Hi All

I am working on a new CNC Mill that I intend to publish… In MEW if it fits the magazines publishing criteria or in any event here on the forum.

The frame of the machine will be fairly simple to build…. made from Laser cut steel plate sections bolted not welded together, this eliminates a lot of the distortion introduced into a structure by welding.

While not essential it will be designed to be filled with an epoxy aggregate for extra vibration damping and stiffening as used by the major machine builders these days. It is intended to test the prototype with and without it and compare the difference.

The cad files for the frame will be made available to individuals free of charge. not commercial resellers.

I am encouraged to build it after the success of the small CNC router I posted on the Mach3 thread on this forum. you can see a short video and a few pictures here….

http://www.model-engineer.co.uk/forums/postings.asp?th=74182

As before Mach 3 and smooth stepper for software and interfacing.

Having spent many of days on AutoCad making a number of different 3D solid model concept designs I think I have a viable plan!

Now a few questions that need answering:

I would appreciate any constructive comments.

What size should the work area be, (the area that can be reached by the cutter). Length width and height I will add 100 mm to the height for the tool itself.

Tentatively for travels I have used 512L x 312W (12mm is for a 12mm cutter to cut the sides a rectangle 500 x 300)

For height 200+100 for the tool itself under the spindle.

There is enough room for a 4th axis on the table

The overall size is a consideration.

Currently the bench area needed is about 1000 x 600 allowing for table travels.

The table will be drilled and tapped M10 at 40mm centres. Alternatively builders wit a larger manual mill can make a T slotted table. Ideally to be sent out and surface ground.

Spindle?

Should a difficult to make but useful int 30 or 40 ball bearing spindle be used? or something a lot simpler using a Chinese ER Collet holder. it is assumed the builder has a lathe of adequate size.

What sort of drive should be used? These days a VFD and a 2800 rpm induction motor is Ideal.

direct drive 1425 RPM Motor Maybe for 500rpm to 2500 rpm? Maybe a step up and down pulley giving a wider speed range Say 1.5 to 2 KW

Or maybe a Chinese water cooled high speed spindle? (not very useful for steel but good with non ferrous metals, and wood)

The machine is driven by Rolled ball screws on all axis. Hopefully with backlash eliminating nuts. 

Cost: Not cheap, substantially less than many extruded aluminium machines I have seen on the net. It will depend on how well you source the components. The good news being that the competition is fierce these days… linear bearings, ball screws, step motors and drives are all getting cheaper.

And then there is the pleasure of building a machine from the ground up…Yes it will require a lot of time, precision fitting and measurement to align and set it up.

I would really appreciate feedback

Thank you

Cheers

John

Edited By John McNamara on 24/02/2013 11:59:27

Hi John

I am aiming for a steel cutting milling machine not a router. The frame is heavily ribbed internally, It may have to be filled with epoxy concrete. or other to damp vibration. It should be stiff enough. It will use the jointing system I used on the router posted. It will not be like the Ally tube jobs you see on ebay.

And yes smaller is better to keep the material cost down, Hence my questions: How big is big enough for most of the recreational work we do?

Cheers

John

Edited By John McNamara on 24/02/2013 13:23:32

Edited By John McNamara on 24/02/2013 13:30:21

Hi John.

Nup! Keep thinking on it?

Cheers

J

Hi David

You are on the right track!

The question is what working area would be the Ideal size?

Cheers

John

Gee Its 2am this side of the pond

have to see you tomorrow.

Cheers

John

Hi Roger

A vexing question? As the Z axis travels down it moving down and away from its support creating an overhang in the vertical plane. It is easy to add height as long as stiffness is not compromised. I will work on it. (Remember this is not a knee type mill the spindle assembly moves up and down)

What is the height of the typical work piece we work on? And what is the maximum height of all but 1% of the work we have actually worked on. in other words the 99 percentile.

I am trying to keep the size of the machine, and the cost down.

Maybe in the end it will have to be in two size versions to fit the needs of various builders.

For want of better words a micro and a maxi.

Cheers

J