Frustrated. Have questions.

[maspeir]

I'm in the process of designing my first router. It will measure 24"x24" (I'm going for between an 18" and 20" cut) and be made out of 80/20 extrusions. In the course of doing research, I have come up on MANY stumbling blocks to this.

A short list:

1.) It would seem that I need a CNC machine to make a CNC machine. But if I have a CNC machine, I don't necessarily need a CNC machine... SO I either need to know someone that has one or spend an ungodly amount of money to get the parts I need machined at a machine shop. Am I missing something here?
2.) I have found a pretty good deal on ball screws. McMaster sell them by the inch and I can get nearly the entire quantity that I need for less than the price of a single screw at other places. SCORE! Oh... But wait! It isn't that easy... I need to support the end of the screw. Let's see... 24" x 1/2" ball screw: $20+-. End mount block: $380!
3.) Whether I go with ball screws or Acme screws, I need to have the ends turned. How do I go about this? How much will it cost? I have terrible fears of someone clamping the screw tightly into a lathe, damaging the screw.

One other question. Is DIYing a CNC machine basically for bragging rights or is it for economics? The reason that I ask is that the total price I am coming up with is in the multiple thousand dollar range for a very small machine. Is this correct?

[ger21]

1) If all your parts are aluminum, they can be cut with standard carbide woodworking tools. If you have a tale saw and drill press, you should be able to make any parts you need.

If you don't have the ability to fabricate your own parts, then you might want to look at a kit like at Home : Fine Line Automation


2)very few of us use ballscrews, but if you have to have them, then look at the complete packages on Ebay from China. You can get them cut to length, with the ends machined and include bearing blocks for less than the cost of the bearing block at Mcmaster Carr.

If you don't want to deal with China, you can get cheaper bearing blocks at Misumi USA.

But a single 6' length of acme should do you're entire machine. Get nuts from dumpsterCNC - anti-backlash solutions for home and industrial linear motion

3) Some people just use 1/2" ID bearing and shaft collars to mount them. Like this.

CNCRouterParts

I turned my own with a grinder and drill
http://www.cnczone.com/forums/diy-cn...out_lathe.html

4) If you don't have to pay anyone to make parts for you, then it's far more economical to build yourself. But you're not paying for your time. If your time is valuable, then you may be better off paying for a turn key machine. Typically, you'll pay less than 1/2 of what a comparable machine will cost. Comparable being the key word. It sounds like you are choosing far more expensive components than most people.

I can say that it's very difficult to built an aluminum machine for less than $1500-$2000, even a small one.

I recommend doing some more research to see what others are doing. Ask the people building similar machines where they got their parts. See what they're using. Ask why they did what they did. You may find you can do things differently and spend a lot less money.

[gio666]

Ballscrew machining if you get all three done at same time,maybe $40 each they will charge on CNC is a good deal,lathe chuck will not damage the ballscrews at all ,acme screw i have no idea what they would charge

[hemsworthlad]

Hi,

Many factors come in to play depending on what you want to do with the machine. It can also be as expensive or cheap has you want to make it and by the same token as easy or difficult.

I can tell you thru experience that for machines under 4 x3 then IMO for ease of building you cant beat ballscrews from china mixed with 8020 profile and supported rail for a cost efficent machine that will give excellant accurecy and repeatabilty in most materials upto Aluminium.

Other than shapeing and drilling Aluminium plates with a bit of bracket making which like Gerry said are all easily done with a decent drill press and bandsaw then most of the other components just bolt to the 8020.

Look at the pic attached, This machine i'm just building building for a friend could easily be made using Bandsaw and drill press.
Yes i,ve machined the gantry sides and end plates on my machine but they could easily be made less shapely and still function the same and be made with hand tools.
The rest of the components like ballscrews just bolt onto the profile, i've used
belts on this machine to turn the motors inside the frame and keep the footprint small as possible because it's going into a confined space and motors sticking out the gantry sides and ends wasted too much valuable space but I have made pritty much the same machine with the motors on the sides and end directly connected to the screws with couplers which you can see in the other pics of the individual piece's.

This machine use's profiled linear rails but supported round rail would work just as easily, use's single 16mm x 10mm pitch ballscrew down the centre on X axis but for ultimate protection against racking would easily accept twin screws with very little extra work.
It has a cutting area approx 40"x30"x5" and will give rapid speeds in the region of 400Ipm or better using 360oz/in Nema 23 motors.

