Intro

After building a 3018 CNC machine, I needed clamps that fit with the slotted bed of those machines. The size and number of clamps needed may differ from job to job, so I decided to make a parametric model in FreeCAD which allows you to adjust dimensions (length - width - … ) easily. The clamp is asymetric, so you can use it with the bolt close to your stock for more force, or the other way, with further reach. Also, the free height in the Z-axis is rather limited, so I replaced the included butterfly nut with a wheel.

Customization

In case you want to create some variants : in FreeCAD, go to the worksheet ‘par’ (parameters) and adjust. Make your changes in small steps and check the resulting models.

Strength

FreeCAD allows you to do strength simulations with its Finite Elements Model (FEM) tools. I did a quick analysis of the design, and the biggest stress is shown in the image. So if you want to make your clamp stronger, you can either increase width, or increase the number of perimeter layers. Top/bottom layers do not really contribute to the strength, so you could even leave them at zero and create a fancy honeycomb look-through clamp.

Printing Instructions

All these parts print perfectly without support, but you need to orient them correctly on the print bed :

• part 2 and 3 : large face flat on the bed
• clamp : on its side

Note : part 3 has 1 (0.2mm) layer between the two pockets, which you can easily break out by inserting the bolt. This layer allows printing witouth support.

Happy printing and milling !