Lets eventualy start this CNC - MKI

[Jacques]

Thanks JazzCNC

It's not very clear on the design, but the intent is to use a belt with pulleys, 1:1 timing. (Very similar to JoeHaris' design) - as I've read, it helps with resonance and gives me the ability to do 1:2, or 2:1, or other rations if I allow a variable positioning of the Nema (which is the intent)

I looked at Profiled Linear rails - just seems to cost a tad more... although, would be easier to fit to the Aluminium profile... Will see what pennies I can get out the couch :)

Thanks for the 3.1Nm vs 4Nm motor advise - I think that's one tick I can put next to - "Buy Nema 23, 3.1Nm motors" :D

Once I have all the input and design tweaks, I'll know what length ball screws to get - So recommendation so far is RM1610 (with the end an extra 15mm for the pully) [This should give a resolution of 0.05mm (at full step) and 0.00625mm at 1/8 step - that actually pretty decent! ]

As for Slaved motors, should I go with 3 Nema's (One belt connecting both Y Axis to one Nema ?) - this will save on buying one driver and Nema, but worth it ?

[JAZZCNC]

I looked at Profiled Linear rails - just seems to cost a tad more... although, would be easier to fit to the Aluminium profile... Will see what pennies I can get out the couch :)

Dig deep because worth every extra penny.

Thanks for the 3.1Nm vs 4Nm motor advise - I think that's one tick I can put next to - "Buy Nema 23, 3.1Nm motors" :D

Remember Inductance not all motors are the same even if same Nm rating.

[This should give a resolution of 0.05mm (at full step) and 0.00625mm at 1/8 step - that actually pretty decent! ]

Don't Full step action will be rough and Don't really think of Micro stepping to increase resolution and more to do with having smooth running motors. Buy Digital drives and you'll get lovely smooth motors with less Micro stepping.

As for Slaved motors, should I go with 3 Nema's (One belt connecting both Y Axis to one Nema ?) - this will save on buying one driver and Nema, but worth it ?

Yes that's what I would do using 10mm pitch screw with 1.5:1 ratio which increases torque and still gives decent performance. I've used this setup on machines with heavier gantry than yours so know it works ok.

[Jacques]

I am looking into the HIWIN Rails - and many people on the forum suggests 20mm because of grease, access to bearings etc. So I take it 20 is good,15mm bad ?

The motors I am looking at can be 3mH if you couple them in series, 12mH in Parallel configuration.

Those drivers are nice, £100 nice - will have to save up for them....

Busy re-designing for the Linear Rails... will post new design within the next week.

[JAZZCNC]

I am looking into the HIWIN Rails - and many people on the forum suggests 20mm because of grease, access to bearings etc. So I take it 20 is good,15mm bad ?

No good or Bad about it really just 20mm are easier regards fitment etc but 15mm will still easily handle any forces.

The motors I am looking at can be 3mH if you couple them in series, 12mH in Parallel configuration.

Think you may have got that wrong way round but if not then don't buy them.!! You want them wired in parallel and 12Mh is way too high.

Those drivers are nice, £100 nice - will have to save up for them....

AM882 drives can be bought from Ali express for around £50-60. Also you can buy Hi-win rails from BST automation on Ali express much cheaper tyhan you'll find them in Uk.

[Clive S]

I am looking into the HIWIN Rails - and many people on the forum suggests 20mm because of grease, access to bearings etc. So I take it 20 is good,15mm bad ?

The motors I am looking at can be 3mH if you couple them in series, 12mH in Parallel configuration.

Those drivers are nice, £100 nice - will have to save up for them....

Busy re-designing for the Linear Rails... will post new design within the next week.

20mm is good because they are much easer to mount than the 15mm especially on the Z.

Zapp motor are a good buy http://www.zappautomation.co.uk/elec...tor-48577.html
or CNC4you as I suggested before https://www.cnc4you.co.uk/Stepper-Mo...s/Nema23-3.1Nm

Drive about £53 http://www.aliexpress.com/store/prod...570168083.html or similar

[Jacques]

Ok - had some time and re-designed it with square rails :)

For the X, I'm thinking of using: 40x80 Heavy Duty Aluminium Extrusion (http://www.aluminium-profile.co.uk/a..._ITM02604.html)
8mm Slot Ix = 26,87cm4, Iy = 101,19cm4, Wx = 13,44cm3, Wy = 29,29cm3

The Y's, similar, but the 40x120 - Those will then get bolted down onto a lovely solid flat surface :) [Later to be upgraded to solid Steel table]

Question 1: For the X, the rails will be 80mm apart (bottom of rails), is this ok? Or should I rather go for the 120mm on the X - which means bigger side plates etc.

Question 2: I've gone for 10mm Aluminium all round (6mm to hold the motor on the Y, and attach the Ball nut housing) - thoughts ?
[ Most of the 'bend' will be in the lateral movement for the Y, and the square rails will 'support' the 10mm... so see no need to go more. ]

All Steppers 3.1Nm with pulleys, 1:1, and 1.5:1 for Y [Powered by 60V stepper drivers]

RM1605 for Z, and RM1610 for X & Y. (ends or F, extended from 15mm to 30mm)
BTS Automation will open end of Feb after their Chinese new year... hoping to order soon :)

[Clive S]

Which drives are you going for when you say 60V AM882 or EM806 about 68V would be better.

If I am not mistaken 90 x 45 and 180 x 45 work better with the BK/BF bearing blocks. But Dean probably chime in with the correct size

[JAZZCNC]

Which drives are you going for when you say 60V AM882 or EM806 about 68V would be better.

If I am not mistaken 90 x 45 and 180 x 45 work better with the BK/BF bearing blocks. But Dean probably chime in with the correct size

Clives correct Bosch Rexroth 45 x 90 slot spacing matches the hole spacing in the BK/BF12 bearings. If using Item section then you'll need spacer plates.

10mm Ali is too thin 15mm is the minimum I'd use. 20mm prefered.

[Jacques]

Thanks - Will look at the difference in specs and price for the AM822 and EM806 - any recommendations ?

I'll look at the 90x45 & 180x45 - thanks!

[Jacques]

Ok,

Re-Designed so all plates are 20mm (except motor mounts, those I have at 6mm - might end up as 10mm...)

I did what Clive suggested and put each piece together as I would.

I should be able to get away by having recessed bolts for the entire Y/X axis, and being able to bolt everything without tapping :) [Y will need tapping]
[ The bolts holding the X plates and bearing support (160mmx50mm) together, can be bolted from the back to the front ]




I 'think' I'm getting nearer to finally placing an order of exact lengths of components :)

Thanks all!