Member postings for John Haine

Being of unknown composition I'd give it a miss - especially if a busbar, that could be a very non-machinable alloy.

Do you really need to do this? Sounds a bit like trying to synch the OCXO of a gpsdo to utc at switch on. Surely what you need to do is know the period of your pendulum oscillator and its dependence on any environmental variables you want to compensate for. But it's the counter that converts frequency to phase (time) that needs synchronising to ntp surely? One thing you can guarantee is that even if you synchronise the pendulum to an ntp tick it's phase will immediately start to drift away. Unless of course you phase lock it, but that's cheating!

Just to say that there's a new forum at

**LINK**

This is set up for discussion related to articles in HSN and related topics, so I have started a thread there to describe progress on this clock. Registration is free.

I think in one of the classic workshop practice books it explained that if you had any play in the h/s bearings then using a front parting tool the mandrel could lift slightly and cause the tool to pull in to the work, while an inverted rear tool would push the mandrel further down. But the two key things that fixed parting for me were first, using a sensible speed rather than back gear; and second using power feed. The first works as the tooth load is much smaller and at a higher surface speed the tool cuts much better. The second keeps an even feed going. I also bought a "kit q cut" parting tool from the (lamented) Greenwood tools which I use in the front toolpost, and I also have but seldom use a rear toolpost.

The problem often is that the operator is very nervous about parting so uses a low speed to "make it safer". Then they feed slowly and probably shakily, the tool doesn't cut at first as the pressure builds, then suddenly bites, digs in and stalls the lathe. This makes the operator even more nervous so next time is even worse!

Nowadays parting using CNC on the lathe I often just run the lathe at the last turning speed and feed at up to 5mm/minute and don't get any problems.

Definitely a Mitsubishi inverter inside. I have asked NT about access to the insides both for the eStop and speed control when I fitted 3 phase to my S7 so I could interface to the cnc controller, but they do not support this. Drilling out the pop rivets would invalidate the warranty, and they supply the unit sealed to be able to warrant emc performance.

The ubx device has a "survey in" function I think, especially for fixed timing applications. I haven't sussed it out yet but if you leave its antenna in a fixed location for 24 hours at least it can then start deriving accurate time even if there is only one visible satellite.

As GPS estimates speed from the doppler shift of the received signals, not from differentiating position w.r.t. time, I suspect that the max speed glitch has a different source.

I'm slightly bemused by the fact that my 2018 Golf has a lithium ion battery under the passenger seat. Apparently this is to run the auxiliary systems such as Infotainment etc when the engine is stopped, which the clever EMS does for example when going downhill or stopped at a junction of in a jam. I haven't had to replace the main battery so I don't know if the aux one means that there isn't any "reset" issue. As far as I'm concerned engine auto stop/start is a boon and I wouldn't be without it.

This may not be too helpful but I would engrave them on the CNC with a rotary axis.

Well you kind of see what they are getting at but starting with a graph labelled A to D but text bullets that are numbered isn't very helpful. Then they talk about maintaining a voltage x frequency ratio - do they mean ratio or product? Doesn't inspire confidence.

Try asking it is 409 is a prime number.

What's the difference? Just use the calculator on your phone or computer. Exactly 25.4mm in an inch, everything flows from that.

The diode is totally unnecessary since it is always reverse biased! I suspect that the "designer" adapted a circuit originally intended to drive an inductive load which would need a diode to catch the inductive kick on switch off. Not understanding why it was there they left it in just in case. From other artefacts of the design understanding was thin on the ground.

The MOSFET seems to be a fairly generic power device and other types would be suitable.  I don't know where your pulses are coming from but the threshold voltage of the device specified can be as high as 4v which is a bit marginal for a 5v CMOS drive.  

Edited By John Haine on 17/03/2023 11:52:12

I can't imagine what D1 is supposed to do as it's always reverse biased. I doubt omitting it would make the slightest difference.

To post a screen shot you need to "save as" a jpg- normally it will save as a png which this site will not accept.

I run GRBL on a Uno for my mill power feed, with a Bluetooth to "GRBL Controller" on my phone. GRBL is a great program for limited CNC, it runs lots of 3D printers and small routers.

The problem with GRBL is that it only takes g-code in on the serial port and turns out stepper pulses - it is in effect a "motion controller". Packages like Mach 3 / 4 nowadays delegate the pulse generation to a motion controller though driven with a more sophisticated set of instructions. The main function of Mach (or LinuxCNC etc) is to manage the g-code parsing, look ahead etc to maximise the efficiency of the system. Also they manage all the stuff like wizards, tool offsets, file management, estop, alarms, and so on. There are programs (like the one I use on my phone) that work with GRBL but as far as I know nothing approaching the functionality of even Mach3. And in my experience integrating them with GRBL is not straightforward. For details see the grbl wiki at **LINK**. Several programs are referenced there. But you could run one of these on your garage PC using an Arduino/grbl for motion control. Note that there is a "CNC Shield" for the Uno that takes 3 or 4 stepper driver ICs and mounts on the Uno - I use one of these on mine.

There are more advanced grbl versions that need a more powerful processor than the 328 and have more features and are much faster - even one that can do backlash compensation. Also there's a "GRBL Lathe" version I think on the Microsoft store. Look for grblHAL - even one that runs on a Pi.

A bit more searching around suggests that there is a CNC controller available from the USA that combines an Arduino running GRBL for motion control and a Pi for g-code streaming. Also Linux CNC can be run at least on a Pi4, and the Beaglebone. Google is your friend.

.nc (though these are text files. Used for g-code.)

.docx (Word)

.xls (Excel)

.xlsx (Excel)

.ppt

.pptx

.zip

.7z (7-zip, open source alternative to Winzip)

.py (Python code)

There are 4 options really, assuming you don't want to use the ancient single core Pentium.

You could just download the last version of Mach 3 which I think is 3.043.062, and pay for a new licence if you can't find the old one. Mach3 hasn't been supported for about 7+ years. Or buy Mach 4 which is the latest product from the same stable. For either of these you will need a new Win PC and, really, a motion controller instead of the old parallel port. But you don't need much of a PC. I use a cheapie miniPC with Win 10 and a UC100 motion controller

Or go the LinuxCNC route, for which you may be able to use the old PC or a new one. I don't think a Pi 2 would support Linux CNC, and I'm not sure if there is any other Pi SW that does.

Or use GRBL that can run on an Arduino, but this is really just a motion controller without the G code streaming so you need other SW, on an additional processor, to do this.

All those options can support a touch probe.

And of course you would need a machine to drive the probe!

Hooray! Looking forward to the new system.