Member postings for Robert Atkinson 2

I did wonder about the different finishes. At £40 including the chucks I was not too bothered It will be more of a bitza if I make my own slides... The headstock looks OK there is even some oil in it.

Photos of bed and head. Not taken any of the other bits yet.

1/ Yes. An open circuit in the start circuit. Either switch, winding or wiring.
2/ Yes many have a thermal cut out. But it could be many things.

Probably time to get a new motor. Or consider a 3 phase motor and VFD.

Robert.

I went to the Dunstable Downs amateur radio car boot sale today.
I was expecting to get some electronic test equipment but came back with mostly mechanical engineering bits.
Find of the day was a Pultra precision lathe. I think it's a 1750 but have to check. Certainly 50mm center height. It is in fair condition and came with a lever action tailstock, 3 and 4 jaw chucks. No tool rest or slides though. The slides are probably the easiest parts for me to make myself. I have some miniature linear rail bearings that would be ideal. The same donor unit that hs the bearings, an optical scanner, also has some leadscrews. I will have to check them out. Not sure when I’ll get a chance to investigate the further, got a couple of busy weeks coming up. Other purchases included a unknown high speed precision drill press. It’s the kind used for PCB drilling. It is older and very well made. Direct drive from a universal (brushed) motor with the whole assembly sliding in a plain bearing about 2” in diameter. Needs a clean but looks OK. I’ve wanted a drill of this type for years. The universal motor will make it easy to add variable speed control.
Small items were a small Verdict lever DTI in the case with fittings, M&W depth micrometer and a small V block.

Cost was minimal, £40 for the Pultra, £10 for the drill and £4 for the smalls.

I did get a few items of test equipment too.

Robert.

Because it's hotter

If the VFD / machine is connected to a fixed outlet, i.e no plug & socket, the outlet MUST have a isolation switch. Ideally this should be able to be locked in the off position with a padlock.

Robert.

Edited By Robert Atkinson 2 on 20/05/2023 09:03:38

While you may have used it for that purpose an NVR is not intended to protect against residual voltages. An isolator will perfom that function if required. Or as DC31k says a notice and wait.

While an isolator is a good idea, it does not have to be a switch. At least one standard, EN60204, allows a local plug and socket to be used. So using a IEC60320 inlet (e.g. C14 type as used on computers etc https://en.wikipedia.org/wiki/IEC_60320) on the enclosure containing the VFD is adequate. It also reduces the chance of touching the pins.

Robert.

While it is better to remove them, the losses in a the choke and power factor correction capacitor are pretty low when running a LED replacement "tube". If you doe remove them the fitting should be claerly labeled to that effect.
Better overall to just replace the whole thing with an LED fitting. I got some KBAT4 units from TLC and they are good.

On a connected note fluorescent lamps are effectively being banned by the EU from 1st of Feb 2024. They have removed the exemption from the mercury ban. Of course we in the UK are not in the EU any more so it won't affect us. No, wait, the UK has passed a law, almost identical to the EU one, removing the UK exemption effective 1st Feb 2024......

Edited By Robert Atkinson 2 on 19/05/2023 21:48:52

Your Plan will work, but there are some issues.

1/ The motor must be connected directly to the output of the VFD (inverter) wihout any switches, fuses etc.
2/ You need to provide an enclosure for the VFD.
3/ You need to provide Stop, Start and FWD/REV switches / controls. It may be possible to repurpose the existing controls depending on what they are. For anything other than your own hobby use it should also have a emergency stop and isolator to comply with safety regulations. You can maim yourself but not employees or members of the public.
4/ You could leave the VFD set at 50HZ but that is wasting a significant capability. Adding a simple potentiometer will give you variable speed control. You could set the maximum frequency to 60Hz and get 20% higher speed in each range.
5/ You don't need a NVR, the VFD can be set up so it will not automatically start when power is applied.

I agree with DC31K, with a branded VFD there is no need to derate it or buy a larger VFD than the motor rating. It actually has some disadvantages.

Robert

Is the driver they supplied for a a PC or for a MAC?
Drivers are device and Operating Oystem specific (but a instalation package may cover a number of OSs).

The age of the driver should not matter.

Robert.

