Starplates by CNC

[pyromagi]

Hi guys,

I'm fairly new to this forum (and to pyro), but i have managed to write some posts

I have been hooked on pyrotechnics and have decided to try and setup a good workshop.

Therefore I'm looking to make my own star plates, and i actually got a really neat CNC machine at my disposal.

Here is a picture of earlier today when i was cutting up brass cylinders, the CNC machine is in the background.

 

Pic: http://imgur.com/lYTAZyW

 

My only concern is that i don't have a clue how to create the models that the company need.

Does anyone have 2D/3D-models that they could share with me?

Or the measures for 1/4" 3/8" and 1/2" starplates?

 

I would happily trade a starplate for a model, if anyone would be interested in a new starplate.

The company does mostly aluminum work, but brass and plastics are also available.

 

Kind Regards

Pyromagi

[WonderBoy]

Do you know what type of file the machine runs on?

 

 

WB

Edited April 16, 2013 by WonderBoy

[FlaMtnBkr]

I don't know what kind of code/ file the machine runs on but I think most can convert various CAD drawings fairly easily. You can ask what CAD software can be used and most should have a free simplified version you can draw with. That or there should be a native software that you can draw with. Contacting the company or the owner of the machine should tell you what you need to know. A star plate is fairly simple, being a block of metal with holes in it. The biggest decision will be if you plan on using metals in the composition you press. This will determine the clearance between pin and hole. If using metals you will have to use strict and precise screenings of the metal you plan on using or it will bind in the plate anyways. If you don't plan on using metal it will greatly simplify the design, though there are some techniques that will allow it's use.

 

I would say to talk to the owner of the machine and describe what you want to do and they can probably quickly point you in the right direction.

[pyromagi]

Hi, I spoke with the operator of the machine and he said they could convert/modify most CAD models to work with that machine.

But if it was possible they would prefer step files (*.stp/*.step) but AutoCAD (*.dwg) or SolidWorks (*.sldprt) would also work.

 

The company only do manufacturing, they don't have anyone that draws the models, and they are rather busy at the moment.

Still they let me use the machine after hours.

 

FlaMtnBkr, why don't make star plates that covers most stars? Since i have this opportunity with the CNC machine i would like to cover as much as i can. So i would be very grateful if i could get help with the models.

 

Kind Regards

Edited April 17, 2013 by pyromagi

[Mumbles]

What FlaMtnKbk was talking about is that coarse metals tend to cause problems with star plates. Star plates can make any kind of star you want, you just need to tailor some things. If you plan to use coarse metals, especially titanium or ferrotitanium, you need to plan ahead in your design. Decide what sizes of titanium you want to use first. What you want to avoid is metal particles getting lodged between the plunger and wall and tearing up your pump. The general rule of thumb I've seen is that you need to avoid particles between 2x and 1/4x the clearance between the plunger and the wall. Some say 1.5x on the large end, but wouldn't cut it that close personally.

 

For instance, if you had a 100mm ID pump with a 98mm OD plunger, you need to screen out and remove the metal particles between 3 or 4mm (depending on who you ask) and .5mm. This was just an example, chances are your star plate will make much smaller stars and have tighter tolerances. The general rules of thumb still apply.

[pyromagi]

I would just like to get started with pressing stars, mostly for starmines and/or small shells.

So i guess it will take some time before i will use coarse metals in the stars.

 

I do appreciate the feedback/information.

 

Kind Regards

Pyromagi

[SekndAmendment]

Most CAD packages offer student or simplified versions like FlaMtnBker said. Those are great if your goal is learning the software. If you actually want parts made, many of those typically aren't going to work. Nearly all free versions of CAD that I've used will allow you to make 3D models and 2D drawings but the drawings print with enormous watermarks saying, "FOR EDUCATIONAL USE ONLY" over so much of the drawing that it's unusable, and the models can't be transferred to a professional license to print either. The temptation for small businesses would be too great. If you owned a small company it would make much more sense to purchase 1 professional license at $20,000 to use for printing and 19 licenses of student versions at $100 for your engineers to model on, instead of 20 professional licenses at full price. Because of that temptation, the .stp and .igs file formats are not accessible on many free or student versions of CAD programs.

 

You could try Autodesk Inventor. That one is probably the cheapest full license program so there is a good chance the free versions will have a bit more capability. If those don't work I think you could try the $100 student versions. There are some great tutorials on YouTube and you'd be able to put together your starplate in a weekend. The machinist that runs the CNC mill can help you pick spindle speeds and feed rates for the materials you're cutting. Mumbles had some great advice about tolerancing. Make sure your plunger OD has a radial separation smaller than the grain size of your metal powders. Titanium or any ferrous metal is much harder than aluminum or brass and it will destroy your plates if it gets caught in the gaps.

 

Do the machinist a favor and find out where his favorite places to eat are and bring some gift cards with your starplate files, or maybe some 12 packs of his favorite soda/beer. A little appreciation goes a long way.

Edited May 6, 2013 by SekndAmendment