Member postings for Mark Rand

It should be noted that a hydrogen fueled IC engine can produce NOx just as well as a fossil fueled one... Hydrogen is also an expensive energy source at this time, being produced from fossil fuels.

Edited By Mark Rand on 06/11/2017 19:45:35

Well, I don't know about you lot, but my shed's built with 5" of PU foam in the walls and a split unit AC/heater. It maintains +/- 1 degree C from week to week and only changes by 3°C per day if I turn the AC off. Yes, I do work to tenths when I can.

When I've finished reorganizing the shed after converting my gantry crane into a bridge crane, the next task is to re-lap my 36"x48" surface table to the best quality I can achieve prior to using it in the re-scraping of my surface grinder. The precision of the H&W autocollimator I'm using is equivalent to 0.00005" over the diagonal of the table and the repeat meter I'll be using for short disance checking has a resolution of 2.5 micro inches... If I can keep the temperature constant and not introduce other perturbations. I'll be doing my best to achieve that. It's part of the fun of having the workshop.

When I want less precise work, there's the vegetable patch outside.

Edited By Mark Rand on 05/11/2017 23:19:31

Just bloody well get up earlier in the mornings when it's light. it works very well, ask any farmer.

Surely the real debate should be whether one uses anthracite, steam coal or soft coal in one's firebox?

Martin's nailed it! It should be added that in most cases, you'll probably not need to move the ram or head for any job.

If you are working on something that's big enough that you want to use the entire table area without re-setting the work on the table, it's best to assume that moving the head means that you need to find your references again, so have a datum point that you can reach with the available table, knee and quill movements in some position that you can reference from before and after moving the ram. It doesn't matter whether it's some feature of the work that isn't going to get milled off, or some landmark on the table (T-bolt with a centre punch mark on its top or even a known and annoying 'oopsie' put on the table by a previous owner).

Then, before starting work and after moving the ram, set your dials/scales from this landmark and you've now got consistent measurements over the entire range of the machine. If the scope of the job is sufficiently enormous, you can even have a couple of reference datums that you can work out the relative positions of from one setting, then use them to extend the working envelope. At this point you're into making 4" traction engines on Myford lathe territory...

I guess I've stirred everyone else and myself up more than enough with my posts, so I'll say good luck with your researches, whether handbook based or practical experiment based. Please report back what you find out about the ABB units.

As a final datum, the manual for my Danfoss VLT 5000 unit (similar ones avaiable on EBay) states under output data:-

Switching on output Unlimited.

So I know that in my case, the manufacturer has actually stated that in the specs.

Regards

Mark

Don't get hung up on comparing your machine with what it might have beenbrand-new out of the factory. The test is whether any wear that you might have is more than you can live with when making parts. 1.5 thou on any axis is bloody hard to notice on most finished parts, and if you lock the un-moving axes when making a cut, then there's a very limited opportunity for clearance to cause any problems. If, after using the mill for some time, you decide that you really can't live with or work around any issues, then is the time to look into rebuilding.

I was blessed/cursed with getting a Beaver Mk1 VBRP mill that was, to put it kindly, clapped out. 10 thou horizontal and vertical wear on the X ways, 20 thou horizontal and vertical on the Y ways and 10 thou on the knee to column.

After four years effort it's down to less than 2 tenths total deviation from square and 1 tenth play in all axes, but I didn't make anything with it in that time. It was unusable when I started, but I'd have probably been better off to buy a machine that wasn't a basket case to start with.

Basically, use the Bridgeport to make stuff and work out whether you need any better after a year or so, rather than worrying too much to start with.

Have fun, it's what machine tools are really for.

Having held the plastic 240V pendant of a 250kg hoist in my shed with smoke coming out of it. I agree fully.

On the other hand, it was slightly less scary than the occasion when someone had removed the screws holding the metal 415V pendant together on the little 10 ton crane was using at work, I was left holding the back half with one hand and gingerly poking at the buttons with the other.

Luckily, no machine tools were harmed in either case .

