Here is a list of all the postings Chris Courtney has made in our forums. Click on a thread name to jump to the thread.
|Thread: Tool & Cutter grinder options...|
I would echo what has been said about acylic, it isn't suitable for guards, it can shatter. Polycarbonate is widely available, I have bought it from **LINK**
|Thread: Which software?|
Here is a link to the relevent page: **LINK**
|Thread: Grit blasting|
I have one of the smaller Machine Mart blast cabinets (model number CSB20B). They specify a minimum compressor capacity of 10cfm at 80-100psi. I use it to bead blast small aluminium components, and actually run it from a 8,7cfm compressor. It does work, but the compressor is too small, I get away with it because the parts are small, but I spend a lot of time waiting for the receiver pressure to recover.
As others have said, you do need a lot of air, especially if you are trying to clean up heavily rusted or painted components. You state that your compressor is a 120cfm model... if this is correct then it is a pretty large compressor, even my humble 8.7cfm compressor requires a 2HP motor. If the figures are correct, then you have more than enough air for grit blasting with hobby sized equipment.
|Thread: MEW 198 Worden ER25 Chuck|
Yes that makes sense; strange that it hasn't affected all views using the diameter symbol.
The drawing titled ER25 Chuck for Worden Tool and Cutter Grinder shown on page 29 of the digital issue of MEW198 contains a number of gross dimensional errors.
The two views affected are the ER25 Chuck body (central view), where the three external diameters are completely incorrect, both in their inch and metric versions.
The other view is the plan view of the Indexing block where the diameters of the two holes and the counterbore are again completely wrong. For example the dimension of the a 2BA socket cap screw counter bore is given as:
diam 50.32(58.0) where the bracket value is the metric version. 50.32" is obviously wrong! and 58 mm is neither the correct value or a correct conversion of the stated inch value.
Edited By Chris Courtney on 14/12/2012 12:32:45
|Thread: Turning Perspex rod|
One more point I meant to make: The Dichloromethane in the Tensol 12 evaporates very quickly, and seems to diffuse though some plastics. I use a metal container and keep the lid closed all the time except when removing some with a syringe. Some people recommend keeping it in a fridge and using it whilst cold to reduce evaporation. If you are not careful about evaporation then your expensive bottle of Tensol 12 will quickly become too viscous to use easily, and eventually will turn into a solid block.... don't ask me how I know!
Edited By Chris Courtney on 28/09/2012 12:51:05
I do a fair bit of Acrylic fabrication, in particular glueing acrylic sheet. I would be very careful about using Chloroform in a small home workshop... there is a very real danger of anaesthetising yourself!
I normally use Tesnol 12, it works very well as a solvent glue, but it is nasty stuff and you need to have good ventilation, and use gloves to avoid skin contact. If you look at the product data safety sheet **LINK** you will see that the main two ingredients are Dichloromethane (often used as paint stripper) and Methyl Methacrylate which is the monomer of the acrylic.
Please be careful with any of these acrylic solvent glues, they are all fairly harmful.
I agree with you Tony, I only replied to John M about the joint because he specifically said he'd like to see other examples of that type of joint. The idea of providing dxf sets ready for laser cutting by your local laser cutting company has been gathering momentum in the Reprap community and the US Maker movement. It is great to see a solid looking design appearing in the model engineering community. As you say low power lasers capable of cutting acrylic, MDF and Plywood etc. are becoming much more affordable. Once you have a laser cutting system it is amazing the number of applications you find for it.
I like your design John McNamara, it is a good use of laser cutting. Your joint design is not original I'm afraid, here is an example of a 3D printer constructed from laser cut plywood which uses a joint of this type **LINK** I have been using this type of joint for laser cut components for a while now. I don't mean to detract from your work, I've loved your innovative approach in your posting on Epoxy concrete machines. I suspect that this joint has been independently developed by a number of people.
I bought an ER25 collet holder for my Myford Super seven from Chronos about a year ago, it has a run out of about 2 thou (measured on the taper). Chronos replaced it free of charge very quickly. The replacement was much better, but still had a run out of almost 1 thou. I set the top slide to the taper angle using a DTI and the collet holder as the reference, and then used a carbide boring tool to skim the inside of the taper. The collet holder now has no discernable runout.
Carbide tools are much harder than most people seem to realise, it is quite possible to machine most "hardened" steel with them. I succesfully machined the ends of a set of hardened ballscrew spindles for my CNC mill conversion using inserted carbide tools.
|Thread: Kosy nccad8 HELP!|
Glad you've managed to crack it by yourself, it's a great feeling when you manage to cut your first CNC part on a new machine.
It is useful to be able to program parts manually, but once you get a CAM program working properly and directly importing geometry from your 3dsMax you'll never look back.
