Creating sloppy parts to ensure perfect fit - 3D design for 3D printing

To get the best out of 3D printing, it helps if you can design your own parts. In this tutorial series, we will learn to use a free 3D CAD program to do just that.

In this episode, I demonstrate two projects with geometry that needs to be spot on. Rather than design and print over and over until the fit is perfect, I demonstrate purposely creating pas with too much clearance that can be bolted into the perfect place once in position.

0:00 Introduction

0:43 Scenario 1: Tablet holder

4:49 Scenario 2: Electronic door controller

11:06 Conclusion

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[MateFrio]

If you can't have precision you use adjustability.

[marcusone]

Tip: use variables for your "gaps/slop" offsets. That way if isn't quite right, its very easy to change quickly, especially if you have a few spots you have used the same value.

[yru]

Hi, when printing templates you can turn off top/bottom layers and just leave 2-3 layers of "grid" infill around 20-30%. Works very well.

[soggynode]

Something I've found helpful in my designs is a part I printed with several holes that get progressively larger. It looks similar to a drill bit size template. It's printed on the printer I use most often for practical prints with the nozzle and resolution I typically use. I use the printed template to select a hole size in my design based on the screw size and the clearance I need. Since it was printed on the printer with the nozzle and settings I use, I know that's the hole I'm going to get. Not very scientific but it works for me.

[lensman]

3D prinitng is great for prototyping before a design is finalised and the parts are then produced by proper tooling. As a one off project it works great. Right now I am finalising the printing of a 5X7 large format field camera ( not my design ) using my CR10S pro which is working at its limits. Very impressed so far. Its great of you to show how a 3D printer can be made good use of for practical projects rather than just printing useless toys.

[_HighDuke]

Hi Michael, great tips as usual. For the wire/string of the door, I recommend printing and attaching a small spiral spooler to the motor that will ensure the wire spools the same way every time. We use this a lot in building greenhouses.

[aschreiber]

Onshape has a nice Hole tool that will do the counterbore for you using standard sized hardware. It also makes adjustment easier since the last thing you want is to update the diameter but not the counterbore. Also helpful for doing drawings.

I'd also mention you want to be very cautious about print orientation for things like this - you ideally want the part your clamping around to be going along the z axis of your bed when you print (this is a place where a picture is 1000 words...)

[darrennew]

1) Get a metal calipers (like the one in the link), not all-plastic (like the one in the video). The difference in price is well worth the frustration of the 100%-plastic ones being crap.

2) Another way to make it work if you're trying to snug-fit two printed parts that are big enough (say, anything over 15mm diameter) is to make one of them as much as a couple mm smaller, then use teflon tape around it to get a nice friction fit.

[UndCon]

Great as usual!

I add "slop" or margins due to shrinking, Especially on DIY solutions which are the best and gives most satisfaction reward.

Recently I was printing a 1 meter long tube to make a lamp in my office. the shapes was trial and error for a telescopic fit without slop and the parts are printed in vase-mode.

A great RGB-LED strip powered by WLED and an NodeMCU. DIy projects at the finest.

Now a tablet holder for my motorcycle and ADV-buttons for navigation. Makers do what makers do.

[saillife]

Another great installment in the best 3d printing design tutorial series on the 'net! Thank you for putting out this excellent content. You are a great teacher.

[daarshg]

This is a great series and an excellent episode for an amateur, hobby designer like me where I make functional stuff for personal use.

[sddfg]

You see box with adjustable motor mount. I see future home for bees.
As a noob to both 3d printing and design in general I'm really unsure of how tolerances are handled. Thanks for the tips!

[MarcelRobitaille]

9:30 in onshape, you can make slots like that just by drawing a line then clicking it with the slot tool. The slot tool is hidden under outline by default.

[ClokworkGremlin]

Item #1 came out looking very nice and professional. The astute observer will note that the drumhead mounts of the set were actually designed the same way, with an open gap that uses a bolt to close it up and provide tension to keep the part in place.

[MCsCreations]

Fantastic, Michael! Thanks a bunch for all the tips! 😃
And as a Brazilian, thanks for the t-shirt!
Stay safe there with your family! 🖖😊

[louis-ericsimard]

As always great content very well taught. Aside: you'd get much easier designs (and a stronger bolt catch) by using square bolts. The longer moment in the shape allows the plastic to resist torsion better.

[gizmobowen]

88 was the first year I started watching F1. Ya, I know it's kind of late, but I'm in the US and F1 was a foreign sport. Fell in love with the McLaren team and the 15 out of 16 season of Prost and Senna. Your shirt brought back good memories. Don't think McLaren will have that kind of season this year, but hope Oscar does well.

[zenw]

I would love to see you print a gear assembly to increase the lifting force of your motor.

[reverse_engineered]

These are all excellent recommendations! This simple clamp can be very strong even with little pressure on the bolts. The surface area and roughness of the clamp is what allows a little bit of pressure to give a lot of holding force. It's sufficient to even make powerful CNC mills, like the MPCNC. One thing to watch for is not to tighten the bolts very much. It only takes enough to provide friction between the clamp and the tubing. The clamping forces are concentrated where the bolt is, so over tightening will break the clamp there. Tighten it just enough that you get a snug fit of the clamp on the tube. If you can see the ends of the clamp flexing, you're going too far.

Slots and oversized holes with washers are also a universally good trick. It can be difficult to keep things square this way, but it gives a lot of freedom for adapting to imperfect dimensions. Look closely at manufactured parts and you'll see these kinds of approaches used all over the place, especially on cheaper parts. Precision is expensive; we can avoid it with flexibility.

[reverse_engineered]

One suggestion for your door lifter. Instead of precisely mounting the box, you could precisely mount an idler pulley. It would be much easier to align the pulley than the entire box. Being off a bit between the box and pulley won't cause binding nearly as much as being off at the door.

You might also want to make the door less susceptible to binding by giving it some smoother slides. Some V wheels on bearings would hold the door panel nicely, similar to how it is used on cheaper CNC machines.

Of course, both of these suggestions are extra complications, but they may be less complicated than trying to get perfect alignment or using brute force to overcome friction.