Alignment pins

[Anonymous]

I am trying to make alignment pins for a stl that I have to cut up.  I understand the steps to do this but I have problems when adding the simple object to either add the pin or make the hole.  When I add the simple object (square or cylinder) that object is never parallel to the main object I am adding it to.  So I then have to play around moving the simple object till I think it is parallel to the main object.  Is there a setting or step that will make the simple object that I add parallel to the main object

[hfcandrew]

There are some tools, but they are largely variable:

Select All>Align to target

You will probably have better luck just doing it by hand with Transform, eyeball it using the grid. Can you give a screenshot of your object?

[jerry9254]

This provides no steps.  Would you please provide specific directions for those without the experience you possess?  Otherwise you're not adding any value to the webpage.  Thank you.

[fred_dot_u]

You can check out an 18 minute video that provides guidelines for making alignment pins.

[jerry9254]

That video, and many other like it, plainly show dragging a primitive over to a freshly-cut plane, and the primitive is perpendicular to that plane.  I'm tried multiple cut models and in each case the primitive is not perpendicular.  The significance of requiring my pins to be perpendicular to the cut plane is that my model has four parallel bodies that are all cut along the same plane (imagine cutting a model of a table along a plane splitting the bottom of the table top and the tops of the four legs).  In order for four alignment pins to work in joining the two halves of the model, all the alignment pins must be parallel.  If alignment pins are arbitrarily at odd angles, then the pins won't function.  If correcting the orientation of the pins is left to "free hand" (vice a set command(s)), then the pins will likely not function.  Do you have a procedure for aligning pins to be perpendicular to the cut-plane?  

[fred_dot_u]

That's a curious inconsistency. Moments ago, I imported the bunny, selected both ears, then did Edit, Plane cut and chopped the model into three pieces. Because it was a single plane, anything placed on one cut surface will be perpendicular and match the other.

Dragging in a rectangular prism and placing it on the cut surface automatically creates the "pin" to be perpendicular to that plane.

There may be some setting or other anomaly that prevents your dragged in primitive to be properly normal to the surface. As an additional test, I created the cone of a suitable size (large) and added a rectangular prism in contact to the surface. It dragged in and became normal to the surface. While rotating the placement on the surface, the orientation also became properly normal.

Perhaps you are not dragging the primitive into place?

[jerry9254]

I followed your example with the bunny and the cone and had the same results.  I then opened a standard calibration cube, performed a plane cut, separated the halves, dragged over a cube primitive, and placed it on the cut-plane of the bottom half of the cube.  The primitive is not perpendicular to the cut plane (screenshot attached).  Clearly the software doesn't work consistently, which is why I'm looking for assistance.  

[fred_dot_u]

It appears that you've narrowed down the trouble to a non-aligned drag and drop. Do you have the ability to capture motion to a short video?

Observing the dragging movement and the placement indicator for the primitive might be helpful.

[jerry9254]

At the moment I cannot capture video. Not due to lack of capability but because the software has crashed. Restarting the PC has not re-enabled it to start. Uninstalling and reinstalling the software as not enabled it to start.

Moving past this ridiculous development for the moment, you commented about a non-aligned drag and drop. Could you explain that? From where I sit I performed the same process to put the primitive on the bunny and the cone as I did the calibration cube. Please explain what you meant.

[fred_dot_u]

I hope I understand the overall problem properly. My understanding is that you can accomplish your pins/holes objective if the pin is normal to the surface (perpendicular) and that when you make this attempt, it is not. Additionally, it appears that you're able to create a separate set of models in which you are able to get the pins in place perpendicular to the surface. If any aspect of this is incorrect, please correct me.

I've created a number of models from primitives, then created a plane cut on which to place a pin primitive. In all of these models, the pins are perpendicular. I am unable to create a circumstance in which the pin primitive is not perpendicular.

Can you share the model as an upload, perhaps one version without the plane cuts, and another upload with the cuts in place?

I'm hopeful you will be able to solve the problem with the software. In the past, I have had to use a registry cleaner to purge remnants of problematic programs, as well as a deep search for folders hiding in system locations otherwise not easily located.

[jerry9254]

I can open existing models (i.e., bunny and cone), slice them, drag a primitive on to the cut-surface, and the 'pins' are perpendicular to the cut-plane.

When I drag in other models (e.g., calibration cube), slice them, drag a primitive on to the cut-surface, and the 'pins' are not perpendicular to the cut-plane.

I've enclosed the calibration cube STL file that I captured in screenshot.  The model is uncut.

I've enclosed the model in which I'm attempting to install pins.  When I last accessed it before Meshmixer crashed the model was cut and I had four spheres in place (I was hoping sphere geometry would remove the need for pin orientation). 

[jerry9254]

Meshmixer operability restored.  Same issue with pin alignment persists.  Attaching video demonstrating what I'm experiencing.

[fred_dot_u]

Things have fallen apart! Your cube exhibits on my computer the same problem presented in the video. When I import a different calibration cube from my files, the same non-perpendicular circumstances arise. When I import yet another fairly different calibration cube, the same thing happens.

When I drag a cube primitive to the workspace, then delete the calibration cube, the normal placement works again.

It's not necessary to perform a plane cut in order to exhibit this anomaly.

This would indicate that there's some aspect to the calibration cube that throws the normals into disarray. I've loaded the cube into another program, saved it in ASCII STL format and the results are still askew.

Using OpenSCAD, I created another cube, same skewed primitive. A sphere behaves properly, a cone not so good.

I think you've discovered a bug, but I also expect that nothing is likely to be done regarding this problem. The program has been static from a development standpoint for many months/years.

[jerry9254]

I am incredibly grateful for the diligent communication and troubleshooting that you showed today in trying to help me out. Regardless of the results, I want to thank you for your assistance. Enjoy!

[fred_dot_u]

Perhaps a work-around can be accomplished. Create your plane cut on the desired model, but also create a plane cut on a reference model aligned with the objective model. Drag a primitive to the cut reference model, which should end up perpendicular, but be sure to make the setting for new object. This will enable you to use Transform to move it to the objective model, retaining the orientation to the face.

[Anonymous]

MESHMIX d&d parts orients the part's direction along the face's vertex normals weighting the nearest .

Your calibration cube is lowest density. > Means: Plancut gives lowest lowest density too...

This means surface normals show this pattern to align the part:

ANALYSIS>MeshQuery>SurfaceNormal

Means: If you d&d a part onto the cut surface's faces it will be not perpencicular. No bug at all, just an issue of low poly meshes.

You might give this a try:

Select the cut surface's face group and Edit/Extrude at zero Offset. This doubles vertices at the cut's border with correct normals

and MESHMIX will work as expected by you: