Yes I should have used 30mm rails but it would be to expensive so I used 20mm.
The profile under the rails is 140mm x 60mm x 5mm wall thickness.
Tomorrow I'll make new pictures.
Do you think I'll have problem with 20mm rails?
Last edited by DigiSoft; 15-04-2014 at 10:32 PM.
Please do not take my comments as critisism because your machine is excellent, it's just that for me there looks to be a mismatch between the gantry and bed frame.
Well I'm no expert on rails but from what I've read and found with my own machine I think you would have done better using the low profile rails such as Hiwin. Lots of people use the rails you have and they seem to work well but somehow they are not in keeping with that substantial base. Hiwin rails however would have been more expensive.
There 's one thing for sure though and that is the frame and bed will have enough stiffness.
As an experiment maybe you could add some test results to this thread ?
Last edited by EddyCurrent; 16-04-2014 at 09:54 AM.Spelling mistakes are not intentional, I only seem to see them some time after I've posted
'Linear guide' is probably a better term to use than profile rail, to avoid confusion.
I agree that the machine is currently a bit mismatched - by far the lowest stiffness parts will be the round rails. Still, try it and see and if it does what you need then no matter...
The biggest problem with the round type rail and esp the cheap chinese type is the bearings quickly become loose and sloppy so lose accuracy and need regular adjustment.
They are no where near as accurate to start with compared to profiled linear rails which just work and last for years without any attention other than lubrication now and again.
They won't take the abuse Profiled linear rails will take and dusty or abrasive conditions will quickly take it's toll on them unless you take precautions to protect with wiper seals etc.
Like Eddy I agree these rails let down what looks like a nice substantial machine and IMO Profiled linear rails make the difference between Average DIY and Professional machine.
Don't look at it so much in terms of they are expensive which they are not in long run because they give a much better and far more reliable machine but more they will return there investment 2 fold later down the line if you ever decide to sell the machine as they will still work just the same and not be wornout plus appeal more to potential buyers who are prepared to pay more for professional looking machine fitted with correct components.
I agree about the 'Linear guide'. I wanted to use them but I calculated they would cost me 1200 euros. This rails cost me 350 euros. I'll run the machine with this and if there is need for linear guides then I'll make major modifications. :)
Also I wanted to use servos, but that would rise the price even more.
When I finish this machine I'll make small mill with linear guides and servos :) but with smaller axis length because of the price.
Last edited by DigiSoft; 16-04-2014 at 07:28 PM.
Excellent work and that machine certainly won't be walking across the floor.
On the drawings you show the motors connecting to ballscrews directly.! Can just recommend you think about using timing belts and pulleys.
They greatly help reduce resonance which acts upon the motors and can cause rough running and lower performance. On a Box section steel machine this is esp important for obvious reasons and esp if the tubes are not filled with sand or some other form dampening ~(expanding foam isn't much good.!).
You'll also get the benifit of being able to apply a ratio if you ever feel like more speed or need more torque.
I do this on every machine I build regardless of what material it's made from and on every Axis because the benifits far out weigh the cost and extra time.
Last edited by JAZZCNC; 23-04-2014 at 07:57 AM.
Very easily found. Often your local bearing stockist will keep them or get them in for you.
Other option is to use someone like these people Timing Pulleys
The belt type you want is HTD 5mm pitch and 15 or 25mm width, personally I use 15mm. Pulley size I use for 2:1 is 18 & 36 or 20/20 for 1:1 ratio. Don't go too small other wise you have less teeth engaged and the belts wear quicker or worse they jump teeth due not enough teeth engaged to handle the torque.
Equally don't go too large else the inertia of the pulleys starts having a negative impact. If you must use larger pulleys then look for aluminium ones.
Pulleys often come with a pilot bore so you'll need to able to bore them or have them bored for you, the compnay in the link I posted will do them for you at a price. Don't go for taper lock as they are heavy plus you won't find them at small sizes anyway but in any case don't for the larger size in them either.
You'll need to calculate the belt size from the centres of each pulley and pitch/no teeth on pulleys, there are lots of calculators on the tinternet.
Last edited by JAZZCNC; 23-04-2014 at 08:58 AM.
Also you will need this, Jonathans belt length calculator
That's a lovely looking machine, you've done a great job on it, very professional, I like the monitor arm too. I forgot the gantry was made from steel until I looked at earlier posts just now.Spelling mistakes are not intentional, I only seem to see them some time after I've posted
BUILD LOG: New Build - For Your Amusement - MK-2 buildBy Karl in forum DIY Router Build LogsReplies: 11Last Post: 11-06-2012, 07:34 PM