Joe's 1000x600x200 steel and aluminium router started

[Sterob]

Nice work Joe!
I see you are milling small slots to locate perpendicular sections to each other...... I enquired about doing just that in another forum with almost no reaction.
It seems to make sense to me ( no expert) What better way to ensure components are aligned correctly?

How have you found the process? A good idea or problematic?

I'm considering doing the same thing...when I eventually start my own build.

I see you have maximised the distance between your x rails, by placing them top and bottom of the Gantry.
Did that make things excessively more difficult?

Steve

[Kitwn]

Hi Steve,
Joe won't be out of bed yet

There's a fair amount of stuff on gantry design on the forum. Putting rails top and bottom has the advantage of pulling the Z axis closer to the gantry and reducing the overhang. It also gets the rails as far apart as possible for the chosen height of the gantry but makes the construction of the Z back-plate more complex. Alignment of the rails is not 'automatic' in any way and must be done with care.

The option of mounting rails directly on the front of the gantry pushes the Z axis out but can be easier to align, especially if you're using epoxy leveling or a machine-ground plate to ensure a perfectly plane surface. It also makes the Z axis back-pale into a single flat piece. It all comes down to what tools and measuring instruments you have access to.

As long as the first machine you build is adequate to cut out the pieces for a second, better version then you will be on an upward evolutionary slope.

Kit

[devmonkey]

Nice work Joe!
I see you are milling small slots to locate perpendicular sections to each other...... I enquired about doing just that in another forum with almost no reaction.
It seems to make sense to me ( no expert) What better way to ensure components are aligned correctly?

How have you found the process? A good idea or problematic?

I'm considering doing the same thing...when I eventually start my own build.

I see you have maximised the distance between your x rails, by placing them top and bottom of the Gantry.
Did that make things excessively more difficult?

Steve

Hi Steve,

I also thought twice before milling the locating slots on the different plates. On some joints it is not so critical, such as attaching a stepper mounting plate but when you are joining two plates that locate the axis at exactly 90 degrees such as where my gantry end plates join the X bearing plates it is super critical. In this example it was also critical the slots in the top of the X bearing plates were not only planar with the plate surface but also identical depth on both X bearing plates.

When I mill out shapes from plate I clamp the plate to MDF so the cutter clears the mill table. MDF (particularly when it has sat in the garage for a year) is not sufficiently uniform for accurate Z milling. Therefore I mill these slots after the outside profile has been finished. I set the Z height on the mill and lock the axis then I clamp each X bearing plate to the mill table directly and mill the slot. I do both plates without unlocking the Z axis so they should be identical.

Before doing any of this critical stuff (particularly milling the gantry extrusion flat where the Y rails are mounted) I checked the mill table was flat within 0.01mm over the entire travel with a DTI in the spindle. You don't want to do this if your saddle is sloppy or any long work really.

I'm an amateur machinist at best, only been playing around with the manual machine for a few months really so take this advice with a pinch of salt. The slots are within 0.01mm in depth over their length which is good enough and no worse than the milled plate itself. It is quite satisfying when you get a friction fit on the joint between two plates.

Also bear in mind that the milled plate isn't exactly whatever nominal dimension you purchase, mine in nominally 16mm but is infact 16.055mm thick, also your cutters are not exactly whatever dimension they are supposed to be. This means if you just mill the slot to the DRO readout it wont be the correct width.

What I do is designate one side of the slot as the reference since my cad drawing assumes 16mm plate, then mill that. Then open up the slot and use a piece of clean spare plate to test the slot until you get a nice fit, this is much more accurate than trying to measure with a vernier or micrometer as the slot is too shallow.

[devmonkey]

I see you have maximised the distance between your x rails, by placing them top and bottom of the Gantry.
Did that make things excessively more difficult?

Steve

Not really no. If you want the rails to sit flat then you have to mill the extrusion anyway particularly with 15mm rail on 8mm slot.

When you set the rail you will need a setting tool to offset the reference edge of the rail from the edge of the profile, I am making the assumption that the extrusion itself is straight. The setting tool with be a pair of L shapes milled together so they are identical with a hole so they can be bolted to the T slot. The short part of the L will then form a reference surface to locate the rail.

Note I'm referring to the rails on the gantry as the Y rails.

To get the separation of the Y bearing plates perfect is a little more involved since it is very hard to accurately measure the extrusion depth, again this is a nominal dimension when you purchase the profile, mine is nominally 160mm but is infact around 159.8mm, and now a bit less after I milled the flat for the rail.

So I slot joined the lower Y bearing plate to the rear Z plate but I didn't slot joint the upper Y bearing plate, I think this would have been impossible. Rather, with the Y bearings on the rails and bolted to their plates, I assembled the lower plate onto the Z axis and tightened. I then clamped the upper plate with a long clamp across the back of the gantry tensioning it against the lower plate and slightly pre-loading the bearings, then spot drilled through the holes in the Z plate into the upper Y bearing plate.

This means you only have to locate the holes in the rear Z plate to around 0.5mm accuracy...also should note that I'm using M6 bolts for these joints and I drilled 6mm holes, the 0.2 or so play of an M6 bolt in a 6mm hole is generally sufficient to align things if you are milling accurately, you don't need 6.5mm holes for M6 as is usual, although I could only do this as I counterbored with a 12mm endmill in the milling machine rather than an M6 counterbore which would have required 6.5mm holes.

I think it is much better with the rails top and bottom not just because of the increased distance between them but because of the reduced spindle overhang. My last machine which was much larger than this had the rails on the gantry face and although it was very simple to mount them it was less stiff due to the overhang.

[JAZZCNC]

Nice work Joe!
I see you are milling small slots to locate perpendicular sections to each other...... I enquired about doing just that in another forum with almost no reaction.
It seems to make sense to me ( no expert) What better way to ensure components are aligned correctly?

How have you found the process? A good idea or problematic?

I'm considering doing the same thing...when I eventually start my own build.

I see you have maximised the distance between your x rails, by placing them top and bottom of the Gantry.
Did that make things excessively more difficult?

Steve

Got to be careful here because it can and often does actually does make things harder for your self and not always more accurate by milling slots etc.? Reason is unless you can accurately machine all the major areas of the machine accurately then you will need some room for adjustment.

If you have read the forum you'll see I've said it many times that at DIY level the key to a great machine is to build in as much adjustment as possible. Nothing as changed in this statement.
Groves etc that are fixed will limit your ability to adjust out any errors coming from other areas that haven't been done to the same level. This is when you regret doing it.
The larger the machine the more this adjustability comes into play.

A better way I find at DIY level is not to limit adjustment with slots etc but use dowel pins that can be drilled and reamed after the machine adjustments have been made. This locks the machine in place but doesn't limit adjustment.

I would only consider milling slots etc if you can build the whole machine to the same level.! . . . . If not you will regret limiting the adjustments.

[devmonkey]

Got to be careful here because it can and often does actually does make things harder for your self and not always more accurate by milling slots etc.? Reason is unless you can accurately machine all the major areas of the machine accurately then you will need some room for adjustment.

If you have read the forum you'll see I've said it many times that at DIY level the key to a great machine is to build in as much adjustment as possible. Nothing as changed in this statement.
Groves etc that are fixed will limit your ability to adjust out any errors coming from other areas that haven't been done to the same level. This is when you regret doing it.
The larger the machine the more this adjustability comes into play.

A better way I find at DIY level is not to limit adjustment with slots etc but use dowel pins that can be drilled and reamed after the machine adjustments have been made. This locks the machine in place but doesn't limit adjustment.

I would only consider milling slots etc if you can build the whole machine to the same level.! . . . . If not you will regret limiting the adjustments.

Wise words about infinite adjustment.

I've built 4 machines in the last 20 years and milled slots in all of them for plate-plate, albeit these were all done on CNC not a manual mill. My approach has always been to make each sub-assembly locally square/aligned and only adjust between sub-assemblies (usuallly by shimming bearings). For example my gantry end plates are squared to the gantry and X bearing plates in 3 dimensions helped by milling the slots, this complete gantry/Y assembly will always be locally square assuming I can setup a milling machine properly to take a straight cut which I can. However the gantry itself could be twisted, unlikely but wont be known until final assembly, in which case X bearing interface with X plate will need shimming.

Sometimes you can't accurately determine a location for a joint until assembly in which case I estimate it and drill the pilot holes for the bolts then spot through to the joining plate with a centre drill once assembled, this was the case with the upper Y bearing plate on this machine. I don't use slots for this type of joint. However the slot in the bottom Y bearing plate guarantees that the two Y bearing plates (and therefore the Y bearings) are exactly the same distance behind the Z axis.

If I was using a hand router to cut aluminium as some brave chaps on here do then I definitely wouldn't be milling slots.

[devmonkey]

Once I fit the gantry end plate assemblies to the gantry I wont be able to mount the Z assembly without removing one of them, therefore I think this it is time to align and tighten the Y rails to the gantry in their final location.

For this I have just machined some precise setting tools, they were machined as a pair to ensure they are identical.



Here they are attached to the gantry, they bolt into the T-slot. Plan is to snug them up, the milled faces should then act as a reference surface to match up the reference edge on the hiwin rail, they will be moved along for each rail bolt. Note that I made them long enough so they extend across two of the high points that are on the reference plane on the face of the gantry extrusion.



First gantry end assembly bolted in place, I used countersunk M8 bolts rather than cap head to reduce the amount of material removal for the counterbore, meant the countersinks had to be done on the mill as there is very little adjustment vs a cap head. As well as the 8 M8 bolts into the end of the extrusion there are also two M6 bolts bolting up through the X bearing plate into the two T-slots on the bottom of the gantry.



Bottom view showing bolts fixing up into extrusion:


Plate-plate joint using the alignment slot:

[JAZZCNC]

I've built 4 machines in the last 20 years and milled slots in all of them for plate-plate, albeit these were all done on CNC not a manual mill.

This is my point unless you have the tools and knowledge to use them then it's better that you don't limit adjustment and instead lock it down when setup.

As you probably know Mr. Enstein comes into play when setting up a CNC machine.? Any adjustment usually an equal and opposite reaction somewhere else and you soon end up chasing errors around the machine. This is when you appreciate the adjustment you built into the machine, esp on large machines because small errors get big very quickly as it gets wider and longer.!

[devmonkey]

As you probably know Mr. Enstein comes into play when setting up a CNC machine.? Any adjustment usually an equal and opposite reaction

Mr Newton I believe.

Yeh don't mill slots unless you have a mill.

[devmonkey]

Y rails are now fixed in their final position using the setting tools described above, worked very well and was super quick to do. Both gantry end assemblies are aligned and bolted to check final fit, everything looks good. Note rubber mallet, this is a precision build honest ;-)



Other than ballscrews everything from the X plates upwards is now complete, will move back to the steel frame next, need to decide whether to pour epoxy or attempt to rig up a mobile surface grinding contraption to bring the frame into plane.

Jazz when you fettle beams holding the X rails into plane do you just scrape by hand checking with a precision level and blueing off a surface plate large enough to span the two X beams? Or do you just level each beam locally then shim one side to bring into plane? My last larger machine had X beams that could be adjusted independently up and down with the rail attached, this one has beams welded to the frame.

Cheers, Joe