Let the fun begin !!! ???

**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.

Click image for larger version.

Name: shaft machining.jpg
Views: 414
Size: 129.9 KB
ID: 13000

Click image for larger version.

Name: Z AXIS ASSEMBLY.jpg
Views: 429
Size: 134.9 KB
ID: 12999

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.

**PAULRO** · 11-08-2014

Cheers Eddy, how long was the delay from Chai ? also did you get the ballscrews machined locally or by chai and if so would you recommend it? i might get it done locally because i have access to a lathe but if it's not too costly to get it done by Chai i might go that route but then i have read that some of the screws turn up slightly bent. i have used suppliers from china in a previous life ( job) and remember some of the parts delivered with poor packaging and very little protection ( not all suppliers ). it's very helpful to have the experience of previous builders who have gone down this route, hence all the questions!!!

**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.

**PAULRO** · 12-08-2014

i had intended to use 20 mm rails on the z axis but after reading the various posts of your good self I am now going to use 15mm rails and guides to suit so i think a redesign is in order.
the rear plate should be shorter alright i just left it long enough to house the motor with a body of 100mm long and a plate to hold it.
i suppose the travel of the z axis could be longer but i went with that travel because of all the discussions about the length of the lever created by the extension. i suppose it's another trade off , keeping it to a minimum while having enough scope to machine to a reasonable depth. i'll get cracking at it again tomorrow, my shutters are starting to descend !