[twistedfuse]

Hello All,

Firstly let me say i hope i have posted this is the right place, not too sure. And secondly what a wonderful site this is. For years now i have been thinking about building one and this year i finally bit the bullet and bought the Hobby CNC 4axis 300oz kit. All my circuitry is now built, all i can say is "wow" and i havent even built the machine yet. The main reason for electronics first was that i wanted to commit to building this machine and it is definately a good way to do it. My machine will have rails of 932mm (full rail that supplier had) for the main x axis, 700mm for the Yaxis and 280 for the z axis. And i am hoping to build a cutting area of approx 700x500x150 so i can get into model building, PCB manufacture for all my electronic projects, sign making and anything else new that i can do of course.

ANyway onto my build and problems so far. I have had best luck this week, secured old stock from a supplier of proper linear bearings for dirt cheap. They are 35mm linear rails, bulky and huge but hey, its within my price range, ill just build around them. So luck is on my side and even tho i dont have them yet i have started the frame work for the base. I will post pictures when i feel its at a good stage. The frame will be 40mmx40mmx1.6mm thick. I think most of the machine(gantry as well) will be built somehow with this and 6mm plate aluminum for extra strength.

Next on my bill will be to drill and tap all the holes when i have both the rails and frame together. After that will follow the gantry build and egt 2 axis working then make the final z axis.

My first problem is i have to get some leadscrews/ballscrews. I have a local bloke who has been heaps of help so far and is really nice. He ahs offered me a 5TPI screw for at least my main axis. Now my question is: Because im making circuit boards will this thread pitch be too coarse for the intricate work i need?

I am hoping to have built my complete machine over the course of the holidays i have (next 2 weeks), mostly at night and in the mornings as i work everyday. Well i know it will not be completely finished but at least i would like it to be cutting in 2 weeks. I will probably cheaply go for all thread until i find a good deal on proper screws, then slowly replace anything to get higher accuracy.

Anyway, thats about it for now. Is there anything i should be aware of for my build? Any comments etc.

Thanks in advance,

Daniel

P.S Attached are some quick renderings of my machine. The main one is now outdated as the gantry will be slightly different. New gantry proof of concept is attached tho.

P.P.S If there are any aussies out there willing to sell some leadscrews/ballscrews please email me or post here as i would really like to keep costs down.

[Greolt]

Sounds like a good start Daniel.

Those linear rails should do a good job.

Just remember they are only as good as the surface they are fixed to.

Having the rails it is probably worth going for rolled ballscrews and you will have the potential for a pretty good result.

Most Aussies I know get their ballscrews from HomeshopCNC http://www.homeshopcnc.com/index.html

Where in Aus are you?

Greg

[twistedfuse]

Hello Greg,

Yeah i thought that they'd do the job. Bit of pain figuring out the Y and Z axis as the bearing carts running are something like 110mm long x 70mm wide x 45mm hight(over all with rail). Shouldnt be too hard, just means now that ill only have 1 cart per rail on the z axis and maybe 1 for the y axis. They are huge so im sure they'll take alot of weight. Just need to get the rails now to completely figure it out. As for what they are mounted to, well i changed it to some thick walled aluminum tube still 40x40mm. Might use some extra bracing as well bu ill see.

I was reading the madvac site and it said he used epoxy to fill the top where the rail was running so the lot was nearly 100% flat. Should i do this?

Ultimately i will try for precision ballscrews as like you said, the machien has good bearings and i would like the highest accuracy since i will do pcbs.

As for where i am, i live in Nowra, NSW. About two and a half hours from sydney.

I should post first pictures next week.
Cheers and thanks again, can't wait to have the machine running

Daniel

[twistedfuse]

Hello Again,

Good news today, after getting my cnc machine frame complete. It came out looking very nice and light as well. I ended up getting it all done with 40mm x40mm Aluminum Tube with 2.5mm thick walls. Very strong.

Next is the linear rails which i am due to get this week sometime(probably thursday) so i will post some pictures of those as well. It will be a tedious night of drilling and tapping the holes for the rails as well as alignment. My mate is awsome again, he has lent me his dial indicator so that will help greatly. Are there any other quick alignment ways to make alignment faster and easier. Im thinking about using some clamps and a laser to get general alignment and put some prssure on it then tap it with a rubber mallet softly to move the rails in alignment with the dial indicator.

