# Parametric Dimensioning

Hi,

I’ve just been introduced to the wonderful world of Parametric Dimensions on a course for Fusion 360 and think this would be a fantastic addition to the LB armoury. It would be extremely useful for;

scaling up designs eg small, medium, large versions,
using different thicknesses of material eg using 5mm not 3mm acrylic and
where dimensions have to set in stone eg Braille dot spacing.

What is PD? Basically, you can give lengths and other dimensions names. You can then define other related dimensions using these names as variables. Here’s an example;

I want to cut a box in three sizes. Normally, I’d have to calculate the dimensions manually but with PD I just define the base sizes and then add a Scale Factor. Say the LxWxH of the smallest box is 100x150x200mm. I define the following Parameters (aka variables) as;

BasicLength=100mm
BasicWidth=150mm
BasicHeight=200mm

I can then add scaling variables;

ScaleFactor=1.0

And then I create the Parameters used to generate actual shapes;

ActualLength=BasicLength * ScaleFactor
ActualWidth=BasicWidth * ScaleFactor
ActualHeight=BasicHeight * ScaleFactor

On the model, I can then draw a base using these variables not the numbers.

To vary the size and shape of the drawing, I simply edit the ScaleFactor to 2.0 for medium box and 4.0 for a large one. PD then automatically recalculates all the dimensions and re-scales the drawing.

Another example would be cutting a box joint. The tongue and grooves of a box joint are all dependent on the depth of the wood you are making the box from. If the wood is 10mm then all the joints are based on that to make the joints perfect.

Also, say you have a design in 3mm perspex and want to redo it in 5mm. All the joints, slots, holes etc need recalculating. With PD, you just change the relevant parameter and hey presto!

You can also add in tolerance factors for different materials eg perspex versus wood to achieve a tight fit.

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what happens when you export the design to an SVG or other vector format, do all the lengths just become fixed at the current value?

LightBurn is primarily a laser control software package. As nice as a feature that may be for some people, in my opinion, I thinkl that the development time is best spent adding more controllers and things like dual tube support. You can always just use fusion to do what you wanted then export the dxf into LB.

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Yes. As far my tests go. Have only done it to DXF so far but imports into LB precisely how I want it.

I’m not saying it is absolutely the top priority but should be on the list. If people tried it, they’d realise quickly how valuable it can be everyday that you have dialled-in dimensions that you can’t accidentally change.

I’ve used this in CAD packages like SolidWorks and Fusion. Let me just say that there’s a reason those packages cost thousands of dollars. This is very hard to do, and would need to be built into the system from the base up - it would touch nearly every editing operation you could use.

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I’ve been using Onshape (3D CAD to laser cut panels from acrylic or wood that are used to make finger joint enclosures and once you get the basic idea set up with parametric dimensions it is almost trivial to modify the design. A user-created feature in the design lets me create the finger joints and automatically adjust the tabs and slots for kerf and the material thickness. Once the 3D design is completed each panel is exported as a DXF file for cutting with Lightburn. Here’s one example in 1/8" acrylic.

I’m definitely a fan of PD. I’ll take a proper look at OnShape when I get chance. I like the fact that it has a free educational plan - should be ideal for small scale and hobbyist work.

I am hoping that F360 and the likes of OnShape will also help me save wastage as some of the more complex pieces friends ask me for are hard to get right first time. Up until now it has been trial and error but PD and 3D rendering should allow me to get it right first cut and save my pennies.

I realise something like PD will not be added anytime soon but when the wonderful tech team do a re-write some time in the future I hope they will include it. Helps make everything more precise and flexible.

Why do you want parametric dimensions added to LB? Why not simply create your designs in software suited to the task and use LB for what was made to do, controlling the laser?

I am hoping, over time, that LB will be the only package I need. I also find the interfaces in other packages, especially 3D ones, very confusing. I love the straightforward nature of LB’s look and feel. I don’t want or need to learn much more complicated tools.

All the design features currently added or being added (eg geometric shapes) are presumably with this aim in mind. I hated using other machines in makerspaces where I had to design in one package, transfer it across, hope the import was successful and accurate and then faff around using a laser control package. It was clunky and timewasteing. LB’s Swiss Army Knife approach is far more enjoyable to use. I sit and design and then immediately output.

No other readily available and affordable software allows you to design and make in one package.

Being able to repurpose a design for a different thickness of material just by changing one variable would be extremely powerful.

Just an idea - Keep LightBurn primarily a laser control software, like Anthony said.

Users that already have CAD packages will use LightBurn only for Laser control - cleaner UI as well.
Users that want something - one stop shop - can buy the whole package.

There are already so many good CAD programs, LB has excellent import capabilities already, so if you want to use a full feature CAD program that is an option that works well. I would rather see LB development focused on the CAM side.

I would prioritize path optimization and control. Would also like to see some right click menus added so many of the deep features in LB could be more easily exposed (and used)

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There are undoubtedly a lot of good CAD packages out there but for Laser work you only need a tiny fraction of the facilities. It’s also a huge learning curve if you have no background in CAD or 3D. Already gone through that pain with various Adobe packages. LB offers a simpler and more laser-relevant package.

You could also argue for dumping the design facilities and rastering as there are so many good progs like Illustrators, CorelDraw etc out there already.

The authors are combining the best of the design and laser control worlds. I’d just like to see (one day) some of the 3D design facilities that are useful. PD is relevant to both 2D and 3D design and rework.

If you look at the interface of LB and all the new facilities added over the last six months, it has gone far beyond a control package firmly into design. Originally I had to use Illustrator for design work and LB for output.

I rarely use Illustrator now. LB has so much good design stuff in there now.

Very true, the existing design features in LB are extremely useful. But I look at them as just a way to edit an existing design once I am ready to make it and notice an issue. I also use the design tools to customize an existing design to add Text and align graphical elements. I don’t ever do complete design work in LB mostly because I am already familiar with other packages (Vcarve, Aspire and Fusion 360)

So I understand your point, but for me I would rather the developers focus on the parts of LB that are vital for the toolpath creation and user interface. Since I rely 100% on LB for those functions and have other tools that already work great for the design side.

Maybe once all the CAM functions are implemented, the devs can start adding more CAD features.

– Edit –
After saying all that I did just think of one CAD feature that would be really useful in LB. The ability to create an outline around an object (Vector or Bitmap), with variable offset. Many times I import my design or image and need to just quickly cut it out of a piece of material. So a Boundary Vector tools would be a “Nice to Have”

Isn’t the boundary tool already implemented? Sure it is for vectors.

I think it is the Offset Shape tool on the sidebar.

Jump to about 9:50 in this video to see a clever use for the offset tool (and to see it in action):

So is there a methodology or is it software that add in to Fusion 360?

Not really sure what you mean but PD is a fundamental part of 3D design and CAM packages.

PD allows users to ensure that dimensions are maintained no matter they appear on a design and any changes are automatically replicated throughout a design.

I use Sketchup and I think the equivalent is called dynamic components. Only on the paid version. I was looking for way to employ it myself in my simple designs so that things would fit when the materials are different.