Resize a STL File For Me

[MarkF]

I forgot to tell you that you will get a better finish
on the top of the knob if you use a smaller layer height.

For me, working layer heights are 0.08mm to 0.28mm in 0.04mm steps.
The 0.04mm height is so the stepper motor doesn't have to do partial steps.
With even steps, all the layers will have the exact same height.

I saw a video a long time ago on how to calculate what the even step height is
give a particular stepper motor and lead screw pitch.  Can't find it anymore.

[bostonman]

I assumed playing with layer heights would need to be done. The initial print was to get an idea of what I was working with.

The layer height was decreased, but forgot what I tried. Either way, it’s a great knob and don’t mind tweaking things a few times to get it correct.

The only suggestion I thought of was mankind it more hollow to save filament, however, I may try printing in TPU (whatever the gasket type filament is that I have) to get the rubber affect the original has so too hollow and it may be too soft. At the moment I just have clear, so maybe I’ll invest in grey if it proves to be a good alternative.

[MarkF]

Found it!  Had it bookmarked all along.
Here is that video on layer height and exact motor steps:

 


Also, here is a video showing how I calibrated my three axis and the extruder:

 

[bostonman]

MarkF,

You've been following the TPU jamming issue thread and wanted to update this thread.

I printed the knob (forgot the settings I used for the G Code) after fixing the TPU jamming issue and the knob looks great.

The diameter is perfect on both the face and base, and the height is perfect.

You've provided information on how to tweak the design, so I'll go back and read them because the design needs some changes, and I'll tinker with it when I get some time.

All that I need to do is:

It has 11 flutes and the original is 12 (you provided directions on how to add/subtract flutes).

The flutes could be deeper as they are not as pronounced (could just be the limitations of my printer and the resolution)

The face lacks the dip (I tried a better resolution setting and the dip doesn't seem to be visible). I'm uncertain if the dip isn't being exported correctly into the STEP file or the printer just is lacking the resolution.

The hole for the shaft needs to be larger

From what I see, printing with TPU (I forgot which infill setting I use) is perfect. The knob is solid with a nice slight rubber feel. I expected it to be soft, but it's perfect.

If I perfect the knob size, I'll probably plan to purchase grey TPU filament so it matches the rest of the knobs.

[MarkF]

Good job.

As for the dip, I seem to remember the top just has a flat spot.
You should be able to change the knob profile to add a dip.
It would be changed in the sketch being revolved to get overall shape.

The flute deep is a real compromise as it tends to break the model.

I'll take another look if you can't get it fixed.

[MarkF]

I couldn't resist having a play with the knob while watching the news this morning.

I fixed the number of detents to 12 and over exaggerated their depth and width.
The problem with them is probably due to TPU being so soft. 
They wouldn't look good if printed in PLA.

I also added an arc depression on the top of the knob instead of being flat.

I didn't adjust the D-slot hole.  You know best how much to change it.

[bostonman]

Thanks, I'll download this soon and try printing it.

The original knob doesn't have very deep flutes (or detents?), but, I think due to the better resolution design, they are more defined in appearance. The knob doesn't have to be identical, just needs to look decent and fit, so I'm not trying to make it perfect.

Keeping in mind I didn't tinker with any fine tuning when I printed this latest knob (I used the previous GCODE but don't remember the settings - I think 0.12 resolution), the face was rough.

I attempted to sand it, but sensed it wouldn't sand well since it's more like rubber, and seems I was correct.

Any methods I can use to smoothen the face when I get a print I'm satisfied with?

[MarkF]

You will still have to tinker with the shaft hole.  Version 5 of the knob is the same size as version 4.

As for smoothness, you can go to fine layer height (the smallest I ever print is 0.08mm) or you can try the 'variable layer height' option.

What slicer are you using.  I wrote a program to parse a gcode file and extract the most relevant setting used.  It is mainly for the PrusaSlicer since they append almost every possible setting to the end of the gcode.  It also parses gcode from Cura.  But, it is hit or miss because they only append a few settings (totally unpredictable what they include).

Screenshot:
 


** UPDATED 'G-CODE VIEWER' TO INCLUDE ADDITIONAL OPTIONS PARSED FROM 'SLIC3R' G-CODE **

[bostonman]

I use Slicr3r (see attached screen shot).

It's one I downloaded upon first getting my 3D printer and grown (somewhat) acquainted with it.

Maybe my Anet A8 is more capable of printing a smooth face, but I haven't had much luck with the finer details of a print, so my opinion has been: that's the best my printer can do.

Certainly I plan to tweak the settings, and maybe that's all it needs, but the last knob (printed in PLA) had all the settings tweaked and still needed some fine sanding.

[MarkF]

I have tried Slic3r before.
Just looking at it again, I see on the tab for 'Printer Settings' -> 'Extruder 1' there is a Min and Max layer height.
The default that comes up for me is Min = 0.15mm and Max = 0.3mm.
Change the Min = 0.08mm  (or 0.04mm for an extreme case).

Also on the 'Print Settings' -> 'Layers and perimeters', you can try the 'Use adaptive slicing' option.
(You could temporarily change the Min=0.04mm and Max=0.2mm from before just for the knob print.)

Overall, you will never get a perfectly smooth surface.  Not sure of any technique for smoothing TPU.

[bostonman]

Overall, you will never get a perfectly smooth surface.  Not sure of any technique for smoothing TPU.

I agree on never getting it perfect, and, for a $300 printer, I don't expect perfection.