The screen dump seems to be of a simulator run from some G code that you have hand written. Your code looks ok to me; obviously the outer profile and the four holes are shown correctly. The move that seems to be causing the problem is:
G3 X-30 Y40 J10
The screen dump shows this move correctly, ie a CCW move starting at X-40 Y30 ending at X-30 Y40 with the centre of the arc at X-30 Y40. This means that your system is set to use absolute coordinates, with the I and the J values as incremental.
One slightly unusual aspect of your G code is that you have omitted I and J values when they are equal to zero, and X or Y coordinates when they have not changed since the last move. Some CNC controllers allow this some don’t; your simulator seems happy with this for all the outer moves and the four holes.
I would suggest you try the following on the offending line of code:
1) Explicitly set the I value to 0, just in case, ie.
G3 X-30 Y40 I0 J10
2) Erase the line and then re-type it, in case there are some non printing character embedded, or if you’ve used the letter o in place of the number 0. It sounds silly, but I have seen it happen often enough.
3) Check that there are no typos in the line following the highlighted line, or indeed in the rest of the program, sometimes the location the program stops at is not exactly where the error is located.
The error message is as helpful as most error messages are…. It will mean something to the programmer who wrote the simulator, but no help to anybody else!
You obviously understand G codes, so don’t be afraid to experiment, try different values and shorter program snippets until you find what is causing the error. As far as I can see there is nothing obviously wrong with the program you have listed.
|Thread: Sulphuric acid|
My late Father joined the RAF just prior to WW2 and used to recount his experience of side arm training. A veteran Sergent addressed the assembled office cadets along the following lines:
"Gentlemen, this is a Webley revolver. If you are ever confronted by the enemy I suggest you throw it at them, because it is the only way you are likely to hit them"
It seems to be in line with Cornish Jack's experience!
|Thread: Kosy nccad8 HELP!|
I have 3ds Max 2012, but mainly use Inventor as my design tool. The general workflow to get from a model to a physical part normally requires an intermediate stage requiring a CAM (computer aided manufacturing) program. The CAM program generates the machine moves (normally G codes as you are discovering) from the geometry produced by your CAD program, or in your case 3ds Max.
Having a quick look at the website for nccad8 it seems that it is available in three versions:
CNC, Standard, and Professional.
The CNC version is purely software to control the milling machine motion and cutting spindle. To use this version you will either have to manually write G codes, or you will have to purchase a separate CAM software package (more of this later).
The Standard version is a CNC controller and a basic CAM package. It will allow you to produce 2D parts from your 3ds models. It works basically with profiles of the part; for example if you were to draw a rectangular plate in 3ds with a few holes in the middle, you should be able to export this model to nccad8 and produce the cutting paths from there. The most common format for this type of CAM work is the dxf file format. 3ds Max allows you to export in this format (click the M symbol upper left and click export, a “select file to export” box will pop up… the various available file formats can be seen via the “save as type” text box at the bottom of the box… use the pull down menu.
The Professional version allows full 3D models to be handled. The most common format used by CAM packages for 3D models is stl format…. Again 3ds Max will allow you to export stl files. I’m not familiar with how nccad handles the process of allowing you to generate the cutting paths.
This process of exporting in an intermediate file format is almost universal with CAM packages, unless you go to very high end versions, and even then I doubt you will find any CAM system that directly handles native 3ds Max formats.
If you have the basic version of nccad8 then you might want to consider a separate CAM package. There are lots to choose from, but most pretty expensive, particularly the full 3D versions. A relatively low cost series of CAM programs are produced by Vectric in the UK. www.vectric.com. The two you want to look at are Cut2D (equivalent to nccad8 Standard) and Cut3D (equivalent to nccad8 Pro). The beauty of these is that you can download free demo versions (fully functional except you can only save their sample files). They both come with excellent help files and “getting started” guides. If you work your way thought these (not very complex) you will have a far better idea what is involved generating cutting files from model files, and will hopefully help you understand what nccad8 might be able to do for you.
I hope this is helpful.
Edited By Chris Courtney on 16/08/2012 20:10:00
|Thread: Lithium Ion Batteries|
As Andrew says it is not a good idea to try and “zap” Lithium Ion batteries, they really don’t like being mistreated.
About 10 years ago I worked on an industrial estate adjacent to a company who manufactured mobile phone batteries, including Lithium batteries. One Friday afternoon we heard their fire alarm go off and looked outside to see a small amount of smoke coming out of a vent on the roof. Apparently a fork lift operator had dropped a pallet of lithium battery cells. Within ½ hour the entire roof of this new 50,000 sq ft factory had collapsed and a huge column of multicolour smoke and fire was pouring out. The by the end all that remained was the twisted outer wall. Fortunately we were up-wind about 400m away and were told to stay put by the Fire brigade. I have never seen such an intense fire, with huge amount of multicoloured smoke, it would change from white to black, and then purple as the fire reached various stores of different chemicals. People and schools up to 10 miles downwind were being warned to stay inside.
