[Geof]

.....I think if you had stop blocks inbetween parts and they were close enough in tolerance to each other it would work.....

Good idea; slug of urethane, separator piston, another slug, etc.

The parts (are supposed to) have a tolerance of +/-0.002" on length so I do not need much deformation in the urethane. It would be nice if I could accommodate the occasional piece that varied by 0.020". These are small parts parted off from barstock and occasionally a chip sticks to the end of the stop which means that part may be short. With our current fixture these parts sometimes spin and break the cutter in the mill.

Your experience with the urethane pressure distorting the fixture is something I considered. I plan on using honed hydraulic tube with the part clamping pistons actually protruding through holes bored through the side; this, I hope, will remove the need to deburr the inside edges of the side holes because the urethane will not actually flow into the hole. The hydraulic tube will be clamped in a split block to support it both axially and radially because it is going to be severely weakened by the side holes. While typing this I just realised if I make the ends of the side pistons hemispherical the urethane will ba able to flow past them more readily.

One thing I need to determine is what kind of psi will need to be generated by the urethane. Our current fixture for these parts has a clamp straddling two parts held in the center by a 3/8"-16 cap screw tightened to something like 8 or 10 lb-ft. I need to get some idea of what force is being applied to each part with this kind of bolt tension.

[Kmed]

The other thing I did not mention is any air gaps (hopefully none), will have to be considered in your displacement via the screw. we had a few bubbles in our original design, which was basically a cast piece then placed into the machined housing. The results worked but were not repeatable enough for production, and I would not hold parts with it. We wound up pottting the urethane in the sleeve, with much better results. I will see if i can run a rough FEA on it this week.

[Geof]

I was driving up to Starbucks for my mid-morning latte when I thought about casting the urethane behind the side pistons.

Then realised a round housing is not necessary it can be rectangular and two part to facilitate the casting process.

Also realised that maybe the end screw applying pressure will be inadequate, there is bound to be some gradation of pressure along the length.

Now I am considering a two piece sliding wedge affair along the back of the urethane; something like a gib with a stationary wedge against the urethane and a sliding wedge between this and the housing.

This would also allow me to use a eccentric cam lock system because the first bit of fast rising cam travel would be taking up clearances and compressing air bubbles then the cam slope would decrease for a final high force closing.

[Vern Smith]

Not to throw cold water on a brilliant idea but considering the time and materials expended to make the single point activation fixture might it be simpler using 6 or 8 or 10 SHCP's and give the operator a drill motor with an Allen wrench in the chuck? I'm assuming you will not be making 10,000 of these. This method might be light enough to use the pallet option previously mentioned.

I'm currently putting on my hard hat and body armor.

Vern

[Geof]

..... I'm assuming you will not be making 10,000 of these....Vern

Wrong assumption.

The current method uses a hand drill and two 'pallets', one being processed the other being loaded. (Can you call them pallets when they are 16" long and 4" wide?)

I only expect a small(ish) improvement in productivity using single point clamping arising from being able to fit maybe 20% more parts per pallet, but if I can do this and reduce the fiddlyness of loading and tightening numerous bolts at the same time it makes running this part less onerous on the operator.

[Vern Smith]

[quote=Geof;576490]Wrong assumption.

Raise the price.

[Geof]

This was a 1/2" five flute running at 6000rpm, 1.24" deep cutting a 3/4" wide slot through 1" hot rolled at 120ipm with a stepover of 0.025". I wrote an incrmental loop that took a semicircular bites while it incremented in. My version of trochoidal machining.

Each slot took a bit under 40 seconds, just under 8 minutes for the lot.

Now my only complaint is the big pile of very sharp chips. Maybe I can use them to make some metal fiber reinforced concrete.

I also did a video and now I have to figure out how to upload it someplace.

[Vern Smith]

You might want to check with Ward before you post the video, he could consider it an advertisement.

[Geof]

You might want to check with Ward before you post the video, he could consider it an advertisement.

?? Elucidate please.

PS With my level of computer competence it will probably never get posted.

[Vern Smith]

If you cannot do any better than pull up an advertising video to hijack a thread I suggest you go stifle yourself.

(wedge)

[Geof]

(wedge)

Ah, okay, I guess I am a bit slow sometimes.

[pdoherty]

Geof,

Very cool. Care to share your code?

Paul

[Geof]

Geof,

Very cool. Care to share your code?

