[jimmyjames1981]

Ok, here goes, my first design was for a 4x2 router table but i decided on a 4x4 since the cost isnt that much more. For the build i will be using all 3/4" 6061 aluminum plate, i have bunch of this stock i acquired a while back and need a use for it anyway. I did look at the 8020 t slot stuff but geeze... that stuff is high dollar.... Anyways all the parts i will have waterjetted out oversize and then machine them in my brothers haas mill. the linear slide rails will be from glacern machine found here Glacern Machine Tools - Linear Rails and Bearings

the screw shafts will be 1/2"-10 5 start from mcmaster which will do 2 turns per inch, i havent decided on steppers yet but i do think i want to be in the 450-600oz in range to have ample torque to turn that size acme and have speeds upward of 1000 inches a minute for the rapid. The anti backlash nuts will be from dumpstercnc found here dumpsterCNC - anti-backlash solutions for home and industrial linear motion

now for the thrust bearings etc, i will be using steel thrust needle roller bearings that are good for 2,000lbs and 13,000rpm found here McMaster-Carr along with using hardened washers with them as well. For the pillow bearing i will be using high load bearings found here McMaster-Carr, they are good for 5000rpm and 1200lb load, they will be press fit .

I attatched some pictures of my current assembly, its nowhere near complete but its a start, i still have to do the mounts for the nema 34 steppers, mount locations for the proximity switches and a bunch of other stuff along with designing the table itself and the bearing block mounts etc.

One thing im not sure about is my thrust bearing design is i only use thrust bearings on the outside and then shaft clamps from dumpter and no thrust bearings on the inside, the way i have it configured i dont see a need for thrust bearings and clamps on the inside

Let me know what you think, also maybe a stepper motor recomendation?

[jimmyjames1981]

I also plan on using the porter cable 7518 router and ordering it with just the body only, does anybody know the dimensions of the 7518 body so i can design a mount for it?

[Falcon69]

4.2 inches in diameter

[ger21]

If you can afford them, you'll probably be much happier with Hiwin rails from automation-overstock.com, but they'll probably add $500-$750 or so.
I spent $1300, for two 67", two 96", and four 15" (2 Z axis).

I have no experience with Glacern's product, but the Chinese one's I've seen have a small amount of play in them.

Also, you won't get 1000 ipm with 1/2-10 5 start, and 600 oz motors will probably be slower than smaller 380oz motors, which are capable of higher rpm's.

With those screws, you're probably looking at 400-500ipm max.

If you want to go faster than that, look into going with rack and pinion.

[louieatienza]

I'd agree with Gerry... I've seen reports of 750ipm rapids with 5-start but to me this would be very difficult to achieve with normal steppers and drives. Even if you could spin a stepper at 1500ipm (with load) you run the risk of damaging your Delrin leadnut (or cause it to bind from the heat), but I think your screw would whip excessively far before that. You might want to look into using ballscrews and servos to achievev your speed (my best guess off-the-cuff would be 10mm pitch ballscrews coupled to 400w servos.)

[jimmyjames1981]

I Would love to run linear guides but they are a little too expensive for this build, i was contemplating some thk rails from ebay but couldnt find anything over 1200mm, also for accuracy i will onoy be cutting scrylic for some filtration parts for aquariums and maybe some acrylic name plaques for christmas presents, i will not be doing any aluminum milling , so im thinking that with the rails i have mentioned it will be plenty accurate for what i want to do, if i need anything super accurate i can do that on my brothers haas mills. I would be happy with +/- .01 on my part dimensions.

Thats a pretty neat setuo you have, have you ever had any problems with your tool offsets being different between the 2 spindles?

[jimmyjames1981]

I want to add that im not sure why i wrote 1000 ipm, i was thinking 1000 rpm divided by 2 revolutions per inch, 500ipm is plenty fast for me

[Pplug]

Well, it sounds like everything looks pretty beefy. However there are two places that I see that could be improved. You are spending all this time and quality materials but are using lead screws? I would think ballscrews would be a better choice with not that much increase in price. Last the router is a bad idea. The bearings and runout are the failing point. A Chinese spindle and inverter would be a choice.
Good luck!

[jimmyjames1981]

Well, it sounds like everything looks pretty beefy. However there are two places that I see that could be improved. You are spending all this time and quality materials but are using lead screws? I would think ballscrews would be a better choice with not that much increase in price. Last the router is a bad idea. The bearings and runout are the failing point. A Chinese spindle and inverter would be a choice.
Good luck!

The increase in price going ballscrews over acme screws is actually a pretty big jump, with acmes i can do the whole machine for about $250 including anti backlash flanged nuts from dumpstercnc, going the ballscrew route would cost me well over $1000 for everything including nuts, ends etc. And on the spindle, going a cheap chinese spindle will still cost me $1000 with all the needed accessories, going with an off the shelf router all i need is the router body, and a collet set, which will save me another $600. This is a budget build and im not looking for +/- .0001" accuracy. Of course i would love to have a nice spindle motor, high precision ground ballscrews and high precision guide rails, but with all that added up it would at least double the cost of my build, maybe later on down the line i can upgrade the spindle motor, leadscrews and guide rails, but for now id like to get it built and see how it does, im not that picky on accuracy on this machine,

With my given components and if assembled accurately, what would think my accuracies would be on a machine like this?