As for smoothening the surface, the only idea I had for TPU was maybe forming a metal cup, laying the knob in it, and heating with a heat gun. Most likely it needs better control and will just distort more than just the surface.

[MarkF]

Added additional parsing for Slic3r g-code output.

See above:  https://www.eevblog.com/forum/3d-printing/resize-a-stl-file-for-me/msg5605071/#msg5605071

[bostonman]

Using FreeCAD v21, I figured out a few things such as how to tinker with the D shaft hole, but I can't figure out how to increase the dip on the face.

Not sure why FreeCAD isn't clicking with me.

[MarkF]

The knob port to FreeCAD 0.21 is pretty messy.
I re-made it in the spirit of version 0.21 (attached).
Also attached is an annotated screenshot of the FreeCAD tree.

Generally, there are three sketches to define the knob:
  1) The overall knob blank (Sketch) which defines a vertical profile: height, width, depth, top dimple and outer edge
  2) The hole for the D-shaft (Sketch002)
  3) A flute vertical profile (Sketch003) which is pedded and then 12 instances via polar array

The top dimple/dip is defined by an arc in (Sketch) for the knob blank

[MarkF]

... but I can't figure out how to increase the dip on the face.

This is how the basic knob is created with Sketch then Revolution:
Just decrease the height of the line along the z-axis (you're changing the arc endpoint, not its radius).



If you mean the flute depth, that's done by positioning Sketch003 and its V-shape angles:
In Sketch003, the distance from the origin to the profile point is specified.
  Sketch003 -> Pad -> Fillet -> Array -> Cut

[MarkF]

Hours of FreeCAD 0.20 Tutorials demonstrating advanced drawing techniques for those interested.

  https://www.youtube.com/playlist?list=PLWuyJLVUNtc0UszswD0oD5q4VeWTrK7JC

(At the time of this posting, the tutorials are based on the previous FreeCAD version.  Newest version is 0.21.2)

'Mangojelly Solutions' has several other playlists of FreeCAD. 
IMHO his tutorials are some of the best I've found.

[bostonman]

Does a way exist in G code to change the layer height on a specific layer range?

The knob prints fine with 0.3mm layer height and looks good, but the face is sloppy. The dip on the face isn't noticeable (I'm going to tinker with the depth in FreeCAD) and the face isn't smooth.

Printing the whole thing in 0.12mm causes the printer to jam - I've already discussed this issue in another thread and know/understand the reasons - but don't have much time to fiddle with the printer. I'd like to print the whole knob at regular layer height and then when it prints the face, start a short layer height.

[Ian.M]

G-code isn't that high level.  What gets sent to the printer is just a bunch of sequential XYZ moves at a specified speed and extrusion rate (including zero and negative for retracts) + some other stuff for temperature and machine control.

Changing the layer height, infill density or other slicer parameter is a slicer function.  Some slicer software can slice different regions differently or even dynamically vary the parameters layer by layer, others cant.

[bostonman]

Interesting.

I assumed the layer height was part of "speed" and amount the G-code tells the Z axis to move. Guess G-code doesn't play as much of a role as I thought.

I had one successful print with 0.13mm layer height, but even with that, the face wasn't close to smooth.

It seems more that the TPU gets dragged around a bit before it cools due to it being elastic type, so trying to get finer details on the knob face is harder.

[MarkF]

G-Code just tells the printer how to move.
The real work is done in the slicer software.

I use PrusaSlicer (and I'm sure Cura also) has variable layer height.  You would need to see if your slicer has that capability and how to configure it.  If so, I would print the lower part at 0.20mm and the top at 0.08mm.  If not, just print the whole knob at 0.08mm and find a good book to read   

If you haven't already, cut your print speed way down.  At least 25% to 50% of you PLA print speed.

FYI.  The G-Code is just a text file.  Open it in a text editor and explore.
        Reference:  https://marlinfw.org/meta/gcode/

[bostonman]

Still uncertain I understand the difference between "groove" and "revolution".

Long story short, I wanted a 3/8" acorn nut cap (i.e. no threads). Last night I tinkered with making one using revolution (groove is still confusing to me).

I made a horizontal line, up a bit, over a bit, and down to the same horizontal line. This made the "wall" of the nut". One vertical line on the Z axis, and joined the vertical lines with a three-point arc (one arc for the outside and one arc to make the inner wall). After I performed a revolution and it was what I visualized.

I'm uncertain what a "groove" can do that revolution can't.

[MarkF]

Where do you come up with these oddball layer heights?

I think I mentioned this before...  I recommend you use a multiple of 0.04mm layer heights because of the pitch of your lead screw and they do not require a fractional turn of the stepper (which it can't do). 
(ie.  0.08mm, 0.12mm, 0.16mm, 0.20mm, 0.24mm or 0.28mm.  IMHO: layer heights outside of these are too small or large for a 0.4mm nozzle).

[themadhippy]

difference between "groove" and "revolution".

just a guess but  could it be grove cuts out  the shape around an axis whilst revolution builds

[MarkF]

Still uncertain I understand the difference between "groove" and "revolution".

If you're asking about the two different tools, the 'revolution' is an additive action while the 'groove' is a subtraction action.

There is a 'Fasteners' tool bench for making bolt and nut threads.  Can't remember if it's one of the workbench you need to add or if it's there by default.  Goto Tools > Addon Manager to install it.  Another interesting workbench is the 'Assembly 4' which allows you to attach bodies together into movable parts to see the animation.

[MarkF]

There are always multiple ways to skin-a-cat.
You can make a body with a revolution of the shape you want to remove and then use it as a cutting body to remove it from a second body.