[Tadas25]

Hi again.
After talking with few other CNC peoples I'm confused...
They says that R&P is not good thing, and I should go with ballscrews (preloaded with no baklash).
If it is so, I should change all design...

I spent few hours to assemble the test design. Let me know what you think guys. for X, Y axis will be nema 34 size stepper motors.

Or maybe I should stick with previous r'n'p design ?

T.M.

[PaulRowntree]

I think that ball screws giver higher accuracy, at the price of more difficult alignment and slower speeds. Check out the screw whip tables to see what type of screws you will need to support the speeds you want (diameter, turns per inch); most of the manufactures will have this information.

[ger21]

If you use ballscrews with a 25mm pitch, and about 20-25mm diameter, whipping shouldn't be an issue. But the price might be an issue.

[RossMosh]

Stick with R&P. It's nearly impossible to get wrong and you won't notice or care about any of the downsides once it's up and running. If you get the wrong size ball screw, you will care because you'll suffer from whip, slow speeds, or a number of other issues.

[Tadas25]

I'm not sure how to calculate rpm's. But one person calculated:
the 1500mm long 2005 ballscrew this will be about 700 RPM, so would be 3500mm / min.
Is this enough ? What speed you guys have ?

On internet I saw machines with r&p, and ballscrews they all work well. So I'm confused.

the speed isn't main goal. I would prefer accuracy instead.
I have to make decision today. Cause tomorrow aluminum parts will be cut (I can stop process if I need to... DO I NEED ? :drowning: )

[PaulRowntree]

I haven't seen anyone complain about the accuracy of r&p, nor ballscrews, when cutting wood; metals may be a different story. Most complaints about accuracy that I have seen come from belts or chain (like mine), but even these can be made to work well (and they are fast like r&p).

On the other hand, a lot of people (most people?) are disappointed by low speed, and unless you can run a slow spindle, feeds should be kept high to avoid burning bits. 100 ipm is a good target, more is better.

You really do have to do the math and estimate your (a) accuracy with r&p, and (b) speeds with the screws, and decide.

[Tadas25]

well,
I decided to try r&p and see the results my self.
I have redesigned main table frame. surface on table will be ALL in use.
Extended Y axis. So cutting area will be 1700x1200mm.

What you guys think about nema 23 steppers that I gave link in earlier post ? Or I should go with bigger - nema 34 steppers ?

[CarveOne]

For that size machine NEMA 23 motors of 380 oz and 495 oz will be plenty of power if you use a Gecko drive and the proper PSU voltage. I'm using four G203V drivers, four 495 oz motors, C11G breakout board, and 72vdc PSU on my 60 inch wide by 12 foot long DIY machine. It easily jogs at 1,400 ipm with CNCRP R&P installed.

The G540, 381 oz motors and 48v PSU is a lot lower cost and will outperform many other driver system kits. The resonance reduction feature alone is reason enough to buy Gecko stepper drives.

You won't regret going with R&P for most things. You may have some issues with engraving small text in metal name plates if the tension is not correctly set on the R&P drive assemblies.

CarveOne

[Tadas25]

I have decided make vacuum table. From earlier CNC machines I learned that job holding with clamps isnt good.
But I'm totaly new to vacuum and need your help guys to setup this system.

I have bought vacuum motor (see attached pic's). Can you help me with designing vacuum system and table itself.

So where to start ?

Thanks !

T.M.

[PEU]

Check MechMate CNC Router - Build your own with our detailed plans for ideas of a proven design that uses rack & pinion. It uses Nema34 steppers with 3:1 or more reduction.


Pablo

[Tadas25]

Hi all,
its me again

A little update.
Few design renders and few photos of cutted aluminum parts. Sorry for quality of photos, those was taken with phone and poor light source. Parts was cutted but not machined yet. I will post update as soon as parts will be machined

[UKGuy]

HI Tadas25

Sorry i just had to jump in on your thread and to let you know that i think your drawing are awesome! just wish i could draw like that let alone design something like that! Im starting a new router project soon so i will be following your thread with massive interest!

Keep up the good work buddy! and to all the other fellas... keep up the good advice

Regards
Derek

[Tadas25]

I'm here with a little update.
And need some help with vacuum system.
I dont have any experience with vacuum system at all. I have draw'ed pic with components (missing vacuum switch'es, cause I cant find any) so that someone of you guys can tell me how to connect these (or add more) components and make a working system. And I need to know what size of tank I need (or how to calculate it ?).
Thank you !

UKGuy -> I'm glad that you like my drawings / cnc machine

[ger21]

You generally don't use any tank at all.

[Tadas25]

Hmm, is my purchased and listed few post above vacuum pump powerfull enought to connect directly to vacuum table ?
P.s. what tubes should I use ?

[Phife]

Hmm, is my purchased and listed few post above vacuum pump powerfull enought to connect directly to vacuum table ?
P.s. what tubes should I use ?

That pump will not work very welll for the applications you want to use it in. It can only pull 3-4"Hg and really you either need at least 10" and a lot of CFM (hundreds) or a pump that can pull 24" and 5-10 CFM, I use 3 of the latter.

Go over to the vacuum hold down forum and have a good read, lots of info there. http://www.cnczone.com/forums/work_f...m_fixture.html

But basically, you can either get a large regen pump (10hp) and use 2-4" PVC pipe for high flow lots of leaks applications or get a low flow high pressure pump like the Thomas, Gast pumps or the ones the guys use over at Shopbot.

For the low flow high pressure pumps you want to use gaskets or seals to keep the pressure, you will lose hold if you have leaks. I use a 4" diameter by 30" long PVC reservoir for my system, just to give me a large burst of vacuum to pull a part down initially. Generally you dont need much of a reservoir. I also use 1/2" braided vinyl tube to connect everything.

[ger21]

You might also want to read the links at the bottom of this page to the shopbot forums.
ShopBot Vacuum Motors

[Tadas25]

Hi All. I was bussy with my other (non cnc) project's but its time to move on with this. Attaching pictures what I done so far. Now I'm waiting my order for all other cnc components (including electronics, rails and other stuff), they should be till christmas .

I have a question. My aluminum parts not looking good. What can I do to clean them ? Maybe sandpaper or polishing paste or other method ? What you guys recommend ?

Thank you.

T.M.

[PaulRowntree]

I use a fine steel wool to get that dark grey out (it makes lots of fine Fe and Al dust, so wear a mask), and you can apply clear coat (lacquer ?) to keep it looking shiny.

[Tadas25]

I use a fine steel wool to get that dark grey out (it makes lots of fine Fe and Al dust, so wear a mask), and you can apply clear coat (lacquer ?) to keep it looking shiny.

Thank you for reply. I will try find steel wool in Lithuanian shop's. But here, almost as always are no such things that you can easy buy in other country's... So, maybe there is alternatives ?