View Full Version : Thinking out loud

22-03-2016, 05:18 PM
Hello people,

I have an CNC router table, far from perfect, that I've been building for the past ten months now. It's nearly finished, and I should make the first few cuts in a few days.

The machine has a 2300x1800mm footprint, and has a working area of about 1500x1000x15mm. It is made of 24mm thick MDF, weighs about 300kg. The router is a 2.2kW water-cooled spindle with VFD. I've got a nice control box, works like a charm with 4xAM882 drivers, 4x4.2A Nema23 425oz.in motors, 70VDC linear PSU, and all the main safety things required. I've got SBR20UU on all axes, and Z has an SFU1605 300mm long, Y an SFU1610 1300mm long, and X has two SFU2010 2000mm long.

Problem ?

When I designed it, I just went too big, and too weak for the size (not stiff enough). I can barely work in that room anymore, it was a huge mistake that I made.
(note that this is an outdated photo, braces are to be added to the gantry, obviously)

So ?

Well, I'm re-considering things. I would like to discuss here your thoughts on building a smaller machine, much, much smaller, or even buying a good kit, that can fit my electronics and spindle. Building it myself is cheaper, that, I know, but considering the time it took me to design and build this one, I'm not too sure I'm up to the task. However, I could use this machine to machine some parts for the new build, that would definitely save me a LOT of time.

I've seen some builds here on the forum. Boyan has some nice ones, made of steel 10x10x3mm steel tubes. I've seen Graeme's machine, it's beautiful. I know most, if not all of you always do epoxy levelled machines. Again, I'm not too sure I'm up tot he task.

To be honest, even a ShapeOko would be great, but I can't fit a 2.2kW spindle on it, and my motors and PSU will be overkill for it.

So, what do you guys think ?

All the best, and still alive !

22-03-2016, 07:41 PM
Well I'd say stay away from Kits like Shapako they are far too weak IMO and not very well designed. I've not seen any Kit that's worth a damn.!!

Equaly you don't need to go OTT like Boyan with 100mm tubes for simple router.

So really the thing you need to ask your self is what do you mainly intend to do with the machine.?

Budget is also key because the honest truth is that you get what you pay for and to have decent machine that will be hassle free and cut correctly with good finish cannot be done on the cheap.

22-03-2016, 08:38 PM
I intend to work with plastic / acrylic / plywood (60%), hard woods (25%), and aluminium machining (15%). I would say I need a work area of 800mmx800mmx150mm.

As far as budget goes, I've got all the electronics ready, and spindle as well. I can finance part of the build by selling some of the part I've got already (rails, ballscrews), since I'd replace them by HWIN rails and shorter ballscrews.

Boyan Silyavski
23-03-2016, 04:43 AM
Why dont you make 900x600 machine where the gantry is on the long side? such way machine stays reasonably small and could take bigger jobs. Or even better-same but 1200x900, so it could take directly big sheets width.

23-03-2016, 07:47 AM
Didn't realise until seen boyan's post that the machine is inside house in small room. The answer to this problem is simple.?? Go

Vertical machine saves massive amount of space and still allows large cutting area. Also because of gravity most the chips fall away to bottom so it's much easier to keep clean. Very easy to build a enclosure around it, Esp if on end wall with two walls either side. Basicly think Wardrobe.?
In tight space trapped between two walls it's easier to load and access material because have full access to cutting area.

There are NO disadvantages to vertical machine only positives and some like longer tool life and better finish are very welcome. Also great if like me you suffer from back pain because no more bent over large machine.!!

23-03-2016, 10:20 AM
There are NO disadvantages to vertical machine .!!

Do you use/need a brake or c/balance on the Y carriage

23-03-2016, 11:44 AM
Do you use/need a brake or c/balance on the Y carriage

Depends on which way gantry is positioned and in both cases while motors are powered up then No provided motors are sized correctly.

(I'll call the actual Gantry Y axis and the moving carriage across it X axis.)
If the Y axis moves L to R then the motor Detent and resistance from screw is often enough to hold the X axis while motors not powered.

If the Y axis travels Up/Down then yes you'll need either counter balance or like I used to do on my old machine is always park it upto a bump stop when finished cutting and powering down motors. While cutting or when motors are energised then no it's normaly not needed.

My current machine uses a counter balance but this mostly because I inerited the machine and the motors are under powered for the weight of the gantry which is quite heavy when positioned verticly. So I needed to balance the weight to help the motors while cutting. On my last machine that did have correct sized motors this wasn't needed while cutting.
Even thou I don't need to I still tend to park the Gantry against hard stop when being left for long period to remove pressure from the screws and couplings etc.