It will easliy handle cutting Aluminium in light pass's and coupled with a decent spindle will route wood and plastics to a high accurecy and repeatabilty all day long standing on it's head spining.

This machine could easily be built for under $2000 dollars probably nearer $1500 if you shopped wisely, even with Profiled rails.
If you use Ballscrews and supported round rail from china coupled with a nice G540 package then for around $1500 you will have a very very nice capable machine.

I know this for fact because I do it here in UK and in the states you have access to far cheaper components than we do here.

It doesn't have to be hard or expensive if your prepared not to cut corners and buy from our eastern friends.! Again thru costly experience I've found it doesn't pay attempting doing it on the cheap it just frustrates and costs more in the long run and you still endup with an inferior machine.

Good Luck. . . .Happy building.

[maspeir]

Thank you all! ger21, the links you provided are simply amazing. This is exactly the information I was hoping to find.

Please keep posting suggestions and tips.

[JD_Mortal]

Ger21 is a CNC-goldmine... If it wasn't for his info, I would still be pondering how to turn my screws. (My first attempt wasn't bad, but his way resulted in much better results.)

Needing a CNC to build a CNC... Well, that is half true. You can use a bad CNC to make a good CNC. Which is most-likely what you will do in the future. After building your first CNC, you will have a better idea of what you actually need, not just what you wanted. Need more power, more stability, faster speed, more room, more accuracy, or just another CNC machine.

Virgin builders should not attempt to build $5,000 rigs, in my opinion. Which is why I went the low-ball route, but that is me. I figure that a $500 rig will pay for itself in a few jobs, where as a $5,000 rig will take more than a few years, if it is built with the same knowledge as my $500 rig. I can build in stages, as finances roll-in... I'd need a loan to complete the $5,000 setup. If I had $5,000 I would have just purchased one built by someone who knows what they were doing.

As for the end-block mounts... $380 is way-high... For that price, the end-block better out-live your entire frame. You simply need two sets of thrust-bearings held tight with axle-collars, against a plate with a hole in it. That plate can be the frame itself. Thrust bearings can be found on ebay for $5-$20 each, depending on the size and quality. Car axles, which are higher precision and contain more metal, are not even that expensive. The main purpose of the mounting plate is to absorb all the thrust-movement in both directions, so the motor does not take that abuse, and push the axle off the magnet-core, damaging the stepper and axial-bearings inside the stepper.

As for the ball-screw or slot-screw... I would say ball-screw, if you can find a decent price, with the specs you need, if you have motors with great holding power. If your motors do not have great holding power, you will have better luck with the slot-screws, which have greater friction and are less prone to unscrewing. That lower friction in the ball-screws is a not "better", it is just less friction, which results in faster movement. Technically, having less contact which is also rounded, makes them worse, in my opinion. The balls wear, the flutes wear more ways than slot-screws, and they can not be "fixed".

The common wear on a ball-screw, is slack from compressed balls, divots from ball compression on the flutes, non-round or gouged flutes from stuck debris, patterned divots from excessive holding forces or jarring on the flutes, mushroomed flutes from normal travel wear. Resolution, buy another setup.

The common wear on a slot-screw, is slack from worn slots, gouged slots from stuck debris, altered slots from excessive holding force. All of which can be fixed, or compensated for. Resolutions include grinding altered slots back to full width, filling gouges with filler or welds, and the use of anti-backlash nuts or sacrificial nuts that limit that damage. (Ball-screws can't use sacrificial materials, as they depend on the precision and hardness of the bearings and bearing-nut. The screw is sacrificial on a ball-screw.)

All of the above is to be taken with a grain of salt... If you are cutting only MDF, foam or other light duty materials, ball-screws will NOT have those issues. (Except perhaps the unscrewing issue with a 3-start, 5-TPI or other low-turn setup. Breaks can assist with unscrewing too, but that is just another thing to power and pay for, and control.)

