New CNC router build in Melbourne

[cnc3678]

Hello all,

after finally getting some cash together, I've started purchasing the main items for my first CNC router build. I hope to cut both wood and aluminum on a sturdy table measuring roughly 1200mm x 1500mm. The table base will be constructed using 50x50 & 50x75 (4mm) box section steel and will ultimately carry a 16mm aluminum top.

The gantry design will be based on a number of DIY versions that I've seen in this forum over the past 3 months or so. I'm particularly keen to eliminate as much flex as possible based on some valuable experiences shared by a colleague at work.

After doing a quick youtube course in Google SketchUp, my base design for the table is shown below. For high rigidity, I've gone with 4 linear rails (25mm) on the Y-Axis and will use dual 20mm rails for X-Axis. The Z-Axis is on order from K2CNC as I want to save me some time on the build.

The rails & screws arrived today from China and I have to say that the experience was very good with Chai from linearmotionbearings2008 (ebay) delivering on his promise to pack the items well. When negotiating on the shipping, remind him to pay attention to the padding on the ends as they get a beating on their way over.

So my journey begins...

[cnc3678]

Back again. I'm refining the table design as I'm going along and trying to determine how I can make the table sides and top true after the frame is welded. I'm assuming that the heat will distort the strcuture and I'm not confident that I can mount and align the rails accurately using shims.

I was curious if anyone in Melbourne has dealt with engineering companies that will be able to mill the welded plate rail surfaces?

I'd be grateful if anyone can pass on their recomendations.

Cheers,

Richard

[kiwichris]

Hi-ho...

Can't help with an firm in Melbourne, being from NZ...

But I'd have thought you'd spend a small fortune if you wanted a company to make a jig to hold your table and mill it. Not exactly the easiest thing to put under a machine, and it's going to have to be a large machining center, or a very complex jig setup for a surface grinder of some type?

The only machine I've seen in use of that size here in NZ was costing $450 per machine hour...

As a total aside, your dual rail design is interesting... Is that not just inviting alignment problems between the four rails you have for one axis?

Cheers, Chris H.

[eric5501]

G'day Richard, I may be preaching to the converted here but I was taught that to prevent warping put a space inbetween the two pieces you are welding eg. the unfluxed end of a 2mm welding rod, a coin or whatever depending on the thickness of the metal you are welding. Place tack welds all around then fill in welds. As you are welding square tube there shouldn't be any warp.
I live on the north side of Brisbane, good luck with your cnc.
Regards Eric

[cnc3678]

G'day Chris and Eric,

thanks for your posts and I agree that the dual rails does pose a great challenge with accurate alignment. I'm hoping that my trusty Mitutoyo dial guage will help me solve this issue.

However ensuring that the bed is flat and the sides perfectly parallel is my biggest problem and I guessed that I would be up for >$500 for a machine shop to do this. So I need to think about this one....

Thanks for your support - this is one of the most interesting projects I've ever undertaken and is a nice distraction from the stresses of my day job.

Cheers,

Richard

[ELM3060]

G'day cnc3678
I am also new to the CNC forums and have only recently bought both a Hafco HM-50 mill with rotary vice, arbors etc and Hafco AL-960 digital lathe at auction $5000 for both. I was planning to build a similar router to yourself but then decided the mill would be a better option for me and will try and learn some basic milling before modifying it to cnc.

I am no engineer, so what I say could be very wrong but in my opinion;

Rather then the two 20mm linear rails welded to the frame as your sketchup shows, I would have thought you would get far more strength and accuracy out of the two rails riveted to one 70 or 100 mm rail.

The large depth of a single rail will give you far more strength and limit the flex. By accurate clamping and industrial sized rivets used every 50mm, there will be no material tensions from welding.
Also your frame shows no angle bracing to help stop side motion or twist, a deep single rail will give greater bracing than two thinner rails, though I believe your frame should still also have angle bracing.

Good luck with it.
Cheers Ed

[cnc3678]

Hi Ed,

thanks for your feedback. The linear rails I've purchased sit on aluminium supports and I had intended to bolt them through the box section and secure with nylock nuts. I'm also leaving a gap between the rails to that I can connect the y-axis screw nut to a aluminium cross-member between the gantry supports (not shown in the design yet). However I agree that I need to brace the frame more and will incorporate this into the final design.

I'm going to visit a couple of engineering places this week to see what I'm up for. I suspect that I'm in for a shock.....

Cheers,

Richard

[kiwichris]

Just thinking about this...

You're up for a lot of pain if you crash your router and it knocks one of the sides out of alignment as well... Twice the pain of realigning a normal router setup even.

[cnc3678]

A design update.

After a fruitless exercise trying to find an engineering place with a large enough mill, I gave up and decided to re-design the position of the y-axis rails. I'm now placing them top and bottom of two 100mm x 100mm horizontal box sections and will rely on the accuracy of the metal width and shims to get the alignment right. I also completed the design of the gantry and have attached a few 2D views

My 2.2kW chinese spindle and Hitachi VFD have arrived and I've also tested one of my 425Oz steppers with Mach3 and all looks good. So on to buy some metal and get started on the welding.

Regards,

Richard

[cnc3678]

Well I've changed my mind again about the design and included two changes:

1. I was not confident that I could get a rolled box section with accurate and consistent dimensions end-to-end and decided to change the support for the Y rails to 90 x 90 extruded aluminum.

2. After seeing some youtube videos of other cnc routers cutting dovetails and tenons, I've added a side plate so that I can mount timber vertically for this type of work. It meant losing some Y-Axis length, but I think it is worth it.

The redesigns are shown below. I'm now confident that I can move onto purchasing the steel.

[hacker7]

Hey Richard not that it matters now .........well maybe it does cause you will probably build another table. Anyway "glacern.com" here in the states is where I got my rails and bearing"s from at a very good price. Rich

[chris123]

Hiya,

I'm also from Melbourne, I make aluminium parts in my spare time. I plan to build a CNC gantry type mill in the future and will need some help finding suppliers.
I originally bought a small mill and have done a manual to cnc conversion on it
Now I need something larger and I was thinking of going gantry type to mill the aluminium.

I have the electronics part down just need some exposure to the different design of a gantry. So my plan was to purchase a simple kit, see how it performs, if I can improve it and hopefully build something larger and more suitable based on my findings.

I look forward to see how this project goes