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Topics - John Mac

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1
Show"N"Tell ( Your Machines) / DIY Epoxy Frame based CNC MILL
« on: January 21, 2019, 08:20:46 AM »
Hi all

Its been a while since I popped in here, been pretty busy work wise.... and not enough workshop time.



Anyway I have started building a new CNC Mill and have started a blog here: https://www.model-engineer.co.uk/forums/postings.asp?th=139042

As you can see the build uses Mineral Castings (Epoxy granite in the US) The molds and many of the parts are laser cut steel.

I decided to make it as small as possible due to my small workshop space is at a premium. As you can see it will fit into a 1 Metre (about 40") cube plus the stand. It will not be a light machine and will weigh several hundred kilograms a kilogram is equal to 2.2 pounds approx. the travels are 520 x 300 mm If I had more room I would have made the 300 mm 700 mm Z axis is 250mm clear under the gantry plus tool shank allowance. For the odd time I want more clearance I will use the manual V mill. Less Z travel should improve the stiffness.

I have a mach 3 license so will control it with that. Drives will be DC servos old from stock but in good condition.

Currently the cross-member and two columns are cast. the base is next maybe this week. Nearly all the components and the molds are laser cut steel already done. So far I am really pleased with the accuracy of the castings.

Anyway if you are  interested keep an eye on the thread I will keep posting as the build progresses.

Regards
John

2
*****VIDEOS***** / Laser Cut Frame CNC Router New build
« on: February 14, 2013, 03:22:12 AM »
Hi All
 
A CNC router made from Laser cut 5mm steel plate with almost no welding. driven by Mach 3. and smothe stepperr USB card.
 
It was designed using Autocad in 3D a commercial program however there are many free CAD packages that can generate DXF files to give to a laser cutting service.
 
Almost No Welding? The design uses a joint design that is effectively (two) mortise and tenon pairs together with standard fasteners between the pairs, to make each connection) ; in this case M5 high tensile nuts and bolts, to join the various members together. Using this method there are zero sheer (well almost) forces on the fastenings only tension forces. I believe it could easily be scaled up to at least 12mm plate. Laser cutting has very little undercut; however there is some so plates will not ne perpendicular to each other and need to be supported in two planes to counter this. make sure the attached plates are interlocked in sets of 3 opposed at 90 degrees. Buy doing this using my best More and Wright square to test the joints I could see no light. bolt holes aligned so perfectly that there was no eye observable misalignment. There are no tapped holes in the plates. The bolts and nuts fit in slots you can see the slots in the views.
 
If you are wondering the only welds are the end plates of the 75mm sq tube rail supports, We are going to make a new machine with joined 5mm plate instead of these tubes. It will be more accurate and lessen the packing we needed to set the rails true on the RHS (we used a surface plate).
 
Laser cutting is now a fairly competitive area and the group was able to negotiate a reasonable cost for the work roughly steel cost plus steel cost x 2 for labour. The machin positioning accuracy was .01mm. we allowed on top of that .1mm (point one) clearance for the joints and no allowance for holes.
 
When the parts came back from the cutting service there were small (tiny) dags here and there. about 4 hours work total with a small file to clean all the joints and it went together like a clock. No welding distortion...... We redrilled all the round 5mm holes to clean them out as they were already laser cut it only took a few seconds per hole. the holes were positioned far better than I can do with a centre punch. Yes the machine could have been made by hand methods but have a look at the parts photo. how many hundred man hours. I have spent a fair number of hours just turning all the rotating parts .
 
The machine also uses Chinese round shaft linear rails and a z axis ball screw. You will be amazed how the cost of these have fallen on EBay and the like. X and y drives are 5mm timing belt.
 
All the rotating parts use flanged ball bearings 8mm and 12mm again the internet provided a source ...VXB Bearings were very helpful and are a good starting point. The flange is clamped between the frame and a laser cut plate with 4 M4 bolts

The design is a collaboration with a great friend Leo S and The Bright Men's shed group, Bright is a central Victorian country town. A Men's Shed is a community supported building equipped with various metalworking, welding and wood working machinery; members pay a nominal fee to pay for tea and coffee. and are free to use the equipment (after doing OH&S induction and training).

