Machining the flange - cockup central

Here's the toolpath in Fusion CAM. Fatboy here fancies using the 8mm end mill to drill out the 9mm bores for the fixing bolts. More sensible punters would opt for a 9mm drill. More about this later...

In the CNC12 controls, the gcode is loaded and ready to go.

That seems to be going OK, although the ramp feedrate is abysmally slow. Can't be arsed to rerun the toolpaths, though.

It doesn't sound happy with the grievously slow ramp. It's in danger of rubbing rather than cutting - the last thing you want when machining stainless steel, since this is liable to cause work hardening. You really need to go big or go home but yesterday I wimped out and cut the feeds and speeds by the best part of 50%. Furthermore, cutting a slot using a profile toolpath with 100% optimal(?) load possibly isn't clever. An adaptive toolpath might have been a bit more obvious and sensible.

But it seems to be coping ok so far....

By this point, the bores and bolt holes are done. The bolt holes were probably a stupid thing to do - using an 8mm end mill to bore a 9mm hole leaves very little room for chip evacuation. After the first couple of holes, the swarf changed from nice clean ribbons to something more like filings. I think I had damaged the tool before finishing those bolt holes.

Next (last) is the profile operation. This should ramp down progressively as the tool runs around the outer profile. The stepdown was a rather girlie 2.6mm per pass. That's barely using the tool - and I've almost certainly buggered the tool by this stage.

On the second pass, by which time tool was cutting at its "full" depth of 2.6mm, there was a loud click and a change in the sound of the tool cutting. And instead of cutting chips, it was trying its hand at stir welding.

So that's the end of that (rather expensive) tool. On the upside, the machined bores are a nice fit to the tube. 

So without further CNC carnage, I'll simply flash up the bandsaw and liberate the flange.

With some angle grinder and belt sander action, I've recovered the flange from the stock.

That doesn't look too bad, although perhaps 7-8mm thick stock would have been a better choice.

The 32mm tube is a nice snug fit.

Looks like a reasonable result if you overlook the fucked up end mill.

CAM setup for the flange plate

I have a couple of these end mills from SGS Tool (now branded as Kyocera SGS). Called "V-Carb 55SS Short", aka "Series 55":

They are recommended for steels, stainless steels, cast iron and high temp alloys, so should be good for my 304 stainless flange. And furthermore, they both appear to be in decent condition ie not buggered or chipped.

The reason for looking them up is to get the recommended cutting feeds and speeds:

For profile cutting with an 8mm cutter (2nd column), it looks like 3090rpm; for HSM (adaptive), 4665rpm and feed rate 26um per tooth (profile); 51um per tooth (HSM).

Double check that I understand correctly:

• 51um feed per tooth for 5 flute cutter at 4665rpm >> 1194 mm/min
• 26um feed per tooth for 5 flute cutter at 3090rpm >> 396 mm/min

Yes, that computes correctly. 

I don't understand this bit:

Ah:

So it means "keep Ap below 12mm for profile and 16mm for HSM" and "keep Ae below 2mm for profile and 0.4mm for HSM". It's difficult to see how I could keep Ae below 8mm when machining a slot. I guess this means that it's only intended for finishing, not roughing. Ooof yes:

So, possibly not the ideal choice here. What else have I got? I have some V7 INOX cutters from YG in 8mm with 0.5mm nose radius and necked shank with flat (Weldon) shank, p/n EME32906-1. Those are a bit exotic for this application but at least they are rated "excellent" for stainless steels including 300 series.

The data wasn't easy to find but it's held on a Hungarian YG site.

Here's the feeds and speeds table:

For 300 series SS, they recommend 3820rpm, 435 mm/min, Vc = 95 m/min and 28um per tooth. Again, sanity checking gives:

• 3820rpm x 28um x 4 flutes >> 427 mm/min. 
• And the surface speed resulting from 3820rpm and an 8mm cutter >> 96 m/min.