Yup. That was a cheap 500W single phase, Chinee hoist bought from Lidl (Switch replaced by next day delivery of a better unit from cpc.farnell.com). The VFD is a 23kVA Danfoss VLT series unit.

Disconnection is no problem at all for any modern VFD. The potential reflected transient voltages seen at the VFD output in normal running are as great as those that could be caused by disconnection. This is why the IGBTs have integral freewheel diodes to cope with that problem.

The C-E voltage is limited by the DC bus voltage and the flywheel diodes.

Edited By Mark Rand on 02/11/2017 01:11:01

First off, Don't expect a definitive answer or possibly any answer, in just a couple of hours. If people read your post, but don't respond, it's probably because they don't know the answer.

Second, where was the indicator mounted to start with? or have you adjusted the other two gibs to get the best fit everywhere?

1.5 thou of play on each axis may be acceptable for a worn machine, but it means that you'll have to lock the non-moving axes every time you take a cut. The new condition is less than half a thou of movement (typically a couple of tenths) at any point on any axis and no more than three thou of backlash in any feed screws at any point. To achieve this, you'll almost certainly have to learn how to re-scrape a machine.

Basically, adjust the gibs so that movement is a little bit 'firm' at the ends of the travel and live with what you've got. If you're happy with the results you get, that's good. If, with time, you feel you need more precision, then be prepared to learn how to scrape and make precision measurements and plan on taking one to four years on a complete rebuild...

Mea máxima culpa. Some of us are sad enough to actually enjoy rebuilding our machine tools. We probably need pity from those folk that get on and build things with them!

PS:_ I'm a very slow typer

Edited By Mark Rand on 01/11/2017 23:03:56

I bought an eight foot tall and wide 2 ton gantry crane from an EBay seller in Pershore. When I got there it turned out that they had meant to say 16 foot tall and wide.

With the aid of a loaned angle grinder I cut it down to pieces that could be stuffed between the rear doors of my short wheelbase tranny van and with ropes to hold it in and stop the doors flapping and the use of my (red) T shirt tied to the bits hanging 8 foot out of the back of the van, I carefully drove the 60 miles home.

At home I cut the bits down to what I needed, welded them back together and am still using it 15 years later .

[RANT MODE]

If the manual specifically states that downstream switching is not allowed then that's one thing.

If the VFD was designed in the last 20 years using IGBT output stages with output current monitoring, instead of GTO thyristors without, it'll be quite happy with downstream switching. It's as simple as that. What do you think all the computer UPSs, camper-van 240V power supplies, grid-tied inverters on solar panels and inverter welding sets are, if not fixed frequency inverters which can cope with downstream switching?

In the meantime, I'll just carry on running my workshop with its half a dozen 3ph motors from the single VFD on the other end of the 3ph sockets around the walls.

[/RANT MODE]

Edited By Mark Rand on 01/11/2017 21:50:57

Edited By Mark Rand on 01/11/2017 22:03:36

Edited By Mark Rand on 01/11/2017 22:04:21

If you don't want to tell them you you are, you are under no obligation to view their free content...

And the Miller's red glare, the welderrs bursting in air,
Gave proof through the night that our flag was still there;

Or something to that errect.

PS:- Bloody IPads only change the meta-data, not the file itself.

very long post. Sorry...

Two answers to different posts:-

Blade pitch:- There should be a minimum of three teeth in the cut and as few more as possible. Anything less than a 10/14 variable pitch is only really useful for cutting thin tube. That pitch will do for the thin stuff if you have a very light feed on the 4"x6" saws or a slow hydraulic feed on the 7"x12" saws. I tend to use an 8/12tpi blade for most work and a 6/10tpi blade when cutting more than 3". Obviously, most of the time I use whichever blade I put on last if it's just a single cut, because even a slow cut can be quicker than changing the blade.

