Making a Wax Mould on the Modela

= Making a Wax Mould on the Modela =

Purpose
I wanted to learn how to design a wax mould and program the Modela milling machine to cut the mould so I decide to make a 3D mould saying “Eddie Fablab”

Software Used
Google Sketchup 7 3D modelling Solidworks 2005 3D modelling Modela Player 4 milling machine program

Process
Firstly I tried using Sketchup 7 to design my mould above but found it very difficult to create the 1mm radius around the tops of the letters so I changed to Solidworks 2005 as I am more familiar with the software. The main difficulty with using Solidworks was that I had to create the letters from lines and arcs rather than just typing in letters so this took some time. However the radius was easy to add by just selecting all of the top surfaces and selecting the radius tool.

I saved my file as an .STL file by selecting this from the drop down menu in the ‘Save as’ window.

I then opened the STL file in Modela Player 4.

Select ‘Modelling wax’ material from menu at top right Click on ‘model’ icon Click on ‘New process’ icon •	Roughing o	Cutting surface = top o	Drill = 3mm square o	Cutting area = partial 	Cutting area •	Drag the red box to the required size (I deliberately kept this area quite small so my job wouldn’t take too long) 	Depth •	Start depth = 0 •	End height : Drag the red line to the required cutting depth (Again, I didn’t want to go very deep so as to keep the milling job short) o	Tool path type = Contour lines 	Down cut o	Cutting parameters = default o	Create tool path ‘right now’ o	OK Click on ‘New process’ icon again •	Finishing o	Cutting surface = top o	Drill = 3mm square o	Cutting area = partial 	Cutting area •	Lower left o	X = copy from roughing process o	Y = copy from roughing process •	Upper left o	X = copy from roughing process o	Y = copy from roughing process 	Depth •	Start depth = 0 •	End height = copy from roughing process o	Tool path type = Contour lines 	Down cut o	Cutting parameters = default o	Create tool path ‘right now’ o	OK
 * Select correct top surface button so that letters are readable
 * click OK
 * Click on ‘Modelling form’ icon
 * Margins = automatic
 * Depth = move red line to just below bottom of design
 * Slope = make sloped, top = 10
 * Click ‘OK’

I wanted to rough my mould only first so I could see the results so selecting the ‘Finishing1’ process and clicked on the ‘cutting/no cutting’  icon. This greys out the icon next to the ‘Finishing1’ process.

Modela set-up •	Find or cut a piece of modelling wax of sufficient size •	Make sure the bed of the Modela is at the front. If not press the ‘View’ button to move it there.

						 X •	Hold down both ‘up’ and ‘down’ buttons simultaneously to clear the machine buffer. The green light next to the buttons will flash for a short while and then remain constant. The buffer is now cleared. This is very important or you may find the machine may start cutting a previous job. •	Tape the back of your wax with 2-sided sticky tape and stick the wax to the Modela bed, squaring it on the bed grid. •	Find the correct sized tool and loosen the small Allen key fitting and carefully remove the current tool. Place the correct tool in the holder and re-tighten with Allen key.

•	Ensure that the tip of the tool is higher than the top of the piece of wax, if not move the tool upwards by keeping the ‘Up’ button pressed. •	Press the ‘View’ button to move the bed to the back of the Modela •	Go to model in Modela Player 4 •	Click on ‘Set’ from the top menu o	Select ‘Cutting position’ from the drop-down menu 	Estimate or measure the X and Y distance from the tool tip to the corner of the wax material 	Enter these distances into the tool movement co-ordinates 	Click ‘Move’

