Finished at last (well almost!)

[Ali Kat]

Hi Guys,

Its been a long time and the admin have been asking where I've been!!!

Well the truth is that my work has taken me away from the CNC build and things got delayed. But a recent hip replacement operation has given me the chance to complete the build on a table I started 2 years ago.

The table is nothing special and follows a lot of the usual design conventions found amongst other home builders but I'm quite pleased with it for a first attempt and will put a few pics up so that the critics can decide if my time was spent wisely or not!

This first pic gives a general view of the machine. I'll post a few more and you can let me know what you think.

BTW I have hit a snag - whilst the mechanical stuff has been a logical process of design, try and redesign until it works, I am not so hot on the software so I could do with some advice on what to use to get cutting.

Cheers,

Nick

[Ali Kat]

My outline idea for the machine was a smallish, compact design with a good degree of accuracy but without spending an absolute fortune.

I am lucky to have a fairly well equippped workshop with a huge Milwaukee milling machine (non-CNC but DRO equipped), a couple of lathes and a small Step Four Basic 540 desktop craft miller.

To be honest, all I've really done is manufacture parts that hold all the standard fittings together - I've not really made anything of significance.

Next post will give some more details.

Another general pic of the machine and a closer view of the Y and Z drive axis.

[Ali Kat]

The overall dimensions were set out after I bought a piece of T-plate off Ebay. This was 700mm long by 375mm wide so this is what I started with.

First off was to draw the plate up in Cad and start playing with ideas. I'm a fan of the Bosch extrusion range so a quick download of their cad files allowed me to do a virtual build on the computer.

I knew that I wanted to use linear tracks for the X axis and these were again sourced through Ebay. After many, many different designs were tried out I decided that I would fit 45 x 45 extrusions as close to the long edges of the T-plate as possible and run the linear bearings along the inner face of these members.

As I was using 12mm track I had to "relieve" the slot in the Bosch extrusion to get a good fit. The two extrusions were clamped up on the big mill and a brand new 12mm cutter was set up. The two slots were then milled out to a depth of 1.5mm to give a good seat for the tracks.

Here you can see the tracks attached on the underside of the table.

[Ali Kat]

For those of you wondering what the various brown bits are I should explain that I decided to try using Tufnol for a lot of the pieces.

I was not to keen to use MDF or any other sort of wood based material as my carpentery skills are not the finest in the world. I had come across Tufnol before and was impressed by it's strength and ease of machining - it seemed ideal for generating parts with my little Step Four machine.

So far, this material has proved to be a good move - that statement is probably going to be the kiss of death and I'll be told that is warps, melts or generally self destucts after 6 months!!!

Anyway, it was easy to select an appropriate thickness for a particular part then draw up the shape in cad and transfer it via a *.dxf file to the Step Four. I use mainly 1.5mm, 2mm and 3mm solid carbide cutters on the little Step Four and these have worked well with the Tufnol. The finished accuracy has been superb with "bearing fit" tolerances in all cases.

Cheers,

Nick

[Ali Kat]

I'll put some more pics up later if there's any interest but, meanwhile, here's a pic of the plate that I made for the end of the machine. The idea was to tidy up the open end, provide a place to mount the stepper connectors and to play with the Cad / Step four capabilities of following intricate outlines.

I think it worked fairly well. I used 2mm epoxy glass plate for this item which was machined very quickly in a single pass and fitted very well to the end of the table. I haven't got around to learning how to cut alpha-numerical shapes yet so the "X", "Y" and "Z" were simply lines drawn with cad. The connectors are standard 4 pin DIN sockets from Maplins.

Cheers,

Nick

[Jason Marsha]

That's a cool looking machine. I always like to look at the machines that have fine finishes unlike the just in time ones that I build.

Software:

Mach3 to drive the machine http://www.machsupport.com/
Vectric VCarve 5. http://www.vectric.com


Jason

[Ali Kat]

Well thanks for the compliment, Jason. As with everything, there are still some flaws with the design but I'm still pretty pleased with it.

I'll give the vetric site a go and see what it can do. I'm already running Mach 3 on the computer that controls this table but I find it quite confusing and not as easy to use as the software that comes with the Step Four machine.

Cheers,

Nick

[Ali Kat]

Here's another pic of part of the machine - this time it's the Y axis drive motor.
I like the idea of Huco type couplings but this would have had two bad side effects: firstly the motors would be sticking out the side of the table making them vunerable and unsightly and secondly, it would have meant more difficult machining in my chosen materials. Therefore the design was developed using timimg belts with parallel motor / ballscrew arrangement.
In the pic you can, hopefully, see the rotating plate that holds the Y stepper motor which gives a fair degree of movement for tensioning the Y drive timing belt.
I have used a similar set up on the X drive motor / spindle but using a parallel sliding plate rather than a rotating plate as on the Y drive. The X-drive utilises a standard Huco coupling as this was the most effective way of doing this.

Just for the teccies! the pivot point of the Y drive is a socket head screw with shoulder (damned expensive!) whilst the top screw is a standard socket head with a washer.

[Ali Kat]

Thought I'd post another pic of the Z axis.

This shows the use of Tufnol components that were cut out on the Step Four cutter and assembled with fairly standard bearings etc.

The Z axis side plates hold flanged 12mm linear bearings that run on 12mm hardened steel shafts giving the Y motion. Motion is controlled by a 12mm ballscrew - the nut is out of sight in this pic on the other side of the Z assembly.

The Z axis motion runs on two vertical 8mm hardened shafts with an 8mm ballscrew driven through a timing belt. Tension on the timing belt is achieved by sliding the Z motor plate back and forth.

For this machine I decided to incorporate the tool holder with the bearing supports and ball nut retention to simplify the parts. The plates have been cut with a 20mm hole for fitting a Proxxon long neck grinder spindle with clamping as per the usual method of cross drilling and threading the slotted end of the holder. This is the only area where Tufnol has to be treated carefully as it is a laminate material and drilling and threading can split it easily if you get a bit ham fisted with it.

If anyone was interested, I have all the drawings for the parts in cad (dxf) format.

Cheers

Nick

[yngndrw]

It looks very nice, good job.

[jhop2]

Very nice. I'm not familiar with the gantry material. It looks sturdy. The main problem I hear with non-metal gantries is some people complain about flexing. You will be able to see it in the carving if that is an issue, but a simple brace can fix it. Mach3 does have a learning curve, but the vidoes on the website are excellent and I use Mach3 without issue. The cam software does most of the work you just import it into Mach3 and run it. Vectric is the cam software I use. It is easy to learn and the tool paths it generates are amazing. I started with cut 2D then upgraded to VCarve Pro. If you can afford it VCarve Pro is well worth the money. I hear Aspire is fantastic also, but way out of my price range.
As far as time well spent, your result speaks for itself. I remember the first time I cut something on my machine....I was so happy, I felt like a kid, except for the part of having a well deserved cold one.
Nice work.

Jim

[stevespo]

Great looking machine! Well designed and meticulously constructed. Maybe we'll get a chance to see it in action?

If the Tufnol is similar to the phenolic plate I've used for jigs/fixtures (Garolite, Micarta), it should be very stiff and durable. This is a fabric or paper base and epoxy resin holding it together.

Steve