Topics

1

General Mach Discussion / Improved Home Switching Idea?

« on: April 03, 2016, 05:36:01 AM »

If we assume a machine with all limit switches on one input and a separate input for each home switch and wire it up with any old decent Normally Closed micro-switch at end of travel we get home positions but with accuracy and repeatability which is often dismissed by owners of pro systems and rarely proves good enough to pick up halfway through a finishing operation.

But what if we add a cam somewhere on each stepper shaft or ball-screw which operates a second switch wired in parallel to the end of travel limit switch for that axis?
The cam switch will operate once per turn but the home circuit will only open with both switches open, tune the cam switch to open/close a fraction of a turn after the linearly actuated switch is open and the accuracy and repeatability should be significantly better than is achievable with just linear switching.

Sound feasible?

 - Nick

2

General Mach Discussion / 3.3v To 5v Bi-Directional Converters

« on: January 03, 2016, 03:25:41 PM »

Has anyone tried the SparkFun bi-directional logic level converter to deal with differences between PP & BOB logic levels?
https://www.sparkfun.com/products/12009
It looks like a few of these in a fairly simple package might deal with the woes associated with modern PPs
I've ordered a pack of 10 to play with,

 - Nick

3

General Mach Discussion / Low Profile PCI Express Parallel Card?

« on: August 11, 2015, 03:21:32 PM »

Does anyone know of a decent PCI Express (the type for the sockets that are about 1" long) parallel card?
This build is for an Ethernet Smooth-stepper but it's always nice for PCs to be interchangeable and a parallel card would give me that,
TIA,
Nick

4

Mach3 under Vista / A Big Thank You

« on: June 02, 2015, 07:16:42 PM »

To all the usual suspects and other contributors who answer support questions here.

Today my old Windows XP PC finally bought the farm, with the help of the search tool and the wealth of information available here I was able to get a clean-build Windows 7 PC up and running with Mach 3 fully configured in an evening.

Thanks Guys!

 - Nick

5

Show"N"Tell ( What you have made with your CNC machine.) / Rohm Air Pistol Valve Cap

« on: April 15, 2014, 07:18:48 AM »

The left hand of the two is a phoshor bronze replacement for the plated brass original on the right.



The two problems with the original are
(i) only 2 turns of thread engagement into a cast zinc body of a 12mm OD holding against 800psi
(ii) the product is now obsolete rendering all parts low stock or unobtainable.

My replacement uses the full thread depth in the frame giving better engagement on a previously partially stripped thread (& so scrapped target pistol) than OEM, to achieve full thread depth a mechanically retained, off the shelf O ring replaces the OEM plastic seal.
The whole job is milled, apart from polishing ;-)

 - Nick
P.S. A big thanks to a great forum for the help and support that's helped me to get from no experience of CNC to here in around 12 months  

6

Show"N"Tell ( Your Machines) / Small Tools, Tool Offsets & Toolholders

« on: April 07, 2014, 06:02:14 AM »

My CNC Mill came with a Coventry Quick Change Holder installed plus 1 x 6mm endmill holder and 1 x 10mm endmill holder to fit it.
Once I'd implemented Tool Offsets I had visions of a rack of tool holders with permanently fitted tools, on investigated pricing for additional holders, at £65 and upwards each that will have to wait a while, in the mean time I came up with a viable alternative for tooling up to 7mm -



The ER11 collet chuck shafts were cut down and flats cut, the 10mm shafts allow a tool to be perfectly repeatably installed in the 10mm holder with just a grubscrew, they're far more affordable at £15 or so each.

The funny looking holder with a big thread is a JT6 holder I picked up at a local tool shop, I fitted it with a Myford spindle nose, that lets me use my Myford ER25, ER32 and ER40 collet chucks  

 - Nick

7

Show"N"Tell ( What you have made with your CNC machine.) / Milling something I'd normally turn

« on: April 06, 2014, 05:47:30 AM »

I prototyped this manually on the lathe, (I don't have a CNC lathe yet) and found the 5 different internal diameters and depths plus threading the second (18.6 ID 8mm deep) section entirely do-able but didn't really fancy doing a batch of 10 or more that way.
I'd modelled the job in CAD as the back face has geometry which can't be turned - a closely spaced combination of straight and circular features.
Only after I'd CNCd the rear face did it occurr to me to flip the part and CNC profile the IDs, then thread milling crept into my mind and while I had the fixture set up picked up a 14tpi threadmill and cut the full thread in one pass.
Here's the first one off the mill -



There was no reason not to bung it on the mill, it just seems I'm still dragging around my Manual Machinist's Mindset which has me thinking round parts should only be in a lathe - I'm now working on that

 - Nick

8

*****VIDEOS***** / ECC 4th Axis Test

« on: April 01, 2014, 05:19:01 AM »

I've finally got the Ebay Cheap Chinese 4th up and running with the help of a compatible driver board from Routout CNC, this video shows some testing for a part I'm currently manually machining, two sides have been faced, the compound curved section has been roughed out with a 6mm 2 flute endmill and part of the first pass with a 6mm 2 flute ball end mill is shown.



I now have to machine a permanent plate for the 4th axis & it's tailstock with eccentric buttons underneath to fit the table slots for axis alignment and Y position plus one for X position. 
Apologies for the ropey camera work, also the video quality was far better before uploading to Photobucket

 - Nick

9

General Mach Discussion / Work & Tool Offset Backup Location?

« on: March 26, 2014, 03:16:16 AM »

I use a copy of Mach 3 without the driver installed on my CAD/CAM system and keep the Mach 3 XML and profile XML files updated from my working system.
I don't get the Work Offsets and Tool Offsets transferred across, does anyone know where Mach 3 keeps them?
Thanks,
Nick

10

General Mach Discussion / Homing & Offsets Advice Request

« on: March 24, 2014, 07:59:11 AM »

Having reached the point where I have a firm enough grasp of CAD/CAM to model and process through to 3 and 4 axis G code the things I'd like to machine I found the setup and workflow habits I'd aquired with one-off parts to be less than optimal for batches of parts with several tool changes - I've been zeroing the DROs for each setup and for each machining session and tool but kept getting a sneaky suspicion there must be a better way.

Searching the forum provided several hints but without all the components in one place so the following is what I've ended up piecing together - can anyone who uses Home, Home Offsets, Work Offsets and Tool Offsets sense check this for me please?  

I'm trying to get to the point where homing gets me back on Zero for the current part/fixture/tool, is the following the best/easiest/quickest process?


 
Given that I have accurate, repeatable home switches on X, Y & Z which all home in a +ve direction I've added Offsets (Home Off) under Config - Homing/Limits to give me a zero position where I want it - currently in the table centre with plenty of Z clearance for vices, fixtures, 4th Axis etc. and some allowance for tool clearance.

I suspect that I now need to add work offsets to give the correct DRO readings for edge detected or probed part & fixture edges & faces then add other Tool Z offsets to correct for each tool I want to use.

I'm nearly there but do I first add a height offset including tool holding for my probe/edge detector then add work offsets relative to that and then add cutting tool offsets?
TIA,
Nick