I also decided to get some panels/skirting done from my mate with the plasma cnc, that way i can make some simple mounts that will be perfectly aligned for the rail carts and motors etc. Also the sides of the gantry as well as behind both rails will be done as well just to add stiffness and make it more ridgid. Also make it look cooler. lol

Anyway, i will keep you all informed of my progress. Thanks again,
Daniel

[twistedfuse]

Hello Everyone,

More great news today, finally picked up my rails. In the picture the ones on the right are the 932mm long main rails, left are 700mm rails and the 2 small ones are 300mm. One block from each rail will be removed off the two sets of smaller rails as im sure the 35mm rails will handle the weight.

Now im not sure if im allowed to do this but im here to say if you decided to get some linear rails and dont want to wait around get in contact with a NSK rep as the guy i went through was way beyond helpful. Now im not trying to sell them but just telling you all that i had a great dealing with them (Sydney/Parramatta Branch) and would like to highly recommend them.

Anyway, my excitement has got to me so ive been pushing these things a little bit, doesnt seem to be as smooth as i would have thought but im sure i just have to move them a bit to get them going. Cant wait now, things are really looking forward. Going out today to get some bolts and screws and taps and drills to help with the construction. Im sure it'll be a long night tonight. lol.

Cheers Everyone,
Daniel

P.S If i was going to tap the tube so that i can mount the rails...would i use a drill bit 1mm smaller to drill the hole then tap it or would i use one that is 0.5mm smaller???

[Greolt]

WOW there pretty beefy rails you have there!!!!

One block per rail will be fine for the Y axis. With the Z azis I would only be using one rail and one block.

It is going to be heaps stronger than your frame anyway.

As far as taping drill size, you need a tapping drill chart. You could find one on the net I'm sure.

When you are picking up your drills, taps, bolts etc. ask about a wall chart with tapping sizes etc. Good thing to have in your shed.

I think you will need to consider what material you are going to tap to attach those rails.

2.5 mm aluminium will not be enough thread I reckon. Can you get nuts on the back?

Greg

[FPV_GTp]

hi

" P.S If i was going to tap the tube so that i can mount the rails...would i use a drill bit 1mm smaller to drill the hole then tap it or would i use one that is 0.5mm smaller???"

some times it is one millimeter differance in diameter between a the hole size and the thread actual outer diameter size but not always the case

Invest in a vernier caliper and measure lowest piont ( minor diameter ) in the thread and the high point ( major diameter ) and subtract the two from each other and this will confirm the actual clearance differance between threads sizes for a specific thread , 1 mm is not always the case. The actaul whole size is the inner minor thread daimeter that you have to drill to cut a correct thread size for a particular bolt thread.

Like Greolt siad 2.5mm is very little material to obtain enough thread for engagemnet. Most likely when you tighten the bolts you will strip the threads you have tapped , specially in alloy.

thread chart UNC Coarse http://www.efunda.com/designstandard...s/screwunc.cfm

UNF Fine http://www.efunda.com/designstandard...s/screwunf.cfm

Just curious what did the linear slides and mounting blocks cost you ??

What motherboard and drivers are you going to use ? stepper motors or servo motors ??

cheers

[Rodm1954]

If you run into trouble with your tapped holes then re-drill with a clearance hole (a drill bit the size of your bolt) right through both sides of the tube. On the inside of the tube drill again with a clearance hole for the nut. Then fix nut from inside the tube onto bolt through rail.
Nice machine by the way.

[rustamd]

If i remember correctly, to find out drill size you need to substract pitch from diameter. Example: To tap hole for M4x.7 bolt you would get this equestion: 4-.7=3.3

[rustamd]

Here is very big drill and tap size chart:

http://en.wikipedia.org/wiki/Drill_and_tap_size_chart

[twistedfuse]

Hello Everyone,

Thanks for the replys, started to think not many were viewing the thread...lol. I would have still posted tho. As for the tap size i have been thinking about it alot and trying to decided about how i will do it. I was thinking about the nut idea and thought that would be the best but at the time i wasnt sure if tapping the tube would be enough so i thought it would and i was going to do that. The main problem that i came across first was the fact that the clearence hole(Bolt Hole) for my rail is 9mm and i found out there is no such thing as a 9mm tap so i had to get 8mm with 8mm socket head cap screws(will the 8mm give me more of an advantage as it can be slightly adjustable?). I didnt buy them yet as i was unsure and now you all have shown that i should probably put a nut on for extra assurance.

Also will i be able to find 9mm round head bolts to suit? Looking to get some work done tonight/ this weekend. Hoping to have attached the x and y rails by the end of this weekend.

Greolt, you said use 1 rail for my z axis. How would you recommend i do that? I have seen it before but thought if i decided to do aluminum, the off balance would cause something to bind. Am i wrong? As usual i would like less z axis so i can have a larger cutting space. I will be looking to use a die grinder and a dremel with the later mainly just for balsa wood and fine work like PCBs.

