Let the fun begin !!! ???

**JAZZCNC** · 07-08-2014

At this length then go with 16mm you'll be ok, 16mm will allow slightly faster acceleration due to less inertia. Resolution with 20mm isn't a problem because the ratio effectively makes it same as 10mm and even with 1:1 ratio 20mm res you'd still have enough to cut the mayan calender.

There's very little between the 3Nm and 4Nm motors in terms of performance so you wouldn't really see much differance. Either will work fine with what your planning to use. Just run them around 70Vdc and you'll be fine.

With bearing blocks/ballnut then all you need is to leave a enough clearance in case you over run limits. In which case the limits should stop the machine so you need enough clearence for the over run. That said your better fitting hard stops in case of over run and have the bearing blocks just past these.
To be honest I wouldn't sweat over it you can control this with adjusting limits and they take a fair old bang to damage anyway so worst you'll do is knock something out of alianment.

Let me just say if your at the point of planning in cad to this level of detail then your wasting time that could be better put to use building the machine because in reality you'll more than likely to see a better place to put them on the actual machine.!! . . . . . Time to put the pencils down and pick up the tools.

**PAULRO** · 07-08-2014

it's time to put the overalls on o.k i should have steel middle of next week so i'll be fighting iron the following weekend. i'm just gathering the most info before i start into the build. i will be missing in action in the near future for a couple of weeks so i'd rather take time at this stage and plan it out . having said that i have enough info to get me up and running.

**EddyCurrent** · 07-08-2014

Just for the crack, keep a spreadsheet of everything you buy and the cost, maybe categorise as 'mechanical', 'electrical', 'sundries'

**PAULRO** · 09-08-2014

it time to source linear rails, ballscrews , ball nuts , bearing blocks etc. so i'm looking for contact details for chai. i have found an email address for him but i'm getting no reply. i have looked at zapp but want to do a compare & contrast before i purchase. so if any body has his web address can they send it on?

cheers Paulro

**EddyCurrent** · 09-08-2014

please check your pm inbox

**PAULRO** · 10-08-2014

i have touched base with chai and just need to work out the 16mm ballscrew lengths. i also notice that the bearing shaft diameters for BK and BF are different and am curious to know why this is.

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this is my z axis end view, it has 20 mm rails and a travel of 160 mm. i'm thinking of a z axis ballscrew length of 400+ 30 for for a timing pulley. i'm sure this is enough or should i go more?

**Clive S** · 10-08-2014

I may be wrong but the BK end will have AC type bearings and the BF end will have a radial bearing they use a larger bearing at the BK end. Not sure if they make the ac bearings in the same sizes as the radial.
You will need to order the F measurement on the screw to be at least 30mm I think Chai standard is 15mm. ..Clive

**EddyCurrent** · 10-08-2014

Originally Posted by PAULRO

this is my z axis end view, it has 20 mm rails and a travel of 160 mm. i'm thinking of a z axis ballscrew length of 400+ 30 for for a timing pulley. i'm sure this is enough or should i go more?

If the backplate is 400mm same as the spindle mounting plate you will likely want the outside faces of the bearing blocks to be 400mm apart so they are flush top and bottom, this will allow the maximum travel.
So the BK bearing is 25mm thick (excluding the end cap and locknut) the BF is 20mm thick, so that gives a ball screw length of 355mm between shoulders. Then 12mm turned section on the BF end, 69mm on the BK end (E+F = 39+30). Total length = 436mm. You have to allow for the Z ball nut thickness , this will reduce the overall travel, I drew mine out using Sketchup to make sure I was getting the expected travel.
Also you might as well get the ball screw as long as possible because the price difference for a few mm is going to negligible.
I know it might slow the build but in my case I waited until the ball screws arrived before cutting metal. It was easy to size the metal to the ball screws but impossible the other way round if in error. That's one of the reasons I built the electrical panel first, waiting for the stuff from China.

**JAZZCNC** · 12-08-2014

Originally Posted by PAULRO

this is my z axis end view, it has 20 mm rails and a travel of 160 mm. i'm thinking of a z axis ballscrew length of 400+ 30 for for a timing pulley. i'm sure this is enough or should i go more?

Why is the rear plate so long.? you only need the rear plate long enough to fit bearings onto and give travel required. If your only wanting 160mm of movement then you would get away with shorter back plate and ballscrew.
Also one thing to take into account if your trying to get every last bit of travel out of screw is to allow for the bolt heads holding ballnut, you can easily loose 10mm depending on how tight you make it.
Regards the Z axis screw bearings then with screw being so short you don't really need one at the bottom if you want to keep cost down and it makes setting up that bit easier.