Here we go again . . . MK4

[Clive S]

After a day there were lots of black specs and a general browny dust settled onto the part (hole now top left).

I read something about this in an earlier post and I thought it said you had to keep it on a low light to keep it warm for it to work

[komatias]

.... it on a low heat to keep it warm for it to work

Fixed.

Have you tried putting more alum powder in to see if your concentration is too low?

[routercnc]

Hi Clive, Komatias,

I'd also read about constant heat but I don't have a hot plate and using the oven/hob was not allowed so I periodically drained some off and topped it up with water from the kettle. It was wrapped in insulating cloths to keep it warm for as long as possible.

I added about 100g of powder initially, and changed the whole lot for a new batch of 150g after a day or so. There was always some undissolved powder in the bottom even with lots of stirring which meant it was saturated at maximum concentration.

It was working, just slowly. I think a hot plate or keeping it fairly hot would give it more chance, I'll see what I can get hold of.

I don't know if drilling with the masonary bit would have taken 15 minutes without the Alum powder treatment or if several days in the Alum had softened it. I'm nearly through with the drill so when I'm next in the workshop I should break right through.

[komatias]

Masonary bits are too blunt. You would also need to spin backwards to aid removal of the tap. I have used special carbide spade drills to remove taps. The only place in the Uk that has them is
http://www.drill-service.co.uk/Produ...60000&Tool=377
Seriously considering stocking some in 2016

[routercnc]

Good to know thank you. I'd ordered a solid carbide 3mm drill a few day ago, but these look better still.

[JAZZCNC]

Please Don't get me wrong on what I'm about to say has I'm not pulling down what you have designed, it looks and sure will work great. But This design seems an awful lot of work and complexity and extra cost for no major benifit over a fixed gantry design.!

By this I mean the wide Gantry and wasted space at each end mean it will have about the same foot print and give about the same cutting area of Fixed Gantry.
If used Fixed gantry design with lifting Y axis allowing none lifting Z axis meaning minimal Z axis extension, essentialy just tool length would have been much stronger and far simpler design IMO.

Like I say just an observation which for the sake of others thought I'd mention and not pulling down what you are building or doing. It's looking great sure will work great and i'm looking forward to seeing it come along.

[routercnc]

Hi Dean,

Thank you for the comments. I understand where you are coming from and I agonised and developed this design over the last 6 months or so, including looking at fixed gantry ( I think you are referring to that blue framed fixed gantry on youtube ?). I looked at different parameters trading this and that and trying to work through all the options. I think this is version 14 !

In the end I'm pretty happy overall with this concept and think it will be pretty stiff. I also thought long and hard about the arrangement of bits to make sure slip planes were in the right direction so that bearings were not trapped and pre-loaded, and that it could actually be built in a particular order without leaving impossible joints to make.

I also wanted it to look as neat as possible so a bit of the design is for aesthetic reasons as much as anything (e.g. curved cover plates on Y axis, metal junction boxes where the energy chains end)

I'll keep you all posted, but this is probably a long build so you'll all have to wait to see if it is any good at the end. I intend to do a few simple cuts on the current machine at different feed, speed, DOC,etc and film them before it is decommissioned. Then do the same simple cuts when this one is complete to compare the finish, sound (when does resonance, chatter start kick in) plus measure the static stiffness.

[gojones]

The major benefit of this design is the ability to machine a workpiece that is way larger than you could fit in a conventional fixed gantry mill. You could place one end of a 20' beam on the bed and machine one end, or even machine the entire length in stages.