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Member postings for mgnbuk

Here is a list of all the postings mgnbuk has made in our forums. Click on a thread name to jump to the thread.

Thread: Complicated post
09/03/2020 11:02:44

Boxford VM30

Auction ending on the 12th includes a Boxford VM30. No quill on these, but this one looks pretty unmolested, if a bit grubby. £87 + fees at the time of posting.

Nigel B

Thread: If you have a couple of hrs spare
07/03/2020 10:36:30

The main reason unemployed Brits don't take low paid work is doing so immediately reduces their benefits. In effect they work for nothing. Short term work also generates a lot of bureaucratic hassle with the DWP, including the strong possibility than benefits won't resume smoothly when the paid job is over.

If you look furrther into the current arrangements, Dave, you will find that your description is inaccurate. The benefits system has changed to be more responsive to changed working patterns.

Nigel B.

Thread: Coronavirus
06/03/2020 19:56:55

So, how exactly does one "prepare" Izal medicated toilet-paper before use?

Take one or more sheets, as required. Screw up the sheets into a ball & roll the ball between your palms. Straighten out the ball & the sheets will be found to be softer, without the shiny surface. Repeat the process a number of times if a softer result is required.

As for toilet paper, I will panic when the local supermarket has no tinned soup.

A novel, if somewhat messy, alternative use for tinned soup.

Nigel B.

06/03/2020 14:09:02

Were non of you taught how to "prepare" Izal paper before use ?

Nigel B.

Thread: NEMA selection for electronic leadscrew
06/03/2020 14:06:56

Link to Joe's rattle damper

**LINK**

scroll down to 07/11/18

The "link" doesn't appear to go anywhere ?

I came across steppers with feedback (hybrid)

I thought those were refered to as "closed loop" steppers, rather than "hybrid" ?

There appear to be a couple of suppliers of "off the shelf" viscous dampers (Vexta & Lin Engineering) but both appear to be US based & I have not yet come across a UK source. Rattle dampers seem easy enough to make (though trial & error as suggested by Joe) - maybe Dave could 3D print a hub & try one out made that way ?

My interest is driving a Denford Triac CNC vertical mill, with the initial control system being an Arduino running GRBL fed by a Raspberry Pi 3+

Nigel B.

06/03/2020 10:36:39

That suggests to me that problems with lack of torque are possibly due to poorly set up drivers or too-weak power supplies.

Which is why I was interested in the drive being used - limited testing with a couple of cheap single chip solution drives (Toshiba TB6600 & TB67S109ATFG) and a Stepperonline digital drive on a 2.2Nm Nema 23 motor from Arc Eurotrade has shown noticable differences in performance using the same 36V power supply.

The digital drive from Stepperonline performs much better than the other two - quieter, much less resonance & the motor warms up more, suggesting that the current is higher than the cheapies (not had a meter in circuit yet to check the actual currents) . This drive was more expensive, but not outrageously so (£13 delivered versus £5-6 each for the cheapies) but is rated for 50 V DC supply or 36V AC compared to 30 or 40V for the others - I have yet to try a 48V supply with the Stepperonline drive, as it only arrived last week.

Testing so far has not involved driving anything, just the motor alone being driven while hand held (the resonance can be so bad with the cheapies it dances about on my desk) & it may be that adding a driven load will change things (just adding an aluminium pullley changed the resonance somewhat).

Nigel B.

Thread: If you have a couple of hrs spare
06/03/2020 10:17:44

I used to work with a lot of this equipment. Siemens PLC controls

Have you got over that yet ? I loathe working with Siemens automation equipment.

Nigel B.

Thread: Holding block for ISO 30 shank
04/03/2020 15:36:49

simply put the arbor in the mill and clean up with a lathe tool clamped to the table.

Depends what the OP means by "face", but no good for machining the face of the flange on DIN 2080 or QC30 holders to reduce the thickness to make them work with Erikson Quick Change flange clamping nuts, as machines fitted with that type of clamping often have solid spindles & no provision for a drawbar. Erikson recommended mounting the toolholders between centres & grinding the flange face to suit.

Nigel B.

