Let the fun begin !!! ???

[PAULRO]

At last i have an opportunity to get some images of the intended build posted for comment. i have read a lot of material on this forum and tried to include as much advice as possible . i haven't purchased any materials yet even though i'm itching to get started , but taking the advice given to other potential builders from Jazz, Jonathan , among others, i will build the frame first and then once i'm sure of key dims. i will take on the mechanical purchases and build. the gantry images are posted as a reference to my intended build but as always i'm open to suggestions.

the frame size should take a half a standard sheet ( 1220 x 1220 ) built from 80 x 80 box section. 5 mm wall for the top rails and 3 mm for the rest. the adjustable bed ( yellow) will be held in place by graduated 50 mm x 6 mm angle ( green) secured to the frames uprights. the stand alone box section ( blue ) is detachable to allow space for a fourth axis , eventually!!

i have a choice of extrusion for the gantry ( length 1610 mm ) either 100 x 50 , 4.18 kg/m, 120 x 40 , 4.35 kg /m or 120 x 40 , 6.8 kg /m .

the linear slides, 20 mm hiwins , ballscrews 16 mm and aluminum plate for gantry , 20 mm . i haven't any motor specs yet so i didn't finish the z axis assembly . I might use 20 mm linear slides on the z axis ( off cuts from the 2m x rails ) or just purchase 15 mm rails. i will use epoxy to create a plane for both x axis and a permanent bridge for this and the x axis motor to belt drive the twin ball screws, OR use separate motors for each x axis ballscrew. all to be decided with the advice from the experienced builders here, hopefully!!!! i'm also looking for some motor dims, nema 23 , 3nm. they seem to be the weapons of choice for what i'm about to take on , so if any one can point me in a direction for a reputable supplier that has dims i can use to finish the z axis dwgs i would appreciate it. cheers Paulro.

[EddyCurrent]

Maybe you could incorporate into the fourth axis space something to allow this; http://www.mycncuk.com/threads/7688-...9686#post59686

[PAULRO]

ya , that is a great idea. that's what's great about this site , ideas get bounced around and seeds are sown. i've been on this site for the last year getting as much info. as possible and getting cash together at the same time for a router build. can't wait to get stuck in. i'm confident of the mechanical side of the build and have some electrical experience but will need help to get me through the potential pitfalls i think i will find myself in. hopefully i can rely on the experience of the previous builders on this forum.

[EddyCurrent]

The gantry ends look quite substantial but I'm not sure how well the structure will resist twist at the centre, here's some info relating to that subject.
Machine stiffness; http://www.mycncuk.com/threads/7155-...4942#post54942
Stiffness calculator; http://www.mycncuk.com/threads/2214-...5791#post15791

[JAZZCNC]

Hi Paulro,

Got your PM.

Yes the gantry will be fine for your use as a wood router and yes I've built one about same size using same design so know it works. What you doing with the ends of gantry and how you connecting to ballscrews.? Drawing with gantry mated to frame would be good to see.

Regards Y axis ballscrew mount then you'll need to brace the drop bracket more.

[PAULRO]

I could go with a heavier extrusion if that would aid the machining of plastics and aluminum (light gauge) from time to time. i have a choice of extrusion for the gantry ( length 1610 mm ) either 100 x 50 , 4.18 kg/m, 120 x 40 , 4.35 kg /m or 120 x 40 , 6.8 kg /m. i don't know if that would make for a better or worse situation.



the images above show the gantry attached. i have yet to spec motors so haven't any motors mounts designed. i'm currently getting through Irvings tutorial on motor specs. what a great read!! i'm hoping nema 23s 3nm will do the job , by the way if i do go with these motors should i go for the heaviest i can get? any thoughts on this and the gantry extrusion choice would be appreciated.

[PAULRO]

by the way i'm going to use timing belts to connect to the ballscrews

Paulro

[JAZZCNC]

100x50 will be fine but if possible get the HD version.

3Nm motors will work ok with 16mm screws but with 20mm you'll need to slow things down due to extra inertia so you'll get lower rapid feeds.
You'll want 10mm pitch which will be more suited to wood and plastics. Now if you use 20mm pitch screws and gear 2:1 ratio then you will still get same feed rates as 10mm pitch with 3Nm motors but with a couple of nice advantages.?
The ratio halfs the speed 20mm pitch gives but this gives same feed and resolution as 10mm so we get same speed but with half the screw speed but at same time doubles the motor torque. Lower screw speed means less chance of whip on long screws so it's win win.!



You'll need to run the motors around 70Vdc on decent drives to get best from them.