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Serious Homemade Manufacturing Equipment on a Shoe String Budget

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This is an instructable to show you how I took an idea I had for a machine from the 3D into the real-d and how you can apply the same techniques to your design problems.  My wife and I run a small 3-year old product design, manufacturing, and retail business named Past Primitive (www.pastprimitive.com).  As we have experienced more success, we needed a way to keep up with the manufacturing pace required for one of our popular products the Past Primitive Pocket Stove.  One of the biggest bottlenecks in the process was the porting--putting the holes in the stove where the flame comes out.  

We operate on a cash only basis for all our purchases and investments.  This means we have less flexibility to grow quickly, but on the flip side are much more stable and able to weather hard times without feeling pressure because we have no debts to pay down. 

 
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Step 1: Research & Resources

Determine...

The first challenge is to determine which manufacturing problems are deserving of mechanization, or are best handled by your own skilled hands.  How you determine this will depend mostly on the resources you already have available and how much your time is worth to you.  Starting out our time was so cheap, we were willing to do many processes by hand, but as we achieved more success and needed to increase our manufacturing capacity while maintaining quality and be fast enough to allow us to focus on the many other important aspects of running a business e.g. actually selling the products we manufacture. We realized we needed to either streamline our process ourselves or outsource the manufacturing.  Traditional manufacturing channels are often very expensive for short runs, so those were out of the question considering the financial capital we could invest and our lack of desire to go into any debt.

So how did we know which process to streamline first in our stove manufacturing? Most of the time I believe this is quite obvious, it will be the task you dread the most at any given time.  It was no different for us; the mention of porting more stoves after the hundreds and hundreds of stoves I have ported made me want to hide under the sheets and cry.  But when you have a dream and passion for your business you push through that feeling and just cry and hide under the sheets when you go to bed at night.

And after more thought about the numbers behind the porting process we determined the biggest road block to efficient and quality manufacturing of our alcohol stoves was the porting process for the jet ports (that's where the flame comes out).  There are 24 holes in each stove. After a few dozen stoves that adds up to a lot of holes.  At first we used a custom template and a hand punch to punch the 24 holes.  This took 1-3 minutes per stove depending on how focused I was at any given time (the longest part in the whole manufacturing routine).  After doing a dozen or more stoves, maintaining concentration became a major challenge; not to mention the ability to just keep up such a monotonous task at all.


Research and take account of resources...

Once we determined what we process we wanted to enhance, the research phase began along with taking account of what resources we had available to us.  I looked to the Internet, fellow professionals, friends, family members, anybody who may have input on how we could streamline the porting process.  

I broke down the manufacturing problem into sub-problems and researched them individually. This can be informal, something you do in your head as you go, or if you like the allure of recording your thoughts in the real world, write it down. I think it's important to note that during this discovery phase, research and accounting for resources are integrally linked.  

That's a good thing; being linked helps avoid unnecessary work.  For example if I know that I do not have access to a CNC router as was true in my first attempt to solve the porting problem, the processes I would study to help build the different solutions to the problem at hand would exclude CNC build techniques.

Also this outline process provides a chance to start defining important issues such as tolerances of your quality control, desired speed of the process and other factors that are necessary for the machine to meet your requirements of use. Some will be obvious others will be discovered after first prototypes.  Do your best to be thorough, but don't let a lack of vision, knowledge, or solutions stop you from moving forward with your ideas.  Often the problems that need to be solved or how to solve them will not become apparent until you've started crashing through the steps clumsily. Look at this outline as a rough draft for an outline of a big paper you are going to write.

Below is an example of how I informally broke up the issues that needed resolved to build a machine to port the stoves, took accounting of the resources I had available, and defined target requirements to make the machine useful. These will help keep you focused.  I am not going to go into the details of what I discovered from my research in this step, I will share that in the later design and build execution steps.


End Destination: A custom tool that increases speed of porting stoves, maintains quality, and allows any lay person to operate.

General Requirements:
  • Index 15 degrees 24 times around a circle with less than +/- 0.005" accuracy of port placement from port to port.
  • Be able to port a stove blank in under 30 seconds.
  • Load and remove blank in a few seconds.
  • Be operated by unskilled person safely.
  • Be durable, be capable of porting hundreds if not thousands of stoves before part replacement. 

Mechanical Sub-system Issues to research: 
  • How to time porting punch-to-punch, 1 hole per 15 degree rotation?
  • Power source and power transmission system to be used?
  • How to secure stove top blank for the porting process?
  • How flexible should the system be, should I be able to vary number of holes, and angle at which blank is ported?
  • Materials to be used?

