Chris
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Hi jonjon, there is a Yahoo group for HobbyCNC customers that may host some of the specific info you’re looking for.
The RPM/speed of your system depends on lots of factors in addition to the motors themselves. There are some links to in-depth info below, but a couple of important things to consider are how much weight is being moved, and how quickly your controller computer can signal to the motors. Either of these (and other) factors could limit RPM even if the motor is technically capable of a certain spec.
basic principles of stepping motors
How fast can a stepper motor spin?
V2.0 uses metric hardware, and the thickness of the sheet stock doesn’t affect the design (so you could use 12mm plywood).
Hi Leon, the DXF files have no default units (units are decided in the software with which you open the DXF). I’d recommend double-checking that you’re asking your software to interpret the units as inches.
Out of curiosity, is there a reason you’re building version 1.0.1?
My guess is that your current transformer might not be able to supply enough current (even though the voltage is correct). The HobbyCNC specs call for a 10A power supply, which is what we’ve had good results using on the DIYLILCNC (though other setups might need more or less current).
If you have access to a benchtop power supply , you can dial in the amount of voltage and current you need. Otherwise you could get the transformer, capacitor, and other parts needed to build out the HobbyCNC power supply before completing your tests.
mortegah, what are you using for a power supply? Specifically, what are the specs for voltage and current? This could be causing problems, also it could be an improperly soldered connection (all it takes is one!)
@CRODGERS, sounds like you’ve got a pretty good handle on the range of options. Very broadly, the choices will depend on budget and whether you want a high-precision machine or one that can churn out lots of parts (or both). Here’s a napkin-drawing version of how these options look:
CHEAP
MIDRANGE
PRICEY
belts chains acme rod ball screw rod
bushings skate bearings precision bearings
angle rail linear bearing rail precision rail
OK PRECISION
MIDRANGE
HI-PRECISION
For the specific project you mention, the difference between belts/chains/threaded rod will probably not be important – your requirement is quantities of oddly-shaped parts with relatively loose tolerances (assuming you don’t need your xmas trees accurate to .001″).
You are right that core parts of the system (motors & electronics) are re-usable in different mechanical setups. With our design, the motors/controller are the biggest expense, so once you have that you would have ability to play with different bearings, etc.
The difference between <100 oz/in stepper motors versus 425oz/in is pretty big. Probably something around 150-200 is more than enough, though is also depends on if/how gearing is set up.
@CRODGERS – yes you could pretty easily cut shapes like this with a CNC.
Roto-zip blades would work, you can also get carbide end mills from places like McMaster-Carr or Onsrud that are specifically for this type of cutting.
You would use a spoiler board underneath to protect the base. Our design makes it pretty easy to replace the base even if you totally trashed it. You’d also need to secure the piece you’re cutting out to keep the xmas tree or other shape from moving after it is cut –either with double-sided tape or a few tabs connected to the rest of the stock would work.
You could certainly get more consistent results with a CNC, but depending on your volume it might not end up saving you work (although cutting on a CNC is definitely cooler than a scroll saw, imo). Another option would be to make one template for each shape and cut them with a trim router, using the template as a guide. This would improve consistency too.
Michael, I have seen this before when using a board other than the HobbyCNC. I think what’s happening is that there’s not enough torque to get the motor & all that’s attached turning.
Make sure that everything is tight mechanically (bearings, belts not too loose/tight, etc) and also double check that your voltage regulation is set correctly on the HobbyCNC board (too little and you won’t get enough torque). You can see how to do this with a multimeter in their documentation.
You could also try lowering the acceleration, though 2i/s seems pretty conservative already.
@Caesarae, pardon my ignorance, but what is a CNC key machine? Is it a machine for duplicating keys that you’d use in a lock? An example would be helpful in knowing what the machine’s requirements are.
keraynopoylos, there is a 3D Rhino file in the shared CAD doc’s:https://docs.google.com/folder/d/0Bx7IYFr3lQoAZXJKemJtZmczLWc/edit… they’re a little buried in the instructions page, we’ll try to make the location more obvious.
I think the YouTube comment a little misleading about end mills having rpm limits — it’s a little more complicated than that.
The poster gets it right, though, acknowledging that the right bit makes all the
difference. There are a huge variety of bits available that are specially shaped to do different things. As far as rpm, it’s not that there’s really a limit, it’s more that you need the right bit rotating and traveling at the right sped for your material. This can be somewhat subjective/variable depending on your machine and how it’s set up — for example sometimes you’ll want a very particular finish to the thing you’re cutting, while other times it won’t matter.
A great way to get a ballpark for spindle RPM and feed speeds is to use a chip load calculation, which you can get from the manufacturer. Here are a some examples (1, 2) with great explanations for how to do the calculation.
I like to get bits from McMaster or Onsrud. they both have huge catalogs with great descriptions of different bits.
@gera229, the case in the picture is a slightly earlier version of what’s in the plans for V1.0.2.
You can send files to share as attachments to info at diylilcnc dot org. Thanks!
@gera229, the case in the picture is a slightly earlier version of what’s in the plans for V1.0.2.
You can send files to share as attachments to info at diylilcnc dot org. Thanks!
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