[handlewanker]

Hi......big kettle of fish getting opened up once more....LOL.....Thomas is wringing his hands in the background and saying 'why oh why did I not post my design before they can rip it to shreds without seeing it'....LOL.

Joking aside.......I've worked on two type of machine where you have a separate bed for the table apart from the machine proper and not attached to it.......built mainly for those large fabricated structures that need to be machined after construction where welding has taken place.

The first one was/is a Ravensburg lathe which I worked on in 1959 as an apprentice and later as a fully qualified fitter and turner, one of those type with the huge 2 1/2 metre diam face plate chuck and this has the head stock on a base and the bed and slides on a separate large cast iron base that allowed the bed to be moved around to cater for long jobs or those that were a large diam.

Now this lathe could do screw cutting too, and to couple the leadscrew on the bed with the headstock it had a stepper motor which allowed the leadscrew to do any pitch wherever the bed was placed on the base.

The second machine was/is a Swift floor boring mill that had the same type of configuration with the column sliding on a bed that was separate from the second base bed where the jobs were mounted on.

So, horses for courses.......if the design can produce better results, then the designer will get a polished halo when he goes upstairs......all good designers go to Heaven I'm told.....LOL.

BTW, the Swift floor borer mill did not have linear ways but it did have long box ways that were pressure oil fed when the column was on the move.

In the design by G59 I don't think the spindle sticks out too far from the column as it has to be able to cover the furthest part of the table or at least cover the work envelope that the machine is made to do even if the table is much larger to enable long and wider jobs to be mounted on.

There is an advantage in having a separate fixed table design....it can be as large as you want without the need to have to move it around, catering mainly to mount the job on.

But this comes at a price......for very large machines it's usually mounted on a separate foundation sunk in the workshop floor, whereas for a smaller machine as G59 has drawn, it would require the work table to be mounted on a base that was integral with the column slides to enable both to maintain accurate alignment.......that is quite a large fabrication as opposed to the conventional layout of a mill.

I think that design would only be anticipated where the need to machine large pieces of work were envisaged.....having two vices on the table indicates that it is not in that spectrum.

I love the size and configuration of the column structure that G59 designed, and if it were a part of the design that Skyfire constructed with the SVM-0 and 1 series I think that would be really getting to the point of a new look at mill design for CNC moves.....away with the toffee apples on a stick designs.

I think FEA analysis has a lot to do with column design inadequacies as it gives the designer the false impression that a toffee apple on a stick can be adequate for at arms length spindle support without vibration under load as long as the information input was accurate.

Thomas still has to throw down a design concept for evaluation and a ball park idea of what type of work it will cater for.......the regs constraining that design are just boundaries to the imagination and differ from country to country.

So Thomo....lets have some conceptual sketches of the Wunder machinen....Ja?

BTW, once the Chinese see it they'll have a working model on EBAY before the ink is dry on your drawings......LOL.
Ian.

[carlowens]

lol, yeah kamsker must be busy building a prototype from cardboard and paper mache so we can get an idea of what he's intending to build.

[aarggh]

You also criticize a concept that you have no idea what the dimensions are other than what I said the work envelope would be.

You also have no idea how or even what it's made of, or how heavy it is.

aarggh, arm chair engineering is Ok, but only if you can bring constructive criticism into it.

Which is why I had the word "surely" at the end, to make it clear it was an opinion that was questioning the points raised!

You can laugh all you want, I wasn't trying to offend, I simply based my remarks on what I could see, and what I thought was common sense regarding flex and forces based on my own experiences and observations.

If I'm wrong, then good, it's an interesting design, and until you posted it and I subsequently googled it, it would have never occurred to to me to make a travelling column mill, as it still seems to me a fixed column machine would offer better machining for a set price range against a comparably priced moving column machine? This argument seems not at all different to the fixed gantry/moving table arguments, in that everyone seems to concur the moving table is by far the easiest to build, and offers the most rigidity, so I'm still unsure how in a moving column mill the theory is reversed, and a moving table is the same or less rigid than a moving column mill, unless the moving column mill requires far more design, costs, and materials to compensate for that?

I also don't own a Tormach, I have a 750kg knee mill, but do agree 1.5HP is possibly a joke for a machine that size, although many owners seem to have done exceptionally well with them, so it must more than suit a lot of people, but that's a purely personal choice. I'm very happy with my simple 3HP mill myself.

