A 3025 Moving Table CNC Router Build.

[handlewanker]

Hi, this is the final rebuild of the model and shows modifications to the bridge mainly and the side supports at the base.

Originally I had a 10mm thick plate 150mm wide and 400mm long running across the face of the bridge to mount the linear rails on, but after examining the model a better way was found and the bridge now has two seperate 15mm thick strips 60mm wide welded to it to mount the rails on.

This gives an open space in the middle to clear the X axis ball nut.

The side columns have been modified as well and will have two 10mm thick plates welded to the bottom and also another two to the base to make mounting pads for the side columns to bolt down on.

The next step is to source the steel tube, and as it's not all that expensive the cutting of all the pieces of the frame will be included in the buy.

The two photos show the final redesign of the bridge and base, and will be the way it will get built after a few measurements are taken off.

I prefer to work directly from the model, and just take the measurements off without going to a drawing stage, as the model was built exactly full size to give an indication of the various component positionings.

[himykabibble]

lol

[daniellyall]

it looks like its going to be very strong

[handlewanker]

Well I hope so, there'll be enough steel in the build to make it practically unbreakable, but only the real thing will prove the design.

I'm hoping to mill steel, so if it doesn't shake itself to bits I'll be happy.

Next step is to go and buy some tube and get welding.
Ian.

[DYSEQTA]

Really keen to see how this turns out. Keep it up!

[handlewanker]

Hi, it'll be an ongoing thing for the time I take to do it, but as it's an all welded tube construction, that part of it will be the easiest......the fitting out with steppers, spindle and electronics will be an as sourced and available for the most economical cost, but not mainly by the "cheapy" route.......some things you just have to pay the money for to get the results.

The most important part is that the model gave the ideal ( for me) construction layout without going to Cad evaluation or cutting and recutting metal to make it short and stiff to resist cutter loads without deflection.

Gantry and bridge mills are not the best design for milling steel and other hard metals, compared to a column mill made from castings etc, so I have to constantly ask myself why build a bridge mill from tubing when a column mill made from a steel plate all welded construction could give a more robust design and do all I wanted.....well the answer is I'm waiting for a mill from China and this started as an acorn and just grew into an oak tree.

The Kitmill 2025 moving table router design sold on EBAY for $1,200 was a big nudge to get into the CNC field, but I wanted to go a bit further in the spec category, and steel tubing is one way to get tough without resorting to castings and heavy machining etc.
Ian.

[handlewanker]

Hi, just got some costs for the steel tube.

The available steel tube is 76 X 38 with a wall thickness of 4mm, so that's near enough to the 80 X 40 tube I wanted and the cost for an 8 metre length is approx. $100 plus a cost for the cutting which varies wherever you go.

The next nearest size is 75 X 50 with a 5mm wall, costing $110, and that can go to a wall thickness of up to 6mm too.

I will probably only need about 4 metres of tube, so at $100 approx for an 8 metre length it would be cost effective to get two lots of material cut for two machines and maybe sell one to cover the cost of the overall build.

That's not a bad plan for economy, but could be iffy if the design turns out to be problematic and I have pre-cut parts that need to be changed.

In the past I've indulged in short tube off cuts for various projects and just butt weld them together without any problems, so that's the course I'll take with this build if I need to amend the design in mid stream.
Ian.

[handlewanker]

Hi, just a quick line........went to the steel merchants too late before Christmas, so I'll have to wait till Jan 5 '15 when they next open.

I had to revise the steel tube dimensions to what they stock or could get it, and the choice fell between 76mm X 38mm with a 4mm wall or the next size up of 75mm X 50mm with a 5mm wall, so I decided on the 75X50.......cost varies but for an 8 metre length it's about $168 to $175 and cutting either nil or as much as $7 a cut, but one place offered to cut it in 4 pieces for nothing......I'll re-cut it at home to the final sizes.
Ian.

[handlewanker]

Hi, today I bought the steel tube, 75mm X50mm X5mm wall X 8 metres long.....cost at $150 for cash including cutting into 4 pieces approx. 2 metres each to fit on my trailer.......money talks.