[hemsworthlad]

Sorry JD not meaning to be deliberatly arguementative (we seem to have disagreed a lot lately) and dont know how much experience you have with ball screws regards CNC but most of what you say regarding ballscrews is not correct in my experience and quite the opposite.
Yes your correct that when the screw wears it's scrap but unless you are either severly abusing them(running dry or beyond spec) or a major jam up gouges the screw which doesn't happen very often(never happened to me or anyone I personnaly know) due to the way the nuts are tightly sealed then they wear and last much longer than acme screw & nut and for longer periods without maintenance.
Anyone with a mill will tell you what a pain in the arse lead screw can be regards wear and maintenance.

The balls do wear eventually but can be replaced easily enough and again if run correctly and lubed correctly the nut body doesn't wear and it's a simple change of balls(Ah ah any body who's stripped a ballnut down will laugh at this comment due to the tedousness of the job) and it's like new again.

Unless you have a very heavy Z axis or really really really weak motors then unscrewing is not a problem and I've never experienced unscrewing on any machines i've built.
My Z axis is quite heavy with 2.2KW watercooled spindle with beefy mounting bracket, the stepper motor is also attached to the front plate and travels with it along with the profiled linear rails for strength not the bearings. . . so all in all it dont come much heavier for DIY CNC and it never moves so much as a 10th/mm when powered down. The motors is a 3nm nema 34 which is about as small as it gets in 34 sized motors and not much more holding power than an larger 23 when at power down.
To be honest i've thought of using a 23 because it will probably get better accelleration than 34.!

If maintanied & lubricated correctly and run within the screws parameters then ballscrew will out last Acme lead screw with less maintenence required and work with far greater precision. . . . . . . ABUSE it and yes it will die quickly (possibly more so than ACME) but so will anything thats abused.
Used correctly they are hassle free and last for years and with the price of ballscrews from china it doesn't make sense to use lead screw IMO.!!

Again sorry to contradict but have to tell my actual real use experience.

Edit: We agree on one thing thou.? . . . Ger21 is a Goldmine. Lol

PS:My machine 99% of the time cuts aluminium dry some times upto 15 hours a day and the screws work in a pritty ****y enviroment constantly getting pummeled with chips and they look work has good as the day they where fitted which is over 2 yrs ago with absolutly no sign's of wear and still Zero backlash.

[ger21]

That lower friction in the ball-screws is a not "better", it is just less friction, which results in faster movement.

Not really. I'm with Hemsworthlad on this.
Ballscrews are typically 98% efficient, where as acme is typically 40%-60% efficient. This means that with the same motor, and if both screws are the same turns/inch, the ballscrew will provide double the force. It's like using a motor that's twice as powerful.

And you'll never wear out a ballscrew cutting wood on a small router, unless you run it dry with no seals for several years.
my day job is programming and running $100K+ routers. I've seen ballscrews nearly buried in sawdust running for over 10 years with no problems at all, pushing 1000lb loads at over 1000ipm.

Having said all that, it's hard to beat acme screws for a homebuilt machine. They offer very good performance at a very reasonable price. I use them on my machine, and I'll use them again on my next one.

[JD_Mortal]

Well, that is not a disagreement... Not in my eyes. LOL.

Like I said, if your holding power is adequate... If not abused... If not cheap...

You obviously have high quality ball-screws, over-rated for your application, and adequate drives. But those things need to be taken into consideration in advance to the purchase. I didn't say it was easy to destroy them, I just listed the "common issues". Where I worked, those common issues were quite common on all our equipment. But, in all fairness, we were running 24/7 with machines near the upper limits of use/abuse. When buying cheap china-items, it is usually safe to assume "used items" will already have some of these issues, which is why they were pulled from operation. With new items, that are cheap, you should also expect that they will encounter these issues faster than your over-rated ball-screws. (I am not using over-rated in a derogatory manor, I am simply saying that they are capable of much more abuse/use than you are delivering to your ball-screws. Eg, you have tanks to drive to the mail-box.)

There was no mention of motor-sizes, or force-loads (milling materials) mentioned, so I figured that I would cover all grounds.

I can also provide citations if needed, but any google-search will turn-up pro's and con's stated above too.

It is hard to say, "it doesn't happen", just because you don't see it happen. That is like saying ghosts don't exist, because you have never seen one. If you never saw one, how would you know. (If you haven't had those issues, like I have, then you can not say they don't exist. You can only say that you have never had those issues, which is not saying anything at all. That is like me saying, "Unicorns are safe to feed, because I have never been bitten by one.")

