View Full Version : Casting parts for JGRO Machine

06-05-2006, 12:36 PM
Hello all,

I hope this is the right place to ask this question. If not I imagine the moderator will move it to where it belongs.

I finished my JGRO router and am happy with it. The deviations I made from the main plans was that I used love joy couplers and 3/8-16 all thread for all leadscrews. I was worried that the 110 oz-in motors I used would not be strong enough to pull the Z axis that carries a 2-1/4 HP Hitachi router, but to my surprise, it does the job.

My first two play cuts taught me a lot about getting things lined up and I am happy.

My third cut led me to a broken router clamp. The one I made from wood I knew would be too weak to hold it for long. So I decided to put a couple of hose clamps together and strap the thing together long enough to make a pattern for a new router clamp that I want to cast from Aluminum. Additionally I want to make patterns for the pipe supports. Now these could be made by hand with just a little work, but I would like to be able to make these on the machine.

I have learned enough G Code to cut things and have learned enough TurboCAD to make a drawing and save it as a DXF file. I have figured out enough ACE Converter to convert that drawing to G-CODE to cut it out. But here is my problem.

For those of you who cast metal, you know that the pattern has to have enough draft (taper) to pull it from the sand to keep from breaking your mold. How do I get the machine to cut the draft for me. Say that I want to make the Y axis pipe support. You know that this is a pretty simple pattern to make. A 2-1/2" square block with a 1-1/2" hole bored in the middle. As a pattern though I want the sides and bore to taper. I want the top surface (that closest to the cutting bit) to be the above dimentions but I want the bottom surface (that which is sitting on the cutting table) to be 2-5/8" square and the hole to be 1-3/8" in diameter. The end result is that I have a 1/16" taper on all the edges of the block and bore.

Can someone give me enough information to get to this point? I am as lost as a ball in tall weeds.

Thanks in advance for any help you can provide.

Warm regards,
Joe H.

06-05-2006, 08:09 PM
I am planning on making patterns using foam... no draft :o

But I would have to try making cutting a tapered side, figure if I can draw it in Solidworks then Sheetcam should be able to convert it.....

Solidworks has a draft function pretty slick the router would just step over and down to form the angle of the draft (smaller step makes smoother angle but takes longer to cut) BUT converting if to gcode doesn't work with sheetcam (2.5D not true 3d)

06-05-2006, 09:12 PM
go to www.mcmaster.com and search for "tapered endmill"

06-05-2006, 11:03 PM
wow.. learn something new everyday!

06-05-2006, 11:52 PM

Thanks for the tip. I had not thought of a tapered end mill. I will check it out.


I have considered trying lost foam casting but am wondering what foam to use and how to keep a good cast surface. I looked at build your idea and bobs metal casting. I guess I need to take the bull by the horns and try it.

Joe H.

06-06-2006, 12:04 AM
now I have never done this... but... I have seen where others dip their foam part in plaster. then put it in the sand. When poured the plaster leaves a much smoother surface and is just chipped off once the casting is done. I seen it somewhere in these forums. I am sure someone can point you to the right thread.

06-06-2006, 12:50 AM
For foam casting checkout.... http://www.buildyouridea.com

06-06-2006, 10:03 AM

Thanks a bunch, I will check it out.

Joe H.