I bought the whole 8 metre length, enough for 2 machines with only 200mm scrap left over, so next coupla' days will be power hacksawing it to reqd lengths.....26 times, and then the cut outs on the ends for the base cross members to fit under the side rails for welding.

I still have to go out tomorrow again to get some flat steel bar 50mm X 15mm X 300mm long for the base mountings for the bridge and some pieces of 40mm X 20mm for the linear rails to mount on after welding them to the base cross members and machining flat.
Ian.

[louieatienza]

Ian that design looks pretty good, though for something small like this I'd recommend reconfiguring the Z axis so that the rails move up and down. You can suck that spindle in more, at least the thickness of the plate you're using now, and possibly more with some creative pocketing. It would require making the bridge legs a little taller, but since they do not move anyway it wouldn't be a big concern.

I made a small CNC with a similar configuration that I sold to a high school teacher, and his robotics team used it to win top honors at a local college contest!

[handlewanker]

Yeah, after Defeng went on "holiday" I got desperate in wanting to get into CNC machining, and as I already have a small jig borer mill that "could" be converted to CNC with a lot of work, I decided to design from the ground up and the thing that prompted me was the deign for a small router on EBAY that featured a moving table.

As soon as I saw that design concept, the opportunity to beef it up for more ambitious machining planted a seed that blossomed into a concept model and now to a pile of cut tubing.

I prefer the moving table design as opposed to the moving gantry for heavier work as it allows you to go big with the bridge and side frame supports, which, as I intend to mill steel will hopefully make this possible.

The work envelope is only 300mm X 250mm and a height of 130mm, but that is the work envelope I need.....anything bigger and it starts to get rocket science in the structural design.

I find if you go bigger the proportions start to get out of scale, whereas with a certain work envelope in mind the machine just gets designed around the travels needed to do it, and I like it as compact as possible.......more structure in unnecessary places is just more material to flex.

Taken to the ridiculous for scale.....if this 3025 design was doubled to give a 6040 type layout I would need tubing of 150mm X 100mm with a wall thickness of 10mm, and this would give me a table work area of 600mm X 500mm.

That is fairly practical, as you don't double the size of the cutter or the depth of cut with a double size work piece........it means a machine base length of 1.2 metres.

It also means ballscrews of 30mm diam and HIWIN linear rails of 30mm....stepper motors also need to go double if available.

The spindle would stay the same as it's not practical to go to 160mm diam with huge cutters etc.

Being a moving table the present design has a base length of 600mm which is a common characteristic for the moving table whereas the moving gantry is only as long as the table needs to be.

At present the work area is 300mm X 250mm, but as I anticipate fitting a 4th axis and tailstock to it I lengthened the table by 100mm at each end so that the 4th axis doesn't impinge on the work area.

The 100mm overhang at each end is a non working area so it doesn't affect the rigidity of the table on the rails and I still have the bearing blocks at the ends of the table work area hence the need for a base length of 600mm.....I'm considering fitting three 20mm HIWIN bearing blocks to each side of the table, as the outlay is quite small for the extra bearing capacity it'll give.
Ian.

[handlewanker]

Ian that design looks pretty good, though for something small like this I'd recommend reconfiguring the Z axis so that the rails move up and down. You can suck that spindle in more, at least the thickness of the plate you're using now, and possibly more with some creative pocketing. It would require making the bridge legs a little taller, but since they do not move anyway it wouldn't be a big concern.

I made a small CNC with a similar configuration that I sold to a high school teacher, and his robotics team used it to win top honors at a local college contest!

Hi, I'll have another look at the Z axis layout, as a lot depended on the ball nut housing, rail and bearing block height and thickness of the mounting plate etc.

There being two ball nut housings backing onto one another for the Z and X axis and the length of the linear bearing blocks themselves to add to the width of the Z axis plate.

