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Messages - joeaverage

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6121
General Mach Discussion / Re: Work coordinates
« on: October 31, 2017, 04:39:22 AM »
Hi Trevor,
you say that you've set up your limit switches and they are working. What about home switches? How do you reference your machine?

Soft limits, work co-ordinates are just so much hot air UNTIL the machine is referenced.

What sort of controller are you using?....parallel port or USB external controller?

Craig

6122
General Mach Discussion / Re: Feed Rate All Over the Board Question
« on: October 31, 2017, 04:11:08 AM »
Hi Billy
the calculations are:

0.5mm diameter x Pi=1.57mm circumference
1.57 x 24000=37700 mm/min=37.7 m/min surface speed, a long long way short of 250 m/min recommended for copper, but as fast as my spindle will go.

With small diameter tools chip loads of between 1-2% of diameter are indicated. A 1/4 inch endmill can tolerate 3-8% of diameter being that much stronger.

2% x 0.5mm diameter = 0.01mm (10um) per tooth per rev.
2 (flutes) x 0.01mm x 24000=480mm/min

So a feed rate of 480 mm/min results in a 2% of diameter chip, I usually back it off a little...to in this case 400mm/min.

Engagement= 0.45 (depth of cut) x0.1 (width of cut) / 0.5x0.5 (diameter squared)=0.18 or 18% Engagement ratios of 10-30% are common with small tools
but with larger tools 50-100% are possible.

When plunging and slotting:
0.225 (depth of cut) x 0.5 (width of cut) / 0.5 x0.5=0.25 or 25%  Note that plunging and slotting are by far and away the hardest of cutting ops and while the
engagement ratio is in the zone I slow the feed to accommodate the difficulty of the cut. The main problem is chip clearance, this is where flood cooling
helps. At some future date I hope to have some high pressure coolant nozzles to assist with chip clearance when plunging or slotting. As it is I slow the feed to half
of normal chip load ie 200 mm/min.

Craig

6123
General Mach Discussion / Re: Feed Rate All Over the Board Question
« on: October 31, 2017, 03:25:39 AM »
Hi Billy,
I don't do much engraving but do use a lot of really small endmills. I agree depending on where you look or read there is a wide range of feeds and speeds.

One thing which I have noted is that the surface speed for a given material and a given tool and surface treatment is consistent across a number of published
sources. With softer materials like aluminium and brass the speeds are quite high and considerable latitude can be taken. Try the same with mild steel, it won't work,
try it with a medium to high tensile steel, or even worse, an austenitic stainless steel and your tool briefly glows red before breaking!

When I started I thought (wrongly) that because I had a high speed low torque spindle that I would spin small diameter tools fast with very low chip loads when
cutting steel, it didn't even come close to working! In the end I had to make a high torque spindle, or at least high torque relative to the size of my machine, 6Nm,
and I'm running direct coupled so max rpm is only 3500. It makes mincemeat of steel, even tough stuff like stainless.

I think your application will require you run at max rpm, 8000 is hardly earth shaking. I would be tempted to run at the high end of the feed range. If you go too fast
the tool life will suffer and any upset will cause breakage. A bit less than that and you'll get good productivity and fair toolife. You can slow the feed down even more
and while the tool life might be good it will have to be  as it will take an age to cut anything. If the feed rate is too low all you end up doing is giving the material
'a damn good rub' which workhardens the material, heats the tool and achieves piss all.

A lot of sources suggest that carbide shouldn't be run cooled, I find that flood cooling, as much as I can get in fact, gives me best results. In part its due to chip clearance,
nothing promotes wear, heat and edge build up like re-cutting chips. Flood cooling helps bigtime with toollife and cut quality.

When I cut heavy copper circuit boards (the copper is 0.42mm thick!) I use 0.5mm 2 flute carbide uncoated endmills at 24000 rpm with  as much cooling flow as I can
squirt at it.  I cut through the copper in one pass and a little bit into the fibreglass underneath, a cut of 0.45mm depth with a 0.1mm stepover at 400mm/min.
When plunging or slotting when taking the first cut I cut to depth in two passes, 0.225mm then 0.45mm at 24000 rpm and half speed feed ie 200 mm/min.

