Member postings for John McNamara

Hi All

I stumbled upon the following post on another UK forum.

"DIY laser leveling using webcam and laser level."
Link:

The poster provided a link to the software source code on Github
It creates a Gaussion graph of position, I tested the software using a crude test setup.

I obtained repeatable accuracy of 0.039mm (.0004" and I am sure that can be improved with a better setup....... remarkable.

Regards
John

Hi Sam

I know that modern watch faces are often Pad printed. (As well as billions of bottles and the like) It works well on curved surfaces.

I also read somewhere that this process goes back 100 years?

I wonder if the raised text might have been done by this process or a similar process.

Here is a Search that revealed a few good links......
**LINK**

Regards
John

Hi All

One of my treasured books.

Howe does an outstanding job describing formulas on metal and wood finishing.
Also high precision toolmaking in general from an old school manual perspective.

I bought mine many years ago. for the tech info, The gunsmithing part is secondary.

**LINK**

Regards
John

Hi

My first lathe was a vintage Colchester it was a version of this one. I was very sad to let it go due to lack of space.
It used splined centers for the change gears.
That looks like a very nice set in good condition. There should be a 127 tooth Gear.

The flat belt driven black japan finished lathe second photo down. **LINK**

Regards
John

Edited By John McNamara on 09/08/2019 09:44:16

Hi all

I test fitted and aligned the X axis saddle that carries the Z Axis today. Those following this post will remember I set the gantry yesterday using a 0.01mm dial indicator set against two bearing blocks. With the carriage in place I was able to use a straight edge allowing me to test the full travel of the carriage. there was a 0.005mm error in the height. No problem, I tweaked the height of the gantry casting to reduce this to less than 0.001mm along the full travel. Remarkably this was better than the accuracy I obtained setting up each rail individually, that was using 1 bearing block. The saddle is mounted on 4 bearings. Averaging must have worked in my favor. I am very pleased with the result.

Testing the X Axis travel height.

This photo shows testing the X axis travel near the tool in the horizontal plane.
Remarkably no adjustment of the alignment done yesterday was necessary.
The indicator moved less than 0.001mm

Once the table is made It will be installed and tested in a similar manner.

Regards
John

Hi All

Now that the rails are attached I have reassembled the cross member and test aligned it. This is not going to be the final assembly, there is further steps to go that will require it being disassembled again.

As the photos below show I have test aligned the components using the linear bearing sliders reference points. I wanted to test the alignment system built into the machine. As noted earlier in this post there are built in adjustment screws to enable the cross member to be set parallel and perpendicular to the to the rails that will support the table. I had no trouble aligning the reference points to .01mm on the dial indicator if it was the final assembly I would have used a .001mm indicator. The rails are already aligned to +-.001mm to my straight edge.

As you can see I have used a Moore & Wright precision square sitting on a parallel bridging two linear guide bearings.

The linear guide bearings have a ground reference edge, this has been used to check the height using a dial indicator siting on a steel block to increase the height resting on a linear guide bearing. (The assembly was moved alternately to the left and right rail until the zero point on the indicator was the same for both sides)

The height adjustment is made using the two vertical jack screws on the top of the cross member, you can see a T handle and hex key if you study the photo. There are also 4 jack screws to set the gantry to perpendicularity to the table guide rails. see the two Allen keys I left in position. I have also marked the various points referred to with arrows.

Also as noted earlier in this post once the machine is finished I will fill the small gap between the columns and the cross member with metal filled epoxy. **LINK**
The jack screws will have done their job. I do plan to do the first cutting tests without the epoxy in place. That will be an interesting experiment. It will significantly reduce the vibration damping of the cross member. It will be interesting to see how much?