Ther result is very pleasing indeed. clean accurate cutting.

We are now working on a new design 2400 x 1200 x 150h work area using the same methodology.
Cheers
 
John McNamara

Images and video below........

Cad Design:


Laser file:


Overview (Table is temporary)


Every rotating element runs in flanged or circlip type ball bearings (clamped in laser cut holes)


A couple of movies....
 
The first test 120 mb file:
http://www.mediafire.com/?3atxyt94f76xk7c

A bigger test 500mb file:
http://www.mediafire.com/?6yeg2c78d3vwivp

3
General Mach Discussion / Rotary table dividing calculator
« on: January 28, 2012, 06:49:41 PM »
Hi All
I guess this is decidedly non CNC related however it may come in handy on your manual mill.
It is written in Excel (no macros) you can change it as you wish.
Enter the number of divisions and it will display all the decimal angles together with the same angle in DEG MIN SEC.

http://www.mediafire.com/file/yxheh2nvg2h3q7j/Dividing Calc 1.zip

Cheers
John



4
Hi All

I have been working on the design of Vertical mill based on Epoxy concrete
The highlighted cube shown below is 500 X 500 X 500 mm, not a small machine but it may be scaled down.  The same principals can be used on other machines.

The Flat surfaces are cast on a surface plate with containing formwork.

This is the first draft and it is a bit rough. All the major parts are in place. I will post updates as the design evolves.



A power point presentation of the design objectives can be found here (2MB):
http://www.mediafire.com/file/5c1obos9oksx3xg/Epoxy%20Concrete%20Machine%20Des%20%20PPT%20MACH3%20.zip

All the Cad Files for the project including the above power point can be found 5 MB here:
http://www.mediafire.com/file/n9pd9bitdg1l2ef/CNC%20MILL%20EPOXY%20CONCRETE%2030_04_2011%20Mach3%20.zip

Cheers
John

5
Show"N"Tell ( Your Machines) / Epoxy Bearing Material and Method
« on: April 18, 2011, 08:47:01 AM »
Hi All

Attached is a powerpoint I did for epoxy bearing material
It was presented in Melbourne Australia


A piece of threaded rod with epoxy nut described.
Cheers

I posted a copy of the file here:
http://www.mediafire.com/?xpdu1z75t6hm70a


Macka

6
General Mach Discussion / Bridge Beam
« on: December 11, 2008, 03:00:39 AM »
Hi All

Attached is a couple of images of a possible approach to a guide way.

I have used adjuster bars 20mm square Mild steel plus the pyramids to seat and precision locate the 25mm round shafting (Pre drilled at 120mm spacing as per the Thomson spec sheet)

These bars could be made on a small mill.

Ideally after rough cutting at the local plasma or laser cutter’s shop.
Only the ends, back and V’s would need to be machined. The rest could be left as is.
In fact there if the shop had one of the latest machines only a few thou would be left to finish square.

The spacing between the V’s could be set by milling one first then locking the table and using the first one as a reference for the other, for the final cut. If done carefully it should be possible to get it to a few tenths.

There is a fair amount of drilling and tapping to do, and a lot of alignment to set it up but the result should be “Spot on”. All the adjustments are lock nutted. The top and bottom adjustment jams the bar between the ends of the beam. The in and out adjustment is lock nutted through the web of the beam. Using the same threaded rod that is holding the Roundway.
Note the nut behind the bar to tension that. The holes in the web of the beam are drilled oversize to allow adjustement.
 
This beam 310 UB40.4 has a 6.1mm web. I guess that is the weakest link in this setup. It is beyond my ability to calculate the deflection under a load perpendicular to that face. But for wood or Aluminium cutting it should be fine? The illustration is about 1500mm long Although I plan to make it 3600mm long

It would be interesting to know the Deflection If any member would like to do it I would appreciate hearing from them. 

Just doing a bit of brainstorming at the moment, there may be a better way, in fact an alternative method is bugging me right now!

If it looks OK I will post it.

