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MECHANICS of Millwood

My aim with this site is to help people get closer to the world of numerical control cutters and to give profits (I hope)  information on how to build your own cutter yourself.

For this reason I try to include a lot of information, photos and advice about it.
Sometimes I would be tempted to publish the construction drawings of my cutters too, but I notice that there are people who take advantage of my indications to undertake the production of machines for purely sales purposes, this obviously does not make me very happy.


The structure is made entirely of aluminum, all the pieces are made in  a numerically controlled machining center, the precision of each single piece is centesimal,  the pieces are  barbed  for proper centering and they come  joined by screws, one results  rigid and precise structure.  The structure is anodized for better aesthetics.  The guide system is on  case-hardened / ground steel bars  on which they flow  recirculating ball bearings, of these there are  4 per axis.


The guide bars


The diameter of the guide bars is 20 mm for all three axes.

I do not use prismatic ball bearings (see Hiwin) for simple reasons:

These ball guides / runners, if they are of quality, see Hiwin, Thk, SKF and others, cost a lot, they must then be mounted on a rigid, milled and perfectly flat structure, then they require a chip / dust protection system, otherwise if it compromises its durability and functionality.

The guide / shoes system is usually used on cheap Chinese cutters, needless to say that the quality of these guides / shoes is low to say the least, they are mounted on drawn aluminum profiles, obviously they follow the curvature of this profile.

The round bar system with bearings that I use is simple, spartan, easy to clean, the bending during processing is really negligible and negligible.

The fact of using a system of guides with recirculating ball bearings does not mean that you will also have the possibility of milling steel or simple aluminum.  To typically perform mechanical machining on metal, I recommend you take a manual mechanical cutter and transform it to NC.  With my cutter you can not work steel or iron, except for the processing of small thicknesses of aluminum, brass or similar, if someone offers you a NC cutter and tells you that you can also work steel ... have a sample piece made.

The work plan

The work plan is  made with a grooved profile always in aluminum, with this worktop, the locking of the pieces to be machined is easy thanks to the grooves where the clamping screws enter, however I recommend placing a second 20-mm MDF wood top on this top about mm, and above this place the pieces to be machined, the integrity of the aluminum top is preserved and the pieces are fixed with greater solutions.


Axis movement

To move the axes, use the  bars  trapezoid diameter 14 mm pitch 4 mm, on these  I work a nut made of self-lubricating plastic material.
On the market you will be able to find these trapezoid bars, while the snails are usually found in bronze.
Unfortunately, bronze nuts have a very high play for our applications, they wear more easily and tend to make the trapezoid bar vibrate during rotation.
The nuts that I use I have them made (based on my design), using a numerically controlled lathe, in this way the internal thread is more accurate than a "tapping" type machining and I establish the play that the screw coupling must have /snail.

Absolute novelty of MillWoodXL is that of being able to use also the ball screw system, in fact the structures are provided with seats for both solutions.

You can initially make the cutter work with the normal trapezoidal bars / nuts and if you really feel the need, modify it with the ball recirculating bars.

I added this dual functionality only to do something new and not for a functional or more precise need.


The stepper motors

The stepper motors that I use are bipolar of 2.5 Amp / phase, they are directly connected on the displacement bar, the connection is made by means of an elastic aluminum joint.
The maximum axis movement speed of the MillWoodXL can be set from 1,800 to 2,000 mm / min without loss of pitch.

The position of the Z axis plate that carries the power tool, as well as being pinned, also has the possibility of being set on two different height positions to have ways of having different machining heights.

The attachment for the power tool is for a 43 mm collar, I recommend using the AMB 1050 or even the smaller AMB 800, models like the Metabo are still fine. I remember that the Kress company, for electrospindles, was absorbed by AMB, only the name changes but the products are the same.

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