Regarding linear rails and lifting, we actually do see this here on the zone heaps, whenever someone builds a Z too high, or a frame not solid enough, etc, and it invariably ends up with lifting and looseness in the assembly. So I thought my question there was valid, if it wasn't, then so sorry.

cheers, Ian

[handlewanker]

lol, yeah kamsker must be busy building a prototype from cardboard and paper mache so we can get an idea of what he's intending to build.

Yeah....LOL.....but I expect I'll trip over my beard before we see the real thing.

Hmmmmm, paper mache.....polystyrene foam is easier to cut and gives a clean edge, it also gets thrown away by the ton so cost nix.
Ian.

[Tkamsker]

I have Seen exactely that design (only Miller was adjustable ) in much Bigger size on an Show here
The Idea was that if workpiece is huge (the example was an Ship Diesel Engine ) you better Move the Miller but i did Not thought of doing that on "small" Mill i also like the Idea when you think of automatic Feelings of stock ,.. So i am ok with the Design just stay with my small concerns because i have Seen it in Action but huge ,..


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[Tkamsker]

I have the skill but no time i work on that servo machine and atc .. I draw now enclosures which fit Regulation and can be done by the Laser cuttter Shop. So if i follow their advices they can easier manufacture it nice

[G59]

Well Tkamster, I know the feeling.
Today I put my design through the wringer in the Finite element analysis software, and yes I have to eat my words now. My original design, if I exude a cutting force greater than the weight of the assembly(head), sure enough, the cumulative errors add up to the linear way's tolerances. So end result was errors in excess of 0.005 thousands of an inch. That's just not acceptable to me.

So Yes I was wrong, unless if you never plan on cutting aggressively, it just doesn't work efficiently with the material I have.

So a re design was necessary. I have now tested this version, and it fairs much better, at 3x the cutting forces. Less than 0.001" deflection at over 1000lbs on the cutting tool. This is way over what a BT30 was ever designed for so I will go this route. Still all plate, and I gain 2 inches in Y.

Attachment 260210

[G59]

carl, the original design worked. But after aarggh pointed out hi cutting forces, I at least went back and applied twice the forces on it to see if maybe he was right. Turns out he was. Ha Ha Ha. BooHooHoo.
Whatever.
Point well taken. I never thought of pushing over 300lbs on the tip of the end mill for it to cut. If you ask me, that's a mighty dull cutter. But at least I went and tested it a dozen times in all three axis. That's where I found that beyond the weight of the assembly, the errors would accumulate to the point of a poor finish and major vibrations as end results.
Now, go back and start cutting up your polystyrene and papier mache. Maybe you'll have better luck. let's see you do that in one day.

[aarggh]

The more heavily re-enforced Tormach style re-design looks much improved to me, a question though about the rails, would it be better for the rails to be mounted to the underside of each plate to add to the stiffness and also reduce the crud that accumulates on the rails?

cheers, Ian

[G59]

would it be better for the rails to be mounted to the underside of each plate

Possibly, but being that it will have way covers, I think it is just fine. Putting the rail the other way would also mean a bigger enclosure to cover the same work envelope as the table size would double. Being that I do mostly mold work, I like the smaller table size.
Table is currently 22x16 inches

Another thing is that with the rails this way, no chance of any overhang affecting level. It also lower inertia and keeps center of gravity at it's lowest.

[handlewanker]

and as carl is a snooper and not a maker of anything significant to date, all he can do is make strange sounds that go for logical comment and achieve nothing......I've put a report in so maybe he'll tone down his comments and go with the flow instead of being a pain in the butt.

BTW, G59.....I was getting quite excited to see the design progress with the stand alone table.

The current design is going to prove that while you can think outside of the box, the end result is that you still need to move the job or tool point in 3 directions and to that end all roads lead to Rome.

My opinion is that with the small area table you are restricted to not being able to attach a 4th axis, if required, without filling up the work space with static metal......I think that with the design as it is the table could be extended each end....probably about 150mm..... to give an area that, although the spindle did not cover it, would allow longer jobs to be mounted or an area where the 4th axis per se and tail stock were mounted without taking up table work space.

The extended table ends don't need to be on the rails and the ends could just extend over the rail end as they are just to hold the 4th or whatever is on there.

The extended design with the same table linear bearing layout would still lend itself to full working area support at all times......and if the cabinet needs to be moved out by 150mm each side that's a small price to pay.

I'd like to see the inside layout of the column as it's one area you can visualise from the outside without being able to actually construct it inside......there's an awful lot of gussets needed to ensure the body frame does not become springy and flex under the extended leverage of the cutter to column ratio and they need access to weld them in.

