Joe's 1000x600x200 steel and aluminium router started

[devmonkey]

I'm looking for some recommendations on bed materials, machine will mainly be used for aluminium and composites, so preferably something that can take coolant. My last machine used epoxy soaked MDF which was far from ideal. The plate would need to be 800x1300.

I don't have a large enough piece of aluminium plate. So options I'm looking at are:

1. 20mm Tufnol, can't find this in sheets longer than 1200 so would have to alter the frame, this isn't really a problem. I'm not sure whether this is rigid enough to span the cross beams that are on 400mm centres??

2. Purchase a piece of 20mm aluminium plate large enough, quiet expensive.

3. Locate some aluminium extrusion T-slot bed profile 'planks', I can't find these either.

Thoughts?

[devmonkey]

I'm looking for some recommendations on bed materials, machine will mainly be used for aluminium and composites, so preferably something that can take coolant. My last machine used epoxy soaked MDF which was far from ideal. The plate would need to be 800x1300.

I don't have a large enough piece of aluminium plate. So options I'm looking at are:

1. 20mm Tufnol, can't find this in sheets longer than 1200 so would have to alter the frame, this isn't really a problem. I'm not sure whether this is rigid enough to span the cross beams that are on 400mm centres??

2. Purchase a piece of 20mm aluminium plate large enough, quiet expensive.

3. Locate some aluminium extrusion T-slot bed profile 'planks', I can't find these either.

Thoughts?

A bit more research on different materials, Young's modulus (GPa):

MDF	4
SRBP (paxolin/tufnol)	6.5
Aluminium	69
Steel	200

The deflection of a rectangular section spanning two supports due to a downward force in the middle is inversely proportional to the Young's modulus * thickness^3.

So taking 16mm aluminium plate as a reference, thickness required for equivalent rigidity of those materials are:
MDF 41mm, SRBP 35mm.

Or another way, 25mm SRBP is equivalent to 12mm aluminium.

From this it is probably ok to conclude 25mm SRBP supported on 4 sides over rectangular bays in the machine frame that are 840x320mm is probably sufficient.

[devmonkey]

A bit more research on different materials, Young's modulus (GPa):

MDF	4
SRBP (paxolin/tufnol)	6.5
Aluminium	69
Steel	200

The deflection of a rectangular section spanning two supports due to a downward force in the middle is inversely proportional to the Young's modulus * thickness^3.

So taking 16mm aluminium plate as a reference, thickness required for equivalent rigidity of those materials are:
MDF 41mm, SRBP 35mm.

Or another way, 25mm SRBP is equivalent to 12mm aluminium.

From this it is probably ok to conclude 25mm SRBP supported on 4 sides over rectangular bays in the machine frame that are 840x320mm is probably sufficient.

I would probably use one large piece as the bed, then a second piece as the sacrificial board.

[JAZZCNC]

30mm HDPE makes a nice stable bed and you can cut a grid pattern to make it into a Vacuum bed. I bought a 10x5 sheet for £500 so if you get in touch with plastics supplier you might get a small piece or cutoff piece cheap enough.

[devmonkey]

30mm HDPE makes a nice stable bed and you can cut a grid pattern to make it into a Vacuum bed. I bought a 10x5 sheet for £500 so if you get in touch with plastics supplier you might get a small piece or cutoff piece cheap enough.

Ok thanks, that is interesting, YM of HDPE is only 0.8, how much support did you have under it, or what was the clear span? I guess we are only talking about supporting the mass of the part being machined and the downward force of the cutter, this is probably minimal, like to take a punt on what this force is?

Looks like an 8x4 sheet of 25mm SRBP is £380, this would give me enough for the base board and two spoil boards.

[devmonkey]

Stand levelled on floor and machine craned ontop to check final position, needs to be moved out from the wall a bit so I can fit/service the ballscrews motors. Starting to look like a CNC machine!

[Kitwn]

Looks seriously serious! Make sure you have enough room to move around it while bending over and enough room to fit a screwdriver in all the places you didn't think you'd need to fit a screwdriver when you first thought "I'll put it here!".

[devmonkey]

Finished making the last set of plates, these are for the X and Y axis, ballscrew mounting. Hopefully this is the last of the aluminium work on the manual mill. I still need to make some stepper mounting plates but leaning towards doing those in 3mm steel.The white parts are 3D printed standoffs for the X axis ballnut holders, I didn't have any large enough ally stock so we will have to see how they fare. They get clamped between two aluminium lumps so should be ok, if not will replace when I have some bar stock.

[devmonkey]

Any they all fit:

[devmonkey]

Was still waiting for the pulleys this morning so decided to align the Z axis assembly and fit the ballscrew. I needed a 0.25mm/10thou shim between the ballnut holder and Z-plate, but it was extremely difficult to get the shim into place as the holder is buried between the rails inside the assembly. A bit of lateral thinking and I used some plastic lamination film cut from a normal A4 laminating pouch.

This stuff has the advantage of a) being quite hard after lamination,b) having a heat activated adhesive. So using an old iron I laminated 4 layers of the stuff onto the back of the ballnut holder, this formed the perfect shim. I trimmed it with a scalpel and cut the bolt holes. Worked really well. Z axis is now complete apart from lubrication points. These are a pain with the nipples supplied with the hiwin carriages and the ballscrew so will need some thinking.



Just as I finished the Z the delivery guy turned up with my belts and pulleys, so I spent a rather boring couple of hours, boring, reaming, cross drilling and tapping 8 steel pulleys. All done now. I only installed one M5 grub screw per pulley, each shaft will have a flat on it, hopefully this will be sufficient. I could do with some longer grub screws, or maybe just use an M5 bolt given the low RPMs.