Messages

51

Show"N"Tell ( Your Machines) / Re: Plastic Injection Molding

« on: January 28, 2014, 08:28:15 AM »

Interesting project. I used to have a bunch of hand operated molding machines in my workshop 20 years ago. A couple of them are still stashed away in the attic. Those machines were used to produce low volume production parts and gave out good, precise results from ABS, PP and Acetal. We used virgin and dyed plastic pallets and mostly CNC machined mild steel molds.

Zafar

The single mold I have made for this machine, is made from an aluminum cast. I machined a wooden pattern out of oak, and used it to form the sand mold from which I cast the mold with molten aluminum. This project has been a many-faceted challenge, that is still in progress. The first attempt, (using plastic soda bottles, which I cut up into .500" square flakes) taught me the importance of starting with plastic beads, or at least something small enough to simply be poured into the cylinder, and immediately injected into the mold.
 If one takes the time, to drop them into the cylinder just a few at a time, then what happens is the first few get so hot, that they actually burn before enough flakes can be dropped into the cylinder to fill it. Another item, also learned thru experimentation, is that the mold itself must be heated along with the cylinder.
  Otherwise, when injecting the plastic into the mold, what happens is that the fill port of the mold is all that ever gets filled, before the plastic solidifies (and therefore closes the fill port). The current status, is to build another machine to chop, or grind the plastic soda bottles into much smaller pieces, so that the cylinder can be filled immediately (and the plastic immediately injected).
   The mold heating problem can be overcome, by simply allowing the injector assembly to rest in contact with the mold. I do not have the resources to order plastic beads to test the machine with, so at this point it will have to wait until I can devise a method of producing much smaller pieces to fill the injector cylinder with.

52

G-Code, CAD, and CAM discussions / Re: Table not flat to X-Y plane

« on: January 23, 2014, 04:29:47 PM »

I have a routing table X-Y-Z that the cutting surface in not perfectly flat.  So that when i route something into a piece of material the depth of cut is not uniform.

Is there a way in Mach3 to compensate for non-uniform z-axis depth cutting?  I there a g-code that i can use or calibrate to my table for the z-axis?

Mike

Try this: create a pocket program (just a simple square or rectangle into LazyCAM) and run the gcode produced (the pocket program) to effectively "Plane" the pocket. It should produce a smooth, flat finish. If it does NOT, then you have issues with your Z axis. It could be something as simple as loose mounting bolts of the router clamp, or the Z axis Nut assembly. Or even your current bit is not locked tight enough in the chuck- slipping it's grip on the cutter. Tables which are not perfectly flat, should still yield a perfectly flat pocket, when cut as described above (in relation to the Z axis of your machine). I.E. if the table is not level in relation to the Z axis, then the imperfections (or degrees off from level) will be visible on the BOTTOM of the work piece. The TOP of the work piece should turn out as "perfectly level" with the Z axis. In other words, the work piece will be thicker on the down-hill side, and thinner nearest the up-hill side of the work piece.

53

G-Code, CAD, and CAM discussions / Re: cnc6040 + gecko 540 = many questions

« on: January 23, 2014, 04:17:03 PM »

Home switches are almost a requirement, if you want to "Save Fixture Settings" (I.E. the machine's current position) when you exit Mach3 to turn the machine off. IF the current position of the machine, is your current work offset Zero position, then when you power up the machine (and Mach3), click the Zero X Y and Z DRO's, then rehome the machine. Then click Goto Zero, and it should return to where it was at the time you shut it down. The key is using the home switches. Without a physical frame of reference, (the Home Switches) Mach3 only knows what you tell it. Just don't forget to follow the above steps in exactly the order described, or you will lose your last position!

54

General Mach Discussion / Re: Optical Registration Mark Reading With Mach3

« on: January 15, 2014, 12:51:42 AM »

Not trying to discourage your efforts to find a programming solution, but if I were doing mass production of something like this, here is what I do:
Mount a spoil board onto the table, and use a drill to locate your registration marks on the substrate. Install alignment pins into this first piece of substrate, and into the spoil board. Run your gcode to cut out your profile of this first piece. Remove the piece, and mount the second (and each subsequent piece) onto the alignment pins of your spoil board (after drilling the holes at your registration marks of the piece), and run the gcode again. Sometimes, the simplest solution to overcoming technical limitations can be achieved by just looking at the actual task at hand. (NOTE: locate these registration marks in an area of the substrate that is to be removed, when cutting the profile- this will eliminate the drilled holes from the finished product!) Hope this helps.

