Messages

5391

G-Code, CAD, and CAM discussions / Re: CAD/CAM for Hobby Level Bench Mill

« on: June 15, 2011, 01:13:18 AM »

Hi Peter,

Good to hear that you are on your way. 

Tweakie.

5392

General Mach Discussion / Re: Lead or Ball Screws (lathe Conversion)

« on: June 14, 2011, 08:37:01 AM »

Good points you have raised there Katoh.

I would like to know the answers as well. I must admit I know nothing about lathes but Hood is an expert, he will know.

Tweakie.

5393

General Mach Discussion / Re: Lead or Ball Screws (lathe Conversion)

« on: June 14, 2011, 04:06:54 AM »

Katoh,

I think it all comes down to Backlash.
Under light loading ballscrews can exhibit zero backlash whereas adjusting the double nut on a trapezoid to obtain the same result produces much increased friction.

Tweakie.

5394

General Mach Discussion / Re: Jerky Movement on combined X-Y Movmenet 3 Axis CNC Router

« on: June 14, 2011, 03:53:52 AM »

Hi Rob,

Curious one this.
I do a lot of laminate engraving and have never seen anything quite like it.
Because the effect is not so pronounced on the letter N where the diagonal is nearer to 45 degrees, I would suspect that the software you are using is at fault and the machine is only following the GCode it has been given.
If the individual letters were created to a higher resolution I suspect everything would be OK. Perhaps you could try the attached code (which was created using the Mach Write wizard) and report back on the result.

Tweakie.

5395

General Mach Discussion / Re: Questions about wiring this up

« on: June 14, 2011, 02:57:56 AM »

Now to put the cat amongst the pigeons. 

If you bolt a wire, using a T nut, to one end of a cast iron mill table and then bolt a wire, using a T nut, to the other end then pass a current through the table you will be able to measure a potential difference at various points along the tables surface. Take a look at the size of the conductor in an ammeter shunt and see where the potential difference is measured.
Whilst it would be nice to have everything on a machine at the same potential the deviousness of science will just not allow it. If potential difference exists in an homogonous piece of metal then imagine the situation where various types of metal, plating finishes and fastener materials all having a different PD are combined into one machine.

Earth bonding is a requirement of law within industry and it makes sense that our home workshop meets the same safety standards as industry therefore earth bonding must be carried out in a professional way and there are many good documents suggesting its implementation.
However, we should not confuse earth bonding (which is essentially a safety issue) with signal shielding, they are two separate issues entirely.

For those who would like to re-invent the wheel, by all means connect the shield of your signal cables at both ends but you would be wise to follow the path where others have had success and only connect the shield at the controller end.

It was Eleanor Roosevelt who once said; “Learn from the mistakes of others. You can’t live long enough to make them all yourself”.

Tweakie.

5396

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: June 14, 2011, 01:11:50 AM »

Thanks Sam, I never really thought of it like that 

Tweakie.

5397

G-Code, CAD, and CAM discussions / Autodesk 123D - Free 3D Design Software

« on: June 13, 2011, 12:14:43 PM »

On a tip from DanZ the beta of this is available for free download at http://www.123dapp.com/

Also available are a number of free 3D models.

Tweakie.

5398

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: June 13, 2011, 02:24:49 AM »

Last week I urgently needed a couple of gaskets so, just for fun really, I used the same technique used a couple of years back to make the crankcase gasket for my OS61. Provided the casting or part requiring the gasket is small enough to lay on the platen of a flatbed scanner it is fairly easy to get an image then, after a bit of cleaning up, an outline DXF can be produced and converted to GCode.
My laser will not cut all types of gasket material and there are limits to the maximum thickness for the stuff it will cut but these fellas are 0.8mm thick and came out pretty well. I only needed one of each but made an extra while I was at it. 
Gaskets made this way would be ideal for Steve, building his excellent V8, where neat and precise cutting is important but it takes time, mainly in the preparation and cleaning up of the artwork.
This took me just over the hour to make some parts which I probably could have cut with scissors in 10 minutes but it has made a very tidy job of something, with a bit of luck, I may never ever see again. 

Tweakie.

5399

General Mach Discussion / Re: Controlling 120v solinoids

« on: June 09, 2011, 11:40:12 AM »

This is the way I would do it.

Use SSR's similar to the one in the picture - they have opto isolation on the input and can be driven by either 3.3V or 5V logic from your parallel port. The output pins you choose should be configured 'Active Low' within Mach.

Tweakie.

5400

G-Code, CAD, and CAM discussions / Re: CAD/CAM for Hobby Level Bench Mill

« on: June 09, 2011, 05:49:19 AM »

Peter,

If you download the trial version of Cut2D you will soon get the feel of it and see just how quick it is to learn. It does not try to do lots of other functions, it just sticks with what it does well. There have been a few negatives as it uses 'ramp plunge' rather than 'lead-in / lead-out' but I never found this to be a problem, in fact it can be an advantage when cutting nested parts from a sheet where space is tight.

Tweakie.