Note! At this point the program reported an error: “Output failed”. This was caused because the machine type and drivers were set incorrectly. To fix this I had to do the following: •	Select ‘File’ from the top menu o	Select ‘Select machine’ from the pull-down menu o	Using the pull-down menus select the correct machine model and Printer name o	Click OK •	Repeat the Set process above. The tool should now move near to the bottom left corner of your material •	Using the arrows move the tool to the correct starting point. You should set this point at least 5 mm from the bottom left of the material to allow for a space to re-zero the height if the tool is changed. •	Click on the ‘Model position’ icon  to align the edge of the model with starting point of the tool •	Click OK •	Now you are ready to start the roughing process so click on the ‘Cut’ icon To get a smoother cut on the finishing I decided to use a round tool bit instead of square so went for a 3/32 inch round tool (2.38mm) •	Click on the ‘+’ icon next to the ‘Finishing1’ process to expand the parameters •	Double-click on the ‘3mm Square’ icon and change the tool to 3/32 inch ball

Mini-Tutorial – Creating a new tool in Modela Player 4 The 3/32 inch ball tool was not available for selection so I had to create and register a new tool: •	Select ‘Options’ – ‘Add/remove tool’ from the top menu. •	Click on ‘New’ •	Type in the tool name, i.e. “3-32 inch ball” •	Select the Tool type from the pull-down menu, in this case “Ball” •	Select the Tool material from the pull-down menu, in this case “High speed steel’ (These can be found from the tool supplier specifications – ask the Fablab Manager) •	Enter the flute diameter – if as in this case the tools are in imperial sizes this will need to be converted to metric. 3/32 inch = 2.38125 mm •	Click on ‘Cutting parameters’ •	Choose ‘Material’ as “Modelling Wax” •	Click on ‘Set parameters’ •	Click on ‘Register’ •	The tool should now be selectable from the tool menu End of mini-tutorial

•	After changing the tool size you will need to re-calculate the tool path so click on the ‘Create tool path’ icon. •	Now as we did before click on the Roughing process and click the ‘Cutting/no cutting’ icon top switch it off. •	Do the same thing to switch the Finishing process on. •	Now you will need to change the tool: o	Press the ‘view’ button on the Modela machine so that the job moves to the front. o	Use the Allen key to loosen the tool chuck and carefully remove the 3mm square tool and store in the correct place o	Put the 3/32 inch ball tool into the chuck and re-tighten, ensuring that the tip of the tool is above the height of the wax material. o	Press the ‘view’ button on the Modela to move the job to the back of the machine o	To move the tool back to the corner of the wax material click on ‘Set’ from the top menu 	Select ‘Cutting position’ from the drop-down menu •	Click ‘Move’ o	Now loosen the Allen key and allow the tool to drop down the to wax material o	Re-tighten the Allen key o	The tool is now zeroed to the same height as the previous tool. •	Click on ‘Cut’ icon and the finishing process should begin.

Learning Point After my finishing cut I realised that I had not calculated the tool size according to the requirements of my design which had resulted in material not being removed between some of the letters and inside the gaps in A’s and B’s as the tool was too wide to fit into these gaps. The tool size chosen should ideally be less than half of the width of the smallest gap (although it is possible to use a tool that is no bigger than the width) and no more than twice the size of the smallest radius required. However the smaller the tool, the longer the job will take so you should use the biggest tool possible to achieve the required results.

I would have ideally liked to use a 1/32 inch (0.79 mm) tool to cut between the letters as the gap was 2 mm. However, the 1/32 inch tool is only 2.7 mm long before it tapers out and the depth I need to mill was 3.31 mm. Therefore for the gaps between the letters I chose the 1/16 inch tool as it has a longer shaft but still fits between the gaps.

So I changed the tool, created a new finishing process using the 1/16 tool and ran the process as above.

The wax was now ready to make a rubber mould.

Learning Point I used the ‘Contour lines – Down cut’ for both by roughing and finishing processes. However in the finishing process this resulted in a tool path that only circled the letters and did not cut the full design. This left a ridge of deeper cuts all around the letters. This made me realise that in most cases the finishing path type should be set to ‘Scan Lines – X+Y’ This would have created a cut path across the entire design and left a smooth base to my design