55

Show"N"Tell ( Your Machines) / Re: Plastic Injection Molding

« on: January 10, 2014, 11:32:42 PM »

Well, the weather finally warmed up here (after 2 days of dealing with busted water pipes!). So I got back in my shop today, and took a few photos of the machine. The original design I saw on Youtube was a gizmo the fellow had mounted in the chuck of a drill press. Not willing to tie up my drill press for such purposes, I set about re-inventing the wheel (so to speak). I built a rack and pinion out of oak, which was carved by Mach3 on my CNC Router table. I mounted an aluminum block, which I had bored to function as the combination heater, and injector assembly. This block has four 350 cartridge heaters installed (one in each corner of the block, with the center bored 1" diameter to accommodate the 1" diameter plunger shaft). A cheap chinese purchase on ebay for the heat controller yielded a box which is at least useful for measuring the temperature. There is no output voltage to the relay, but is still useful for controlling the heat manually. (When the output light is on, I turn the heaters on, when the output light goes off, I turn the heaters off). This was my first purchase from a Chinese dealer on ebay, so.... Anyway, the first test of the machine revealed the importance of acurate heat control. Also, the reason the fellow I saw on Youtube is selling plastic beads for the injection molding machine he was selling. My thoughts of slicing up soda bottles, and feeding them into the funnel mounted on top of the aluminum block failed. The reason being, by the time one is able to drop enough of the little 1/2" square flakes of plastic into the cylinder to fill it, the plastic in the bottom is charred! Further experimentation with lower temperatures is on the agenda. But I can see a definite advantage in buying plastic beads which can be quickly poured into the cylinder, and immediately plunged into the mold. This project has been a real learning experience. The actual mold was a challenge in itself. I carved a wooden pattern using MechCAM Art of a 3D Heart with a Holy Cross in the center. Two concave images were carved into oak, to form the pattern for the mold. This pattern was then used to form a sand mold, and the actual mold was poured with molten aluminum from my foundery oven. After cooling, I mounted the mold onto my lathe, and faced off the mating surfaces of the mold to machine them flat. I then drilled guide holes in one half of the mold, and ended up carving a wooden positive image of the mold to act as a "Key" for aligning the first half of the mold to the second half (in order to determine exactly where the guide holes for the second half of the mold needed to be drilled for perfect alignment with the first half). I.E. I inserted the wooden Key into the first half of the mold, and placed the second half of the mold also onto the Key, and used the guide holes of the first half of the mold to locate the guide holes for the second half of the mold. I determined that the prime location for filling the mold was the base of the Heart, therefore the Heart would be injected upside down. I scribed a line from the center of the base of the Heart, to the edge of the mold to determine exactly where it needed to be drilled, then placed the assembled mold into the drill press vise, and drilled the mold halves at centerline where the two faces meet. I then filed two small scrathes into the face of one half of the mold, to create overflow ports to alert me when the mold is full. The machine I built features a vise assembly for holding the mold in alignment with the injector assembly. Linear rails were used to guide the injector to the center of the mold. However, further work is needed in my design. A locking mechanism needs to be added to keep the injector nozzle firmly inserted into the mold, while plunging the plastic into the mold (because the back pressure pushes it back out of the mold- I learned this the hard way). Anyway, here are a few pictures of the machine so far. Notice the "guillotine" shut-off valve. It's just a piece of angle steel mounted on a ball bearing slide assembly which is spring loaded. A wooden handle was needed to prevent burned hands, when opening the valve for a charge into the mold. The spring load was needed to immediately slam the valve shut, once the injector assembly has been raised 1/8" off the surface of the mold. It will probably take me a few days of experimenting with different temperatures, before I will get a successful cast. I have already learned, that if the plastic is heated too hot, or too long, it becomes a useless mass of brittle, black plastic. Instead of the clear plastic it started out as.

