Topics

slight OT Dave Schwartz Freecad Question

Ant No
 

Hi Dave or other Freecad user.

Having successfully printed him an EOS camera adaptor I'm now trying to print a Vixen dovetail clamp for my friend so that he can mount a weight to balance the camera

I have STL files for the two parts. One part is fine but I'd like to modify the other part. Specifically change a couple of slots to holes and perhaps add a hex recess to the end of two long holes so that a nut can be used for the clamping bolts.

If the last bit is too tricky he'll have to get threaded inserts to press in.

Can I do this in Freecad starting with an existing STL file?

There is a different file I could use that's closer to what I want all ready but that would require me to join two copies of it together as one; I want a 100mm clamp not a 50mm.

That might be easier though. On that one I'd have to turn a couple of holes into slots. There are four mounting holes on a 100mm clamp and I want two holes and two slots.

Any advice?

Ant👣

Lloyd Simons
 

You may want to try the windows 3D builder app. It’s much more straightforward to use for simple changes. I think it could handle most of what you need.

Lloyd

daniel vrolijk
 

I would not windows 3D builder as it's pretty bad even for simple stuff. I don't even think you can measure stuff and dimension stuff. I know since I own 5 3d printers and I use fusion. It says its not free but it is. Download the trial and you can extend it to your liking for FREE. Its a great cad package to learn and it's industry standard. The free tier is the same as the paid one but without render credits. If you want to learn some cad I'd suggest Learning fusion 360 as it's much more powerful than windows 3d builder. And it will help you down the road if you learn it. 
Daniel V


On Thu, May 21, 2020, 6:12 PM Lloyd Simons <simonsl23@...> wrote:
You may want to try the windows 3D builder app. It’s much more straightforward to use for simple changes. I think it could handle most of what you need.

Lloyd

Dave Schwartz
 

Theoretically FreeCAD can import an STL file and convert it to a solid object but its not going to reverse engineer it back to the geometry you would have used in building it from scratch. Apparently it splits up (tessellates) the object into many small triangles to approximate the STL mesh. If the object had many planar surfaces, some of those triangles can be quite large and you can then use them as the base for a sketch to modify the object. This is similar to the pleasant surprise I had that FreeCAD can import an SVG file and convert it (roughly) to a sketch that you can build an object with. This is very handy to use some of the Bahtinov mask generators out there which output SVG files which you can then build up into an object to 3D print.

On 2020-05-21 5:14 p.m., Ant No wrote:
Hi Dave or other Freecad user.

Having successfully printed him an EOS camera adaptor I'm now trying to print a Vixen dovetail clamp for my friend so that he can mount a weight to balance the camera

I have STL files for the two parts. One part is fine but I'd like to modify the other part. Specifically change a couple of slots to holes and perhaps add a hex recess to the end of two long holes so that a nut can be used for the clamping bolts.

If the last bit is too tricky he'll have to get threaded inserts to press in.

Can I do this in Freecad starting with an existing STL file?

There is a different file I could use that's closer to what I want all ready but that would require me to join two copies of it together as one; I want a 100mm clamp not a 50mm.

That might be easier though. On that one I'd have to turn a couple of holes into slots. There are four mounting holes on a 100mm clamp and I want two holes and two slots.

Any advice?

Ant👣

daniel vrolijk
 

This is the generator i use for a focusing mask. I love it. I printed it for my esprit. Basically a free focusing mask in a sense. The only thing you need to get is the material which is a lot less than it used to be. 
here is the thingiverse link

Daniel V


On Thu, May 21, 2020 at 7:26 PM Dave Schwartz <Dave.Schwartz@...> wrote:
Theoretically FreeCAD can import an STL file and convert it to a solid
object but its not going to reverse engineer it back to the geometry you
would have used in building it from scratch. Apparently it splits up
(tessellates) the object into many small triangles to approximate the
STL mesh. If the object had many planar surfaces, some of those
triangles can be quite large and you can then use them as the base for a
sketch to modify the object. This is similar to the pleasant surprise I
had that FreeCAD can import an SVG file and convert it (roughly) to a
sketch that you can build an object with. This is very handy to use some
of the Bahtinov mask generators out there which output SVG files which
you can then build up into an object to 3D print.