Reflecting on the design of this machine and in particular the way the rails for X,Y,and Z are all located on flat planes that are generated separately and the way the rails were easily aligned to very high accuracy makes me realize that the the biggest errors will be caused by my scraping and lapping of the bearing support plates. Before assembling the machine I will revisit the lapping and try to improve the accuracy I documented earlier in the post. I guess this is being obsessive but It will be worth the effort. Unfortunately all the geometric errors, temperature effects, deflections due to gravity and vibration etc will be compounded, Time will tell what the final result will be?

Regards
John

Edited By John McNamara on 07/08/2019 14:32:01

Hi All

Before reinstalling the cross member the ball screw mounting plates need to be set up. These plates are located in pockets in the casting attached by 4 M4 countersink screws. There is a space under the plate to allow its height to be adjusted to the correct mounting height for the ball screw assembly. once the final height is established the void behind the plate will be filled with epoxy by injecting it through the central hole in each plate.

The plates will be drilled for the ball screw bearing after marking out in position.

In order provide an opposing force to the adjusting screws small pieces of rubber were placed behind the plate. A straight edge with an attached dial indicator resting on the rails was used to align the mounting plates. A simple process.

Three photos below:

Below is a photo of the tapping setup used to attach the rails. After drilling I used a modified T handle tap mounted in the drill press. The T handle has an attached shaft that slides in a bush mounted in the drill chuck. This keeps the tap vertical and also reduces the chance of tap breakage. After about fifty tapped holes in "gummy" 16mm steel laser plate I am pleased to say there was no breakage. Carefully cleaning the tap for each hole and liberal dose of Trefolex aided the process.

Regards
John

Hi All

At last I have had some time to work on the mill. I have installed the rails for X,Y and Z. The images below only show the X and Z rails. I have removed the cross-member sitting on the Base casting and it covers the Y Rails, it is very heavy. Also note that the cross-member is rotated 90 degrees from its installed position. to allow drilling and tapping.

The first step was to drill the rail support bars using the Jig I built, I showed this jig a few pages back in this post but thought I should attach a couple of photos showing a test set up here. As you can see I utilized part of an inexpensive (I found it in a bin!) hand drill stand, it was made by AEG. The column attached to the removed base was 25mm mild steel. I simply replaced it with a piece of 25mm shafting I had to hand. I turned a boss and fitted the column to a piece of mild steel plate. this plate was also drilled to fit one of the linear bearings that was later to be used on the machine Also note the second boss at the rounded end of the plate, this was precision bored to fit the 25mm drill bush carrier.

The drilling bush is hardened and ground with a short taper that engages the rail when the bush carrier is pressed down perfectly centering the drill. see the second image below. At the top of the bush carrier is a second hardened bush, the long series 5mm drill is fully restrained.

Type 25 linear rails as used here are drilled 7mm and counter-bored for for M6 cap screws. The difference between the 7mm hole and the 6mm screw allows the rail to be accurately positioned after drilling and tapping. This sounds like a lot however it relies on very accurate placement of the mounting holes. both with regard to spacing in this case 60mm, not just for one rail but two! Both rails must be parallel.

Any errors above 1mm (+-0.5mm )and THE RAILS WILL NOT BE ADJUSTABLE

I thought on this for some time an the method I have designed is the result. It has worked very well. It relies on accurately positioning the rails before drilling using the cams on each side of the rail and a known accuracy ground straight edge. A stretched piano wire and a cheap USB microscope would also provide an excellent reference, particularly over several metres where straight edges become very heavy hard to find and expensive. I have done this before, it takes more work but the result will be the same.

Anyway in this case I have a good 1200mm straight edge and I used it. As you can see I used only one edge.

The first step in the process is to accurately position the straight edge parallel to the rail supports, The cams have limited travel and an error here will create problems later. It does not have to be in the center as long as you have access to it for a dial indicator. I used a 0.001mm dial Indicator.