Thread: Coronavirus
04/03/2020 14:12:39

Power of attorney

Link to government power of attorney site. My wife did both for her mother without using a solicitor and, due to the MILs circumstances, without charge.

Nigel B.

Thread: NEMA selection for electronic leadscrew
04/03/2020 12:23:39

I am using a Nema 24 on my Warco WM 290V [ 4 Nm allegedly] running 1:1 & it is underpowered on heavy roughing cuts

Out of interest, what drive are you using with this ?

Nigel B

Thread: lathe spindle runout
04/03/2020 11:26:13

Regarding bearings on machine tools,horizontal mills tended to use taper roller on heavily loaded horizontal bearings and on the heavy vertical heads,whereas the higher speed light vertical mills tend to use ball bearings.

TRBs don't like running fast with high preloads, as they generate a lot of heat. Timken used to make a version called the HydraRib that could vary the preload with hydraulic pressure - I had seen them in the Timken catalogue, but only came across one on a DeVleig jig borer. There was a two pressure hydraulic circuit that put on a high preload at low revs where high stiffness was required for heavier milling then changed to a low preload at high speeds - the change was automatic via a solenoid valve that switched over at a particular gear range.

there was no comment on why the bearings had only lasted 3 months of round the clock running.

Probably a "greased for life" installation & in that application "life" was 3 months. Had something similar with a Marwin gantry type router that used motor spindles (a heavy duty electric motor with the shaft being an ISO40 spindle). These ran right at the top end of the bearings rated speed & typically lasted 9-10 months between bearing changes. The Kluber grease had to be accurately weighed & carefully applied, then "run in" over a couple of days by carefully increasing the speed in small steps while monitoring the internal temperature of the tool taper.

I got to visit the Bridgeport works in Leicester on a DTI "Inside UK Enterprise" visit - they built up their spindle cartridges in a clean room & had automatic "running in" rigs to get the spindles correctly run in before they were fitted to machines.

Nigel B.

Thread: NEMA selection for electronic leadscrew
04/03/2020 11:08:12

There are also NEMA 24 motors that are slightly larger (60 square vs 57 square) but use the same spigot & mounting hole dimensions as NEMA 23. These can be obtained in 4 and 4.5Nm holding torque, so maybe a viable alternative to a NEMA 34 4Nm if space is tight & you need more torque than a NEMA 23 frame can provide. Stepperonline do these & I have also seen NEMA 23 rated 4 & 4.5Nm at CNC4you.

Nigel B.

Thread: VFD remote (pendant) design
03/03/2020 09:23:48

More links (with international shipping) will be very welcome

I've had a quick browse on Ebay.de & Ebay.fr and at the lower end of the price scale most of the suppliers are the same UK based outfits as Ebay.co.uk & show free delivery to the EU - didn't check the particular suppliers I linked to, though, but probably worth asking them if their products seem the best option.

As ever, if you can stand the wait it is a lot cheaper to buy from China direct. Obviously the current situation will impact Chinese deliveries, but Hong Kong doesn't seem to have been as badly affected & items I have ordered from HK have arrived within the expected time frames.

Nigel B.

03/03/2020 08:20:03

16mm is also another option - used these for switchplates at my last employment as they are more compact than 22mm

Ebay UK supplier

has a variety of colours with a changeover contact (momentary action in this listing) - £3 each

22mm switch

another UK supplier for 22mm switches if the larger type are prefered - £4.05 each not too expensive ?

Nigel B

Thread: lathe spindle runout
02/03/2020 13:34:32

What I could see though was that the runout was absolutely not synchronised with the rotation of the spindle.

I have seen this once before on a Timken crossed roller bearing, and it was the bearing that was the cause.

Application was a vertical borer table bearing and, when checked, the axial runout was within limits (0.04mm at 1500mm diameter). The machine had been rebuilt & the table bearing had been refurbished by a bearing specialist - inner & outer races reground & new rollers made - as a replacement bearing was on 2 years delivery.

