New Build of a Joe's CNC Hybrid R&P 8x4

**JAZZCNC** · 19-03-2018

Originally Posted by GrahamWhite

The machine itself is called a hybrid and I will be adding the upgrade of rack and pinion instead of ball screws.

R&P isn't an upgrade to ball screws it's very much going backward.!

However it is little easier on longer machine provided it's done correctly.

Now regards the machine then to be fair unless you got Plywood cheap then could have built a frame made of steel for about same or not much more. Obviously you'd need to be able to weld but steel isn't that expensive.

Also if your thinking to use the V bearing and Angle style setup for linear rails then please let me urge you to save up and buy some proper linear rails, even the round type if you must.
All your doing with V bearings is building trouble and wasting money because they will stick, wear and be inaccurate. You'll be for ever chasing issues.

Often people think they'll start off and upgrade as they go along just like your thinking but the reality is that rarely happens and even when it does still lacks in many ways because can't make silk purse out of sows ear.!
Also the costs of intial build plus any failures plus upgrades will work out more than doing it correctly first time.

You don't seem to far down the line with only base made so I'd urge you to maybe stand back and take look at what can be done in steel.
I know 100% you won't regret it if you did. Also know you will regret building joe's machine at some point.

Sorry to be negative but it's in your interest we say it.!

**GrahamWhite** · 20-03-2018

Cost for me is a major consideration I'm afraid.
I would rather have a machine that needs adjusting from time to time,than no machine at all.
I looked at ball screws after your comment (the original machine actually had lead screws not ball so my fault there) and while on short runs theyre fine - it is suggested for 3.0m that at least 25mm screws would be needed- at £300 each just for the screw that's a bit out of my budget!
I am seriously gonna consider going with square linear rail though - even if it's 15mm - £120 for 2 rails with 4 bearings@ 1500mm long each side and then double rail on the X axis as well.

**JAZZCNC** · 20-03-2018

Originally Posted by GrahamWhite

Cost for me is a major consideration I'm afraid.
I would rather have a machine that needs adjusting from time to time,than no machine at all.
I looked at ball screws after your comment (the original machine actually had lead screws not ball so my fault there) and while on short runs theyre fine - it is suggested for 3.0m that at least 25mm screws would be needed- at £300 each just for the screw that's a bit out of my budget!

R&P is good for a long machine provided done correctly but can't compare to ballscrews for accuracy or reliability/repeatability. Also requires much more upkeep and if not done correctly wears quickly and can be a pain with sticking etc.
Yes you would need 25mm screws that's true but don't let people tell you they are no good for long runs because that's simply not true. They just don't know how to do it correctly.
Also if bought from China they won't cost £300 each. Last long screws I bought cost $198 for 2 x 2850 25mm dia 25mm pitch. Obviously got shipping etc but if you buy in package with rails etc you will be very surprised at the price.
You will pay more for those CNC router parts R&P kits than you will for ball screws.

Originally Posted by GrahamWhite

I am seriously gonna consider going with square linear rail though - even if it's 15mm - £120 for 2 rails with 4 bearings@ 1500mm long each side and then double rail on the X axis as well.

Again check out China you'll probably get 20mm for same or less money. Also While it's possible I Wouldn't join the rails, difficult to get clean join and if not done correctly you'll get premature wear of bearings. Also no need because can get 3000mtr lengths.

Go to this site and email Fed Lee asking for quote. Mention Dean from Uk sent you and you might get a pleasant surprise.!