Paul

Here you are.

%
O10006 (MULTIPLE CROSS SLOTS)
N1 (G54 AT CENTER OF BASE)
N2 G00 G20 G40 G49 G80 G90 G98
N3 G53 G00 Z0.
N4 G10 L12 G90 P1 R0.5
N5 (-----)
N6 G54
N7 G52 X7.15 Y0.
N8 M97 P1000
N9 G52 X5.85 Y0.
N10 M97 P1000
N11 G52 X4.55 Y0.
N12 M97 P1000
N13 G52 X3.25 Y0.
N14 M97 P1000
N15 G52 X1.95 Y0.
N16 M97 P1000
N17 G52 X0.65 Y0.
N18 M97 P1000
N19 G52 X-0.65 Y0.
N20 M97 P1000
N21 G52 X-1.95 Y0.
N22 M97 P1000
N23 G52 X-3.25 Y0.
N24 M97 P1000
N25 G52 X-4.55 Y0.
N26 M97 P1000
N27 G52 X-5.85 Y0.
N28 M97 P1000
N29 G52 X-7.15 Y0.
N30 M97 P1000
N31 G00 Z1. M09
N32 G53 G00 Z0.
N33 G52 X0. Y0. Z0.
N34 T1 M06
N35 G53 G00 X-10. Y0. Z0. M30
N36 (---)
N1000 T1 M06
N1001 M03 S6000
N1002 G43 H01
N1003 G00 X0. Y1.5 Z1.
N1004 Z-1.24
N1005 G41 D01 X-0.379 Y0.79
N1006 G91 G01 Y-0.025 F120. M97 P1100 L50
N1007 G91 G03 I0.379 J0. X0.758 Y0. F80.
N1008 G90 G01 X0.379 Y0.78
N1009 G03 I-0.379 J0. X-0.379 Y0.78
N1010 G01 Y-0.8
N1011 G03 I0.379 J0. X0.379 Y-0.8
N1012 G01 X0.379 Y1.
N1013 G90 G40 G01 X0. Y1.5
N1014 G00 Z1.
N1015 M99
N1016 (-----)
N1100 G91 G03 I0.379 J0. X0.758 Y0.
N1101 G90 I-0.379 J0. X-0.379 F400.
N1102 M99
%

[Geof]

I have no idea if this will work but that below is the link to one of my videos on you tube (I hope).


[ame="http://www.youtube.com/watch?v=aFlu3uLtXK8"]YouTube - P3080017[/ame]


EDIT: Good grief it worked!! I am going to blow my cover as an incompetent nincompoop if I am not careful.

Another one; no stopping me now;

[ame="http://www.youtube.com/watch?v=Vwsg-nNDD6U&feature=channel"]YouTube - P3080018[/ame]

[pdoherty]

That rocks. Thanks for sharing it Geof.

[Vern Smith]

Geof,

You might be endangering an entire industry. They are getting $10.000.00 and up for CAM programs to do what you did with 40 plus lines of code.

[Geof]

...to do what you did with 40 plus lines of code.

And almost half the forty are redundant.

But hand programming an ellipse gets a bit tedious and programming an elliptical pocket using trochoidal machining would definitely be a fulltime retirement project. I do know the benefits and lmitations of both ways.

[Caprirs]

GeofCAM.

[Kmed]

I have no idea if this will work but that below is the link to one of my videos on you tube (I hope).


YouTube - P3080017


EDIT: Good grief it worked!! I am going to blow my cover as an incompetent nincompoop if I am not careful.

Another one; no stopping me now;

YouTube - P3080018

We know youa re incompetent. You put all the chips at the back of the machine so you have to pull them forward. 180 the way you are cutting and have them dump right into the chip auger. PS dont try to video tape it with the door open cutting this way ...


BTW looks good. I know one CAM vendor is testing a new algorithim out and it has been working wonderfully. I dont have the programming skills with out the computer.. takes me way to long.

[Geof]

We know youa re incompetent. You put all the chips at the back of the machine so you have to pull them forward. 180 the way you are cutting and have them dump right into the chip auger. PS dont try to video tape it with the door open cutting this way ...

But nobody noticed I took one of the videos from the side on a Super MiniMill. I don't have a chip auger but I do have a honking big hole in the right hand side of the enclosure which is very handy for pulling chips out through.

PS: With a polycarbonate window to keep chips and coolant inside when the machine is running.