Fixturing and toolpaths for noobs

[koenbro]

I struggle with completing parts, and don't know how to release them from the stock. Consider this part:


It is a simple circular adapter with four holes and a protrusion with a shoulder. Overall 0.5" thick, and working it out of 0.64" thick alu plate. I was able to to the spot drilling, through drilling, and the rest of contours, but then I am left with a piece still attached at the bottom in the stock. What are the best practices to complete the job?

This time I took a crude approach and cut the contour out with a bandsaw then flipped into the vise using the stickout and am going at it with a fly cutter, little by little, but would like to program this (the first face with all the steps was CNC'd). Any advice is greatly appreciated.

 

[Cadillac]

Mill off the last .140 after flipping over.

 

[mmcmdl]

Are you looking to remove the extra square stock on the bottom ? If so , put it on parallels and mill it off .

 

[tq60]

Should change order of operations.

Fly cut the bottom first to make it flat.

Flip over and place on parallels then do all of the top stuff.

Make to size by removing material.

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[mmcmdl]

Flip over and place on parallels then do all of the top stuff.

If I'm seeing this right , it would be hard to cut that circle if it was down in the vise . I think his OOO is correct .

 

[koenbro]

I would like to avoid the bandsawing part and would like to automate the back side as well.

So I guess I need to face the stock, both top and bottom, then measure its thickness precisely and input that thickness into Fusion 360 setup as the stock size. Then do the tops size holes and contours, then flip and face the bottom with the flycutter? but then the piece will fly away as it is not supported/held.



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[mmcmdl]

If I was making this . I would start with round stock , face and turn round diameter in lathe . Bore soft jaws for the mill and mill the square , face cut to final thickness and do all your holes . 2 set-ups . Not sure what stock or machines you have , but it's how I would do it if a production run .

 

[tq60]

Looking again at the model it seems like there is a square shape on top that it looks like you are holding it in the vice by.

A lathe would work as well.

Your hold in the vise should be fine.

Maybe smaller cuts.

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[dbb-the-bruce]

It's not entirely clear what kind of answer you are looking for - do you want to do the entire job with CNC? how many are you making?

I've been teaching myself CNC and I too have struggled with fixing and holding. Considering the part you have, I'd drill the holes and then figure out how to temp bolt it to the CNC bed (bolt hole grid or sacrificial plate). Get some thin ABS plastic sheet (for sale signs etc, at the HW store) and use it to space the stock off of the base by about .030 or so. Set your Z zero to about .002 - .005 below the top ABS surface and you are good to go. The point being that however you set Z over cut the outer most profile/contour a few thou deeper (into the ABS). I usually face one side and flip, remove any extra off of the top.

Make a lot of small 2.5 D parts out of 1/8 or 1/16 brass stock. So I can use double sided tape or super glue to hold the stock. The most reliable I've found is double sided tape the ABS to the base and super glue the stock to the ABS. CNC a slight recesses about .1 deep for stock registration.

This part looks like it wouldn't be that hard to do by hand (with out CNC - possibly quicker if you are only making one). If you have a lathe and/or round stock to start with. Turn the cylinder section and then cut the square stuff into it on a mill (do the holes then to)

 

[Boswell]

here is another approach.
1. use your face mill or fly cutter to clean up one side of the rough cut stock
2. Flip the part over and clamp to the mill table with a piece of sacrificial MDF between the part and the table
3. Complete the milling of the part.

Alternately you can put a spacer under the part as long as it does not stick out from under the finished profile. for a small part like this, MDF is probably easiest.