View Full Version : Feedback on 1.0 design

15-08-2014, 02:39 AM
Worked this up in Sketchup so as to get a visual on an idea thats been in my head a while.

The main purpose will be decorative hardwood, plastics, mdf, and functional aluminum piece work. Really no cutters over 7mm and mainly in the 3mm and smaller range. I have a few years experience as a machinist and I'd like to think this layout looks good for what I intend to throw at it.

I do not however know all the maths that you folks do as far as spec'ing for rigidity et al.

The base will be an epoxy granite attempt (a project in and of itself); rails @ SBR16 & C7 screws @ RM1605 from Chai on eBay; typical 2hp 80mm cartridge spindle with ER11 collet; 25mm cold steel carriage plates; 12mm mounting plate for the X & Y axis motion hardware cast into the frame.

Working with Travels of X 300mm, Y 400mm, Z 140mm (180mm spindle nose to table)

I intend to final level the Y axis bed with epoxy then send the frame out to a shop to finish the X axis rail plate - square it up to the Y axis bed then drill & tap for the rails & bearing blocks. If I can find a (reasonably priced) place that is able to, I'd like to have them finish the Y axis bed as well. At that point, slap the hardware together & shim til I can get the cumulative error under 0.15mm (0.005").

I will also mention that the reason for so much throat on the Z axis is for when I throw soft metals in there. This should leave me room for work holding and allow me to raise the piece up as close to the gantry as I can to get all the rigidity I can out of the job. Any work requiring the full Z travel will be wood, acrylic, nylon, or MDF at this time.

All that being said, please let me know what you think.
Also I'd greatly appreciate any feedback or sources for the formulas that I should be using to best estimate the machine tool design.






15-08-2014, 03:09 AM
Get rid of the round supported rails, and go with profile rails. They're far more rigid. I've seen lightweight machines built from wood where the round rails were the weakest part of the machine.

15-08-2014, 06:58 PM
Round rails and epoxy granite = Ferrari with yantangfooi tyres

Looks nice ;-)

15-08-2014, 08:27 PM
If he EG turns out to be a waste of time then Ill save all the hardware and slap together a square tubing rig like everyone else. ;)

15-08-2014, 09:07 PM
Erm the epoxy = Ferrari

It's the round rails that are , erm , ok'ish , as mentioned save that little bit more and get some proper rails to go with the epoxy

15-08-2014, 09:15 PM
You still won't want round rails. They're just not suitable for a high quality machine, imo.

Lee Roberts
15-08-2014, 10:57 PM
Round rail will be fine for wood and light work, though like G suggests if you want depth of cut, faster machine speeds and a decent finish in metals then spend more going for linear guideway...as you know.

Would love to watch the build log for this if you do go down the poxy road.


16-08-2014, 04:06 AM
Interesting, and thanks for the feedback. Much appreciated.

So, is the supported round rail really that loose? I'd like to say that I'm okay with babying the MRR, but I know that will grow old sooner rather then later so I am certainly looking into profile rail.

I basically scaled down the design idea from a Mazak that I run pretty often, and love. However after a few hours of looking more into this I'm beginning to wonder the following scenario:

Build a "cheap" heavy duty router in the style listed above (with round rail) for the decorative work that doesn't require anything tighter then 0.3 - 0.4 mm or so. This will allow me to expand the X & Y and reduce the Z and worry a bit less about rigidity...
Build a stout metal mill. Classic vertical mill, stout "L" shaped base with minimal throat and reasonable X & Z travels. Most of the metal workpieces in mind require no more then a 100 x 100 x 100 (mm) cutting envelope. This, with some more thoughtful table design will allow me to "justify" the profile rail expense, as most other components will be the same or less actually. I'll basically save this for the aluminum, brass, and the super rare carbon steel parts.

Granted it is at least a good excuse to have two machine tool projects. The wife will understand I'm sure :friendly_wink:

Robin Hewitt
16-08-2014, 09:01 AM
You are nearly there but you are misunderstanding the fixed gantry advantage. The supported rail mounts to the table and the bearing blocks go close under the tool tip. Turn the rails over and get the support where the cutting happens, where you need it, lose the overhang.

16-08-2014, 10:41 AM
nice design njcook.
like others said profile rails the way to go.
and if you haven't already,make provisions for splash guards/coolant return during the build keeping the screw and rail free of it.