On 2020-05-21 5:14 p.m., Ant No wrote:
> Hi Dave or other Freecad user.
>
> Having successfully printed him an EOS camera adaptor I'm now trying
> to print a Vixen dovetail clamp for my friend so that he can mount a
> weight to balance the camera
>
> I have STL files for the two parts. One part is fine but I'd like to
> modify the other part. Specifically change a couple of slots to holes
> and perhaps add a hex recess to the end of two long holes so that a
> nut can be used for the clamping bolts.
>
> If the last bit is too tricky he'll have to get threaded inserts to
> press in.
>
> Can I do this in Freecad starting with an existing STL file?
>
> There is a different file I could use that's closer to what I want all
> ready but that would require me to join two copies of it together as
> one; I want a 100mm clamp not a 50mm.
>
> That might be easier though. On that one I'd have to turn a couple of
> holes into slots. There are four mounting holes on a 100mm clamp and I
> want two holes and two slots.
>
> Any advice?
>
> Ant👣
>



Drew 🔭📷🚴‍♂️
 
Edited

I have imported STL files and converted them into solid and/or bodies which FreeCad can alter. FreeCad has a option for simplifying the shapes which removes excess triangles, etc. As Dave pointed out they are very difficult to use and alter. You cannot really take measurements of them. You can approximate a measure by eye but you cannot snap to a vertex and get an exact measurement. Still it can be done.

I have found that Cura slicing software can rescale a STL part. It can change the part by percentage or dimension (in each axis separately if needed). I have found this useful on several parts. Taking a 50mm clamp and rescaling for 100mm is doable this way.

Alexander Varakin
 

If it is vixen dovetail, should be pretty easy to build it in Freecad itself - create a sketch and then pad it. 

John Petterson
 

I would suggest using Tinkercad for something simple like that.  It can easily import several copies of this, then (using square 'holes" cut away parts of some of those and stretch one with a hole into a slot, and then paste them together to make a longer one.  Or simply stretch one to the size you want and then put holes into it.

Others here will laugh about using this, but it works well for me without a big learning curve.

 

John

Ant No
 

Thank you Lloyd but, as has been said, I don't think it will quite do the job.

Ant👣


On 21 May 2020 23:12, "Lloyd Simons" <simonsl23@...> wrote:
You may want to try the windows 3D builder app. It’s much more straightforward to use for simple changes. I think it could handle most of what you need.

Lloyd

Ant No
 

Very good advice Daniel but I fear the learning curve on fusion may be too steep for my friend to get his clamp anytime soon.

I'm aware of it's excellent functionality. John Scherer created an awesome model of his G11 with it.

We have discussed it before and my main reservation apart from the six months of dedicated study it would prolly require is that it is cloud based.
I dislike that both on principle and because I only have mobile data with no hard-line broadband.

Perhaps I shouldn't rule it out but, in addition to the above, Dave's comments later make me think perhaps nothing will do what I naively thought was a simple task.

I assumed the construction geometry was preserved in the STL file and I could modify an existing file with relative ease. Apparently not so much.

Ant👣


On 21 May 2020 23:29, "daniel vrolijk" <danielvrolijk55@...> wrote:
I would not windows 3D builder as it's pretty bad even for simple stuff. I don't even think you can measure stuff and dimension stuff. I know since I own 5 3d printers and I use fusion. It says its not free but it is. Download the trial and you can extend it to your liking for FREE. Its a great cad package to learn and it's industry standard. The free tier is the same as the paid one but without render credits. If you want to learn some cad I'd suggest Learning fusion 360 as it's much more powerful than windows 3d builder. And it will help you down the road if you learn it. 
Daniel V

On Thu, May 21, 2020, 6:12 PM Lloyd Simons <simonsl23@...> wrote:
You may want to try the windows 3D builder app. It’s much more straightforward to use for simple changes. I think it could handle most of what you need.

Lloyd


Ant No
 

Hi Dave

You have to understand my complete ignorance here. I know I used Turbocad a little back in the day but I've forgotten literally everything but the name.

When I import an STL file and select isometric view I can see the object I want to modify.

The lower right menu is on CAD.

Now you mention mesh, I have found that if I click the data tab at the lower left then it tells me I do have a mesh with 1422 points, 4296 edges and 2864 faces. Clearly not how I was thinking.

It seems I need to convert this to a sketch but I don't see how to do that?