Tracking:- It doesn't hurt to clean the wheels, guides, guards, etc every time you change the blade. Woodspoiling bandsaws usually have soft/rubber/polyurethane wheels because they get used with narrower blades that end up with the teeth riding on the wheel. A hard wheel would destroy the set of the blades in short order. Horizontal metal cutting bandsaws don't get abused into cutting circles, jigsaw pieces etc. so they can use blades of the same, larger, width all the time. A metal wheel lasts far better, especially if any coolant is used. Once the tracking has been adjusted so the blade runs lightly against the flange of the driving wheel, the next adjustment is the roller guides.

On the 4"x6" saws, with a single bearing on each side, adjust the guides so they're tight, less a smidge. You need enough clearance so that the weld can get through, any trapped swarf won't stall the blade in the guide and the bearings will last for at least a few blades. For the 7"x12" saws with two bearings side by side in the guides, it's simpler. Adjust the guides so that one bearing of each pair is firmly gripping the blade and the other one can be stopped by firm finger pressure. That'll give you good guidance of the blade without overloading the bearings.

The last adjustment is the blade tension. A saw with any pretensions to industrial use, will have a tension gauge, but the 4"x6" and 7"x12" saws we folks use don't tend to have that. For our saws, the correct blade tension is approximately "As tight as you can get it with one hand on the knob. Trying quite hard really!). after setting the tension, run it some more with the cover open, because the frame will probably have bowed a bit. Once you've got it running cleanly at this tension, it's unlikely to slip off the driving wheel unless you've managed to stall the blade, and that's less likely with the correct tension.


As for coolant choice, because my saw can go for a while without use and because I use it on my lathes, I use ISO46 cutting oil in the 7"x12" bandsaw. I only use it when cutting more than 1" section steel. Everything else gets cut dry. The soluble coolant I use on the surface grinder is enough of a hassle on that machine and I don't want two sets of tanks to worry about rancid coolant in. To be honest, once I've got the permanent airline and compressor setup I hope to install next year, I'll convert the bandsaw to a minimum coolant/mist setup.

It may have been built with a plastic gib (having been sold as a kit), but that probably isn't optimal for the size of the lathe. If you've got more than 1/8" of space for the gib, try to use cast iron. If less, then use mild steel or gauge plate, depending on what you have available. Try to use all the available space to give as thick a gib as possible. This will improve the load distribution from the adjusting screws and make things stiffer (in the 'tippy' sense, not the 'slidy' sense).

Got up at 07:00 and spent a pleasant day wrestling an 8.05m long RSJ into my 8.1m long shed, then maneuvering it so that it was on the far side of the crane A-frame that I'd lifted it in to the shed with. This involved an auxiliary hoist and poking the end of the beam out of the hole in the back of the shed that's supposed to have a window in it.

Unfortunately, mid-afternoon the pendant for the electric auxiliary hoist managed to weld all of its switch contacts together (Up and Down). This lead to a release of magic smoke into the environment and a certain amount of bad language. Leaving the beam held up at one end with the gantry crane and resting on a step ladder at the other end, I trotted off to Screwfix and got one of their little 1 tonne chain hoists. (The 2 tonne one is only £10 more, but I needed it now, not tomorrow...).

Having fitted the new chain hoist to the trolley that had held the electric hoist, I managed to get the beam on the far side of the gantry crane with only another three hours effort.

After A break for teatime I finally got the beam suspended over the four columns that are supposed to support it and the bolts placed in the mounting holes. I called it a day at 21:30. Tomorrow I'll have the simple job of tightening all the bolts, leveling the beam with the jacking screws I put in the column feet and screwing the columns to the wall.

The whole project is aimed at converting my gantry crane into a bridge crane so I can move things up against the shed wall instead of having to waste a couple of feet for the gantry to run in.

PS:- the Screwfix chain hoist might have a rated load of one tonne, but I'm not sure that it has the industry standard 4:1 safety factor for lifting chains.

Edited By Mark Rand on 26/10/2017 23:18:33

Edited By Mark Rand on 26/10/2017 23:19:14

Edited By Mark Rand on 26/10/2017 23:21:47

They're all 64 1/2" blades!

I guess that it's a good job that we aren't dependent on your imagination then...

The isle of Wight .