Because Lithium reacts violently with water to produce Hydrogen, the Fire brigade more or less had to just wait until it burned out; they sprayed water on the office areas and the outside walls, but couldn’t use water on the actual factory space.
I’ve worked with a number of battery charging systems for various battery chemistries, but after watching that fire, I’m always very careful with Lithium containing batteries.
|Thread: Small Steps and Early Beginnings - Flycutting|
There are lots of online calculators for feedrate and cut depths, but most of them apply to heavy industrial machines. The KX3 and the Super X3 are, like most hobby level machines very light weight compared to industrial machines.
I use a calculator called GWizard **LINK** with my CNC converted X3, unfortunately it isn't free, but does come with a 30 day free trial period. The best thing about it is that the associated website and blog contains a huge amount of information about machining and engineering in general (all free). Even if you are not interested inthe calculator the website is well worth a browse.
The advantage of GWizard is that it can be set up for hobby type machines (ie low power low rigidity) and seems to give sensible results. Whilst you can use trial and error for manual milling, because you get a lot of feedback about the cutting conditions via the handwheels, it is not so easy with a CNC mill.
One approach is to use GWizard for a trial period and estabish some good cutting conditions for your machine with a range of cutters, then simply make a note of the cutting conditions, which you can then use when the trial period expires.
|Thread: Which New Mill Vice?|
The two end jaws are accurately located in machined recesses, it is only the centre "fixed" jaw that can be adjusted for alignment. There used to be a data sheet on the Warco website which showed the various combinations of jaw and workpiece positions.... it was a little cryptic, but once you have played around with the vice for a bit it makes sense.
I'm not sure what Roger regards as a heavy cut, but I've never had any problems with any cut I was prepared to take with an X3! I have however removed the swivel base from mine, I find that it is not particularly useful with a CNC mill, and removing it does increase rigidity a little.
I would recommend getting the extended height jaw set, the standard 25mm high jaws are a little small for many jobs.
I have had a DH1 vice for about 18 months, which I use on my CNC converted X3 Mill, I too purchased it from Warco. Mine was shipped in a plywood box rather than an MDF one, my box also had some transit damage due to the vice moving about, although the vice itself was undamaged.
I have to say that I am generally very happy with it, and it has proved to be a very versatile vice. It is capable of holding much larger workpieces than other vices of similar size. To achieve this the vice is very unconventional. The outer two jaws are located on a moving bar, and the centre jaw can be fixed in a number of positions. The centre jaw is held by two M8 bolts. To get the fixed jaw parallel with the moving jaw, you need to slacken off the two M8 bolts on the fixed jaw and then close the vice and press the fixed jaw against the moving jaw (or use a parallel spacer) and then tighten up the M8 bolts on the fixed jaw. The lack or parallelism between the jaws you are seeing should be easily corrected as described above. You need to do this every time you move the fixed jaw position.
The only problem I have found with the vice is that the 3mm rebate on the jaws has a slight radius in the corner, which makes it difficult to hold square edged components.
|Thread: Fan motor|
I agree that a minimum 5 year lifetime for a cooker should be reasonably expected, and that Clive's experience of a failure afer 3 years is exceptional. I would hope that he would be able to get legal redress if necessary. Fan ovens do seem to suffer from a problem with the motor bearings. I had my previous fan oven for about 20 years, and had to replace the fan motor after about 10 years of operation, followed shortly by the heating element. When the fan failed for the second time my wife decided that she wanted a new oven so I didn't get the chance to replace the fan again.
My point about the designers choice of fan bearing still stands. On average a typical fan oven probably only operates for a few hundred hours per year, so to achieve a 5 year operating period they are proabably only need the the average fan to last for 3 or 4 thousand hours. A small number of early failures are probably much cheaper to deal with than to increase the fan cost to improve the operating lifetime. I'm not saying I approve of the approach, but is the norm these days. I expect many perfectly good ovens are replaced simply because the owners want a new one to go with an shiny new kitchen.
The only lubricants I can think of that will operate at 200 deg C and above are silicone based oils and greases. They are not ideal lubricants, and I'm not sure if they would be suitable for use in a sintered fan bearing. As Ian has suggested I imagine that the actual bearing temperature is kept rather lower than the oven temperature by the air flow from the fan. The designers have probably simply used a standard sintered bearing with mineral oil, on the basis that it will last for a few years and then the entire fan assembly will be replaced.
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