First project! A Maya Calendar

[Jonathan]

That looks good. There's a more ambitious one here if you want to try it. This is the one I cut, aluminium naturally:

90deg 9.5mm v bit - 40 mins (it was quicker but I had to slow the feeds right down as I have a bit of flex in my machine and slowing it down to compensate well enough)

When the machine isn't sufficiently rigid it's better to lower the depth of cut and keep the feedrate at the correct value. The reason for this is clearly you need to lower the force on the cutter, which lowering the depth of cut will of course do, but you don't want to lower the feedrate as that lowers the chipload (assuming constant spindle speed), as that will cause more wear on the cutter and more heat.

[cncJim]

Hi Jonathan, That is the one I thought about having a go at, but the total time to cut put me off! Also I don't have a dedicated dust removal set up of dust shoe yet (should have been my first project but I got carried away!) and standing around for 3-4 hours with the vacuum didn't sound fun! Your cut in aluminium looks ace! I will definitely give this a try in wood one day.

Thanks for the advice, that makes sense. Would it also be possible to lower the spindle speed and feed rate to keep the same depth of cut (and keep the correct chipload)?

Jim

[martin54]

looks good Jim, hopefully I will be doing stuff like that once I get the machine sorted properly.

[Jonathan]

Thanks for the advice, that makes sense. Would it also be possible to lower the spindle speed and feed rate to keep the same depth of cut (and keep the correct chipload)?

Yes to an extent, but bear in mind the available spindle power drops with speed so if you go too low the spindle may stall, hence it's safer to advise keeping the spindle speed near the calculated value.

[cncJim]

Yes to an extent, but bear in mind the available spindle power drops with speed so if you go too low the spindle may stall, hence it's safer to advise keeping the spindle speed near the calculated value.

I see - Thanks for that.

Another question if I may - I noticed that after the circle profile cut it was uneven in a couple of places. It seems to be on the Y axis and from what I have read I think it may be backlash in that axis, does that sound right? one side of the circle it was very obvious, a slight jut out from the circle, the opposite side not so much - I wish I measured it now but I gave it to my Dad for fathers day!

[Jonathan]

I noticed that after the circle profile cut it was uneven in a couple of places. It seems to be on the Y axis and from what I have read I think it may be backlash in that axis, does that sound right? one side of the circle it was very obvious, a slight jut out from the circle, the opposite side not so much

Backlash can cause the effect you describe. It could be something else, like a slightly loose pulley/coupling, but that seems less likely since the rest of the part isn't all over the place. If you're machine is driven by ballscrews then you're unlikely to notice their backlash on wood, since it's very small (<0.05mm). That's not the case if you've used ACME or threaded rod...

[cncJim]

Backlash can cause the effect you describe. It could be something else, like a slightly loose pulley/coupling, but that seems less likely since the rest of the part isn't all over the place. If you're machine is driven by ballscrews then you're unlikely to notice their backlash on wood, since it's very small (<0.05mm). That's not the case if you've used ACME or threaded rod...

That's a worry then as I do have ballscrews! Just got a dial gauge so i will check later and report back :)

Jim