap and continue tapping. Removing is also done very slow...!
Tapping a hole were you can see the tap at the other side sticking out(thinner parts)tap in one session, first remove the material sticking to the tap and then remove the tap, again very slowly.

Needles to say tapping in printed parts takes time...

If you tap in one go without cleaning the tap, the rubble will destroy the thread completely.

[Alien 13]

I do like my metal  inserts especially if the thread has to be used multiple times like in a camera adapter etc. I have on occasions printed my own plastic inserts with 100% fill that can be push fit or screwed/bonded using superglue into the main part which might only have an infill of 40%.

I have used this type of insert on quite a few projects.

Thing to make sure of though is that any force applied is in the direction away from the head end so that the insert is being pulled into the part not out of it.

Alan

Edited July 12, 2022 by Alien 13

[DaveL59]

16 minutes ago, Chriske said:

One more important issue about tapping in printed parts... GO S*L*O*W... very slow...!
It is a soft material indeed and you might think tapping fast just because it is very soft.
Well, the problem is that the material will not release by itself from the tap, while your tapping in printed parts. The trick, like tapping in metal, turning the tap once in a while counterclock a little bit does not work in printed parts at all.
Blind holes (depending on how deep you need to go) are done in 4 'sessions'. Tap a few mm and remove the tap completely, clean the tap and continue tapping. Removing is also done very slow...!
Tapping a hole were you can see the tap at the other side sticking out(thinner parts)tap in one session, first remove the material sticking to the tap and then remove the tap, again very slowly.

Needles to say tapping in printed parts takes time...

If you tap in one go without cleaning the tap, the rubble will destroy the thread completely.

I'd agree, much the same with any plastic material as it can deform as much as cut. Also make sure the tap is clean and sharp if you want to create a good thread. A well used tap that has been used in metals will have dulled a little, still usable but in plastic might not perform too well.

What sort of screws are you planning to use in the threads? I've used nylon when I've tapped threads into acrylic tube which worked fine but they weren't really carrying any load.

Edited July 12, 2022 by DaveL59

[CraigT82]

Ok I'm probably going to redesign the part slightly to allow me to use a nut and washer on the back face.  I can avoid any kind of tapping or inserts then.  Don't know why I didn't think of that first actually.

Thanks for the input everyone! 

Edited July 12, 2022 by CraigT82

[Chriske]

These inserts Alan posted higher up, I use them all the time.
They're intended to be used in wooden constructions but they work just perfect for printed projects too.
Ours here look a bit different.
Anyway, I heat them a bit for easier insertion in printed projects.

[adyj1]

12 hours ago, CraigT82 said:

Ok I'm probably going to redesign the part slightly to allow me to use a nut and washer on the back face.  I can avoid any kind of tapping or inserts then.  Don't know why I didn't think of that first actually.

A trick I have used is to print the internal areas that surround bolt holes at 100% infill (whilst still printing the rest of the print that doesn't come under stress at 20% infill). I know then that when I'm tightening up a bolt the plastic all around that area is solid and won't fail through overtightening...   

You use Cura's 'Support Blocker' to create a cubic area of the print, then 'Modify Setttings for Overlaps' to customise the infill of that area. I've added a picture but it isn't necessarily that easy to work out what's going on, so here's the Filament Friday video that I got the tip from - https://youtu.be/su_m5zV9rvA?t=129 (in this one he's strengthening a loophole, but you get the picture).

HTH

Ady

 

 

[Chriske]

Prusa slicer can do the same thing if I'm  not mistaken.

[Len1257]

For none critical parts I just tap into a predefined hole. For mechanical structures I embed nuts into the material. Easy to use the Cura Infil Mesh tool to reinforce the area. Just have to create some basic support structures. Tried heating the nuts in but not a fan, results variable to say the least! 

[CraigT82]

Have put in some 'turrets' on the back side of the top plate to capture nuts.  The focuser will mount to the top.

Not sure if the 6 tabs to mount the base to the tube will be strong enough, they're only 2mm thick

 

[Chriske]

Made a quick drawing showing 4 different ways to work with nuts and bolts in printed parts.
The one on the right is a hole big enough to add a insert Alan showed higher up.There are some special insert for printed parts. But they're not as good imo.

Edited July 13, 2022 by Chriske

[Alien 13]

50 minutes ago, Chriske said:

Made a quick drawing showing 4 different ways to work with nuts and bolts in printed parts.
The one on the right is a hole big enough to add a insert Alan showed higher up.There are some special insert for printed parts. But they're not as good imo.

The "wood" type inserts are  far superior in my view provided you get the hole dimensions correct (easily done with a test print), another useful re-purposed item are the extruder gears that can be push fit/glued into the plastic and make excellent rod couplings for knobs or other parts..i.e. these.

Alan

 

Edited July 13, 2022 by Alien 13

[CraigT82]

Yeah I do have a pack of those brass wood inserts which I could use, however I don't have the luxury of test printing (don't have a printer - going to get it done on Craftcloud) so hole size needs to be right first time.  I think simplest for this piece is to use nut & bolt with the nut captive.

[AstroKeith]

7 hours ago, CraigT82 said:

Have put in some 'turrets' on the back side of the top plate to capture nuts.  The focuser will mount to the top.

Not sure if the 6 tabs to mount the base to the tube will be strong enough, they're only 2mm thick

 

Those 2mm tabs will not be strong enough. Expensive when they break too!

Try and move the 6 screws into the main body.

[CraigT82]

Just to close of this thread, I redesigned the base and removed the 6 tabs, I will use small metal angle brackets to attach the base to the scope - brackets will attach to base with bolts/nuts and I'll decide placement once the base is offered up to the scope.

Have ordered the base on craft cloud to be printed in ABS with 40% infill.  Cost was £13.

Cheers

[kbrown]

I like using V-Coil thread inserts.  So far I've been using all sizes between M2 to M10 and they always just work. For for example M3 thread I would simply model a 3mm hole which typically ends up printed a bit smaller. I'd print it with at least 3 perimeters. Then just use the drill bit and tap in the V-Coil kit to get the hole prepared for the insert.

Edited July 27, 2022 by kbrown

[CraigT82]

Base arrive today, perhaps a little flimsy with 2mm wall thickness but I’ll give it a whirl and see how I get on. At £13 for the print I’m not too fussed if I have to draw and order a stronger mk2 version.

[EarthLife]

Why not buy yourself a printer ?

It's very nice having the freedom to print your own parts whenever you like, although 3D printing can (and does) come with much frustration and despair at times