Messages

7641

General Mach Discussion / Re: Z stepper movement

« on: August 07, 2010, 01:46:57 AM »

Hi Bernie,

I suggest that your 'steps per' are incorrect. Is there any possibility that you are not saving the axis settings after you are making the changes ?

Tweakie.

7642

General Mach Discussion / Re: Unipolar stepper motor with ULN2003?

« on: August 07, 2010, 01:26:40 AM »

Well done Sage for getting it right - I forgot to subtract the motor coil resistance, and I had two goes at it 

(My tutors always said that the degree in Mathematics and Computing was wasted on me - I think they were right  )

Tweakie.

7643

General Mach Discussion / Re: Help with 4th axis

« on: August 06, 2010, 01:09:08 PM »

Just something to think about.......

Angular mode is the most common and also the most useful way in which a rotary axis is used but there are alternatives to this,

When engraving on the surface of a cylinder, for example, it is convenient to have the rotary axis set for (linear) movement in mm but as this will vary, depending on the diameter of the work, there is a trick to getting it just right. One method for finding the ‘Steps Per’ is to calculate how many steps are necessary for the axis to complete one revolution and divide this figure by pi. In my case this is 200 (steps) x 8 (micro steps) x 60 (reduction ratio 60:1) / 3.142 (pi) = 30553.787 steps per to enter in Mach. Now this figure represents a linear movement of 1mm around the circumference of a 1mm diameter cylinder. In order that this can be used for any diameter of cylinder another calculation has to be performed and that is 1 divided by the diameter of the work (1/diameter). The result of this calculation is then entered into the rotary axis scale DRO within Mach. (My version of Mach did not have an A axis scale DRO (like the X,Y &Z axis have) so this had to be added using Screen4 (For reference the A axis scale DRO is OEM Code 62 and it’s associated LED is OEM Code 44).

As an example, to engrave on the surface of an 80mm diameter cylinder it is 1 / 80 = 0.0125 so 0.0125 is entered in the A axis scale DRO now a GCode command of G0 A10 will rotate the axis so that the surface of the 80mm diameter work rotates 10mm. Using this method means that simple, conventional, engraving programs and existing GCode programs can be used for engraving onto curved surfaces.

Although perhaps not quite as accurate as when the axis has been set up for angular movement in the first place - entering pi / 360 or 0.00873 into the A axis scale DRO will allow the axis to then operate in degrees ie. G0 A10 will rotate the axis 10 degrees.

Tweakie.

7644

Show"N"Tell ( What you have made with your CNC machine.) / Re: 3D Printing.

« on: August 06, 2010, 11:53:22 AM »

Got some more parts made – well just one part really (times 4). I have a fascination for identical parts that interlock and this seemed like a good opportunity to laser cut some 6mm acrylic for the walls of  my build jig (there is no doubt about it, a laser is the Dogs B’s for cutting acrylic). The tabs are a little on the tight side so they have not been fully pressed home yet, but this is how it will assemble and then be bonded with acrylic solvent. The lifting mechanism will sit inside and support the build table. Lots more parts to make but I am getting there slowly.

Tweakie.

7645

General Mach Discussion / Re: Mach3 for embroidery machine

« on: August 05, 2010, 06:04:43 AM »

Sorry Larry, I am no expert on using the G98 / L.. and M99 return commands as I don't think I have ever used them other than in the pre-coded Wizards where I had no problem with the code slowing down.
Not much help I am afraid. 

Tweakie.

7646

VB and the development of wizards / Re: Activating/Deactivating E-Stop from within VB?

« on: August 05, 2010, 02:25:55 AM »

Thanks for that clarification Terry, it all makes sense now.

(I just get the Buggywhipper sorted now you introduce Buggerwhipper  )

Tweakie.

7647

General Mach Discussion / Re: PWM and routers?

« on: August 05, 2010, 02:17:09 AM »

Jimmy,

PWM speed control works really well with 3 phase motors and their associated controllers but you run into problems with brushed motors overheating if they are slowed too much for too long (they all seem to have internal fans for cooling the windings). This doesn't mean to say that it can't be done though, just be aware of any temp rise in the motor. 

Tweakie.

7648

Show"N"Tell ( What you have made with your CNC machine.) / Re: 3D Printing.

« on: August 04, 2010, 06:30:05 AM »

Thanks Graham, thats a beauty of a machine and the quality of the work produced is, I think, second to none.

I wonder how long it will be before we can all afford to buy one (without taking out a bank loan) ?  

I made the other two arms for my Z2 lift mechanism. It really looks so wierd that I just had to post a picture. (If I didn't know what it was I don't think I would ever be able to guess it's purpose)
I still have to fit the tyres to the bearings but so far and perhaps suprisingly it works exactly as expected.

(it rests on three points and supports a plate which also rests on three points - as the centre part has an internal spring, acting in torsion, it will support the weight of the top plate and the working medium whilst allowing verticall movement with a parallel motion).

Tweakie.

7649

General Mach Discussion / Re: Zoom

« on: August 04, 2010, 01:48:43 AM »

I use the scroll wheel on my mouse.

Tweakie.

7650

General Mach Discussion / Re: limit switch triggered

« on: August 04, 2010, 01:46:46 AM »

Hi Bernie,

This is often caused by electrical noise being picked up on the limit / homing / estop cables and wiring. Others have reported sucess by adding a 0.1uf miniature capacitor between every input and ground (at the controller end).

Screened / shielded cables (grounded at the controller end only) should also resolve the problem.

Tweakie.