Newbie- Going from a rough alum casting to a CNC'd part

[mlabruyere]

Here is an example of what I want to be able to setup:

See from time stamp 3:50

YouTube- Robo CNC Router : Part 08 :Casting a aluminium dust collector. (Lost foam)

YouTube- Robo CNC Router : Part 08 :Casting a aluminium dust collector. (Lost foam)

How do you properly index the part to the CNC machine? I can do the cutting of the foam, doing the rough casting....indexing is a new thing to me.

If anyone has video's or documents (posts, PDF's....etc) I would appreciate it. I still have a lot to learn.....

My machine is a rigid gantry (8020 based), Bosch 1617 router, 626in/oz kelig steppers (X axis has 2), Gecko G540 driver, and Mach3 software. I have a probe (DIY) I use for setting the Z axis but I can program it to detect the X and Y edge as well if I need that.

Matthew

[mlabruyere]

Oh well.....the person that posted the video was very helpful so I'll try what he recommended.....I was hoping for some insight or at least a push in the right direction here.....

[metalworkz]

Hello,
I do green sand casting and am not familiar with all the tweaks used with lost foam. I now have a CNC mill but did all the finishing work on my castings with my manual machines(lathe, metal shaper, horizontal mill) For indexing if you position the part with 2 edges along the X0, Y0 you should be able to set it up within a decent tolerance without special indexing of the part. It is those odd shaped parts that present more of a problem, but if you can draw it in CAD with the best 2 sides along or tangent to the X and Y axis you should be able to duplicate it with your setup on the machine.
For more accurate work you may need to obtain an indicator and more precisely locate the spindle with the work.
If you leave a little more material on the rough casting you will be able to do a light cut and then adjust accordingly and still have enough material for a good part.
For casting I find that a green sand mold using Petrobond sand can produce excellent results with very intricate design features and will have a very good rough finish when removed from the mold if rammed properly and good gating and sprue positioning is implemented. I believe a the roughness seen in the lost foam method is due to the gases released and maybe the mold was not vented very well to prevent this.(My guess) If you cannot get it done with lost foam perhaps you can do it with green sand molding? Good luck with your projects!

Regards,
Wes

[vigilante212]

Well you need 2 witness markes on seperate surfaces. Exp X and y, most castings leave 1/8" - 1/4" on any surface that needs to be finished Divided this in half and use a measured quardinate on the finished part for center adding the total you got from the measurement you divided. Then have rough stops that alow some leeway so all points that need to be cleaned up can be set 0 and cut down maybe 1/4 inch on these faces just so you have a nice clean flat surface to work with making sure to face the part as well. Now set up 2 dowel pins one for each edge pressing or slip fitting them into holes you can use for setting up your part make sure they dont stick up past the finished edge. Now using these dowels move over to where 0,0 is located on your part and set it for your machine. You can even use the table as z0.0 as you have already faced it in step 1. Secure your part and start machining. This is repeateable to within usually .005 if done correctly and is the way most cast parts ive ever worked on were done. The only cast parts it doesnt usually work on is really complex parts with strange shapes.