Since 2000
Millwood HISTORY
My first model of CNC milling machine, I decided to publish his photos after several requests from model aircraft friends eager to see what it was like and what its characteristics were.
Its name is MillWood2000, a name that says it all, that is a numerically controlled cutter, created mainly for cutting balsa (but also plywood, PVC, nylon ...) and finished / tested in 2000.
The dimensions and the useful working area can be seen directly from the image.
This cutter has been in operation for several years now and has cut practically everything.
After cutting the ribs and trims of my new model aircraft, he made shapes for children's toys, designed and engraved a variety of badges and badges.
He even made scale models of houses for a technical design studio
As you have seen from the photo, MillWood2000 uses the Dremel mod 395 as a cutting cutter, I decided this because it is of excellent quality and reliability, moreover it has a variable rotation speed from 10,000 up to 33,000 rpm.
What immediately catches the eye is certainly its wooden structure
My aim was to create something simple, functional and economical, using easily workable materials available in specialized shops at a reasonable price.
In the end, the final result went beyond my expectations, the functionality and accuracy obtained are excellent, making ribs and frames of my new model aircraft had become fun.
Another reason that prompted me to create the cutter was to understand its operation in detail, starting from the operation of the step motors (step motor) to the electronics that control them, from the programming code (G-code) to the various control and programming programs of the cutter.
But returning to the wooden structure, if we look closely at the key points, I used as a sliding system some ground steel bars that slide on self-lubricating sliding bearings of DU, to stiffen the support surface I used 20x80 aluminum profile, while, on the threaded movement bar, I inserted thrust ball bearings.
To have a perfect sliding of the parts that make up the three axes (XY and Z), I had to make the sliding and fixing holes of the guide rods, using a mechanical cutter, otherwise if I had used my drill press, I would not have surely made these holes with centesimal precision.
It is very important that the three axes slide freely without excessive friction and without “pointing” throughout their stroke; it must be borne in mind that stepper motors are not monsters of power, at least those that are normally used on such hobby cutters.
On the MillWood2000 you see in the various images, I have also inserted the limit switches, but honestly I don't think they are totally necessary.
For maintenance it is sufficient to "dust" the guide bars by vacuuming the dust that forms.
Nothing needs to be oiled as the guide bushings are self-lubricating.
As a Dremel stand I use the same one that comes with the Dremel Stand Base Kit, it has the disadvantage that you have to spend a lot for this complete stand, but it is well done, and lends itself well as a fastening system.
Structure
Electronics
Making the electronic part was the most laborious thing.
I didn't want to buy anything ready since I like to understand how it is composed and how it works; also the prices that I found on the web were quite high.
The design of the motor control boards and the interface between these boards and the computer via parallel port, I got it from Hans Wedemeyer.
The main problem was making the double-sided printed circuits with the photoengraving system, I will have redone them about four times but in the end I did it.
With these cards, based on the pair of integrated L297 and L298, it is possible to control stepper motors up to 30V and 2Amp.
The absorbed current is adjustable by means of a trimmer. On the motherboard, that is that connects to the parallel port of the PC, you can have various options, such as exclusion of the control of an axis or activation / deactivation of the limit switches. As for the stepper motors, I found them from Conrad in France, they are size "23" (57X57mm), bipolar with 200 steps / rev or 1.8 ° per step. For the X axis I used a "17", smaller but does not give problems. As power supply for the motors I use a 12V transformer and about 6Amp, stabilized with a rectifier bridge and electrolytic capacitor of about 10,000 mF: it is more than enough for the purpose. To power the electronic part of the cards, on the other hand, I use a small separate power supply, such as those integrated with the plug to power small radio devices, always inserted inside the container. All the electronic part, including the power supply, is enclosed inside a metal container with a cooling fan inside.
MillWood2004
This is the 2004 model, it had dimensions and performances superior to the first one.
All the details have been made by means of an NC pantograph to obtain an excellent precision and coaxiality of the holes.
The support of the cutter (Z axis), has been made of aluminum for greater rigidity.
The useful working area is 420X297 with Z = 35 mm, practically like an A3 size sheet
As you can see I went from design to implementation, in these cases the use of a 3D CAD helps the design a lot.
For the two axes Y and Z, I used 12 mm beech plywood, very hard and rigid, while for the work surface and therefore the X axis, I used 22 mm birch plywood, solid and functional.
The countertop has one 22 mm thick which is great for giving strength.
I could have used chipboard instead of plywood (saving a lot), but I preferred not to have problems with the curvature of the top, also given the numerous holes, plywood behaves much better.
The four holes you see online are used to fix the worktop with screws.
The worktop is the only piece that is only screwed on and not glued.
In this way, if the worktop is damaged (an accidental milling can always happen), or if you also want to have a top with holes or guides for fixing the pieces to be cut, thanks to these screws you can easily replace it: you like the 'idea?.
In the image you can note the aluminum plate that will have to carry the support for the cutter (Dremel or other).
The flatness with respect to the plane during the complete displacement on the X and Y axes remains within 0.15 mm.
MillWood2008
As line and conception it mirrors the 2004 wooden model, but the structure is now completely in aluminum, all the pieces are made on a numerically controlled machining center, the precision of each single piece is centesimal.
The pieces are joined by screws, resulting in a rigid and precise structure.
From this model I introduce the worktop in grooved aluminum profile.
With this new worktable, the locking of the workpieces is easy.
The guide system is on case-hardened / ground steel bars, on which special low friction and self-lubricating sliding bearings run.
The diameter of these bars is 18 mm for the X and Y axes, and 10 mm for the Z axis.
Trapezoid bars with a diameter of 14 mm and a pitch of 4 mm are used to move the axes, on which I work a nut made of self-lubricating plastic.
The stepper motors are bipolar of 2 Amp / phase, they are directly connected on the displacement bar, the connection is made by means of a special elastic joint.
The maximum axis movement speed of MillWood2008 can be set from 1,500 to 2,000 mm / min without loss of pitch.
MillWoodEVO
This is the penultimate evolution of the Millwood series, the main novelty concerns the guide system, it is based on recirculating ball bearings (4 for each axis), and the diameter of the guide bars which is now 20 mm for all three. the axes.
All the pieces of the structure are machined from solid and by milling on a CNC center, the size of some parts has been increased for greater rigidity.