So that all checks out. Finally, for slotting, the depth should not exceed the cutter diameter. But I intend to limit the stepdown to around 2.4mm (30%), as the part will be hanging out over the end of the vice and will only be held on by a few tabs on the last pass.

Looks like a deal. I will dial those numbers back a bit, perhaps 15um per tooth (230 mm/min) and 3000rpm. With some stainless steels, running lower speeds and lighter cuts can cause work hardening but hopefully that won't be an issue here with a fairly modest reduction in F&S.

I'll also have to fill the coolant system again. It got a bit smelly, so I emptied and rinsed it out a few months ago.

Automated flange probing using CHIPS?

Flange probing? Fnaaaarrrr!

But seriously, rather than manually position the probe at each of the 8 bores / holes, I guess I could create gcode to do this for me, saving the coordinates to a log file (CHIPS does this automatically). Then I could take the coordinates from the log file and update or create a sketch from them.

Or rather, I could get Mr AI to generate the file for me. I told it to use the CHIPS probing functions within CNC12 and take my coordinates of the approximate hole centres as starting positions. This is what he / it came up with. I've removed a load of blank lines to make it 

(===================================================================)
(       AUTOMATED FLANGE PROBING ROUTINE VIA CHIPS ADD-IN          )
(===================================================================)
( Clears offsets, rapids to approx holes, probes via CHIPS P9114,  )
( and logs True X, True Y, and Dia into probe_cycle_history.xml    )
(===================================================================)
G21 (Metric Mode - Change to G20 if your dimensions are in Inches)
G90 G54
T99 M6 (Load Touch Probe - Adjust tool number to match your carousel)
(----------------------- CONFIGURATION VARIABLES -------------------)
#501 = -6.0    (Z-Depth: How deep inside the holes the probe will trip)
#502 = 38.0    (Nominal Diameter of the 4 Main Bores)
#503 = 10.0    (Nominal Diameter of the 4 Bolt Holes)
(----------------------- [USER INPUT] APPROX CENTERS ---------------)
(--- 4 Large Main Bores ---)a bit more compact.
#10 = 0.000    (Bore 1 Approx X)
#11 = 0.000    (Bore 1 Approx Y)
#20 = 0.000    (Bore 2 Approx X)
#21 = 0.000    (Bore 2 Approx Y)
#30 = 0.000    (Bore 3 Approx X)
#31 = 0.000    (Bore 3 Approx Y)
#40 = 0.000    (Bore 4 Approx X)
#41 = 0.000    (Bore 4 Approx Y)
(--- 4 Small Bolt Holes ---)
#50 = 0.000    (Bolt 1 Approx X)
#51 = 0.000    (Bolt 1 Approx Y)
#60 = 0.000    (Bolt 2 Approx X)
#61 = 0.000    (Bolt 2 Approx Y)
#70 = 0.000    (Bolt 3 Approx X)
#71 = 0.000    (Bolt 3 Approx Y)
#80 = 0.000    (Bolt 4 Approx X)
#81 = 0.000    (Bolt 4 Approx Y)
(===================================================================)
(                     PROBING SEQUENCE START                        )
(===================================================================)
G43 H99 Z15.0   (Apply tool height offset, move to safe clearance Z)
(--- PROBE BORE 1 ---)
G00 X#10 Y#11       (Rapid to approx center)
G01 Z#501 F1000     (Feed smoothly down into hole)
G65 P9114 D#502     (CHIPS Bore Cycle: Appends data to history XML)
G00 Z15.0           (Retract out of hole safely)
(--- PROBE BORE 2 ---)
G00 X#20 Y#21       (Rapid to approx center)
G01 Z#501 F1000     (Feed down)
G65 P9114 D#502     (CHIPS Bore Cycle)
G00 Z15.0           (Retract)
(--- PROBE BORE 3 ---)
G00 X#30 Y#31       (Rapid to approx center)
G01 Z#501 F1000     (Feed down)
G65 P9114 D#502     (CHIPS Bore Cycle)
G00 Z15.0           (Retract)
(--- PROBE BORE 4 ---)
G00 X#40 Y#41       (Rapid to approx center)
G01 Z#501 F1000     (Feed down)
G65 P9114 D#502     (CHIPS Bore Cycle)
G00 Z15.0           (Retract)
(--- PROBE BOLT HOLE 1 ---)
G00 X#50 Y#51       (Rapid to approx center)
G01 Z#501 F1000     (Feed down)
G65 P9114 D#503     (CHIPS Bore Cycle)
G00 Z15.0           (Retract)
(--- PROBE BOLT HOLE 2 ---)
G00 X#60 Y#61       (Rapid to approx center)
G01 Z#501 F1000     (Feed down)
G65 P9114 D#503     (CHIPS Bore Cycle)
G00 Z15.0           (Retract)
(--- PROBE BOLT HOLE 3 ---)
G00 X#70 Y#71       (Rapid to approx center)
G01 Z#501 F1000     (Feed down)
G65 P9114 D#503     (CHIPS Bore Cycle)
G00 Z15.0           (Retract)
(--- PROBE BOLT HOLE 4 ---)
G00 X#80 Y#81       (Rapid to approx center)
G01 Z#501 F1000     (Feed down)
G65 P9114 D#503     (CHIPS Bore Cycle)
G00 Z50.0 M05       (Clear part completely, stop spindle)
M30 (End of Program)

