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Advice

Stepper motors

We often wonder what power / size / amperage the stepper motors should have to use.
For a cutter it is always better to use bipolar motors which are more powerful, at the same size, than the unipolar ones, obviously the electronic board must be for bipolar operation.
Cards for unipolar motors are now very rare.
What I call power is the torque it is able to exert during rotation.
When choosing the bipolar stepper motor, take a 4-wire or 8-wire one, the 6-wire ones used as bipolar with the exclusion of the central wire, normally do not have much power.
If the sliding on the three axes is free and without friction, little power is needed to perform the movements; the additional cutting effort, if we cut balsa or plywood, is not excessive and therefore not much power is needed on the motors.


If the sliding of the three axes has too much friction or if the guides are twisted causing a bad sliding, do not compensate for this anomaly by using more powerful motors, but solve the problem with the guides; sometimes it can also be the threaded rod crooked or a coupling with the threaded nut that is too precise, dirty or misaligned.

 

Stepper motors, during their operation, can heat up to 50-60 °, this is normal. However, avoid leaving the cutter at rest and powered for a long time. Some software and control cards allow you to set a time after which, if there are no operating commands, they disable the power supply to the motors, or remove this power supply in reset or pause mode.
 

Components for DIY
If the motors lose steps, this could also be due to the control software.
I do not recommend starting with the idea of immediately making a super-precise metal cutting cutter, equipped with linear guides with recycled spheres and aluminum worktops, high-speed cutter with tool change.
To do this you must be well equipped with machine tools, preparation and adequate technical knowledge and last but not least, a few thousand euros.
Forget this type of cutter if you only have a column drill and perhaps a bench lathe.
Start with something simple but achievable.
I made my first model of MillWood2000 with few and "poor" elements, found by looking around.
With this first model, however, I gained experience and I understood where I could improve and at what cost.
When you see on the internet a cutter made using drawer guides as a movement system, it does not mean that this is the best or worst construction system, but maybe the person who made it had such guides available or maybe they saw them in a shopping center. and immediately got the idea.
If you see that someone uses car shock absorber rods found in some junkyard, it does not mean that you have to use that idea too, cutting and machining these rods is not within everyone's reach.
Look around and calmly look for a solution that suits you and the equipment you have available, set your wits in motion and if you make a mistake you have always learned something.
On YouTube there are many examples of how to make a simple CNC machine, I have seen that some use old CD players to make mini CNCs: fantastic

Some time ago I saw on the internet a cutter that used plumbers pipes and fittings as guides, coupled to wheels arranged at 120 degrees; the idea was brilliant and admirable, probably who created it was a plumber, but he showed ingenuity and good will.
Everyone is capable of doing beautiful jobs with professional equipment and components, but with water pipes?

3D processing

Would you like / do you want to do some 3D machining? Well, this is possible with any 3-axis milling machine such as MillWood, to do these processes we must however have a CAM program capable of realizing them, if it is simple bas-reliefs from photos or the like, there are CAMs such as ArtCamPro or MeshCam able to do it directly, to do more complex machining it is better to start from a model made with a 3D CAD.
If you are at the first processing tests, I suggest you start with simple 2D machining, then slowly, you venture into 3D.

 

Movements of the axes
While moving the axes, the cutter is noisy.
This is normal, considering that the motors, as their name implies, rotate in steps, therefore with a rotation that is not fluid but jerky, this generates a sort of vibration that is transmitted through the threaded bar to the whole structure, generating noise. .
The noise changes sound by changing the speed of rotation of the motors.
Always rest the cutter (including MillWood) on a straight surface, all four of the cutter feet must rest, otherwise, in the long run, the worktop can deform with obvious consequences.
Do not put various objects on the work surface (screwdrivers, cutters, hammers, ...), sooner or later they will damage you, also avoid objects under the cutter, I tell you this from experience.
Do not put too much oil or grease on the guides or on the threaded rods (at least not on the MillWood), these, in contact with the dust created during cutting, would form a harmful clump.

I usually remove the dust (sawdust or shavings), using a vacuum cleaner, then spray silicone oil on a rag and pass it on the guide bars.
For the threaded rods, after having cleaned them well, I "brush" them with grease using a brush to which I cut the bristles short, the trapezoid bar must be "painted" with grease, not "filled"
It may happen that when you cut a rib it is necessary to hold the balsa board with your fingers, especially when you are at the end of the profile to be cut.
With your fingers close to the cutter that cuts, do not look at the monitor or the neighbor who is hanging out the laundry, pay attention to the cutter that works, it is not nice to get your nails done with this.

 

Precise cuts 
When you cut balsa or plywood, it can happen that smoke comes out from the cutter that cuts, this is due to the friction of the cutter with the material to be cut and it is a real burn, the cut profile will in fact be blackened, and it is a symptom of bad cutting.
The causes of this drawback may be due to the cutter that cuts badly because it is not very sharp or kneaded, to the high rotation speed of the same or to a low cutting speed.
I advise you to check and test in the order I have shown you, and to perform these tests on a sample of the same material to be cut; then make a table showing the type and diameter of the cutter, its rotation speed, the type and thickness of material to be cut and the cutting speed, always update this table and keep it at hand, it will always be useful.

The cut profile of the ribs, especially if of a small thickness and of soft balsa, is slightly rough and "hairy": this is normal, you cannot expect the absolute perfection of the cut as if it were brushed with 400 grit sandpaper, but remember the precision you have obtained, moreover, a slightly rough and dust-free surface makes gluing or coating with various heat-shrinkable products more effective.

However, to reduce this effect (I do not want to define it as a defect), use the following trick: on the work surface place a crepe cardboard like that of take-away pizzas, on top put three tablets to be cut (this depends on the thickness of the same and the length of the cutter edges), then cut the sandwich.
With this system, with a single cut, you make three pieces, of which those in the middle of the sandwich will have a better cut profile.



For the moment I think it is enough, otherwise I take away the satisfaction of finding solutions and improvements that are the best thing about using these CNC milling machines (including MillWood).

I hope these "written ideas and thoughts" are useful to you

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