Cheers

John Mac

7
Tangent Corner / Designer resource Sites
« on: December 10, 2008, 08:10:46 AM »
Hi All

I stumbled on this site while looking for Cap screw dimensions... It Googled straight up.
http://www.roymech.co.uk/Useful_Tables/Screws/cap_screws.htm

Or Screws in general
http://www.roymech.co.uk/Useful_Tables/Screws/

Or Useful_Tables
http://www.roymech.co.uk/Useful_Tables/

Or The Home page
http://www.roymech.co.uk/

If you stumble on a link it is often rewarding to strip away the levels one at a time....You never know what you may find.

Cheers

Macka

8
General Mach Discussion / Wire Alignment
« on: November 25, 2008, 09:26:09 PM »
Wire Alignment
________________________________________
Hi All

I posted this on CNCzone a while back. hence the references to a lathe.
I kept copies of all the docs so if anyone is int drop a line.

This note is about getting things straight…….Very straight.

Some time ago an old but looked after Heidenreich and Harbeck lathe came my way. The bed length is about 2 Metres and weighing at three and a half tons, this is a serious lathe!

Over time there is slight wear on the bed and I am contemplating scraping her back to perfection.

One day I went into a bookshop and found a new copy in the second hand section of Connelly’s book for 20 bucks. Yep I grabbed it. For restoring old machine tools I know none better. I have already used it as a reference. Scraping is not that difficult just hard work. and common sense. I found a couple in the US here

 Amazon.com: Machine tool reconditioning and...
One of the mysteries of alignment is using a tight wire as a straight line.

How to do this this proved to be a bit harder to track down

However the following sites have helped a lot to understand the theory.

http://www.slac.stanford.edu/cgi-wra...-pub-11465.pdf    (EDIT the link is down at the moment)
it is now here:
http://www.slac.stanford.edu/pubs/slacpubs/11250/slac-pub-11465.pdf

http://www.physicsforums.com/archive.../t-220848.html   (EDIT the link is down at the moment)
It is now here:
http://www.physicsforums.com/archive/index.php/t-220848.html

http://www.spaceagecontrol.com/calccabl.htm    (A good calculator)

I guess before the Egyptians they were using a string line

On a more 21st century note here is a link to a MIT
J. Paradiso is still there.

This would make an inexpensive electronic readout system for a tight wire alignment system. As used on linear accelerators. So it is quite accurate.

http://web.media.mit.edu/~joep/papers/WireReadout.pdf

There are other references on wire alignment on Google scholar

http://scholar.google.com.au/scholar...ment&hl=en&lr=


So now I have a plan!! The next bit is to get the time to do it, in the mean time. I would be most grateful if the CNC crowd had any further Ideas.

Cheers

Macka

9
General Mach Discussion / Mach 3 Sewing Machine
« on: November 24, 2008, 08:33:56 AM »
Hi All

An exciting time.. Over the last couple of years I have kept an eye on Mach 3 from the numerous forum posts both here, the CNCzone and on You tube. Mach 3 has become irresistible.

I work in the rag trade so for me the use of CNC will be a little different to metal working or routing. My interest is in stitching, while the overall system accuracy for stitching is a lot less than precision machining. There are other problems that must be overcome. The system I intend to create will be in the form of large Router table. With the added complication that the sewing axis will require 2 synchronized drives to drive the needle and the hook and thread bobbin separately, (The mechanism under the table of the machine) a simple 1:1 ratio but not constant speed and with a speed range of 500 – 4500 rpm, and this speed must be relative to the tool path speed. Not an easy task from my enquiries so far.  Yes it can be done mechanically but not without a lot more hardware.

My previous experience was retrofitting a CNC sewer. It took a lot of time. The hardware had to be hacked to enable user programming rather than going back to the supplier it was encrypted, or rather obfuscated. (Not uncommon for textile machinery) I also wrote a VB program to feed it with code its native code not G code. The software reads a DXF file using polylines and converts it. The math routines may come in handy again.

Today I would chuck out the hardware and start again.

I would be pleased to hear from any fellow Rag trade members, it would be fun to discuss some of the issues that relate to stitching.

Cheers

John Mac

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