First Post, First Project, & Some Questions

[dave benson]

HI Kelly

I ran the last file posted through to completion with GRBLMachine,
It's the same as the first file but has the long comment lines removed so
this one may be the one to run.
These files are just to check the feedrates and don't include all of the mops.
I'm gonna waffle on a bit so skip the boring bits.

So at this point you have fired up CB and drawn your geometry and applied
a standard pocket mop.
You have run the file on the machine and determined that 30 in\min and 0.125 in
depth of cut  is as fast as the machine can handle, this is because there are much
higher loads on the cutter in the corners.

With a standard pocket mop that's what your limited to feed rate wise.
With a troc mop 30 in\min is the minimum speed and you may be able to
increase the feedrate safely to 45 in\min without the machine loosing steps.
It could be much higher which is determined by trial and error.

There's plenty of information on the web regarding speeds and feeds
for various materials,however these are predicated on the user having
an industrial cnc machine in excellent condition and may be far to optimistic
for your machine.

Pocketing can take a long time so is there a faster way to do the pocket?
Yes this is where trochoidal\Peel milling can help a lot. It's used extensively in industry.
https://www.harveyperformance.com/in-the-loupe/introduction-trochoidal-milling/

Because the tool paths generated by the Troc mops put less load on the cutter
and machine for the same (MMR) Material removal rate you can increase the feedrate
quite a bit.

If you are a home gamer and (time isn't money) this may be all you really need.

If on the other hand you want to make these things by the gross (or don't want to listen to the router all day) then using the feedrate adjuster will shorten the cycle time another 40 to 60 percent but you don't get something for nothing as there is quite a bit of work to optimise your geometry to make it suitable for the feed rate adjuster, this is why in the CB file I posted much earlier in the thread looks so different, all those extra mops the geometry being cut and shut extensively.

At this early point in your CNC'ing shenanigans, you may decide that a troc mop without the
extra drama of preparing your drawing for the feed rate adjuster is the go.

In this case to get the best out of the Troc mops you would still have to modify your geometry
a little because the tool paths generated from your one big pocket shape (the runners) are
still not the optimum for troc mops.

With just replacing the pocket mop's with a troc mop  and not adjusting the drawing at all, you should still be able to run 45 inches\min.
You could then run the file with successively  higher feedrates until the you stall out he steppers
then back off the feedrate 20% this would then be your feedrate to set in the mop.
Dave

[Tool-n-Around]

.....One thing to know, is that for a spiral milling mop, the hole is cut at the cutting feedrate and for a drilling mop the hole is cut with the plunge feedrate.....

I had been a little uncertain about this but this clears it up. Thank you.

Comparing apples to apples the drilling method is twice as fast and more importantly the holes will be placed as accurately as your machine can manage and will be round enough for bolt clearance holes…….When I was at the manufacturer website I did look at the specs for positional and milling accuracy  ---> positional accuracy 0.001   actual milling 0.004. This is right for the motion system you have, but it's predicated on a new machine with the correct cutter, cutting soft materials. Dave

…and also very good to know and I will incorporate into my future standard operating procedure.

The second file runs with a variable feed rate mode  60 inches a minute for the straight a-ways and variable (according to cutter load)  from 60 to 25 inches a minute in the high load areas (the corners).

.....Because the tool paths generated by the Troc mops put less load on the cutter and machine for the same (MMR) Material removal rate you can increase the feedrate quite a bit. If you are a home gamer and (time isn't money) this may be all you really need.

I will study those files. Although I am a home gamer, and this is pretty much a one-time part, because of the limitations of my machine I can see the value of variable speeds/feeds and Trocs for material removal. Even on a one-off part, for harder materials, both are very useful for my machine.
I can’t say I’m a big fan of the phenolic composite, but it’s a decent choice for the application. It has a strong odor when machined. Reminds me of my foundry days because phenolic resin was a common binder in shell cores…….but I’d prefer not to smell it in my shop. I will machine polystyrene foam, wood, plastics and occasional light aluminum work.

I have a rather large backlog of machine upgrades and tuning to perform so I’ll finish up this project and then concentrate on those. I will post my results.

Thank you so much for so generously devoting your time to my CmBam initiation and learning.

Best,
Kelly

[dave benson]

HI Kelly

I can’t say I’m a big fan of the phenolic composite, but it’s a decent choice for the application. It has a strong odour when machined. Reminds me of my foundry days because phenolic resin was a common binder in shell cores…….