But no. In the end it bearly seemed worthwhile. I'd have to determine the approx hole centres and also manually transcribe the output (ie accurate / actual hole centres), no matter what.

So no, I couldn't be arsed to go this route. Instead I just used the CHIPS boring macro to acquire the coordinates and entered them directly into the Fusion sketch. But it looked plausible.

Probing the exhaust manifold flange bore positions using CHIPS and Renishaw touch probe

I haven't checked the setup of the Renishaw probe for some time now. Any eccentricity (runout?) of the probe tip will lead to errors in the measured bore coordinates. The eccentricity is measured using a mechanical DTI with very low tip force - obvs you don't want the probe tip to move before the DTI moves. We are trying to measure the runout of the probe as you rotate it 360 degrees. For this, you need to remove the electrical connecting cable.

This Baty DTI resolves 10um, which is fine for my machine, as I will be doing well to achieve much better accuracy than 10um. Or even to get close to 10um to begin with, after careful setup.

The eccentricity is corrected by tightening and loosening the 4 bolts holding the body to the arbor. There's a steel ball bearing that acts as a pivot. I managed to get the runout well below 10um, like 2-3um ie barely registering.

Also measured the diameter of the ruby tip. This has a nominal diameter of 6mm and measures at 5.985 using a 1um micrometer.

Using an old HST bearing as a precision ring gauge, I can check the calibration of the probe as it stands. This is almost convincing - an error of around 12um.

Then I ran the "tip map" function, which plots the measured radius at different angular positions around the ring gauge:

This was before adjusting the probe runout

I managed to get this output at one stage. No idea how this happened, as it's clearly bollocks. If only!!

And this was the final result.

Better check the flange is reasonably horizontal:

Then I started probing the bores, setting my origin at the centre of the first one.

2nd hole:

3rd hole:

4th hole:

Then on to the bolt holes. These are M8 threaded (6.8mm tapping drill) with a 6mm probe, so very little room around the 6mm probe tip.

1st bolt hole:

2nd bolt hole:

3rd hole:

4th bolt hole:

All done. Now what angle is the flange plate at?

This is the angle to the Y axis. If the measured angle was zero, the probed face would be dead parallel to the Y axis.

Here are the various bores and holes drawn up in a sketch:

Extruded, looks like this. The bolt holes for this side of the flange connection are 9mm (M8 clear).

And after some CAM and toolpath setup, I have some gcode ready to go.

The 2D drawing shows the extents of the model that need to be accommodated withing the 100 x 10mm stock.