I would select ball-screws, as I said in the post. However, that is for my use. That still does not make them better. They have a specific use, and that use is not universally, hands down, "better", or they would not manufacture slot-screws anymore. Including budget, availability, wear, and application, into that term "better".

Again, my intentions were to raise awareness, as opposed to just saying, "yes, they are better, get them". It is a design choice, not an issue of popularity or illusion. (Unless you know the other related factors, judgement can't be made in that direction.)

Ball-screws are often made from...
440C Stainless IAW AMS-5618 and AMS-5630
6061 T6511 Aluminum IAW AMS-4173
17-4PH Stainless IAW AMS-5643 and AMS-5644
Nitronic 60 IAW AMS-5848
15-5PH Stainless IAW AMS-5659
9310 Alloy Steel IAW AMS-6062, AMS-6265 and AMS-6267
6150 Alloy Steel IAW AMS-6448
Nitralloy 135M Steel IAW AMS-6470, AMS-6471 and AMS-6472
Inconel
Monel
8620 Alloy Steel
6Al-4V Titanium

Which is better?
6061 T6511 Aluminum or 6Al-4V Titanium

They are both "ball-screws"... They are not equal, and 6061 T6511 Aluminum ball-screws are nothing compared to any slot-screw. (Most slot-screws are steel, due to the high friction, aluminum is rarely ever used. However, aluminum and cheap-iron/steel is commonly used on many ball-screws.)

[wcarrothers1]

when I did my first one.. I got a mill from harbor freight. One of the smaller (at the time around 900 dollar) gear head mills. Some how I got mine for 600 on a managers special taking a rain check to another store)..

but anyway I did a cnc mill conversion on that. (using it as a manual mill to make the parts to CNC it. Then learned how to use that as a cnc machine.

Then that machine helped build the the 4x8..

How ever after picking up my series 1 CNC bridgeport at an auction (for less then I paid to buy and CNC my round pole mill I might add) making machine 2 has been an even easier more accurate and fun process...

So yes having a mill to make a mill is the way to go. Or finding some one with a mill who will let you use it for some of the parts which just would be to hard to make with wood working tools.

GER is of coruse one of the best resources here at the zone. some day I hope to meet him (seeing he isn't actually to far from me..)..

b.

[LeeWay]

I have never seen an aluminum ball screw. I have seen aluminum housings, but never the screw or ball carriage. Not saying they don't make them, but they certainly would not last long doing any sort of machining.
I only use ball screws on my machines. I started out fitting acme screws to my router. I realized quickly that they would be taking a lot of punishment and would not have a long life for what I was doing. Ballscrews from then on. I have only had to replace the balls in one screw. It was a high quality used screw. Cost less than $10 to do. Back in business same day.

If it is a smaller hobby machine, then absolutely. Acme will work. Probably a perfect choice for a 2' by 2' router.
That said, he is also faced with some machining. I have bought the exact size screws I have wanted or needed off Ebay at a very good price. The thing with most of those is they often come with mounts. No machining needed. Quite cost efficient if you don't own a lathe.

I have 8 ball screws in operation now and will soon add 3 more. No way I would step back down to an acme screw. Not as long as cost effective ball screws are so widely available.

[hemsworthlad]

JD: Just semantics.!!

Bottom line to me is REAL world use and in my world ballscrews rule over lead screw every time.!!. . . BUT like Gerry says thats not saying they are no good and they can be made to work perfectly well for DIY CNC.

My main point was two fold really, 1: To dismiss the wear issue's 2: Dismiss the unscrewing issue with relation to DIY CNC which I some times think you dont account for in your techincal quote's.

My screws are not top quality, they are basic cheap chinese screws probably of the lowest grade steel but they do the job very well.
One other point and my main Arguement against ACME vs Ballscrew's is the price you can buy them from china.
I'm sure anyone who use's ACME screws and I'm sure Gerry would agree if I offered ACME or Ballscrews for the same money or very near he would take the ballscrews every time.

I payed £300($470) for 2 x 60" 1 x 50" 1 x 18" all with machined ends and BK/BF bearing blocks nuts etc and 4x motor connectors delivered to UK. The delivery was $90 and presume to US would be cheaper.?

Nothing against ACME I just prefer ballscrews for precision and efficency they offer over ACME.!!. . . . . That said if I was building a large machine just for cutting wood then I wouldn't use either and go straight for R&P.!