Direct forces applied in a steady push to the cutter itself will not move the steel sides to any degree, but if resonant forces are set up the weight of the head and column will act together to move the cutter and destroy it..........if the head/column mass can be "persuaded" to reach resonance, and that means just a few thou at the cutter tip, all the integrity of the ISO30 spindle will achieve nothing.
Ian.

[Tkamsker]

I like your drawing here do you Start now on an prototype ?


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[G59]

I like your drawing here do you Start now on an prototype ?

Yes prototype on latest model will begin in a couple weeks, just have drawings to do.

yeah it didn't take long to completely abandon the other idea.

Not really abandoned. Would work great for a machine half the size.

looking forward to your design kamsker as this is your thread.

Got the message.

[Tkamsker]

Hi,
my thread your thread i think the idea of this thread is to share construction pro & con and ideas
Also to find out what people like and think
so my next weeks are (beside season celebrations - full of things to do
- prepare the servo based machine (due to regulation has to be the most complicated one - ) for test & certification
- do toolchanger for it

so i no have to bring all the necessary tasks in an sensible order to achieve the goals
in timeslots i work also on the act work holding

bit G59 if you are faster with something to show i would happily see your pics as well

thx
thomas

[handlewanker]

Hi, looking at the smaller table and the longer rails supports and I have to wonder what advantage a manual mill has with it's long table but only 2/3 rd's spindle coverage........on the other hand a long job can be mounted on the table and the mill head swung sideways left or right to cover all the table even if the travel was not full length.

So, is the shorter table predominantly for small work envelopes, such as vise or jig mounted jobs?

One question.....where will the table be made......all those Tee slots are a pain to mill.

Another question, what advantage does a Tee slot have over say a tapped hole in a table.....apart from the ability of the Tee slot to have almost any position anywhere for odd shape job bolting.

I know this is pure heresy and I won't be going to Heaven, but it's thinking outside the box for me on this one.

If odd shaped jobs are not on the calendar, I would .....and this is just my opinion........drill parallel holes at regular intervals and have expanding bolts to hold the work......similar to Dyna bolts you use in holding objects to concrete walls or floors etc.

I think tapped holes would be a pain to keep clear of swarf, even if they are clear through the table or get plugged when not in use.

This would lend itself to a steel table that only needed drilling for the expanded bolts when needed.

I'll be making a bridge mill pretty soon, and one feature I'll have will be a thick aluminium table with plain drilled holes as opposed to the conventional Tee slot table either machined or made from extrusions.

To ensure the table top will last to the end of time I'll glue a 3mm thick plate to the top and drill through it and if the plate gets damaged it can be replaced.

The drilled holes don't need to be reamed or have special sizing, just as long as they're all the same, and the expanding bolts will grip just as tightly as any Tee nut can.
Ian.

[aarggh]

Hi Ian,

I often thought a nice tapped tool steel table would be ideal compared to t-slots, but after using my large mill for some time I'm now re-thinking that. As you mentioned the swarf is not a trivial thing to dismiss lightly at all, and it can be a downright royal PITA the way it clings and cruds up everything. Trying to keep tapped holes clean let alone accessible under use can be a tiresome and very fiddly job. The other aspect is that t-slots lend themselves beautifully to sliding material and tooling with little fuss, and actually make setups a little more painfree and fairly quick.

Using expanding bolts in a table means the holes will end up in pretty bad condition after a while as the bolts will slide in the holes when there's crud in them, and then force the crud under pressure against the sides. Might be a problem there?

With table size, I shopped around for ages before buying a pretty big mill, with at least an 600 x 400 cutting area, but after using it I now have my heart set on a King Rich mill, with a bigger work area. The ability to machine reasonable length material in one pass is invaluable.

cheers, Ian

[G59]

I agree with aarggh. If you ever used a fixture plate, you know once it's fixed to the table, it's always a pain to keep the threads clean when you start another setup.

The T-Slots will first be cast at a foundry and finished on the machine. I can get it done here for $375 a piece, if I order 10 pcs . Of course, I would have to supply the pattern.

The table on my design is 550x400. It's big enough for most jobs I would encounter. Yesterday I mounted a 6 inch rotary table on it, and it left me with only 16x16 inches(406mm x 400mm) of useable space.

I decided a small table was good enough for what I did, mostly molds and sometimes gearbox cases and covers. If I need more room, then I'll just fire up the old Tree mill. That old mill has a 48 inch table but only 30 inches of travel.
Small tables can be a drawback, it just depends what kind of work you do.

[Tkamsker]

I think the tapped Setup is for factory Setup where you work days oder week in one Setup then change it to next Setup
So i stay with tslot table for now
I Look for an 600 by 300 work area i hope that will be sufficient ...