Ant👣


On 22 May 2020 00:26, "Dave Schwartz" <Dave.Schwartz@...> wrote:
Theoretically FreeCAD can import an STL file and convert it to a solid object but its not going to reverse engineer it back to the geometry you would have used in building it from scratch. Apparently it splits up (tessellates) the object into many small triangles to approximate the STL mesh. If the object had many planar surfaces, some of those triangles can be quite large and you can then use them as the base for a sketch to modify the object. This is similar to the pleasant surprise I had that FreeCAD can import an SVG file and convert it (roughly) to a sketch that you can build an object with. This is very handy to use some of the Bahtinov mask generators out there which output SVG files which you can then build up into an object to 3D print.

On 2020-05-21 5:14 p.m., Ant No wrote:
Hi Dave or other Freecad user.

Having successfully printed him an EOS camera adaptor I'm now trying to print a Vixen dovetail clamp for my friend so that he can mount a weight to balance the camera

I have STL files for the two parts. One part is fine but I'd like to modify the other part. Specifically change a couple of slots to holes and perhaps add a hex recess to the end of two long holes so that a nut can be used for the clamping bolts.

If the last bit is too tricky he'll have to get threaded inserts to press in.

Can I do this in Freecad starting with an existing STL file?

There is a different file I could use that's closer to what I want all ready but that would require me to join two copies of it together as one; I want a 100mm clamp not a 50mm.

That might be easier though. On that one I'd have to turn a couple of holes into slots. There are four mounting holes on a 100mm clamp and I want two holes and two slots.

Any advice?

Ant👣




Ant No
 

Nice that you made it customisable Daniel. Wish all files were like that.

Since we're sharing, here are my newbie prints. One completed and one aborted due to a design flaw.

https://www.thingiverse.com/make:805841

https://www.thingiverse.com/make:805646

As you can see I resorted to physical tools to correct the completed one. I didn't want to spend the time or the plastic reprinting it.

Ant👣


On 22 May 2020 00:33, "daniel vrolijk" <danielvrolijk55@...> wrote:
This is the generator i use for a focusing mask. I love it. I printed it for my esprit. Basically a free focusing mask in a sense. The only thing you need to get is the material which is a lot less than it used to be. 
here is the thingiverse link

Daniel V

On Thu, May 21, 2020 at 7:26 PM Dave Schwartz <Dave.Schwartz@...> wrote:
Theoretically FreeCAD can import an STL file and convert it to a solid
object but its not going to reverse engineer it back to the geometry you
would have used in building it from scratch. Apparently it splits up
(tessellates) the object into many small triangles to approximate the
STL mesh. If the object had many planar surfaces, some of those
triangles can be quite large and you can then use them as the base for a
sketch to modify the object. This is similar to the pleasant surprise I
had that FreeCAD can import an SVG file and convert it (roughly) to a
sketch that you can build an object with. This is very handy to use some
of the Bahtinov mask generators out there which output SVG files which
you can then build up into an object to 3D print.

On 2020-05-21 5:14 p.m., Ant No wrote:
> Hi Dave or other Freecad user.
>
> Having successfully printed him an EOS camera adaptor I'm now trying
> to print a Vixen dovetail clamp for my friend so that he can mount a
> weight to balance the camera
>
> I have STL files for the two parts. One part is fine but I'd like to
> modify the other part. Specifically change a couple of slots to holes
> and perhaps add a hex recess to the end of two long holes so that a
> nut can be used for the clamping bolts.
>
> If the last bit is too tricky he'll have to get threaded inserts to
> press in.
>
> Can I do this in Freecad starting with an existing STL file?
>
> There is a different file I could use that's closer to what I want all
> ready but that would require me to join two copies of it together as
> one; I want a 100mm clamp not a 50mm.
>
> That might be easier though. On that one I'd have to turn a couple of
> holes into slots. There are four mounting holes on a 100mm clamp and I
> want two holes and two slots.
>
> Any advice?
>
> Ant👣
>




Ant No
 

Hi Drew

Yes, I now realise my expectations of simply customising an existing file quickly and easily are not how things actually work. Mores the pity.

The problem with using cura to elongate the original design is that it would, I assume, stretch circular holes into elliptical ones and change slots into larger rectangles with rounded corners.

Although I won't learn anything new, it may be that I'll just have to print the existing model and look up the best type of insert for him. I have that info store.