I opted to the rails being fixed and the bearing blocks moving on the Z while the clearance of 130mm allowed me to juggle with the hang down and the spindle stick out to get the minimum overhang as this would put a lot of twisting torque to the bridge.

My main concern is the spindle actual, if it is a high speed 24,000 rpm 2.2 kw water cooled type with VFD, while it will be OK for engraving and carving, I don't think it will perform well at speeds in the lower ranges for milling etc and my main need is milling steel.

So I might do a SVM-0 option and source a 3,000 rpm spindle with belt drive for the milling.....early days yet as the eggs are only just laid and need to be cracked before we get to make omelettes.

The outcome will depend on the spindle end as I quite fancy TTS for simplicity and cost effectiveness, whereas ISO 30 can be a cost factor affecting the budget overall, and a power draw bar is a must have.

No ATC is envisaged, that is not unless I utilise the 100mm end of the table to mount a magazine on, but with that I'd have to make the table move 100mm more so maybe it'll be a thought for some other time.

Whatever..... the tool holding will be with ER 32 as I have lots of collets in that type and the shank size of 20mm max will be the biggest I'll ever use.
Ian.

[handlewanker]

Hi Louie, had another look at the Z axis configuration......the reason I have the rails as shown on the model is because the X axis bearing blocks are on one side of the saddle and the Z axis rails are on the other side.

This is because the X axis bearing blocks get bolted on from the back side of the saddle and the Z axis rails get bolted onto the same side which gives access to both sets of screws.

To have the Z axis blocks on the back side of the saddle would make it impossible to get at the screws as they would have to be inserted from the X axis side, but the X axis bearing blocks would already be on there.

This is a problem with bearing blocks as they need to be bolted from the back side of the mounting face, whereas the rails have the screws inserted from the top face.

I went down this path when I put the model together and it was apparent that it can only go one way.

The rails for the X and Z axis are going to be HIWIN 20MM type and the length of the bearing blocks dictates the width of the X axis saddle in conjunction with the height of the ball screw housings.

A lot of juggling went on with full size model parts to get the layout as it is.

If the linear bearing blocks were bolted from the top face like the rails, there would be no problem.
Ian.

[louieatienza]

There are a few ways to do it. I won't spoil your fun by divulging them, but if you look around there are many designs that do just that; mainly for the x-y saddle.

As to the linear blocks, they also come in many different configurations, including flanged (which can be bolted down on either side), side mount, etc. THK even makes a saddle style block.

[handlewanker]

Hi, I've looked at the designs that use round bars and ball bushings etc.

While they do make for a compact Z axis arrangement using massive lumps of aluminium to enclose them, they also have an overhang below the X axis slides that is unsupported.

I want to go to 20mm HIWIN rails for more rigidity.

A lot depends on the ball nuts of the X and Z slides as they are quite bulky and add depth to the spindle offset from the X axis slides, even allowing for pocketing of the nut housings.

In this design, the nut for the X axis is attached to the XZ saddle and moves with it between the linear rails of the X axis.

The saddle is made from a 20mm thick aluminium slab.

The Z axis nut is attached to the front side of the saddle and is stationary while the Z axis slide and spindle mounting block moves on the rails.

Doing it that way gives me minimum slide hang down below the X axis rails at furthest travel of the spindle.....approx. 60mm of the slide will hang down and another 60mm of the spindle projects below that at maximum down travel.

The spindle will be held in a double split mounting block attached to the face of the XZ saddle, and this also needs to be bolted in from the back side, but with careful positioning this is not a problem and there will be lots of support for the milling needs.

You can see the layout of the Z axis in the photo of the model in the first posts showing the spindle at it's lowest with a hypothetical 10mm cutter end down on the table......the maximum clearance under the bridge is 130mm with the spindle able to go up a further 100mm to allow for long tools like drills etc

In the Skyfire SVM-0 mill design the request was for ma longer table........a major design change as it entailed new patterns and castings etc.

In this design the table has 300mm in the Y travel, and if it is to go longer all that is involved is longer side tubes, longer linear rails and a bit more ball screw length, nothing that would rock the boat.