The machine had been accepted after machining trials on the customer's own components (quite thin disc hub forgings in titanium & nimonics) & I was having a leisurely breakfast before flying home when there was a call from the customer with a surface finish problem on a much higher job they had taken in & run overnight. After much checking I found that while the axial runout at the table outer edge was always within limits, the actual reading at each point varied if multiple turns were made - easily seen as I marked the DTI reading in marker pen at each measuring point. Turned out that the bearing refurb company had not made the replacement rollers accurately enough (discussions with Timken revealed they used rollers matched to within 1 micron) and, as the rollers move around when the bearing rotates, the individual rollers under the measuring points were different each time. Not enough to show a surface finish problem on low parts, but visible on the tall part. The bearing was swapped out for one from another machine being rebuilt & this one gave consistent results over multiple rotations - surface finish on the component was then OK. The "dodgy" bearing got a set of more consistent rollers & that also performed OK when mounted.

Do you know what the spindle bearings are that are fitted (part number & precision class) ? Axial runout is one of the variables that is tightened up with higher precision bearings & the allowed values vary with bore diameter.

Nigel B.

Thread: Should my pistons be round
29/02/2020 14:01:15

Some digital caliper measurements from a NOS standard bore MZ ETZ 250 piston that lives on a shelf next to my computer at home (air cooled piston port two stroke) :

Nominal standard bore 69 mm

Factory piston size marked on crown 68.95 (used with a "0" marked barrel to give 0.05mm running clearance)

Measurement at base of skirt at right angle to gudgeon pin 68.94 (this is where the factory measurement is taken, so my calipers are close)

90 degrees relative to pin bore just above pin bore 68.88

In line with pin bore just above it 68.81

90 degrees relative to pin bore above top ring 68.71

In line with pin bore above top ring 68.70

No measurement at base of skirt in line with pin bore due to transfer port cutouts. Overall piston length 87.5 mm.

So a taper top to bottom & oval near the gudgeon pin - kind of what you would expect, as the piston head will expand more as it runss hotter & the area around the gudgeon pin has a greater thickness.

Nigel B.

Thread: VFD to motor cable
28/02/2020 22:47:06

connect the screen to cpc (E) at inverter but not at motor.

Can't take that for granted with a VFD - read the specific drive manual & comply with the manufacturer's recommendations for that particular drive, which are frequently to connect the shield at both ends.

Nigel B.

Thread: Coal being phased out
27/02/2020 19:46:59

biomas for starters

Is that the "environmentaly friendly" pelleted wood that is felled & processed in North America, shipped across the Altantic, then delivered to power stations here using diesel trains & trucks to be burned to make electricity?

Nigel B.

No.

Actually it would appear to be yes - on the local news this evening was the announcement that Drax power station is to stop burning coal next year & move over entirely to "biomass". Source of this "biomass" ? It will be supplied as described above - which is where & how the current "biomass" comes from that is currently burned alongside coal. 250 redundancies as a result of the change.

We could always move from natural gas to LPG when natural supplies get difficult or too expensive to come by - the UK is apparently an exporter of LPG, which is a byproduct of oil refining. And stopping using oil for transport won't stop the use of oil - I read recently that transport uses of oil are already less that that used to produce petrochemicals & lubricants. All known oil reserves being exploited ? What about the recently announced field west of the Shetlands that is estimated as being a larger deposit than the North Sea field - just needs the price to rise to make it economic to start on. Likewise the fields around the Falklands.

While the variable horizontal scale of the temperature changes graph refered to earlier makes determining the older cyclic variation patterns with any accuracy difficult, what struck me was that the last 20,000ish years that show as being relatively stable appeared to be the exeception, rather than the norm. If the temperature variations are just returning to the previously unstable norm, it won't really matter what we do - the normal situation will reinstate itself regardless. Time for NASA to come up with a sunshade ?

Nigel B.

26/02/2020 19:18:40

biomas for starters

Is that the "environmentaly friendly" pelleted wood that is felled & processed in North America, shipped across the Altantic, then delivered to power stations here using diesel trains & trucks to be burned to make electricity?

Nigel B.

Thread: ACDC Drives VFD
26/02/2020 19:13:59

Not your specific equipment, but I bought a Sprint Electric DC drive from them for work a year or so ago & they were very efficient to deal with - very quick replies to pre-purchase queries & fast delivery. I had a new drive on site in 2 days from first enquiry & should I have another DC drive go down they would be first port of call.

Nigel B

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