Once the straight edge was clamped in position (It must not be moved until the job is complete), the rails then can be positioned with the cams using the straight edge and dial indicator mounted on a linear bearing to align the rails to straight edge. The cams are drilled and countersunk for a 30mm M8 screw, by rotating the cams clockwise until they bind then then tightening this screw the cams press against the side of the rail foot. Once all the cams are tightened you will find the rail is clamped quite tightly. There is a bit of a learning process to get this procedure right but after a few trials I was able to reduce the error on the indicator to + - one 0.001mm division, as the rails are at this point not screwed down the error will be greater than this but good enough for drilling and tapping.

I used a G clamp to hold down each end of the rails, They were bowed down slightly. Don't assume that the brand new rails you receive from the factory (In this case Bosch Rexroth) will be straight. They have to be bolted down to a flat surface.

Below are 4 photos of the setup used to drill and position the rails using a straight edge.

I will describe attaching the saddle in more detail later, here it is temporarily bolted to the cross-member rail bearings. using the straight edge still installed below it runs within 0.001mm following the rails as expected.
Also note the vertically attached bearings ready for the Z axis carriage.

I temporarily bolted on the Z axis carriage. centering the bearing rails to 165mm exactly. 

The Z axis spindle; This is a big question?
As seen below I have placed a fabricated spindle I started making a while ago. It was designed to have a BT40 taper, Not done at this time.
Once the machine is finished I want to use it for steel cutting, It has the mass and rigidity required to do this.
However I Also have a ubiquitous 2.2kw Chinese spindle given to me by a friend, see photo, I will use this first.

Next is reinstall the cross member

Hi All

If you have not seen Uri Tuchman's work before enjoy.

**LINK**

Regards
John

Hi Bill

Can you post a scanned copy of your scale drawing with written dimensions and the accuracy required.
For say 5mm plate a typical laser should be able to cut to within 0.1mm. sometimes better.
I also would be happy to make a DXF file if it is not super complex.

Regards
John

Hi Chris

And to the patient souls that want me to get cracking on this project. I have been away from the workshop, very frustrating....

The base design is uses laser cut 10mm plates spaced by shouldered steel inserts that are threaded and will form the points of attachment for work pieces. there are also inserts threaded to attach the bearing blocks. Rather than have the epoxy visible on the sides I designed side plates that also locate all thread reinforcement bars. the completed assembly is filled with epoxy from the underside. through a multiplicity of holes.

Once assembled and mineral cast the top and bottom will need to be made flat and parallel. this is a job i plan to farm out to a surface grinding contractor, I could do it by hand scraping around all those holes! but it would take a lot of time, it is also above my skill level. I could also mill it on my vertical mill, but not to the level of accuracy obtained by grinding.

The table is probably the most difficult of all the components of the machine to produce as a fabrication rather than a conventional cast iron casting. I did consider using a single thick steel plate, that would also work fine. as would a cast iron casting. With t-slots. or tapped holes, it will depend on what machinery is available to the builder.

The images below show the design I am using.
The 25 x 25mm Aluminium angles are part of the swarf guarding

Hi Craig

That's a difficult question for me being a bit of a perfectionist. There are many small details that I could improve on and that can go on infinitum! However There is nothing that I really regard as a gotcha,

A better choice of aggregate would have made the process a little easier, The mix was hard to tamp down, As I explained casting over a thick granite surface plate made vibration of the whole mold impossible It would require a massive vibration table, And even if I could have vibrated it I would not like my surface plate to be subjected to that sort of abuse. So I simply tamped and tamped! I still got some surface defects I just filled them after the castings were de-molded. For the next build I Will used a finer aggregate that flows better.

I chose Megapoxy because It is well priced, It is fairly thin when mixed and and it does not contain solvents, I works well for me and the company that sells it is very helpful. I know West system's products are popular with the boat building fraternity in particular. I am sure it would work well also. I have used Araldite (The retail 24 hour product) To Make a cast in place bearing. Google "Epoxy bearing material and method", It also worked well in that application, It is a lot thicker than Megapoxy. And much more expensive. Fine for small quantity use.