FPV_GTp, ill start with the rails. The rails only cost me AU$300. Best thing i did as i was thinking of using skate bearing idea then i just rang around looking for old stock. The guy i dealt with was great and said most only need 15/25mm rails and these werent selling and been around for ages. They cut them to size and he met me halfway to drop them off. Brilliant services. Also got a complete product manual. As for my electronics, im not sure completely what computer i will use but i have already paid for mach 3, and have completely compiled my hobby cnc 4 axis board. Was going to use 2 x axis but i wanted to do rotarty milling later so i will keep the 4th for that. I will post a picture or two of the setup. The motors are 300oz steppers running from the PSU of 29.8v rectified and 8.88A. 2A ea. The black things at the front are stereo connectors, they will be used for the limits/home and tool height indicator and e-stop. I have been mucking around with the electronics learning mach 3 and so on. Really enjoy watching the motors spin under the whim of my finger. lol.

Anyway, thanks for the replies you have helped greatly so far, hope you all can help me through the build and look forward to more suggestions/comments/flames etc about my deisgn. Will post hopefully soon that rails are attached. Just got to find a magnetic base for the dial(wont stick) but i need it since the clamp doesnt fit. lol.

Daniel

P.S The computer i was thinking along the lines of a P4 around 2 GHz. I should be easily able to get one, wanted a laptop but i dont think ill get one for the price i'd like to pay.lol. It will be standalone with all CAD/CAM done on another computer(Dual Core) and transfered with a usb stick. So i just need something fast enough/best for mach 3.

[crocky]

Hi Daniel,

Looks like it is going pretty good so far and they are big rails

I have not been to Nowra for about 7 years now and I think from memory it is a nice place.

Bob

[twistedfuse]

Hello All,

Haven't had a chance yet to do any mounting of the rails. Really starting to get the first cut/drill jitters. The whole alignment thing is really getting me worried. I keep thinking im going to have something out of alignment and it will stuff up the whole thng. I will hopefully get some guitar string tomorrow and use that in conjunction with my monoscope from my telescope to align it and then double check it with the dial indicator. Nervous moments to follow. I am also worried about having one rail below the other and then the whole thing on an angle or something, all the possibilities to go wrong. What would be a good starter point to allow in misalignment to allow...at least to get started???

I hope all goes well. Will try to do something tomorrow. Heres hoping. Thanks for all the support too guys, really sheds some light on these moments.

Cheers,
Daniel

[twistedfuse]

Hello ALl,

Well finally i pushed past the first cut/drill jitter today. It was raining and misserable so it forced me to start. I didnt get round to the x axis rails yet(Probably should ahve done these first) but at least i started and seem to have a good shot at this working out...so far. Anyway, today it was all sorts of fun and games. I had to travel into town a few times to get little tid bits for the build, like deep sockets and so on. But i got the gantry rails mounted and it feels great. Nice and solid. I ended up using the socket heads and nuts, this way the size of the hole is bigger and allows more alignment corrections, but after tightening the nuts there is no play in the rails so i figure they are secured nice and tight. Checking the distance between the rails with a digital vernier/caliper it measured exactly the same on all points of the rail (Graduations of 0.1mm on the caliper). I will double check it with the dial inicator soon but am confident as it also checked out when measuring the distance between the carts on the rails (yet to remove one from each rail).

Im still worried about the stiffness of the carts as well as the weight of the gantry that will be moved by my 300oz motors. Will i have a problem? I will hopefully have my main rails on tomorrow and will hope to have the gantry attached to the main rails soon as well, but i will have to try and catch up with the bloke with the plasma and see if he'd be able to make up the mounting plates and skirting and get them soon, and maybe the drive screw as well. Man he is a brilliant guy, and his machine looks fantastic. Hope mine comes out at least the tiny bit like his.

Anyway, im sure ill post again soon, might try and CAD up an idea for the router mount with 1 rail and post it to see what you all think. Hope to be cutting soon, and plotting a little bit sooner. lol.

Cheers,
Daniel

P.S Nowra is a lovely place, a small town with not overly alot to do(Until my router is built) but its starting to grow.

P.P.S Also started thinking today that i might make the table removable and have one for a vacuum table and one as a normal table and one as a flood coolant table. Just an idea for now.

[twistedfuse]

Hello Again,

Well this morning has been good to me, i got around to attaching the rails to the base frame. When i took these rails out of the package they were full of grease/lube and it seemed to make a large difference in the running of the rails, however they still seem to be stiff and like i said that plus the weight of the gantry are really making me nervous as to the ability of the steppers. I spose if worse come to worse, i can order larger ones or even just chuck the idea of the rotary axis and have 2 running the gantry, that might help but i'd prefer only 1 so i have the option later. What do you all think? Will the 300oz be ok.

