Here we go again . . . MK4

[paulus.v]

..and finally making chips after a 3 year journey! Congratulations!

I would be grateful if you could measure the stiffness in the x and y directions.

What breakout board/ controller are you using? Does it have optocouplers on the inputs? I had the same problem feeding 24v signal to 5v bob. In my case the signal was fed to the optocoupler through a current limiting resistor with a value calculated for 5v input. I just had to replace the resistor with one calculated for 24v.

[routercnc]

..and finally making chips after a 3 year journey! Congratulations!

I would be grateful if you could measure the stiffness in the x and y directions.

What breakout board/ controller are you using? Does it have optocouplers on the inputs? I had the same problem feeding 24v signal to 5v bob. In my case the signal was fed to the optocoupler through a current limiting resistor with a value calculated for 5v input. I just had to replace the resistor with one calculated for 24v.

Thank you Paulus. Great to have it working like it should.

I was planning to measure the stiffness and compare to my old machine, plus a typical commercial stiffness. Depends on when I can get another slot in the workshop. Probably a bit rude to do it when the in-laws are here - although . . .

The breakout board was free with the drivers and is very basic. I think it is called a DB-2505. ?
From memory it has black chips near the inputs which I always assumed were optocouplers. Replacing the resistor sounds interesting.

[routercnc]

Time for one last video in the series ! Some finishing touches . . .




Still plan to measure the stiffness - I may get a chance to get in the workshop today and report back tomorrow on this thread . . . sorry for the delay

[AndyGuid]

Many thanks routercnc for an absolutely awesome build!

Apart from the build aspects that relate to your specific CNC design (some of which is frankly way too complex for me to contemplate), I have learnt so much from your videos about what I can only call "general machining principles", which I would never have learnt otherwise!

Thanks again,
Andy

[Nickhofen]

Most excellent machine build ,I enjoy very much the videos and I hope one day I will make good use of all thiaw tips you shared!

[routercnc]

Thanks Andy, Nick. I'm just a hobby machinist and just passing on what I have learnt along the way. Glad it was all helpful.

[routercnc]

OK so yesterday I managed to take some measurements for the X and Y stiffness of the new Atlas Mk4 machine.

The machine was positioned so the gantry was half way along the X axis, and the Y axis was positioned at the mid point of the gantry. So the X and Y positions represented worst case. The Z axis was lowered 50 mm from home in a typical machining position.

I used a digital luggage scale with a hook on the end to pull on the spindle just slightly above the collet nut (6mm end mill was inserted), while a DTI was pointed to the round section on the collet nut just above the flats.

5kg load was applied (~50 N) and the reading in for both X and Y was somewhere around 0.01 - 0.015 mm. I'm wondering how reliable this reading was given the needle barely moved and 0.01 to 0.015 makes quite a difference on the stiffness values. I guess I really need to buy a 0.001 mm DTI !

Anyway, for Atlas mk4 this works out at:
X between 3333 and 5000 N/mm (0.015 and 0.01 mm respectively)
Y between 3333 and 5000 N/mm (0.015 and 0.01 mm respectively)

My previous mk3 machine was:
X 1000 N/mm
Y 1250 N/mm

So up to 5 times stiffer. It certainly sounds different when machining and as you might have seen in the videos you can certainly take a good cut so long as there is some lubrication. I didn't measure Z this time as it was a bit awkward Vs the previous machine.

I did not have long to explore further but just before I finished I quickly pulled on the ballscrews when the DTI was still on the spindle and could make the needle move a bit. So maybe the limit is the stiffness of the small AC bearings in the ballscrew housings, or come to think of it they might be the deep groove ball bearings? Anyway I think as it is all working well I should stop there otherwise I will never use it to make something !