I guess if you work with composites all the time you would make a high quality mold apply release agent and then cast it. My choice was to apply self adhesive film to all the laser steel panels before they were assembled is a departure from standard practice. No allowance for draft was made. Angling the sides of a mold as you would do for say a boat to allow easy release from the mold was needed as the panels were all removed one by one. I wanted 90 degree corners. The plastic sheet did its job well. Yes, I ground off all the sharp corners with a small angle grinder and a flap wheel, then fine coated with polyester body filler, sanded and applied paint. I got a good finish For a "one off" a lot quicker process than preparing a perfect multi part mold. Remember no draft.

Previously I tried using several coats of release wax. It was an melamine MDF mold. The wax got scratched by the aggregate while tamping. The mold had to be pried off in pieces. What waste of time.

Maybe my biggest error is in not starting my project sooner! Too much research and overthinking and not enough building. The Heavily steel reinforced machine frame I have made has surprised me. Its turned out far better than I imagined.

I am starting to feel guilty for not posting here for a while....am held up at the moment waiting on the linear bearings and ball screws to arrive so I can get cracking.

Regards
John

Hi

Maybe a bullet proof vest would help? But then again maybe not

**LINK**

Regards
John

Hi

Better Autocad drawing technique.

Snap (F9) I almost never use. I also leave Grid (F7) off, the little points are annoying. With ortho (F8) on select a point, enter L for line then drag the mouse in the direction you want to go in and enter a specific length, followed by enter. once the first line is drawn you can keep adding lines by entering a new length and pressing enter. Practice doing this say drawing a box. At any time entering C will close the set of lines you have just drawn so drawing a box only takes 3 lines plus C to make the last line.

I do keep Osnap on (F3) most of the time. If you enter Osnap in the command line you can set the points it will snap to.

Oh Important, I Always start my first line at XYZ zero. Enter L then 0,0,0 as numerals not 0's then [enter] then mouse the direction then enter a length then [Enter]. This way the first part of an object (Normally the bottom left hand corner is set at true XYZ zero). Ortho (F8) should be on. Yeah it could be an angled line, I like to start with a straight line.

Drawing lines of a specific length will become second nature after a while. Using snap gets in the way as it limits you to a standard grid spacing. Most real life objects are not built that way.

Regards
John

Hi all and especially the doubters.

The link below is to his instagram like blog, it details the workshop tool restorations done and many other inovations.
The machines did not look the way they do now.

Oh! and a warning one of the photos shows him wearing shoes, and beware there is also a broom shown!

If you double click on the images they open up often leading to a set of other images.

I do like the way he has approached a 3D printer design, Not the cobbled up bits of plastic that you see all over the net. I don't have a 3D printer but I am tempted to have a crack along similar lines after the Epoxy Mill project is finished, I am waiting for the bearings and ball screws.

Link: On my machine It loaded slowly over a minute or so the images are high res.
**LINK**

Regards
John

Edited By John McNamara on 15/04/2019 01:37:58

I am in awe Mal
Photographic realism in 3D
Looking forward to your next post

Very impressive,

Check out the 3D printer mechanism near the end of the video.

Hi

You may find a sewing machine needle that can be adapted to your machine, maybe you could get a longer needle and remove the thread eye and make a blunt point most will already have a groove. The material will be high quality hardened steel so the result will be durable. It can be ground easily but not turned.

Locally industrial sewing machine suppliers will have needles.

The link below may assist also, Schmetz are a leading manufacturer of needles.
Send them the dimensions of your needle
**LINK**

Regards
John

Hi Douglas
Thanks Vic

It is not the end of the world if you miss an insert, or have to add one later. Epoxy/aggregate behaves the same way as normal concrete, you can drill it with a masonry drill. A new steel insert can then be made and epoxied in place, this is done millions of times a day on building sites.

