operation cnc

[njhussey]

Just one thing I've seen, can you not shift the Y axis to the back of the bearings so the Z axis is nearer the front bearing, looks like you've got the gantry sitting on the front bearing rather than the back?

[Wobblycogs]

You've come up with almost exactly the same design as I did, even down to the materials you've selected. I've switched back to using extrusion though as it's simpler to mount to the gantry sides and I couldn't think of a good way to bolt the two pieces of box section together.

One thing I would add to the comments already made is, depending on the travel of your Z-axis, you might want to make the front plate a bit taller to give yourself a better spacing between you Z-axis bearings. Once you've switched the joints around it's easy to make the change just for the fairly small cost of the metal.

[kingcreaky]

thankyou all for your replies.

Think, i have taken upon your ideas with my new design... although not sure if I understood Neil's post..

anyway... Ive ordered the bits... notice the 5mm plate that runs the length of the gantry in front of the two box sections to aid strength once fixed together. consequence is ive had to move the Y plate 5mm further away.. not sure if im gonna use it but ordered it anyway

£202 with AW!!!

current expendature: £1282

still to buy.. wiring from steppers to control case, control case ancillaries (connector blocks, cut off switch fans etc) pulleys, belts and 2.2kw spindle

[njhussey]

Ok...time for one of my Tony Hart drawings ;)

This is what I was trying to say....to me it looks as though you have the gantry over the front rail, this causes a large overhang of the Z axis and is far away from the bearings. Top scribble.

If you move the gantry so it sits over the back bearing there will be less of an overhang and it will be better. Bottom scribble.

[Wobblycogs]

If I could make another suggestion, add all your bolts and other fixings to your design before starting cutting. A couple of parts I've designed I've been happy with only to discover that I can't then bolt them together or the bolt holes would be too short to have any strength. It's time consuming but cheaper and quicker than cutting parts and then realizing they don't fit.

[kingcreaky]

Right, whilst spending all morning on the bearingstation website buying HTD timing pulleys and belts ive decided to scratch the idea of having one stepper for both ballscrews on the X axis powered by a long belt idea. Instead have one stepper per ballscrew..... This is mainly because I cant buy a belt 2.8meters long but also because it restricts the work area and also, lets face it, im bound to get my dude caught in it at some point... :D
So belts and pulleys ordered... I hope to god my calculations are right...
For a start point, ive decided to kick off with all the pulleys the same...

ive gone for 8 X HTD 5mm pitch,15mm belt width, 30 teeth. with a pilot bore
305M15PB - 5mm Pitch HTD Timing Pulley(Pilot Bore)

so; recalling my school days; 30 teeth x 5mm pitch / pi (47mm diameter)
therefore, 2 pi (r) or 47mm x 3.14 (squared) = 147mm (lets call it 150)

PHG295-5M-15	PHG295-5M-15 5M HTD Timing Belt	1	£4.46	£4.46
PHG490-5M-15	PHG490-5M-15 5M HTD Timing Belt	2	£6.30	£12.60
PHG365-5M-15	PHG365-5M-15 5M HTD Timing Belt	1	£4.90	£4.90

As my wallet is taking an absolute kicking again, I may aswell buy some of this CY cable stuff... Im contious im gonna need about 12 meters to cover all three axis's so can somebody confirm if this is the stuff I want?
Bear in mind my controllers the higher power ones...
1.5mm 4 Core SY Protected Cable Flex

[Jonathan]

The one you have linked to is SY, not CY. SY insn't shielded.

CY Cable - 4 Core 1.5mm2

[kingcreaky]

what a sausage i am, thanks for the link

[kingcreaky]

ali has arrived... everything I need now, short of CY cable and pulleys which are due this week.

made some legs (there are actually 6, but the dog ate one)

[kingcreaky]

Too many of you I am sure, the above is a simple plate. a Plate that can be knocked up in your engineering palaces in a matter of minutes, inbetween jobs, after a few beers.

For me however, this very plate has wasted more brain cycles, sweat, and most importantly self-doubt I cannot help but stand back an admire its sheer beauty. Its elegance...

Its literally taken me two nights... looking at it, measuring it, measuring again. Aligning the pillar drill then repeating the process again and again until I ultimately grew the nuts to trust my measurements, and simply start drilling.


To me, Its perfect. Bobby D! boys...