56

Tangent Corner / Re: Cheap but sturdy 4th axis

« on: January 07, 2014, 10:47:41 PM »

I reviewed the drawings in my Owner's Manual, and realized that there just isn't much detail (or focus) on the 4th axis that I added to my machine. (See the attached file MyCNCV2Design.pdf)
But if you look on pages 9-10 you can see the jist of the 4th axis construction. It's basically just a 2" diameter shaft which I turned on the metal lathe down to 1" diameter on each end, and mounted thru 2 self-aligning bearings (surface mount type) driven directly with a toothed belt and stepper motor. The turned-down ends created a shoulder on each end, which I seated against the bearings (to prevent end-to-end sliding movement of the "Headstock" assembly).
It had the end result of converting my 3 axis router table into a combination mill/lathe. I toyed with it only briefly after building it, but rarely use it these days. I have a 6" diameter 3 jaw chuck mounted on the 4th axis, but usually just use a wood lathe center plate on both the headstock end, and the tailstock end (since wood is all I do on this machine, most of the time). The stepper motor I am using to drive the 4th axis is a 1200 oz in NEMA 34 model (after learning that the 900 oz in model just wasn't up to the task). The orientation (parallel to the X axis of the table) will allow pieces up to 8" diameter x 36" length to be mounted. (Assuming the material is something light weight, such as foam or something when working with something 8 inches in diameter). All that I have actually tried has been 4" diameter, or smaller pine or oak. As for "Cheap", I probably have about $400 invested in the large stepper motor, and the self-aligning bearing assemblies, as well as the toothed belt pulleys and belt. It would probably be about the same investment to make one using a horizontal/vertical rotary table and motor with lovejoy couplings on each. Such a design would have the advantage of being able to switch the orientation from horizontal to vertical without a complete rebuild of the machine. However, the trade-off would be the speed reduction (of the worm gear driven rotary table vs direct belt driven shaft). Anyway, take a look at the PDF, it should give you some ideas.

57

Show"N"Tell ( Your Machines) / Plastic Injection Molding

« on: January 07, 2014, 06:56:40 PM »

I am aware, that this is not a mach 3 project (although mach 3 was used in carving the pattern for the actual mold). But I thought that I would post this here, to see if others have tried such a project. I started construction on this machine 2 months ago, and am finally down to the final stages of being ready to test it out for the very first time. (However, a cold wave has invaded Georgia, and it is simply too cold to be out in my unheated shop for the next few days).
The inspiration for this machine, was (of course) a You tube video. As a way of recycling plastic soda bottles, etc. Although the first one I saw, was actually marketing a kit for installation onto a drill press (and selling plastic beads to feed into it). In my case, I have sliced up several empty 2 liter soda bottles into little squares about 1/2" each. And designed a funnel opening on the machine into which I can pour them for melting.
Anyway, I am just curious to see what others have done along these lines.
As I said, it is COLD here now, so I will post pictures in a couple of days when the weather warms up enough to take the camera to the shop, (without fogging the lens!).

58

Share Your GCode / Re: mac logo

« on: December 29, 2013, 09:05:15 AM »

Hello,

which program you use that it have exstansion *.nc.
There are many programs that produce gcode with the *.NC extension. The file itself, is actually a text file (and can be opened and edited using MS Notepad). The default gcode extension of files in Mach3 is *.tap Although it too, can load and run text files, as long as the gcode they contain is in the correct format. I use MeshCAM Art to produce the gcode for 3D carvings (which outputs the files as *.NC) this makes it easy to distinguish which files are 3D sculptures (*.NC), or simple cut-out programs (*.TAP). Hope this helps you in understanding the differences.
Thank you for answer.

Best regards, G

59

Show"N"Tell ( Your Machines) / Re: Gantry Width

« on: November 10, 2013, 01:08:14 AM »

If you design things (especially things like limit switch mounting) to be adjustable, it makes it possible to "Dial it in" to whatever position is needed to achieve as near perfect as is possible. It seems that no matter how precise the build, there are always those one or two things that just aren't quite right. Designing critical components to be adjustable with things like threaded jack screw holes, and/or slots for mounting bolts can make life much easier. (As opposed to disassembling, cutting, grinding, filing, sanding, etc.- which is usually the alternative when adjustability of the design is not utilized during the design phase). This important tid bit is usually learned at the School of Hard Knocks (experience).

60

Tangent Corner / Re: Thats Bright!

« on: October 31, 2013, 04:09:52 AM »

I too had trouble locating a bright white LED light, so I ended up buying an expensive unit: A 9-LED flashlight sold for $2 at the autoparts store. A $5 transformer, to power it with. A couple of feet of speaker wire, and a couple drops of solder, and it works great. I eliminated the body of the flashlight (which originally used 3 AAA batteries), and just soldered the speaker wires directly to the head of the flashlight. Mounted it onto a piece of flexjoint (that plastic stuff normally used for directing coolant). Makes it easy to position where ever desired. Went through two of these flashlights, before learning that a heat sink MUST be used, when soldering the wires to the head (the LED's are VERY sensitive to heat). Total investment: about $10.