[handlewanker]

Hi, I quite agree, having worked on many machines in various configurations and they all had Tee slot tables etc.......but with the small machine I'm building the aspect of having a Tee slot table is the hinge point to not having the machine or doubling the cost to get the Tee slots cut into a steel or aluminium plate.

I already have a small cast iron Tee slot table from a scrap yard expedition, approx. 400mm X 200mm and about 40mm thick which would do at a pinch......but it has a large weight factor that I think would be a problem with inertia loads if rapids were encountered regularly.

The current design calls for a 25mm thick aluminium slab for the table, and is now going on to 500mm X 250mm as I added some more real estate to the ends to cater for 4th axis etc placement without taking up table work space.

Having an ally table means it would be daft to cut Tee slots into it....they're just too vulnerable to wear, so the idea of the plain drilled holes with expanding bolts appears to solve that problem, and to prolong the working life I'll glue some 3mm steel plate to the top and refinish it........I quite fancy a scraped finish with some curly frosting marks etc.

I think if a machine is intended for production, then it has to go with the general trend or it won't sell, and as I'm only going to make only one of this design it's still open for the final rendition when the table gets into the picture.

I weighed up the cast iron Tee slotted slab weight as compared to an ally slab and the inertia forces that would ensue, so ally wins hands down for simplicity in construction and pure replacement costs if the table ever needed to be replaced.

But I digress, no doubt Thomas has a much more sophisticated design program in mind to pursue compared to a small one off table top bridge mill, but as my old grandmother once said, you can squeeze just as much juice from an apple as a plum, so if the bridge mill design turns out to be really economical and easy to build, who knows, maybe EBAY will have another router/mill in it's listings.

The heart of any machine in the end is the spindle and how it makes the cutter move.

If you're engraving and carving, then a 25,000 rpm model with VFD would be the item of choice, while for milling etc, you'd probably only want to get up to 7,000 rpm and with lots of torque in the bargain and in practical terms that can only mean a belt drive with separate motor.

Having a belt drive immediately gives you bags of torque and the option for QCT....not really a requirement time wise, but definitely a factor to remove the fiddly aspect of tool removal, and I hate having to chuck and un-chuck cutters, drills etc in the middle of a job.....and they always go back exactly as you set them ......QCT can make the difference between tedious tool changing and click click next tool on the go especially for drilling and tapping operations.

If you're in the design mode, no sense in being short in the options department just for the lack of forward thinking.

The main criteria in any machine design is simplicity, and not wanting to be personal, I have direct experience of German design technology....if it can be made complicated, the Germans will make it even more so....simplicity is not in their nature....that is a fact without any doubt.

On this score sheet, the Chinese win hands down, so I hope Thomas is in a different school of thinking when it comes to design and technology applications.
Ian.

[handlewanker]

Hi Ian,

I often thought a nice tapped tool steel table would be ideal compared to t-slots, but after using my large mill for some time I'm now re-thinking that. As you mentioned the swarf is not a trivial thing to dismiss lightly at all, and it can be a downright royal PITA the way it clings and cruds up everything. Trying to keep tapped holes clean let alone accessible under use can be a tiresome and very fiddly job. The other aspect is that t-slots lend themselves beautifully to sliding material and tooling with little fuss, and actually make setups a little more painfree and fairly quick.

Using expanding bolts in a table means the holes will end up in pretty bad condition after a while as the bolts will slide in the holes when there's crud in them, and then force the crud under pressure against the sides. Might be a problem there?

With table size, I shopped around for ages before buying a pretty big mill, with at least an 600 x 400 cutting area, but after using it I now have my heart set on a King Rich mill, with a bigger work area. The ability to machine reasonable length material in one pass is invaluable.

cheers, Ian

Ho Ho Ho.......a King Rich mill.....now that is something to find in your Christmas stocking.

About 15 years ago I bought a well used Bridgeport mill from the firm I worked for when they downsized the tool room, and it was the dream machine for accuracy and useability.......my mate, whom I worked for after retrenchment, needed it more than I did, or so he said, so I sold it to him and bought an Ajax mill on EBAY, similar to a King Rich mill, with a 54" table length, in built feeds and rapid traverse to all axes and an ISO 40 taper......and all for $3.200 due to the feed gearbox being a bit iffy, but soon fixed.

I just did a trial run with a piece of steel and a Dynobolt to see the effect of an expanding taper lock as a potential work holder........no contest, it's green for go.......swarf will not stick to the smooth sides of a straight hole.
Ian.