He would have liked holes with his slots but no doubt will manage with slots alone. I'm just a bit sad it's not possible to easily modify an existing file. I was quite excited at the thought and was thinking of fixing the faulty design I aborted making. I also wanted to tweak some spring stabilising bed corners for my printer.

I thought it would be easy to start with other designs and customise them. It would certainly be a good thing if it was. Encourage more creation by giving beginners an easy in.

I'm a little less excited now but I guess that will recover soon enough.

Ant👣


On 22 May 2020 00:37, "Drew 🔭📷🚴‍♂️" <drewbolce@...> wrote:
I have imported STL files and converted them into solid and/or bodies which FreeCad can alter. FreeCad has a option for simplifying the shapes which removes excess triangles, etc. As Dave pointed out they are very difficult to use and alter. You cannot really take measurements of them. You can approximate a measure by eyes but you cannot snap to a vertex and get an exact measurement. Still it can be done.

I have found that Cura slicing software can rescale a STL part. It can change the part by percentage or dimension (in each axis separately if needed). I have found this useful on several parts. Taking a 50mm clamp and rescaling for 100mm is doable this way.

Ant No
 

I'm sure you're right Alexander, in theory.

But apart from the reality that "create a sketch and pad it" contains mysteries for me, I have no idea of dimensions and angles involved.

That's why I wanted to start with something that had all that information done right already.

I'm kinda surprised that's so difficult verging on impossible. Seems like an obvious desirable thing to be able to do. I just assumed 3d files would be like that. But it is what it is.

Ant👣


On 22 May 2020 00:51, "Alexander Varakin" <avarakin@...> wrote:
If it is vixen dovetail, should be pretty easy to build it in Freecad itself - create a sketch and then pad it. 

Ant No
 

Hi John

Well, I can only give it a go.

I'm no longer sure it can be done but I guess it's worth a try.

I'll check the program size and see if my data allowance is up to the download. Prolly will be, I'm currently on 50gb a month.

Ant👣


On 22 May 2020 05:16, "John Petterson" <j.petterson@...> wrote:

I would suggest using Tinkercad for something simple like that.  It can easily import several copies of this, then (using square 'holes" cut away parts of some of those and stretch one with a hole into a slot, and then paste them together to make a longer one.  Or simply stretch one to the size you want and then put holes into it.

Others here will laugh about using this, but it works well for me without a big learning curve.

 

John

Drew 🔭📷🚴‍♂️
 

On Fri, May 22, 2020 at 05:23 AM, Ant No wrote:
The problem with using cura to elongate the original design is that it would, I assume, stretch circular holes into elliptical ones and change slots into larger rectangles with rounded corners.
Yes, it is not a perfect solution. I find it useful for creating prototypes. I can check the rough dimensions (in my case now a stepper to mount bracket) in the real world. Allows me to get tight fits, etc.

You have to understand my complete ignorance here. I know I used Turbocad a little back in the day but I've forgotten literally everything but the name.
Yeah, that was great surprise for me. I was a 30 year designer, from drawing board to 2D CAD, all special machinery. Even with all of that background I struggled with (still am) 3D CAD. I wondered what the problem was until I realized that it was like someone pulling you out of sportcar and putting you into a helicopter. The 3D world is different from the 2D and the controls are entirely different. On top of that FreeCad has a multiple approach interface that doesn't mesh perfectly. It also  has some great surprises. Wait until you hit the "topological naming problem".

Dave Schwartz
 

The Wikipedia entry on STL files https://en.wikipedia.org/wiki/STL_(file_format) basically describes the 'T' as a triangle or tessellation language. This is describing only the surface of an object by fitting small triangles all over it and storing only the information on the vertices. Some loss of fidelity occurs, especially on curves. The information about the component objects that went into building it up is lost and there really is no way to get it back. If you use my bracket as an example, you can open the original source file and see all the geometric objects that build it up in the left (model) view and see that the rendered image on the right shows all the edges where they touch (are built upon the faces of previous objects). If you open the STL, as you did, there are no internal component edges and the part appears as just a single solid although its surface description is fairly complex as indicated by the mesh statistics. You can see the loss of fidelity where the surfaces of the holes and posts have become extruded polygons and no matter how many faces to the polygon it still doesn't become the original circle.

