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Topics - Tweakie.CNC

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Don't ask why - lets just say that I should not make any bets after downing a modicum or two of ale.



Tangent Corner / CNC fire hazzard.
« on: July 06, 2009, 09:15:21 AM »
Just look and see what happened when this Z axis failed and plunged the plastic bodied spindle into the work and stalled the spindle.
Perhaps the lesson is to make sure the correctly rated fuse or circuit trip is always used for the spindle when machines are left operating unattended.



Tangent Corner / Y Axis problems ?.
« on: June 23, 2009, 02:54:19 AM »
The Highways Dept. have really screwed up this Y Axis (or is it the Z Axis ?).   ;D


Tangent Corner / CNC versus TV.
« on: June 11, 2009, 02:48:40 AM »
Since developing an interest in CNC I don't get much time for watching TV - unlike all my neighbors.


My favorite model plane has an aging OS 61 which is now due for new crankshaft bearings and a clean up. The new crankcase gaskets have always been a pain to make (can’t buy them anymore – people don’t still use engines this old) and as I saw a posting recently about laser cut gaskets I decided to give it a try. I scanned the crankcase and got a reasonably good image which I converted to vector and then to GCode. Cutting at only 40 mm/min the 150mW laser made a pretty good job and didn’t set fire to the thin material as I half expected it to.

A couple of pictures of the laser and it’s control box on my Z axis, the finished gaskets and where they fit on the crankcase.


Not bad for a first attempt but I still have a lot to learn about vector laser engraving. The feed rate and dwell time at the start of each cut are all important and of course there is no Z axis movement.
Here I have used a low power (150 mW) red laser with a 650 nm wavelength fitted to the Z axis.


Tangent Corner / 'BIG' CNC
« on: March 20, 2009, 06:54:15 AM »
I spotted this on Flickr - it is just about the biggest CNC I have seen - how about you ?.


JetCam screen designer / JetCam screen designer/editor.
« on: March 17, 2009, 11:05:33 AM »
Hi all,

The current version of JetCam will not allow the .set screens file to be saved.  :(

Does anyone have a copy of the earlier version (which does allow the screens to be saved as a .set file) which they would be willing to share please ?.  :)



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.


As a winter project i have slowly been building a 4th Axis. I did seriously think about making a scroll chuck but decided on buying a Sherline 3 jaw for the project. All the other parts (excluding the flex coupling) have been made from stock, some parts CNC'd others made on a lathe or mill.
There is still a lot of work to do but I thought I could post some pictures of the progress so far.

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