How to MAKE it
This week I decided to make a mold that consists of two two half-shelfs and a core. Becasue I wanted to make something useable, I decided to make a hight-adjustable feet to compensate position tolerances of a table. The core should be a M10x30mm bolt.
For the 3D design of the mold I used Fusion 360 (for the very first time). We did some tests beforehand and it turned out that Fusion 360 harmonizes niceley with our Modela MDX-40.
Design the mold
- Create a rectangle 165x80 and extrude by 37mm
- Create center help-line
- Create parallel line with distance of 80mm to the border
- Mirror the line along the middle help-line
- Create new construction pane (-15mm in top-view)
- On the construction pane create a circle with its center in the middle of each half-shell. You can use the mirror funtion to mittor the circle on the construction line in the center of the block.
- Extrude (and cut) the circle to create a pocket.
- proceed in a similar way with the two pockets (to position the half of the bolt on each side afterwards: circle, mirror, extrude (cut).
- Then, I realized a mistake. Becasue I wantet to have two 'splints' to lock both shells in position, I needed one shell having 'locating pins' and the other shell to provide corresponding holes. Thus, I had to strip material from one half shells surface in order to have the 'locating pins' jut out.
- Thats why I made the one half shell 5mm thinner (create sketch on surface; draw rectangle on surface; extrude -5mm (cut). And draw the two pockets again.
- To create the 'locating pins' and 'locating holes', I created a new sketch on each half-shells surface, created circles (5mm diameter for the pins and 5,2mm diameter for the holes). It is important that the center positions of the cirkcles are mirrored. The problem here is, that the half-shells surfaces are on different levels of height. You cant simply mirror them. Best is to draw the 5mm circles first, then mirror them. Create a new sketch and project them onto it. Then mirror it again to have them on the other shells surface at the same (but mirrored) position. Create an offset of 0,2mm for the 'locating holes'. Extrude booth, the pins and holes - of course in different directions. Holes need to be a little bit deeper than the pins.
- When you have
- You want to create a 'draft angle' from all vertical vertical faces to make it easier to remove the casted object at the end. A vertical face might make it impossible to remove an object from the mold.
- Chose: Modify > Draft and select neutreal plane (here: top surface, blue coloured) and then select faces that need to be angled, which are the 'top and bottom face of the cylinders'.
- You can then click on Inspect > Draft Analysis and verify whether all vertical surfaces fulfil your requirements.
Now, you are ready for CAM-processing.
- Start choosing the CAM processor.
- Click on Setup: New Setup. You then have to first set the orign. Here, I used Z axis/plane and X axis.
- Position the Box-Point onto a corner of your object.
- Hint: If you have a block of material with smooth and soft surface, then you may not want to flaten the surface through milling. You then can set Stock Top Offset (same with Sides) to 0.
- click on 3D > Adaptive Clearing
- From the ADAPTIVE panel, first select the tool you want to use.
- You may need to create a new one, as shown below.
- In the ADAPTIVE panel you have various options to choose manipulate, if needed.
- On the PASSES sub-panel set the Maximum Roughing Stepdown to half of the tools diameter.
- After all parameter have been set, you can use ACTIONS > Simulate to get a simulation of the toolpath.
- It the simulation looks as expected, you can start the post-process.
- Press ACTIONS > Post Process
- OF course, the proper post-processor of your milling machine is required. We use the 'GENERIC ROLAND RML'
- Hint: Currently, no machine-control interface for MAC. Thats why we use the cloud-invitation feature of Fusion 360 to share the file and open it on one of our PCs, connected to the Roland.
- Save the G-Code to a folder on your PC.
- Use V-Panel (machine-control-software) and set X,Y and Z zero position of your tool.
Milling, Molding and Casting
- Immediateley after you have pressed CUT and loaded the file, the machine starts the milling process.
- For reasons of security, I made a test-cut using soft foam. As soon as I knew the allignments, tool paths and tool settings were correct, I started the real process.
- While the machine was milling I did a test with the resin. We used Pur Polyurethan [ISOCYANATE and POLYOL (UR 3440) at the rate of 1:2]
. Here is the Datasheet.
- It tooks quite a while to do the Adaptive Clearing path milling. Afterwards I did another run using 3D > Pocket Clearing
- Because of some constraints caused by the tools diameter (and security settings), the 'locating holes' were not milled. Also, the chamfers were missing.
- I used DRILLING to create 6mm holes, using the ball-endmill.
- Because the holes still have been to small, I used the 3D > BORE feature. Therefore I changed the tool to a 3mm endmill and let the machine bore the 6.2mm holes.
- Because of the problems described above, I had to make the chamfers manually for which I used a deburring tool.
- Finally, I used a blade to smooth the surface of both half-shells.
I used demoulant/release spray to coat the molds surfaces.
To fix the two halfs I used clamps.
I mixed the Pur Polyurethan [ISOCYANATE and POLYOL (UR 3440) at the rate of 1:2] (40g and 20g) and put it into the vacuum chamber.
- I created a funnel that fit into the spure and pour in the mixed bubble-free resin.
- I put the filled mold in the vacuum chamber and started vacuuming, again.
Then I was waiting ...
Final Result
Next morning I detached the clamps and opened the mold. Al went fine and the hight-adjustable feet was done.
As expected (hoped) there were no bubbles included. The surface is smooth and there are just very thin ridges.
Climbing Holds
Together with my kids, I wanted to make climbing holds/handles for a climbing wall. I had to make postive forms to create negative forms with them. I did not want to make half-shells because of the complexity. I decided that it is easier and cheaper to just use the foam (which of of course will be destroyed becasuse of its shape. They will be scraped out later).
To create the positive forms, we used OASIS FLORAL FOAM, because it is easy to cut, even with a blunt blade. I also used a Forstner drill to provide space for bolts to attach the handle afterwards.
To create the negative form, I used gypsum because it is cheap and easy to handle.
So far, we have created a bunch of positive forms and few negative ones. Next, we will use quartz-powder-filled epoxy resin to make the handles.
Another project - related to casting - is vacuum forming. Here you can see just one example in which I did a mold as a sandwich of milled MDF sheets, which were glued, filled with (bondo) body filler and sand-papered.
Downloads
The file (made in Fusion 360) can be accessed below. For editing please use the PW: FabAcademy
Donwload STEP file