The tubes are all cut now and the next step is to cut out the notches for the bottom tubes to fit under the side frames.

Here's 2 photos of the saw cutting the tube......it's not a conventional power hack saw.
Ian.

[MadeInTheShed]

Here's 2 photos of the saw cutting the tube......it's not a conventional power hack saw.
Ian.

Love it! How long do your blades last, and what is controlling the "feed rate"? Does it take long to cut through?

[handlewanker]

LOL.....this has to be the "it won't work" scenario if ever there was one.

The saw was made in 1982 from an idea in the UK magazine Model Engineer to do a special job requiring flexibility in the job holding etc, but mainly from the lack of a workshop at the time.

It uses regular 12" hand hacksaw blades, HSS type last longer and 24 TPI also last longer than the 18 TPI ones.

The motion can be described as a rocking beam as opposed to a sliding ram etc.

Motor is 1/4 HP 1425 rpm, single phase......speed is approx. 80 strokes per min, with a stroke length of approx. 150mm.

I added a split blade bracing support clamped to the top of the beam to stop the blade from flexing, mainly to see if it improved the accuracy of the cut, and now it will be remade to be part of the machine.

There is no blade relief and it gets it's downward force from the two weights on top of the beam, so it cuts on the back or pull stroke and rubs on the forward stroke.

Blade life is dependent on the material as a thin piece can shed teeth quickly and goodbye blade, hence the 24 TPI blades in preference to the more aggressive 18 TPI type.

The tubing I cut is 75mm X 50mm with a wall of 5mm, and it took 20 cuts to do the complete 8 metre length of tube, cutting from the narrow side to the top.

Each cut took 20 mins, so plenty time to play games on my IPAD between cuts.

So far the blade has lasted well and it wasn't new when it started.

Biggest cut I have done is a piece of square steel bar 100mm X 100mm....coupla hours while I did other jobs.

There is an arm with a roller on top that catches the beam when the cut goes through, so no fancy cut out switches....yet.

The cut was dead square on all tube pieces so that's a boon to start with.

Cost?.....mainly pieces of off cut tubing, some OILITE bushes for bearings, a couple of vee pulleys and drive belts and a 1/4 HP motor.

The work table, made from two pieces of heavy angle iron was drilled and tapped to take plate clamps for work holding.

If time is of the essence, a bandsaw will work quicker, but this one is more versatile in the shapes it will cut and hold........ I set it and do other jobs while it works.
Ian.

[Tkamsker]

Hi interesting solution you found. I own similar mill (heiz 400 t) so i have some years experience .... When i See the Distanz from y axis Support to cuttter this i would Try to minimize because every tenth of millimeter counts .. I cut a lot of strong Alu so probably you Look at that other issue might be weight of Motor which type of are you thinking of ?

[louieatienza]

Hi, I've looked at the designs that use round bars and ball bushings etc.

While they do make for a compact Z axis arrangement using massive lumps of aluminium to enclose them, they also have an overhang below the X axis slides that is unsupported.

I want to go to 20mm HIWIN rails for more rigidity.

A lot depends on the ball nuts of the X and Z slides as they are quite bulky and add depth to the spindle offset from the X axis slides, even allowing for pocketing of the nut housings.

In this design, the nut for the X axis is attached to the XZ saddle and moves with it between the linear rails of the X axis.

The saddle is made from a 20mm thick aluminium slab.

The Z axis nut is attached to the front side of the saddle and is stationary while the Z axis slide and spindle mounting block moves on the rails.

Doing it that way gives me minimum slide hang down below the X axis rails at furthest travel of the spindle.....approx. 60mm of the slide will hang down and another 60mm of the spindle projects below that at maximum down travel.

The spindle will be held in a double split mounting block attached to the face of the XZ saddle, and this also needs to be bolted in from the back side, but with careful positioning this is not a problem and there will be lots of support for the milling needs.

