My new 6040 improvement plan.

[PaisleyPCdoctor]

I'm looking at the hiwin hgr15, hgr20 and hgr25. Not a massive price difference for 500mm length.

I'm leaning toward the 20 but only because 15 seems small and 25 is possibly overkill.
I would have 2x rails on x-axis. I have never touched one of these so I'm guessing.

Not gonna jump in and buy straight away, just need to decide so I can mock up with correct dimensions.

Any recommendations would be warmly welcomed. Thanks.

[Zeeflyboy]

HGR20 is the common choice - HG15 carriages can be very awkward to grease as there isn't a lot of space to get at the grease nipples.

HGR25 is overkill, but on my new machine I ended up using them on the Y-axis just because the dimensions suited my design.

[Desertboy]

If you're going to fit Hiwin style rails the correct choice is the one that's easiest to retrofit to your existing plates if possible at all.

15mm Hiwin are a PITA to fit with 1605 ballscrew and BK12 fittings you need spacers, I fit my ballscrew sideways on, on my Y axis to solve this problem but still ended up with spacers on the X & Z.

15mm was a no brainer for me, even with the extra hassles but I traded time for my original Hiwin's in the end cost me 12 hours on a Sunday and 6 hours in the week for my 1.2m Hiwin's and 45cm ones on my Z. Was it a good deal? Like my friend tells me my time is worth nothing lol.

[PaisleyPCdoctor]

So you went with 2x15mm hiwin on your x axis?

I was looking at my machine last night and weighing up the options. I think I can potentially leave my ballscrew and 20mm shafts on and ADD a 15mm hiwin, possibly 2 hiwin. Sounds crazy, but actually looks easier.

My main worry with the 15mm rails- spec says the attaching holes on the trucks are M3 threads. Is that right? Seems a lot of force for 4x M3 screws to handle.

[Desertboy]

So you went with 2x15mm hiwin on your x axis?

I was looking at my machine last night and weighing up the options. I think I can potentially leave my ballscrew and 20mm shafts on and ADD a 15mm hiwin, possibly 2 hiwin. Sounds crazy, but actually looks easier.

My main worry with the 15mm rails- spec says the attaching holes on the trucks are M3 threads. Is that right? Seems a lot of force for 4x M3 screws to handle.

They're M4's at least my original Hiwin's and the clone rail I linked to are M4, the carriages are also M4.

My spindle mount actually bolts through the mounting plate and directly into the Hiwin's.

My X is 1.2m original Hiwin's, Y is the 1.5m clone rail I linked to (I only paid £99 but they are still a bargain at £120) & Z is 45cm Hiwin all 15mm

There's 90 T nuts holding the 1.2m and 1.5m to the extrusion with M4's you have no issues the extrusion will fail before the bolts lol.

Stainless steel bolts are not strong, high tensile are much much stronger next time I will use high tensile and they are cheaper to boot.

I've destroyed so many M4 A2 stainless bolts the caps round off so easy.

[PaisleyPCdoctor]

I was going to ask how you drilled the holes to ensure proper allignment- I would struggle.the tbolt to extrusion will probably figure in my plans. Much simpler.
Thanks.

[m_c]

The biggest problem is that you'd be bolting the rails to aluminium, not the bolts themselves.

There are various calculators online for bolt strength, and the first one I've just found puts an 8.8 grade M3 bolt at proof load of 2920N, and minimum ultimate load at 4020N. To put that in context, that means you could hang over 400Kg onto the bolt vertically, and it should not snap.
However I very much doubt an aluminium thread would support that 400kg.

I'd be looking at either helicoils, or bigger threaded inserts which I've currently forgotten the name off, to help spread the load on the aluminium.

[PaisleyPCdoctor]

I've destroyed so many M4 A2 stainless bolts the caps round off so easy.

Typical, I always have a bag of m4 a2 Allen key bolts in van. Use them to replace missing ones on machine access panels I work on. Thought I was being clever buying stainless, but I've decapitated 2 so far. I feel your pain. Lol

[PaisleyPCdoctor]

I recieved my 500mm long, 15mm hiwin clone guide rail and carriages today. Sure singly quick.

Looks good, except these have M3 holed on the carriages (2x20mm spacing).
Suppose it will be all right as I'll end up with 2 of these rails in addition to my 2x20mm round rails. I'm sure the M3 threads will take the punishment.

[PaisleyPCdoctor]

I was thinking for ages last night about ways to increase the rigidity of the bed frame. Came up with all sorts of ways that would probably work, but I had a simple idea this morning.

I've got some 900x600x60mm concrete paving slabs laying around. I'm going to place the cnc on one of them and bracket the frame to that. It surely won't be able to twist and it will add a fair amount of mass to help prevent it bouncing around on fast movements.

Best of all, it's free.