Messages

5451

Show"N"Tell ( What you have made with your CNC machine.) / Re: Tweakie's De-Mag.

« on: May 27, 2012, 08:41:44 AM »

Hi Rich,

In general de-magnetizers are something that are used infrequently but many machine shops have professional models (Eclipse) for de-mag'ing their cutters - I think these would work quite well, inverted and slid across the top of a machine table, and perhaps one could be borrowed or hired for the purpose.

Tweakie.

5452

Show"N"Tell ( What you have made with your CNC machine.) / Tweakie's De-Mag.

« on: May 27, 2012, 06:32:48 AM »

Another little project for a rainy day.

After trying one of Art’s ideas of wooden clock gearing using small magnets instead of teeth I encountered a problem. First, one of my small screwdrivers became magnetic then it spread, like a virus, to most of my other small bench tools and having used some steel wool (on a previous occasion) almost all my tools were picking up minute, unwanted steel whiskers.
Having seen a de-magnetizer project on eHow I set about making one and this is how I did it.

Taking an old, unwanted, mains power unit (from a long gone printer) I removed the transformer. The Mu laminations were carefully removed, the ‘I’ sections discarded (well some have been kept as lathe tool packing pieces) and the ‘E’ sections replaced, all in the same direction. The first ‘E’ is the hardest to remove but don’t worry if it is damaged or bent because on replacement they all fit back, except one, so the damaged one can be discarded.
It is only the mains, primary, winding that is used so the secondary windings are just left open circuit.
I fitted a small piece of iron onto the centre pole using epoxy then cut an appropriate sized hole in a project box and glued in the transformer again using epoxy.

When the transformer laminations layout is altered in this way, the whole flux pattern is changed and as a result it is necessary to limit the current flowing through the winding. This is best achieved by using a mains rated capacitor, connected in series (the larger the capacitance value the larger the current and visa versa). The original mains lead was re-used and the de-magnetizer was tested - it works just beautifully and removed all the residual magnetism from my small bench tools in just seconds.

The capacitor I used was a 2uF 400Volts starter capacitor and this is connected in series with the coil. Incidentally if the capacitor used does not already contain a shunt resistor then a 1 Megohm 5W resistor should be fitted across the capacitor to discharge it once power is disconnected.

Tweakie.

5453

General Mach Discussion / Re: computer keep on switching of when the plasma ark(spark)

« on: May 27, 2012, 01:50:49 AM »

Hi Mitch,

Just a suggestion but try running the problem file with the torch switched off - if it runs OK then electrical noise could be the issue. In this case check your grounding connections.

Also check for GND loops - in particular the LPT cable shield should not be connected to GND at both the computer end and the machine frame if they are both, in turn, connected to earth etc.

Tweakie.

5454

General Mach Discussion / Re: Newbie Help Please to a NOT so Stupid Question

« on: May 27, 2012, 01:40:29 AM »

Hi Buggalugs,

I am not sure I fully understand the problem.

Surely your PCB files show the track side of the board so the created drill file would also be from the track side of the board unless you have an axis direction incorrectly set-up on your machine.

Tweakie.

5455

General Mach Discussion / Re: Zeroing the work piece Question?

« on: May 27, 2012, 01:29:28 AM »

Hi CNCexplorer,

I don't know if this is any help for your application but the setting process I use for engraving and wood routing is detailed here http://www.cooperman.talktalk.net/files/17.htm

Tweakie.

5456

General Mach Discussion / Re: REALLY noobie stuff

« on: May 26, 2012, 12:56:27 AM »

Hi Bill,

Take a look at the free engraving program 'F-Engrave'  http://home.comcast.net/~sskroch/Fengrave/fengrave.html

This is quick and easy to learn and will produce the necessary GCode file ready to run from Mach3.

Tweakie.

5457

Show"N"Tell ( What you have made with your CNC machine.) / Re: Constructing a Low Profile Tool Height Setter.

« on: May 25, 2012, 01:26:35 PM »

Hi guys,

Kind of hoping you were providing the units, so I don't have another project to complete. 

Go on - make one - you will not be disappointed.

Hi Tweakie - do you mind giving me your G31 feedrate, your Z axis accel and your steps per please? I'd like to check this out.

Steps 533.3333..., Z axis Acc. 100,  G31 feed  200.

Tweakie.

5458

Show"N"Tell ( What you have made with your CNC machine.) / Re: Constructing a Low Profile Tool Height Setter.

« on: May 25, 2012, 09:18:18 AM »

Hi YNN,

Thank you for the kind words, it is much appreciated.

The contact ring, insulator and plate have all been lathe turned and the flat surfaces are as near parallel to one another as I can make them. These 3 items have then been fitted together using Locktite, under a small pressure until cured, making the assembly of the contact ring as plane with the top surface of the plate as I can. The 3 individual contacts have been lapped so that they each protrude from the rear surface of the PCB by exactly the same amount (as near as I can measure using feeler gauges on a surface plate).
The contact ring, plate and the 3 contacts are all made from A4 (austenitic) stainless steel.

The contact ring rests on the 3 contacts under spring pressure and the overall height of the completed probe measured with a micrometer – this dimension being entered into the Mach3 probing script as plate thickness. Any downward movement of the plate breaks one or more contacts for the G31 detection. Although the contacts are ‘normally closed’, the transistors invert this logic so the probe output is normally a weak High and only taken to a strong Low (GND) when contact is broken.

The amount of movement necessary to operate the probe is incredibly small (unfortunately I don’t have the necessary equipment to accurately measure this) but it is largely dependant on the flexibility in the top cover and operational movement is currently smaller than two of my Z axis micro-steps. It does not seem to make any difference if the plate movement is parallel (centre contact) or tilted (off-centre contact) there is never any contact bounce – it either makes contact or it doesn’t.

This type of contact break detection is used in some of the Baumer Electric limit switches – OK they have far more accurate manufacturing facilities than I have but they claim 1 micron repeatability. I don’t think I am anywhere near to that but, as I said, the triggering movement is incredibly small and beyond my micrometer measurement skills.

The over-travel (after contact break) is approx. 2mm but I have found that with Mach3 version R3.043.062 the G31 appears to trigger an immediate stop rather than a decelerated stop and plate movement is not even visible.

One new thing that I have noticed is that the work piece must not have any movement or flexibility when tool height setting – my vacuum table holds engraving laminate tightly but double sided sticky tape has a degree of springiness and this can cause a setting error. I am not quite certain just what is happening here but it needs further investigation.

You would really have to build a similar device for yourself to fully appreciate the accuracy of the operation but, as shown in a previous picture, it has enabled me to engrave 0.5mm high text to a depth of  0.05mm which I struggled to do before using this type of probe.

Hope I have answered all the questions.

Tweakie.

5459

Show"N"Tell ( What you have made with your CNC machine.) / Re: Constructing a Low Profile Tool Height Setter.

« on: May 25, 2012, 02:30:05 AM »

A couple more pictures of the probe parts.

Tweakie.

5460

FAQs / Re: Pulsing too fast

« on: May 25, 2012, 01:12:12 AM »

Hi Nava,

May I suggest that you do a search for 'parallel port card' to check out others experiences.

As an example http://www.machsupport.com/forum/index.php/topic,11300.0.html

Tweakie.