Thread: decided to make one

the google sketch up design , the blue bits are the pc radiators pumps fans and tank for spindle cooling , has cover plates to force air through the radiators

Why 600 for the Z axis travel-that's incredibly HUGE!

Most decent 3D software has the ability to slice files into layers you can fit under the gantry.

Our router is 3600 x 2000 x 140,but in reality you can really only rout about 3" thickness in the Z direction as the cutter has to be able to go deep enough into a hole & then to get back out of it, to the next area without carving holes in the background to get there...

The steel in the arms & gantry is all about 5" by 3/8" square RHS. (No epoxy!)

Between the two long X rails is a grid of about 40 x 25 RHS, standing up, (i.e. 40 deep), like weldmesh. This is tunable via threaded bolts/grubscrews every couple of feet, adjustable up & down a tad to get it level.

(edited to add our Z axis actually has about 300 mm travel, but you can only fit about 5" clear under the gantry, and can feasibly rout 3"-I havent figured out why, really-perhaps there's some setting in the software limiting it to 80mm instead of 125mm.)

A big thick MDF bed sits over that & when you're ready you skim the bed to make it all level & true. The MDF is tek-screwed (very-well countersunk) into the RHS frame/grid carrying it.

Good luck with yours. I can see the intertia of a tall Z axis being an issue though unless you only creep along slowly in the X direction. You'd need tremendous bracing otherwise, which would limit the X length somewhat, unless you have a much bigger 'footprint'.

600mm zaxis height for foam cores , turning them on the 4th and wrapping in carbon fibre , at a diameter 600mm

was thinking of reducing the height to 300mm and having a removable bed for the 4th axis
, some of the carbon projects planed will need the bed removed anyway (1200 diameter foam would be great ) ,

the epoxy is only in between the rails and steel , and between the welded truss's and the bolted on rail supports ,, i can machine the epoxy accurately but not steel

looking at laminating float glass to 18m cement fibre sheet ( 900mm x 3000 ) to make an adjustable flat table , bench top , adjustable bolts at 200mm centres , to help set out the gantry , any one made one ?
and any one know of a good supplier of straight edges , chasing a "0.001 inch parallel " 1200mm long straight edge , dosnt have to be perfect along its length just super parallel ( some bucks $$$ for some one with an accurate machine ? )

thinkin i might 1/2 the z axis , and have a removable top , to turn 600mm diameter to nothing only needs 300mm travel

so the bearing block foot print of the z is 400mm wide by ( was 600 ) 900 deep , still need the length on the z for a later up date to a lazer ( 1100mm long ) and a carbon fibre winding head with 4 rolls takes up a lot of room as well , 400mm is the roll length

the y to z axis foot print is 600 x 600 x 600 , on 3 rails , with a welded 50x50 tube truss supporting the 4 100x100mm Rhs that will be bolted on with epoxy beds , bolted in absolute true position , dammed up and epoxy cast into the gap of 1mm max ,
to make a truss ( 4 sided ) dead straight is beyond my welding capability and if i send it "south " to be machined i might as well get it gold plated, i cant find a business with a milling machine over 1200mm in darwin ( reason for the epoxy)

x to y axis foot print is 600 , yes , 3000mm rails for 2400 travel sitting on I beams

no legs on the y axis , some solid braced corner posts to hold up the x axis beams ( thinking 125x125mm rhs & rio bar with concrete filling)

Sounds like you have done a lot of thinking about what you want.

I agree with the 300mm Z axis as the height. Anything more would be a waste due to cutter length.

I have seen a machine where the bed lowers to increase the height for thicker material.

Continue to keep us updated and reme,ber to post pics.

how fine is the line on the cross hair lasers ?

am about to make a flat bench out of 1/4inch glass laminated to 10mm cement sheet ,sitting on a bed of fine thread bolts at 200mm centres , was looking for an easy way to zero it

thought a level rail down one side , a cross hair laser mounted on that rail , a steel based bracket with a reference scratch on it , with a 400x USB microscope pointed at the reference line

basicly what i want to do is sit under the table with a spanner , using a magnet to move the reference line and microscope around , looking at the PC screen to centre the scratch in the laser cross hair line , just wondering how fine is the line , 1/10 mm would work well any thicker is no good

should be able to centre it well , 0.04 - 0.06 , so with in 0.02mm

what do you guys think of this way of zeroing a flat bench ?

will have my y axis rails to sit the lazer on , and a USB microscope - $40 , laser $10 , well under the glass and CFC sheet , let alone the steel to grid out the bolts ?

the table will be 900x 2400 , a set out bench to use dial indicators off

Laser crosshair is much thicker than you are asking.

You are relying on gravity to hold down the table - what will you do if there is an upwards bow in the sheet? You will have to run over the table a couple of times as adjusting an adjacent point will affect the the surrounding points.

I use a cap screw through the table and threaded into the support to hold it down and next to it a grub screw threaded into the table to push it up. It works very well but you can't use this method because of the materials you are using.

Originally Posted by SawDustSniffer

how fine is the line on the cross hair lasers ?

dont expect you to get our micrometer out , a guess would be good enough

a pull down bolt and a push bolt at each 200mm grid , place what you want to inspect , jump under and level , then inspect , i was going to use 18mm CFC but though 10mm will get around the natural stiffness
of the 18mm

Originally Posted by rodm

I use a cap screw through the table and threaded into the support to hold it down and next to it a grub screw threaded into the table to push it up. It works very well but you can't use this method because of the materials you are using.

i can still set the bolts in before i laminate the glass over the top , was going to drill and glue in nuts on the under side of the top

At a guess half a mm. The focus varies with distance so it was a bit of an open question..

I level from the top using a dial gauge off the Z axis. Much easier than you are suggesting and you reference the table to both the X and Y axis at the same time.

Having a flat table is important but having a table parallel to X and Y axis is much more important.

But the big advantage is you don't tear the bum out of your pants sliding on the floor under the machine.

no
this is a flat table so i can make my gantry out of steel , its not the bed of the machine ,

it will just be a flat bench for measuring accurately ,
i will use the machine to face the bed on the CNC

Ok in my haste of reading I missed that - sorry

It seems like a lot of trouble to me to set up some steel for assembly. You will get variation in the steel from manufacturing so not sure if you will gain anything by making the table.

I must admit on my first build I imagined all sorts of issues that seemed to either not be there or fudged into other inaccuracies. To get a totally flat table you would need to blanchard grind the surface and the minute you move it to a new position it would need more work to return it to level. I am splitting hairs here and thinking in the range of 1 thou. All materials are elastic and it was demonstrated to me once by a bloke putting a bore gauge in a clinider lining then pressing on the block from either side. The bore gauge slipped down the bore.

The point I am trying to make is maybe you are chasing something that is not possible with fabrication. Your ideas are a breath of fresh air on the forum so don't let me deter you as my opinion is one in many.

yer , im a bit of a perfectionist , but if the y rails have a 0.1 curve to it i will know , and i will end up fussing over it , i want to build it once ,
lol at moving the table , just placing 20kg on the table will change the flatness , hence im looking for an easy quick way of zeroing it

at 0.5mm for the cross hair laser its not fine enough, but still good for 0.05mm , should beable to cut the line by a 10th , lol 0.05mm + or - 0.02mm would still be good

no takers on making me a 1200 parallel straight bar ? , bit of cash for some one with a accurate machine

one steel is open ( xmas brake ) decided on 360mm I beam for xaxis support , i can bolt the removable table cross members to the lower "I" and still have 300mm travel on the zaxis