2 Sided machining

[craigrobbo]

Hey guys.

So i am a CNC noob, but i have been doing my home work.

I have spent the last months reading up on G-code, Mach3 & spent about 3 years learning CAD.

So i managed to draw somthing up, convert it to G code and sucessfully simulate a machining in Mach3 perfect...

So i'm almost set.

The question i have is this:

I want to make a part that requires machining on BOTH sides, and i am using a 3axis moving gantry miller.

How do you guys machine both sides(obviously i have to turn the part by hand) but how do you make sure the machine can mill it 100% accurately since when you take the part out and flip it, its damnned near impossible to get it in the EXACT same position again (especially when tollerances are so tight on CNC) within just a few 0.1's of a MM?

I hope i have put my question out properly.

Thanks

Craig

[mfgbydesign]

Machine two edges and flip it along one of those edges. Use the new corner as your second origin and locating surfaces. Just one way of many, of course depends on what the finished part looks like.

[craigrobbo]

Machine two edges and flip it along one of those edges. Use the new corner as your second origin and locating surfaces. Just one way of many, of course depends on what the finished part looks like.

Sorry, I'm not totally sure what you mean.

Lets just say for example i have a square part, I need to mill a pocket out of each side and chamfer all the edges on both sides.
(this is just a hypothetical situation)

[txcncman]

There are probably a dozen different ways to machine 2 or more sides of a single piece of material. I recommend you start with some basics. Square your material and cut all sides to the finished size before proceeding. Then use a fixed stop to locate the part for machining of finished features on one side and then turn the part over and use the same stop to locate the part for machining of finished features on the second side.

At some point, you will have to learn to use your machine and tools like and edge finder to precisely locate part edges and transfer that information into the machine control.

[craigrobbo]

There are probably a dozen different ways to machine 2 or more sides of a single piece of material. I recommend you start with some basics. Square your material and cut all sides to the finished size before proceeding. Then use a fixed stop to locate the part for machining of finished features on one side and then turn the part over and use the same stop to locate the part for machining of finished features on the second side.

At some point, you will have to learn to use your machine and tools like and edge finder to precisely locate part edges and transfer that information into the machine control.

Thanks for that.

What would you recommend to use as a fixed stop?

I would like to learn more on the edge finger, is their any links to some read on this?

Craig

[txcncman]

Vise Stops - Vise Components & Accessories | MSCDirect.com

Multi Axis Work Stop, 5/8 In Table Slots - Milling and Drilling Accessories - Machine Tool Accessories - 4LEX8 : Grainger Industrial Supply

Vise Workstop, 8, Use W/D Series Vises - Machining Vice Accessories - Machine Tool Accessories - 2MGJ5 : Grainger Industrial Supply

[txcncman]

http://www.youtube.com/watch?v=aUa_B6YIt_M]How To Use an Edge Finder - YouTube

[craigrobbo]

Thanks for the replys guys.

I am struggling though how this helps me flip a part over to relocate the part back in the clamps so its in the EXACTLY same position for reverse machining.

Craig

[tbaker2500]

Let's assume your material block has a 90 deg square corner to work with. Mark that corner. Make sure your vise is perfectly parallel to the machine bed, and chuck up the material with the marked corner in the upper right. Use and edge finder to locate your marked corner, and zero your co-ordinates there. Make sure your g-code for this side uses the top-left corner as origin. Mill this side, leaving the marked corner.

Flip the part over, with the marked corner now being lower-left. Chuck it in the vise. Locate the marked corner with your edge finder, and zero your co-ordinates there. Make sure the g-code for this side uses lower-left for the origin. Mill the rest of the part.

This method is time consuming, and best for a single part. If you want to run many of the same part, it's best to create custom fixtures which the bulk material mounts to, designed to hold it repeatably. A good example of fixturing can found here:
http://www.cnczone.com/forums/tormac...precision.html