Twain is just a "driver". This is a piece of software that provides the interface between a piece of hardware (typically a add-on) and software. Typically to provide a common interface across different computers and operating systems. Thus you can have a standard bit of hardware and a standard user program and only change the driver for different computers.
Some drivers, including TWAIN provide a consistent, available interface on the software side. This allows software to work with multiple different pieces of hardware  and vice-versa. For Twain an image capture application (or function in a image editing program, wordproccessor etc) only has to conform to the Twain software side definition. The program will then work with any hardware that has a Twain driver available. The hardware supplier (or a third party) just has to provide (write) a driver to "drive" their hardware and provide a software interface to the Twain standard.

For MichaelG this means he needs to find an application progarm that has the functions he wants and is Twain compatible. Sounds like this is to run on a Mac computer so there is lots of choice. I can't suggest anything as we do not know what functionality is required.
It is unlikely that a Ardunio application would support this due to complexity and amount of data. A RaspberryPI would if you want something small.

Robert.

Edited By Robert Atkinson 2 on 19/05/2023 08:54:19

If you have an older Office version at home just use the "save as" function on the newer system and select file type as .DOC etc tnstead of .DOCX

Sorry Jason, the machine most certainly does know and care if a single or 3 phase motor is fitted.

Despite the appearence of constant speed a loaded induction motors speed is not constant. It accelerates and decellerates between poles due to variation in torqe "torque ripple" for the same numbrf of poles it is worse with a single pahse motor. Some single phase motors are worse than others. This cyclic variation in torque and speed creates vibration and noise from the machine. More importantly it can affect the surface finish. This is particuarly true of surface grinders. Thwy don't do well when fitted with single phase motors.

Another advantage that has not been mentioned on this thread so far is stopping and starting. Single phase motors do not like a lot of stop-start cycles. This is one reason why Myford fitted a clutch to the S7. Fitting a 3ph motor and VFD to a ML7 overcomes the lack of a clutch.

Robert.

Another issue is if the disk is double density (DD) 720kB rather than High Density (HD) 1.44MB. These have different magnetic properties and some DD drives write a wider magnetic track than newr HD drives. If the disk was formatted in a DD drive then a HD drive may not be able to over-write the old wider track.
There is also the possibilty that the disk has been modified so a HD lappears to be a DD or vice versa. The HD disks have an additional hole on the edge opposite the write protect hole.

Why bother with this disk anyway? Just get one that works. If there is any issue with the disk the data may not be there when you need it.

Robert.

Hi Lynne,

any update?

Robert.

Putting a 3 phase motor and VFD on a ML7 (or S7) is one of the best modifications you can make.

I've done it to my ML7. The difference in vibration and noise is astounding. I knew the torque ripple from the single phase motor increased vibration but was suprised by the difference. As others have said, this should not be about "more" it's about better. I actually fitted a 370W (0.5HP) motor abut it is plenty of power. I also used a slower 6 pole motor. This has a nominal speed of 910 RPM and is even smoother than a 4 pole. It also allowed me to fit a larger pulley on the motor. This reduces transmission losses. The motor is a Totally Enclosed Fan Cooled (TEFC) type. It is not really viable to use an open motor when there is swarf and dust around. Shields can not stop everything, the take time to make and can get in the way.

I can, and will, run the lathe at higher speeds using the VFD. This is not to use carbide tools on large workpieces. It is to machine small diameter parts and most of those will be in soft materials.

Robert.

Try running it off a car battery. I'm pretty sure your adaptor is not man enough.

Hmm,

You don't need a variable voltage "adaptor" and a PWM controller. For inital testing just connect the power adaptor to the motor and vary the voltage. You can wire a change-over switch or just swap the leads to chang direction. I suspect that the power adaptor is not powerfull enough. If it is still slow without the PWM unit you need a bigger powersupply. The clue is 2A power adaptor and 5A motor. I suggest you need a 6 or 8A 12V fixed voltage power supply to drive this motor with the PWM controller. You could also try using the PWM adaptor with a 12V car battery instead of a mains supply.

Robert.

Hi Noel,
It's clear the OP is not going for true high vacuum. He is however looking for the vacuum to be maintained for extended periods without pumping. To do this requires high vacuum techniques.

Robert.

Edited By Robert Atkinson 2 on 11/05/2023 18:55:21

The classic high vacuum sealant AND high voltage electrical insulation is sealing wax. So ideal for this. The type used on old fashioned documents. Just be wary of black wax, it might be conductive. There is actually very few modern materials that are better.
I'm a bit wary of rubber O-rings for high vacuum. copper O-rings (ideally hollow) or pure aluminium gaskets will provide a better seal.

Robert.

Edited By Robert Atkinson 2 on 11/05/2023 16:56:56