When I was doing my eng studies, our teacher organised a tour of the Ford casting plant.
Being a Gear Head he arranged a tour to coincide with the casting of V8 engine blocks.
We were studying  metrology at the time so had a look at the labs sadly the plant has closed down since
when it did close I went to the auction and bought some of the lab equipment.

It was so long ago now that I've forgotten most of the tour, one thing I do recall was that
after casting, the engine blocks left through the side of the building on a monorail for about
3 or 4 hundred meters, did a U turn and entered the factory before going to the vibrators.

At the re-entry to the plant, there was a guy with a small sledge hammer thwacking the blocks.
I was told that he was checking for casting issues by listening to the sound they made.
A few years later a colleague showed me a Go Kart chain guard that he had cast from
an old cylinder head,at the time he had asked me to keep an eye out for old AL car heads and pistons.

Dave

[Tool-n-Around]

........At the re-entry to the plant, there was a guy with a small sledge hammer thwacking the blocks. I was told that he was checking for casting issues by listening to the sound they made.

Sounds like a precision operation. Wonder if the hammer was required to have a calibration sticker . I do lightly rap my clay graphite crucibles. They ring unless they get cracked then it's just a dull thud and time to remove them from service. Also, after I temper an aluminum casting it definitely will ring compared to as cast annealed.

A few years later a colleague showed me a Go Kart chain guard that he had cast from an old cylinder head,at the time he had asked me to keep an eye out for old AL car heads and pistons.

I do recycle automotive castings but I also buy virgin ingot for the stuff that counts.

I did successfully machine the spacer. The machining came off well but the stock wasn't as flat as expected, nor in spec, so lots of mounting screws were required. After I glue the base and lid together, it should be ok. Now I have to make the valving hardware. Pictures attached.

Best,
Kelly

[dave benson]

HI Kelly

Great pictures, the work turned out well.
Sometimes I use tooling plate (which is flat and square) but most of the time I use
Hot rolled stock and square and deck it with either the milling machine itself or my Sacia
Shaper if the stock is to big to fit on the mill.

Brings back memories of this car (1973 XAGT) I had in the early 80's I still have the motor.
Out of the factory 5850 redline and 140 MPH.
A reporter for our national broadcaster (Peter Wherritt) after driving these lead a national
campaign to have them banned on safety and pollution grounds.
https://www.youtube.com/watch?v=1F-4aHT4hno&list=PL15ZKy2pUTxYv2yVtZjSCKxcDjg3gmbrU
Of all the cars I've had and I've had plenty, this is the one I miss the most.

Dave

[Tool-n-Around]

.....Brings back memories of this car (1973 XAGT) I had in the early 80's I still have the motor. Out of the factory 5850 redline and 140 MPH.

I like Falcons but being an American, never had the pleasure. I'm a big fan of 335 Series/Cleveland headed Ford engines. This Boss 302 system is part of the same engine family. I also have a Pantera which of course had a 351c and mine now has a larger displacement/power cousin of the same. In the US we only enjoyed the Cleveland engine for a few years (save the 351M and 400) but it had a good long run in AUS as a 302CI mill.

Best,
Kelly

[dave benson]

My brother has a factory rhd American import 72 galaxy (351M) our own galaxy's were
a smaller version. 351W then later 351CL
The GT's started in 1967 the motor sizes went 289-302-351 Windsor then 351 4v Cl
then they dropped the V8's and went for turbocharged 6 cylinder Barra motors.
I just had a look at today's prices for my car, it's just getting ridiculous.
With an adrenalin junky Dad like ours who raced speedway motorcycles until
he's knees gave out then modified sprint cars until he was 62 it was no wonder
we had plenty of cars.

When I was 16 I bought a 1952 Customline, rebuilt the motor with a Triple offenhauser manifold with R92 Stromberg carbs and hard to get hold of here Johnson adjustable lifters.
Being young and stupid at the time I decided that the car was too slow and put a GT spec 351c motor in it.
Between my brothers and I we have had a 1959 De Soto Firesweep, olds 67 Cutlass, 59 Chrysler royal, 64  Studebaker lark,71 Rambler rebel, 68 GTS Holden Monaro,Import compact Fairlanes (2 off 62 and a 64) V8 260's and a 39 Ford pilot.
I still have a few sidevalve parts and the original Fireball 331cu high comp block and steel crank from the cutlass and the GT motor of course, it's a roller motor and even though I don't have a car to put it in I just can't part with it.

Love the Panteras haven’t driven one but have been driven around in one.

Dave