Lets eventualy start this CNC - MKI

[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]

When you say 10mm is too thin - I agree in some part, but let me try explain my thinking...




On the Y Side plates, most of the "force" will be stopping the X beam flexing, and moving in the Y direction, so on Y1.
The forces on X1 (if the X is bolted down on the bottom plate properly) will be minor.

On the Z axis gantry, the back plate - I agree - 15 or 20mm. It will flex, although the blocks should support it, apart from the 30mm gap between them, so only "bend" that will apply will be on the small 30mm bit inbetween the blocks... Whats bend like on 30mm of 10mm plate?

On the front Z plate, the plate will be bolted to the square rail. Surely the 20mm rails will stiffen up the 10mm plate?

I don't want to put extra weight on it if I don't need to - but you guys know what works and what doesn't....

I like to match the spacing, so will change the design to 90x45 - The BF/BK blocks will be on spacers...so the bolt will go through the BF/BK, through spacer and into profile. :)

I'll then swap out the 120x40 with a 180x45. This will also give me more cutting (working) space.

Currently (according to my calcs and drawings) the Z has the ability to travel at least 120mm.

Thanks!
Jacques

[Jacques]

Can anyone recommend a good supplier for 45x90 & 45x180 profiles ?

Also cut to size Aluminium plates 15mm & 20mm ?

[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!