Hello,
I printed the part shown in the screenshot, which measures 63 mm in length, upside down.
The 3.2 mm holes did not turn out round, but rather oval.
And the 2 mm overhang did not turn out very clean either.
How could I have prevented this?
Kind regards,
ProApe
You didn’t provide a screenshot of the back rectangular recess.
I suspect lack of support or the wring type is the cause.
The holes not being round are partially due to how FDM printers print. The balance is how or if it utilised support material.
You do not start you print orientation, but I guess it was short edge on the base plate.
A screenshot showing the preview in summary view displaying your model and support would help us, help you.
If you want to optimize holes. I’ll offer this. It only addresses the roun hole portion of your challenge. For the nut, I generally use the X/Y compensation and an x-acto knife to drip errant burrs.
Is this your design? I ask because if it is, then you want to go back in and create a teardrop rather than a proper circle for those holes that will be printed horizontally(hole diameter is in the z-axis).
This will give you a shape where the tear drop will compensate for the droop.
Here is one tutorial where that screenshot was taken from. https://www.youtube.com/watch?v=j6508J94VsA
Here is another tutorial using FreeCad with a teardrop plug in. It’s much more technical but if you want something that is single click, this is how to do it: https://youtu.be/Z8zmoXBMvyA?t=562 Advance to section 3, time index 9:20
Alternatively, I came across another trick very recently that I’ve been itching to try out. You can skip the precise-hole diameter entirely and use thread forming ribs. Ribs are where you provide interior notches for the threads to bite into. Again, the FreeCad tutorial above shows a tutorial for the addin at time index 11:00. It produces this kind of shape. Note: What they have done here is rely upon the self-tapping properties of any thread and use the ribs to create a grab-on area. Like I said, I have been looking to use this in one of my next projects.
This last technique is one I find myself using most often because:
Here is a drill-tap combo search from Amazon. I found these to be perfect for this type of application because it does both the cutting and tapping a thread.
https://www.amazon.com/s?k=Drill+Tap+Bit+Set+metric&i=industrial
One cautionary thing if you haven’t cut plastic before. You must use the lowest possible speed and back off periodically as you drill to give the tool and the plastic time to cool. PLA in particular is very susceptible to melting. You’ll figure it out what works best but practice on some test pieces to get the feel. I use a Dremel at lowest speed possible but for the drill tap, they only fit in a drill so I also use a 1/4" driver handle too. Here’s two example that are perfect. they is still powered but low speed and they allow for one to start the cutting manually at first then use the motor once you have cut into the plastic:
For our pleasure, right?
Hello,
Thank you very much for taking the time to reply!
I work with Onshape and don’t know if there is a plugin for teardrips for Onshape.
The simplest method is probably to either draw the holes a little larger or drill them out.
Kind regards
ProApe
Basically any spot on your model that is going to be printed overhung between 60-90 degrees is likely going to have some gravity applied to it. Tops of holes are habitual offenders, so that teardrop is a well known trick.
If you use supports, the amount of “gravity” that can be in total applied to deform your holes is constrained to the Z gap, and you can use that frame of reference to think about what “tolerances” to add.
This is usually best, especially if you are only making one or two prints. It’s not worth the effort to change hole geometry unless you will be making lots of copies.
Besides problems cause by overhang “droop”, matters are also complicated by creating arcs with flat layers, and rounding errors caused when the hole edges and center do not line up with multiples of layer height.
I’ve seen this recommendation several times to deal with those issues:
(r is the radius of the hole and a is the layer height)
In order to print horizontal holes with a better tolerance, it is recommended to model the additional features in the image where the offset distance a, is the layer height of your print. If you are using a small layer height like 100μm you should do 2*a. This will accommodate for any drooping that will occur in the steep overhang sections of printed horizontal holes and the “flattening” of the bottom of holes due to the stacked layer process.
That can be a bit complicated to create for multiple holes, but a parametric CAD program like Fusion or Onshape simplifies the task. Create the sketch and save for future use as a template, using named parameters for the dimensions and calculations. Then simply changing diameter and layer height will scale the sketch for copy/paste into any design. Conditional parameters will even adjust automatically for small layer heights.
A really interesting method!
This question comes up time and again, and every time your answer is almost identical in the best possible way. It’s always a pleasure to read, and I truly think the admins should pin this for the benefit of future 3D printing enthusiasts.