As you can see I have worked these figures out for myself, while I have a published surface speed of 250m/min for copper I have over a period of time refined
that number depending on other cut parameters. One of the early realisations I had was that it doesn't make sense to make a lot of really shallow cuts, it wears
just the very tip of the tool and takes forever to do a job. Now I like to make my tools work for a living about 75% of max and at feed rates that give a decent chip.
Any poor choice or control of your toolpath is likely to result in a broken tool but I'm now getting about 4 hours per tool on the heavy copper boards. When I started
I couldn't get more than 1/4 hour and achieve damn-all in that 1/4 hour to boot!

My suggestion is experiment some. Record the critical parameters, not the rpm or feedrate, but surface speed and chip load. These two are the really useful ones
that will allow you to extrapolate to find new cutting solutions.

Craig

6124
Hi Cheska,
welcome. Those questions are best asked on the main Mach Discussion Board where more people will read it.

Sounds like your home switches, if you have them, are not quite working right.

Craig

6125
General Mach Discussion / Re: Make a pipe bender die
« on: October 30, 2017, 01:54:18 AM »
Hi,
that bender of Ya-Nvr-No looks great.

the code I posted works OK with Mach4 but jumbles it in Mach3. Haven't worked out all the options yet. For instance have set feed/rev when posting
the code but not familiar enough with MachTurn to set the appropriate mode...yet.

Craig

6126
General Mach Discussion / Re: Make a pipe bender die
« on: October 29, 2017, 07:30:51 PM »
Hi Dave,
I use NCViewer and sometimes Camotics.

Just had a thought the file I posted had a .nc extension. Try renaming it to something that Mach3 is more likely
to recognise .tap

Craig

6127
General Mach Discussion / Re: Make a pipe bender die
« on: October 29, 2017, 06:53:41 PM »
Hi Dave,
I posted Gcode, even the original CAM program can no longer recognise it. A Gcode viewer should.

Break it into parts so that one tool creates one path. The order of ops is Facing, OD roughing, then the
all important grooving op that produces the semicircular recess, the the parting op. My guess is that Mach3
cannot follow the tool changes and cannot therefore draw a toolpath.

When I get home i will post the grooving toolpath.

Craig

6128
Mach4 General Discussion / Re: 2.5 carving - Z stepper creeping upward
« on: October 29, 2017, 02:47:15 AM »
Hi,
you can up to five licences active at one time with a maximum of seven licence re-issues in a two year period. Mach4 licencing is pretty generous, not open season
like Mach3, but still generous.

I think your clutching at straws though. Mach4 has thousands of users and probably hundreds with the exact combination you have, if there were a problem
with Mach4 or the PMDX-424 it would be known already. I understand that all the things you've tried have not helped and so you will try something else.

You've tried moving the Z axis up and down repeatedly without apparent fault. Yet when carving it does fault. Evidently it is something about the millions
of very small incremental moves that causes problems. I suspect therefore that if you were to repeat the up/down experiment over tens or hundreds of
thousands of moves the fault would show.

I rather think that some error along the lines that Steve has proposed still applies. I'm wondering if you could make some setting that made the problem worse,
way worse would be best. It would hopefully make plain the problem. Steve has suggested that if you had an active low setting for instance on the step
pin but the output of the PMDX is logic low at idle it could mean that the driver miss one microstep at each axis reversal. Over a period of time with the vast
number of axis reversals when carving the fault occurs. My proposal is to reduce the number of microsteps so that the problem is accentuated. I'm wondering
if the electronic gearing that you now have available courtesy of the clearpath servos could be used. The idea is to reduce the 'steps per' to some low number
but have the servo drives counteract that so the effective 'steps per' is actually higher. So an error occurs where the drive misses one step pulse from the
PMDX but gets amplified by the drive to 1000 steps, the error would stick out  like dogs balls!

Of course this idea may just be the ramblings of a nutcase...up to you to decide.

Craig

6129
Modbus / Re: Can't open serial port
« on: October 28, 2017, 07:34:16 PM »
Hi,
have you enabled Modbus on the Config/Port and Pins page?

Craig

6130
General Mach Discussion / Re: Make a pipe bender die
« on: October 28, 2017, 05:41:54 PM »
Hi Dave,
sorry just noticed I used the grooving tool for the cutoff, this may make a bit more sense.

Craig

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