I found the learning curve of FreeCAD to fit my way of learning. At this stage of life I'm more of a visual learner and I found that I can more easily build up a part by imagining the geometry of its solid object components. The trick is determining what the first component will be. I've had to abandon a model a few times after I realized I started with the wrong thing as the base and got to a situation where I realized I couldn't continue or it would become too complex to continue and I saw a better way. After you visualize that, adding to (or subtracting from) that becomes a fairly straightforward path. I tried to use OpenSCAD but learning its language, remembering which functions and parameters to use and layering them upon each other to get to that visualized object just didn't fit my brain. No matter the sophistication of the context-sensitive editor, it really didn't help you create the original context from the hundreds of primitives where you had to imagine which to choose and how to nest several others to get the component you already couls see in your head. YMMV.

I'm only scratching the surface of what FreeCAD can do. I've only used simple geometry and extrusions (padding and pocketing). Its probably not really suited to sculpting but it works well for the more mechanical things I need or want to do. For more advanced things, there's probably a YouTube video where someone else will show you how to do what you want to do.

Since FreeCAD is a community project like OnStep, it sometimes has bugs or features that don't work right yet. I've found on more than one occasion that I get so far, go to add a new component and it totally screws up the model in weird ways or unrelated places that its impossible to correct. Usually undo works to get rid of that and try a different way but not always so you save when you are at major breakpoints and you can go back to that version because it keeps previous save points as physical files that you can just rename as the working file and continue on from there in a different way.

I've found that one of FreeCAD's most useful features is the spreadsheet. In it, you can describe all your dimensions and give them symbolic names that you use in dimensioning formulas in the objects you create. If you do that systematically, your model ends up with almost no hardcoded numbers in the objects and, if you make a change in the spreadsheet, your model and everything else based on that parameter instantly adjusts.

With FreeCAD and a 3D printer, I've found that if I can visualize a part that I need (and plastic will do for the material) that I can make so many things that I would otherwise have to scrounge around in hardware stores, modify, bolt/glue/hammer to make. And its a lot faster, more accurate and tweakable too.

On 2020-05-22 4:44 a.m., Ant No wrote:

Hi Dave

You have to understand my complete ignorance here. I know I used Turbocad a little back in the day but I've forgotten literally everything but the name.

When I import an STL file and select isometric view I can see the object I want to modify.

The lower right menu is on CAD.

Now you mention mesh, I have found that if I click the data tab at the lower left then it tells me I do have a mesh with 1422 points, 4296 edges and 2864 faces. Clearly not how I was thinking.

It seems I need to convert this to a sketch but I don't see how to do that?

Ant👣

Drew 🔭📷🚴‍♂️
 

I have found this to be the best method to import an STL into FreeCad.  Just for information.

Conversion mesh to solid

  • Switch to Workbench Part.svg Part Workbench
  • Make sure your mesh object is selected in the tree view, otherwise select it
  • Choose PartPart ShapeFromMesh.svg Create shape from mesh ... from top menu
  • Specify tolerance for sewing shape (0,1 is default)
  • A new object will be created in the tree view (with blue shape icon, instead of green mesh icon)
  • Select the newly created object in the tree view
  • Choose Part Create a copyPart RefineShape.svg Refine shape from the top menu
  • A new object will be created in the tree view and the previous one will be made invisible
  • Select the newly created object in the tree view
  • Choose Part Convert to solid from the top menu
  • A new object will be created in the tree view, bearing "(Solid)" in its name, to indicate it is a solid
The created solid has no history and no editable features (like a simple copy in FreeCAD) you can delete all previous objects from the tree view.

Ant No
 

Yes.

Ant👣


On Fri, May 22, 2020 at 08:32 AM, Dave Schwartz wrote:
I can more easily build up a part by imagining the geometry of its solid object components.

Ant No
 

I understand that now but it seems far from ideal. Designed for solitary/business users with proprietary designs not an open community sharing designs freely.

Having to reinvent and rebuild the wheel ever time an object is remixed seems like a ludicrous waste of time and energy. It can only hinder the evolution of designs.

I can see it's all you need to generate g-code for a printer but why not have some equally standard file format that retains all data and always goes along with the STL on open designs.

Just seems dumb.

Ant👣


On Fri, May 22, 2020 at 08:32 AM, Dave Schwartz wrote:
describes the 'T' as a triangle or tessellation language. This is describing only the surface of an object by fitting small triangles all over it and storing only the information on the vertices. Some loss of fidelity occurs, especially on curves. The information about the component objects that went into building it up is lost and there really is no way to get it back.