You can see the layout of the Z axis in the photo of the model in the first posts showing the spindle at it's lowest with a hypothetical 10mm cutter end down on the table......the maximum clearance under the bridge is 130mm with the spindle able to go up a further 100mm to allow for long tools like drills etc

In the Skyfire SVM-0 mill design the request was for ma longer table........a major design change as it entailed new patterns and castings etc.

In this design the table has 300mm in the Y travel, and if it is to go longer all that is involved is longer side tubes, longer linear rails and a bit more ball screw length, nothing that would rock the boat.

The tubes are all cut now and the next step is to cut out the notches for the bottom tubes to fit under the side frames.

Here's 2 photos of the saw cutting the tube......it's not a conventional power hack saw.
Ian.

Hiwin makes profile rail blocks with flanges as wellas THK, NSK, STAR, etc.

But it ts not necessary to use flanged blocks. Chec out mactec54's build, or bartuss1. I used the concept on my small router in the project logs section. Also the aforementioned Skyfire which has the same configuration I speak of for the x-y saddle.

[handlewanker]

Hi interesting solution you found. I own similar mill (heiz 400 t) so i have some years experience .... When i See the Distanz from y axis Support to cuttter this i would Try to minimize because every tenth of millimeter counts .. I cut a lot of strong Alu so probably you Look at that other issue might be weight of Motor which type of are you thinking of ?

Hi, Thomas.......having the model to play with as if it is the real thing enabled me to try actual configurations to get the spindle overhang from the X axis as small as possible, but there is the depth of the two ball nuts that cannot be disregarded as much as I juggled them around, and that along with the height of the rails and bearing blocks all pushes the spindle out from the X axis face.

I think that provided the stick out is controlled, the overhang will not cause a problem as long as the slides are tucked up against the Z axis face and the linear rails are substantial....HIWIN 20 for all axes.....so torsional twisting of the X axis probably won't be an issue with CNC small cuts and lots of them.

There is a big advantage in making small cuts and lots of them as you are not turning the handles to set the cut each time, so the machine does not have to be stressed to it's limit hogging off material to maintain rigidity like cast iron models do.

That concept is the very basis I'm designing from.

My main aim at the outset was for a bridge type router/mill.....something like a Genovoise jig borer layout of which I am familiar, specifically to cut small steel items and for that the rigidity plays a major part.

While a cast iron machine with it's heavier sections would be the norm for a manual mill construction, I did not want to go down the path of just another mill and the massive machining curve that entails.

With careful planning I think it is possible to take advantage of the CNC procedure with milling hard metals like iron brass and steels etc using tubing construction for the main frame

I was influenced by David D'Caussin's UMC-10 build where he utilised heavy wall tubing and all welded construction, so if it works in that mode why not for other designs too.

I have model engineering ideas I want to pursue and model steam engines are just one of them.

There are two modes to think on, and the main one is for milling.

For milling you need a power draw bar.....not negotiable on that score, so that gravitates to the simplest and most economical which is TTS.

The spindle itself is run of the mill in design, angular contacts and radial etc, but the motor is the problem.

Weight being unavoidable for low speed motors (3,000 rpm, 1/3 HP) and high torque, but milling is mostly carried out at the lower speeds and you can get a speed increase by having two pulleys and with VFD.

The spindle mounting will be to enable a high speed spindle to drop in to do some carving and engraving work in a similar manner as the SVM-0 design of SKYFIRE.

It would be interesting to build a milling spindle with a synchronous motor as part of the spindle itself, similar to the design of Bertuss1's.....it could be quite compact if designed carefully and still have the power draw bar option even if it rules out having a hi/lo belt drive set-up.........a 3,000 rpm motor would give you 6,000 with the VFD, so that could be a solution.

I'm thinking of a 3 phase 3,000 rpm 1/3 HP motor as I have one, and if the motor casing was removed leaving just the stator coils, a lot of weight would be removed......the rotor has enough body to enable a spindle to be fitted if it is bored out a bit.

The higher speeds for milling would be for smaller cutters so some fall off in torque would not be a big question mark.
Ian.