Availability of Multi-Start ACME Rods

[Phil Mailloux]

I'm slowly starting to design a CNC and have spent heaps of time reading up on CNCzone. I even went as far as buying the Solsylva plans some time ago. The more I read on it, the more I'd rather build something with 8020 though.

The most complex part I've got yet is getting a good ACME rod for the X axis. I want to build a minimum of 1200mm X-axis. A rod that size woud be out of the question as shipping something that size from the US would be over $200 alone (if not a lot more) because of Auspost's size restrictions. I obviously would want something that gives me over 200ipm for the X. I'll probably buy 1/2-10, 5 start in 3 foot lenghts for the Z and Y from McMaster adn get all the couplings from DumpsterCNC.

So the main question is where in Australia do I get a multi-start, 1200mm, 1/2" or 12mm rod? I've checked out Linearbearings.com.au but they only seem to offer single start.

[rodm]

Hi Phil,
Half inch Acme thread is probably not what you want to use on a 1200mm long axis at 5m/min machine. I assume you just want the speed for rapids as cutting at those speeds will either be shallow cuts or a very powerful spindle/router.
A 1200 long screw should be at least 16mm but preferably 20 and top end 25mm diam.
If you got 10mm pitch ballscrews and ran a stepper motor to 500rpm (Gecko drivers) you can get the rapids you are talking about. Ballscrews are affordable now and certainly within budget compared to importing acme 5 start.
Try here for prices and I think you will be pleasantly surprised. Get the ends machined by him as well as he is well priced there.
http://stores.ebay.com.au/linearmotionbearings_W0QQssPageNameZstrkQ3amefsQ3amesstQQtZkm
Just contact him and ask for any size, length you need. I have his personal email address if you want it. One of the forumites got 1200 length screws delivered through EMS/AusPost no problem.
Another alternative is to go rack and pinion so consider that as well.
If you are still stuck on Acme you can get single start in Australia but when I got it a couple of years ago it was only avaliable in 12 foot lengths and was like a dog's hind leg for straightness.
Welcome to this part of the forum and I hope you follow through with your build.

[rodm]

Phil,
You may want to contact Jason as he has built a CNC machine and is making guitar bodies and necks. He has a couple of years head start into this so I am sure he can offer some sound advice.

[Phil Mailloux]

Thanks Rod, could you point me to Jason's log-in name or e-mail :)

I meant indeed 200ipm of rapids. I'm planning on using the Xylotex 425oz/in kit. For the size of the screws, I mentioned that size simply because that's what Joe's 4X4 CNC uses on the zone and there's plenty of happy people there with it. I'm not sure the Xylotex would be able to deal with 16mm screws though. What do you think? I'm also on a certain budget so I can't go for all the fancy options like as geckos and ballscrews (as much as I'd like to, I don't think swmbo would let me). The ballscrews on the link do look good and are more affordable than others I've seen but it's still too much for me at this time. Especially when compared to a 6' length of rod going for $60 at McMaster. My only problem is getting it here :doh:


I have given the tought to use rack and pinion for the X axis before. If I can't find multi-start screws that can fit the bill locally I'll probably have to go with that and try to learn more in the meantime on that.

Anyone else has seen multi-start screws somewhere in Australia?

[rodm]

Hi Phil,
Jason is JB2060 and his machine and some of his guitar work is on this forum.

I have made a number of machines with 16mm ballscrews and Xylotex drives without any problems. Have you thought about single start acme and using pulleys on the drive? You will have more chance with finding single start screws in Australia.
I still have concerns about half inch screws and the speeds you want to achieve. 1200 is a long span.

[Phil Mailloux]

Thanks again Rod, I started looking around the Ebay sellers old sales to check out his feedback after my last post. I though his prices of "$210 for a 700mm ballscrew" were sort of "meh" until I just realised a minute ago that that price was for 3 ballscrews!!!:o I almost had a heart attack there.

This guy has just become a very good contender for my screws, maybe even for the linear bearings too. Have you bought any of his screws? If so, how's the quality?

[rodm]

I thought you were missing something. :D
Yes I and a few others on this forum have his ballscrews and rails and they are good quality and excellent price - certainly a big jump above acme screws. He is very helpful so contact him with your ideas.

[rodm]

Phil,
I have sent you a PM with contact details. Don't forget to get the end machining done as it is only about $20 for both ends. I can send you a drawing and link for cheap bearings.

[snowyskiesau]

I agree with Rod regarding this seller.
Communication was easy and delivery was quick.
I'm looking for helical couplers at the moment which I'll probably get from him.

[Phil Mailloux]

Got the PM, I wouldn't mind having the link for the bearings and drawing if you don't mind. I will e-mail the seller as soon as I get the funds for the build which is about 3 months away from now. I'm in the costing/design phase right now.

[rodm]

Bearings are here
http://www.vxb.com/page/bearings/CTGY/ANGULAR_CONTACT
The ones I use are 7728 or 7729 and you only need one for each motor end. Get Kit240_1 for the free end - there are ten bearing in this kit. Freight is good and quick delivery.
I will send you the drawing when you are ready to go with the project.
I suggest you price the 8020 before too long as it is not cheap in Oz.