More difficult is machining epoxy/aggregate. It can be done with carbide tools but they will be blunted very quickly. The saddle photos show a lot of large holes as you can see they have been filled to the brim with material. For the saddle I only used washed sand as the aggregate, if I had used gravel it would not have been able to flow into the small spaces in the mold. epoxy sand alone is not that difficult to rough machine, Automotive body filler machines quite well. BTW body filler shrinks a lot on curing.

I used some automotive body filler to smooth the surface of the holes before machining them. The machining went well enough, I did a couple of roughing cuts then finish machined the surface with a .004" cut. Yes It did cost me 2 points on the triangular tool insert. The 25mm holder has provision for two tips however I have found for this operation one tip gives a better finish, I ran at 1220rpm 9 inches a minute feed, about .007" feed per rev. A bit on the fast side for me however I found slower spindle speeds produced a rougher finish. The mild steel material is a bit gummy.

Regards
John

Edited By John McNamara on 23/03/2019 23:16:38

Hi All
15 Images follow

It’s been a while since I posted on the epoxy mill, Inspired by the accuracy of the castings made so far I decided not to use the low cost option Asian bearings and ball screws. Instead I will use Hiwin Taiwanese bearings these can be ordered to a proper engineering specification. I have asked suppliers to quote. This has imposed a delay. While waiting for the Hiwin bearings I have used some Bosch Rexroth bearings I have in stock for testing, these are earmarked for a CNC Router to be built in the future. They have exactly the same dimensions as the Hiwin bearings, so are interchangeable as long as you don’t mix manufacturers, the rail profiles are different. I have used them in the photos below. The router requires 2400 travel and I have two 3 metre lengths and some short lengths acquired as new second hand, hence the need to keep the stock bearings together as a set for use later. It would have been nice to use Bosch Rexroth Linear rails for the CNC Mill however they cost more than double the cost of Hiwin. While waiting for the linear rails and ball screws there is plenty to do.

My original plan was to only use the surface plate for flattening surfaces, I did this for the X and Y rail mounts as described earlier in his post it worked well however it was very slow progress. For the saddle I have used my vertical mill. It is a Shizouka VHRG, being a rather old machine the knee is a little worn. In order to get the best accuracy I had to use the overarm travel as the cross feed leaving the knee locked. The over arm never gets much use over the life of a machine so there is no wear at all. I also set some bolts in the tee slots and machined them using the overarm method. By doing this the only the table longitudinal travel and the over arm travel influences the cut. I am very pleased with the results.

The Z axis saddle casting has been done, This unit is a little different to the frame castings already made, it is more of a hybrid being made from 10mm laser cut steel plates and quite a number of drilled and tapped spacers that have a good fitting shoulders inserted into laser cut holes and glued in with epoxy making a very rigid unit. The spacers were very turned carefully to shoulder length.
This saddle unit fits into a laser cut steel mold that forms the side and the centre channel walls, it also locates several threaded inserts on the top of the unit. It will be cast this week

The saddle unit caries the Z axis, when thinking on the Z axis design I anguished for some time on the best way to set up the linear rails, should the linear bearings move or the rails move? Or to put it another way should I attach the linear bearings to the z axis and put the rails on the saddle or the other way around with the rails on the moving Z axis and the linear bearings on the saddle?
In the end I chose to attach the rails to the Z axis and put the linear bearings in the saddle.

With the saddle and the Z cast and machined at last they can be test fitted for the first time. It is exciting to see the actual components sitting on the bench having seen them on the computer screen for so long, now they have come to life.

Saddle / Z axis assembly

Inserts inserted

Ready for casting

Placed in Mold

Milling Face

Face milled

Bearing blocks test fit OK

Limit Switch housing

Z axis retracted

Z axis extended

limit switch housings fitted

Z axis drive motor plate attached

Set up for milling Milling bolt heads flat for perfect alignment with travel.

Edited By John McNamara on 23/03/2019 11:3