Model Cast & Machine

lawrie

1 Feb, 2020 05:15 AM

Often we make a model of component that are cast and machined to finish. This is an example of a simple cast iron flange that will also be machined. I have used Alibre Design but the same approach will work with any of the main 3D products. By using configurations we have a model that does both for producing the pattern for casting and also details for machining.

1. Step 1:

   

   I have produced the base feature by revolving a sketch. I have allowed 2mm on top face for machining and put 2 deg. of draft on faces required to be able to extract the pattern from the sand mold

   

   Base feature

   

   
   

   I have added fillets to corners as would be standard for both the pattern and casting

2. Step 2:

   

   
   

   The hole is made by extrude cut. As the pattern needs to be removed from the sand mold I have added 3 deg draft. The larger end has to be this side to enable pattern to be removed from sand mold

3. Step 3:

   

   
   

   Here is what the finished casting would look like. As this is being made from gray cast iron I have made the part color a dark gray. I have filled out the properties table for this part to be gray cast iron which then enables the mass of the part to be calculated by the software. The mass of the casting and the material is the starting point for the foundry to price making this part. once the cost for casting is known I would also add this to the part data table. from this point I would produce a drawing for the pattern to be made. At this point in the process I give this initial modeled part configuration a name - cast

4. Step 4:

   

   I start off the next step in the process by adding a new part configuration. I have named this configuration machined

   

   I now model the first cut that the machining process will perform, that is facing off the top face of the casting. When I modeled this part I added 2mm for this machining. I make a sketch which I will use for an extruded cut to remove this material

   

   
   

   
   

   
   

5. Step 5:

   

   Next process in machining this part would be to bore out the cored hole to the required size. Note I have changed the feature color for these machining operations to a lighter gray so that these machined faces will stand out from the darker cast faces

   

   
   

   This is the part alter the first two machining operations

6. Step 6:

   

   The last operation is to add the drilled and tapped holes to which studs will be screwed into to complete the component. I have made these using the hole tool as I can add the M12 x 1.75 thread at the same time. In the real world having the ' real view ' rendered threads as can be had with some 3D applications is a total waste of time and has no practical use. I know the threads are there and so does Alibre Design. When I produce the machining drawing of this of this part it will place the required information automatically on the drawing sheet in a format that complies with ISO standard which is what my drawing sheets are configured to. Also I have added small chamfers to sharp edges as It is good practice to make things ' friendly '

   

   By selecting the cast configuration from the model tree I can take the model back to the ' as cast ' version

   As part of my normal working practice I always work on models of castings that are to also be machined with this configuration based approach . With a simple part like this a ' cast ' and ' machined ' configuration is sufficient. On more complex cast - machined parts often I will break up each machining process into separate configurations. This enables me to run through each separate machining process in the order I see them being done, another check on what it is required to make the real part and a tool for going through the manufacture process, as you see it with the workshop staff. it is all part of the CAD - CAM process. Our software tools can be a big investment, we need to extract the maximum value we can from these tools that we can.