[Pplug]

The increase in price going ballscrews over acme screws is actually a pretty big jump, with acmes i can do the whole machine for about $250 including anti backlash flanged nuts from dumpstercnc, going the ballscrew route would cost me well over $1000 for everything including nuts, ends etc. And on the spindle, going a cheap chinese spindle will still cost me $1000 with all the needed accessories, going with an off the shelf router all i need is the router body, and a collet set, which will save me another $600. This is a budget build and im not looking for +/- .0001" accuracy. Of course i would love to have a nice spindle motor, high precision ground ballscrews and high precision guide rails, but with all that added up it would at least double the cost of my build, maybe later on down the line i can upgrade the spindle motor, leadscrews and guide rails, but for now id like to get it built and see how it does, im not that picky on accuracy on this machine,

With my given components and if assembled accurately, what would think my accuracies would be on a machine like this?

What! Ballscrews and a spindle/inverter should cost nowhere near $2000. I built a 4x4 router for $3000 from scratch with no parts or materials on hand! A 2kw spindle w/ inverter will cost under $400 and the ballscrews with everything including end machining would be under $600.

For less than 1 grand you can have it all including good accuracy.

[jimmyjames1981]

What! Ballscrews and a spindle/inverter should cost nowhere near $2000. I built a 4x4 router for $3000 from scratch with no parts or materials on hand! A 2kw spindle w/ inverter will cost under $400 and the ballscrews with everything including end machining would be under $600.

For less than 1 grand you can have it all including good accuracy.

The ones i have seen around on the net were pretty pricey for spindles, could you point me in the right direction for the spindle and inverter you speak of? Id love to have a more ridgid spindle than a router

[jimmyjames1981]

alright i searched ebay a bit, are you talking about something like this? Everywhere that sells them at this price range are shipping from china, are there any local companies in the us?

[Pplug]

eBay my friend. I used seller linearmotionbearings2008 for the ballscrews and mounts. For the spindle I would suggest a water cooled 2.2kw model. You can ask around the zone for a buyer but the are all just about the same.

[ger21]

alright i searched ebay a bit, are you talking about something like this? Everywhere that sells them at this price range are shipping from china, are there any local companies in the us?

There are at least 2, but expect to pay at least 50% more than the direct from China price.

With my given components and if assembled accurately, what would think my accuracies would be on a machine like this?

Depends on how accurate you build it, but it's not that difficult to get within .002" or so.

Switching to ballscrews and linear rails won't make it more accurate, they'll just make it cut better, and go faster.

[aarongough]

If you have a look at roton . com they have pretty inexpensive 5/8" ballscrews. I don't have any epxerience with them but they seem good, other people have spoken well of them and the price is good. I'm not sure why 5/8" ballscrews are so much less expensive than all their other sizes, I can only assume that they must sell a lot of screws in that one size...

[aarggh]

This seller ( 260824490998 but they are probably drop shipping direct anyway) is in the US. I fully with the others, a spindle and VFD planned from the start is the best way to go, it will be a much more pleasurable and accurate experience. Not to mention far less noisy.

I also agree with the ballscrews. I think most would agree, not spending the little extra difference now, can make things very dificult later on when you decide you do need that minimum of repeatable accuracy.

The costs aren't that much more really, but it could be the difference between ok performance, and a complete rebuild (wasted and lost money) to improve further, or just design the accuracy in at the start. Whichever way you go, your committing to the biggest money drain aside from a mortgage or a car that you'll ever undertake? :drowning: So you might as well plan in as best you can from the start, if it means a little longer to save, that then gives you extra learning and design time!

Well, perhaps kids goes third in there!

cheers,
Ian

[jimmyjames1981]

If you have a look at roton . com they have pretty inexpensive 5/8" ballscrews. I don't have any epxerience with them but they seem good, other people have spoken well of them and the price is good. I'm not sure why 5/8" ballscrews are so much less expensive than all their other sizes, I can only assume that they must sell a lot of screws in that one size...

i checked them out and theyre 5/8" ballscrews are cheap but they only have it in 5 turns per inch size which will slow it down considerably. They do sell "hi-lead" screws in .5"/rev and also sell the anti backlash nuts for them at about the same price as normal acme shafts and nuts. Are hi leads worth a crap?

[Pplug]

I have high leads on one of my routers and it gets upwards of 550 in./m. Definitely worth the price! Drop him a message with what you are looking for and they will help you out. I did that with linearmotionbearings2008 and he gave me exactly what I wanted and cheaper than listed on eBay. In fact, the next purchase I did from him was through PayPal only and I saved even more!

[Pplug]

With 5mm pitched screws, I get up to 300 ipm on my 4x4' machine before screw whip gets to be an issue. My machine uses a g540 with two screws on the y axis. If I had ordered the 10mm pitched screws who knows what the top speed would be! As it is, the kids in school get pretty scared when this massive machine starts moving suddenly!

CNC Build Photos

[aarongough]

I have high leads on one of my routers and it gets upwards of 550 in./m. Definitely worth the price! Drop him a message with what you are looking for and they will help you out. I did that with linearmotionbearings2008 and he gave me exactly what I wanted and cheaper than listed on eBay. In fact, the next purchase I did from him was through PayPal only and I saved even more!

I was looking at hi-leads for another machine that I'm working on, one question: are you able to back-drive the hi-lead screws? They don't list the back-drive efficiency on the Roton site so I assume that they're self-locking the same way that ACME screws are, just wanted to check with someone that actually has the screws.