Best Type of Machine to Build?

[irving2008]

A working area of 600 x 500 will need to be around:

• 800 x 700 as a moving gantry (cutter traverses 600 x 500, need approx 200mm overhangs in both X & Y typically)
• 1400 x 700 fixed X gantry (table moving in X, cutter moving in Y, table 600mm long traverses 1200mm end to end + similar overhangs).
• 1400 x 1200 fixed gantry (cutter stationary, table moving in X & Y, table traverses 1200mm end to end and 1000mm side to side + similar overhangs).

Fixed gantry is more accurate/rigid/responsive if workpiece is relatively lightweight so table & workpiece is lighter weight than router & Y & Z assembly. Arguably easier to construct.

Moving gantry less rigid (and harder to make it so) but takes up less space.

You can (and should) use supported rails for either approach. For fixed gantry the hiwin flat rails make good table runners.

[HiltonSteve]

When I designed my machine I started with the moving table idea but after a few hours on the CAD software decided that it would be easier to make the machine more rigid by using a moving gantry and good quality linear slides, I went for 20mm THK which are fully supported, easy to mount and do a very good job.

Take a look at my build post if you have not already - [ame="http://www.mycncuk.com/forums/showthread.php?t=1058"]My Build - I blame you lot for this....! - MYCNCUK[/ame]

The sizes that you are talking about are very similar to mine, I have a machining area of 800mm x 500mm. The sizes for my machine are in a PDF download on the first post.

My design is quite simple and was easy to put together, I just went a bit over the top with material sizes to get the rigidity and it worked!

[Kevin]

Hi,
I have looked at your build log Steve, a brilliant machine, I will never be able to make something as good as that. Apart from not having the skills to do it I only have a bench drill and limited hand tools to work with.
I was going to use 20mm supported round rail from Zapp for the x and y if I make a fixed gantry machine. still looking at what materials to use, would like to use aluminium but think I will have to start off with 19mm MDF.


Kev

[irving2008]

400mm spacing seems a lot....Mine are 200 taking 200 off the available total travel with the cutter located central... Have you made one yet Irving?

OK my maths was out, should have been 800 x 700, it was 200 on each axis.

My PCB router is 600 x 500 for a 350 x 280 working area. Fixed gantry, table moves in X only. One day I'll get the Z finished and machine the leadscrews (when my lathe is set up right). Just got the driver PCBs from PMINMO.com and assembled most of them last night but waiting on some more bits from Farnell today hopefully.

[Kevin]

Thank you all for your help. Think I will probably start with a smaller fixed gantry type machine - will give me some experience of setting everything up and getting things moving! Then hopefully if I get it working I will be able to use it to make some of the parts I need for the larger machine.

Off to sort out motors and driver boards! hope to start a build log soon - so you can all see what a mess I make of thislol