Well now i have the base rails on i will spend some time adjusting them to get a nice alignment. For now i just placed the gantry ontop of the rails just to see some progress. It really looks nice from my point of view and the thought that i might have something setup this weekend to do some plotting or just to see if it does move is giving me a really good feeling.

Anyway, i am going to do up the dxfs tonight of my gantry to rail mounts and also the sides of the gantry so i can hope to send them off and get them this week sometime. For the mean time i might test the strength of the motors by doing a very crude mock up of the z axis and see how it responds.

Thanks alot,
Daniel

[twistedfuse]

Hello All,

Im really starting to get worried about the machines operational capacity if the stiffness of the rails is going to be a problem. Its really starting to bug me and i havent had a chance to test the steppers on moving even 1 rail by itself let alone 4 carts on my main axis. Man its really taking it out of me, less sleep and thinking about it all day doesnt help. lol. I know they should ease up over time and also under a load but im sure they should be smoother than this.

After doing some research on the net i found a couple of references to some rails that have adjustable pre-load on them. Now i went through the whole book i got as well as extra info but cant find anything for any of the rails from nsk(unless i overlooked it). So i have taken a pic of both sides of the rail cart(note: that is masking tape to hold the bearings in place...i wish i had some of those temp plastic rail transfers) in the hope some people could tell me if that set screw on 1 side is for pre-load or not as well as confirm which one is the grease inlet. Maybe i should grease the complete rail but i heard i'd need to get a full container of grease, completely clean out the old grease, then re-grease it all without loosing the balls. Otherwise they mix and things really get interesting.

Whats everyones thoughts on the process/ideas on how to lighten the pre-load and get it running smoothly. Should i just sit down for half an hour watch a show and run them back and forth to try and break them in? Other thoughts???

Any help would be greatly appreciated as i'd like to move on very soon and start attaching everything together and see her move. Thanks in advance,

Daniel

P.S I hope people like the pictures, any specific shots can be posted and questions answered etc. Would enjoy to hear other peoples thougths and suggestiongs or changes etc.

[Thazul]

Hi Daniel,

I have some of the same type of rails, except they are SHS35 THK brand.
I know mine have some resistance also because of the preload, But when some weight is applied they become super smooth.
Try putting some weight on them, or pressing down on them, then sliding them.
Mine were used when I got them so they didn't come in the new packing grease.
I'm not sure exactly but maybe they need to be cleaned/oiled? (wait for someone with some more experience to chime in here before doing anything to them) I'm still a novice.

Machine is looking good! Keep the pictures coming, can never get enough pics

[twistedfuse]

Hello Again,

Thanks heaps for the reply Thazul, its good to know someone else is using these larger rails. Started to think i over-engineered by way too much.lol. That and trying to keep things cheap made it worse.lol.

Yeah i think i might try to send a message to the nsk rep and see what they suggest. I push down on the rail and it does ease it a bit, but it stil requires some energy to push or pull. Thats why i think maybe the lube isnt plentiful enough or something. Maybe im dreaming it up and maybe the motors with the threaded rod will move the rails no problme as they can exert more power than my arm and the fact that maybe im expecting the wrong thing form the rails(really should test by making a cheap z axis).

I am expecting my Gantry to bearing mounts tomorrow morning so i hope to mount the gantry to the base rails and then skip a few steps and try to knock up a simple/cheap threaded rod leadscrew and see if it can move it or not.

I have decided to use one of the suggestions and go with 1 rail and 1 car for the z axis. At the same time i have also got a contact trying to get a monocarrier and hope that might be cheap and that would make the z axis alot easier as it would be a complete stage(Just add motor, grinder and bam! new z axis)

Thanks again everyone,
Daniel

[Rodm1954]

Hi Daniel,
I would not be worried about the resistance on the bearings. Initiallly there is a slight wear in factor of both the bearings and the wipers (seals) as everthing settles in. Once you have a bit of weight on the rails you will feel it free up and as you have metioned you have quite a mechanical advantage with the screw. Those screws appear to be holding the end seals in place. The adjustable bearings I have seen have screws and a plate parallel to the row of bearings.
Keep going forward and don't dwell on the percieved problems. You are doing well so far.

[LikuiD]

Hey Daniel,

Just wanted to thank you for that great thread, I'm a total newbie to the
whole diy cnc thing, and its really helpful to see how other people start out,
and the common problems they face and such..

I've bookmarked that page, and will hopefully check it daily

Thanks once again !