Messages

7701

General Mach Discussion / Re: BOARD PROBLEM HELP REQUIRED

« on: March 13, 2009, 09:58:09 AM »

Hi Stephen,

Unfortunately it may be the driver board as Hood has said (I hope it is not).
As it is only one axis at fault try testing the components associated with the failed axis - the 2 (large) current limiting resistors with a multimeter to make sure they are not open circuit, also check the 4 protection diodes to make sure they are not short circuit (low ohms in one direction and high ohms in the other - with motor disconnected of course). It would be a bit of tricky soldering but it is not out of the question to replace the TA8435 chip (cut off all the pins and remove them carefully from board one at a time then fit replacement to heatsink then solder pins). There is not really anything else on this board to go wrong.

Tweakie.

7702

Show"N"Tell ( Your Machines) / Re: Laser cross hair tool position.

« on: March 13, 2009, 03:00:24 AM »

Thanks Greg,

I will try that today and see how it goes.

Tweakie.

7703

Show"N"Tell ( Your Machines) / Re: Laser cross hair tool position.

« on: March 12, 2009, 03:13:04 PM »

Hi Dave,

I saw your excellent post when I was researching my project - it just took a while to locate the laser pointer.

I bought the polarizing film as a small sheet. It is laminated plastic and easily cut into the shape required with scissors.

Here is an ebay uk link which will work for a couple of days at least.

http://shop.ebay.co.uk/items/_W0QQ_sopZ10?_nkw=polarising+sheet&_sacat=0&_fromfsb=&_trksid=m270.l1313&_odkw=cnc&_osacat=12576

Tweakie.

7704

Show"N"Tell ( Your Machines) / Laser cross hair tool position.

« on: March 12, 2009, 12:53:53 PM »

A simple project for a rainy day.

I recently bought one of these laser cross hair pointers on ebay. Unfortunately they are not that well made (what can you expect from China and cheap as chips) the focus ring incorporating a prism assembly is a very sloppy fit in its mounting thread and any movement here alters the cross hair position. After some deliberation I made a clamp which bolts to the Z Axis and grips both the body and the focus ring of the pointer - this makes the whole thing rigid and it cannot be accidentally moved once set. Setting it up is a bit more tricky as the focus has to be adjusted for optimum at mid Z Axis travel, then rotated until the cross is exactly X - Y alligned (although this is not so critical if you are only interested in the center position of the cross) and finally the cross must not move position when the Z Axis is traversed up and down. Two or three goes at milling dust off the mounting and it was perfect. Because the reflectivity of different materials and surfaces varies I have incorporated a polarised disc beneath the pointer and this can be rotated 90 degrees. (The light from these laser pointers is plane polarized and by using a rotatable polarized filter the apparent brightness of the beam can be varied between full on and off - allowing for the optimum brightness to be set)

Thanks to posts by Hood and Greg I added a button to the Mach screen and pasted the modified button script (after carefully measuring the offset between the cross hair and tool position, using the Mach DRO's). Brilliant, it works so well I really don't know why I did not do this sooner. At the moment I am using a battery to power the pointer but a 3 Volt supply and on/off switch will be added tomorrow.

Tweakie.

7705

General Mach Discussion / Re: BOARD PROBLEM HELP REQUIRED

« on: March 12, 2009, 03:34:27 AM »

Hi Stephen,

It sounds obvious but recheck that you have the Z Axis stepper coils connected correctly.

Tweakie.

7706

Show"N"Tell ( What you have made with your CNC machine.) / Re: Building a 4th Axis from scratch.

« on: March 11, 2009, 08:57:50 AM »

Well that's it - the mechanicals are all complete now, it just leaves the electricals to be sorted.

Tweakie.

7707

General Mach Discussion / Re: Can "Direction" &"Steps" signals be saved and stored in physical "memory"?

« on: March 11, 2009, 03:21:36 AM »

Hi Richard,

Would be nice wouldn't it - but as Jim has just implied saving 60k of pulses for every inch of movement for each axis you would need one big ROM.

Tweakie.

7708

General Mach Discussion / Re: Help with verify button

« on: March 10, 2009, 01:44:00 PM »

Hi Ron,

I would also check that there is no binding or tight spots on your X Axis slides and leadscrew. This could cause lost steps and the stepped sides to the milling pattern that you mention.

Tweakie.

7709

General Mach Discussion / Re: Strange Problem

« on: March 10, 2009, 01:34:46 PM »

I would suggest that you check the LPT connection between your computer and machine. A broken / intermittent connection on the Y axis step pin (whichever one you have chosen) could possibly cause this problem.

Tweakie.

7710

Tangent Corner / Re: Metal shredder

« on: March 10, 2009, 11:51:43 AM »

Wow ! - don't want to let your CNC anywhere near that.

Tweakie.