Available Resources:
  • Metal Mill
  • Metal Lathe
  • CNC Router with 25" x 25" work envelope
  • Standard Wood Working tools
  • Welder
  • 1 Ton Arbor Press
  • 12 Ton Shop press
  • As much money as my wife will let me spend ($55 in the end)
  • Electrical Engineer Brother
  • Mechanical Engineer Friends
  • CAD program

An interesting point. The problem that proved most difficult for me to solve at first was indexing the blank 15 degrees reliably within the +/- 0.005" of hole placement every time. I went through several designs before I attempted to build one and have it be a big failure.  It didn't even hit the mark of indexing the blank anywhere close to 15 degrees.  Ironically that design was the most expensive and time consuming to build. It's also the idea I thought was the most fool-proof.

This demonstrates a key point that I would like to share. The best laid out plans can fail miserably.  Once again during the research and resource accounting step it is not as important to know everything as it is to keep moving forward regardless of how clumsy and disorganized you feel. You will need to plan for failure, that's not to say you shouldn't hope for success but remember the wisdom that "failure is always an option."


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ajones979 months ago
That stove looks a lot like a coke can penny stove. Alcohol?
albertjo1 year ago
Traditional manufacturing channels are often very expensive for short runs, so those were out of the question considering the financial capital we could invest and our lack of desire to go into any debt.chorusdesign
njords2 years ago
very good posting - a comment I'd like to add (I'm an equipment/tooling/machine designer btw) is in the repurposing of equipment as well. Takes a bit of thinking outside the box so to speak at times but can be solution to things.

for example if you had one of these http://www.busybeetools.com/products/SPIN-INDEX-5-C.html kicking about or spending the 60$ was no big deal then there would be your indexing requirement taken care of I've used little guys like these mounted in different orientations for angle indexing in both custom one of machines as well as manual lathes & mills.

Now everyone has a different set of resources laying about of course. My solution to this would be using an air powered expanding collet that has a foot switch mounted to the indexer that I mounted to an angle plate mounted to a drill press fitted with the appropriately size end mill. I happen to already own all the equipment.

So operation would be after set up & test runs to "dial things in" then press foot switch to collapse the collet, put a body on the collet, release foot switch to grip the body, then with press running mill 1st hole, spin handle to next index, repeat until desired number of ports finish, collapse the collet remove/replace the body repeat.

Same as yourself tieing up my mill to run something like this through would be inefficient.

Often for solving puzzles like this I leave my computer & go sit in the shop and spin around on my stool seeing what can inspire me :)
pastprimitive (author)  njords2 years ago
Yeah, I looked at using an indexer initially and would have probably done that except I wanted the process to be automated, at least automated for each blank so I would just have to put a blank on the holder, turn it on, and it would finish itself off. I still have yet to implement the auto off feature. But it will be similar to a two way switch system with one push button switch to turn it on, and another switch attached to the indexing wheel of the blank holder so that when it completes a full rotation it will turn the machine off.

I too like the idea of an expanding air collet, but I was unaware they existed. Or at least existed at a price I could afford. And I know what you mean about going into the shop and just sort of look at things and mess around to get ideas flowing. One of my favorite places to think is to just lay down on the bed and go into design la la land. Plus I often get a chance to rest.

Thanks for opening my ideas to the expanding air collet, and the decently inexpensive indexer. I took a look at it, the only issue was that it didn't look like it would index 24 holes? I am assuming they have all sorts of shapes and sizes.

Thanks again.
a simple light sensor and reset button will do the trick
I see the superlative contents on your blogs and I perfectly enjoy going through them. No1partypills

that particular indexer doesn't have the 15º indexing (24 holes) but it's not the only indexer out there of course - I machined a new plate for mine with 24 holes it's a pain to take the indexer a apart to switch plates for smaller jobs one day I'll break down & spend the $60 for a 2nd one then leave it set up.

in regards to the air collet like I said it all depends what you have around the shop - admittedly if I didn't already own 1 I wouldn't go spend the $600 plus to buy 1 for this kind of job either :-)

You got a very slick little self contained design going there. I'd be interested in how long the wood gears/parts hold up & keep sufficient accuracy. A future upgrade to Delrin or Nylon for the gears/parts that don't hold up long enough maybe.
gear teeth was made out of wood for many years for some larger machinery, they had a metal body/carrier, but the gear teeth was wood and easy to replace when they wore out, plus they also were very easy to make since all you had to do was make one really wide tooth then just cut off to exact width. This was done to save two resources, time and money and it is simple for semi skilled worker to make.
pastprimitive (author)  njords2 years ago
I am also interested in how many I can put through before the gears wear out. I think the wood gears will probably outlive the need for the machine. They can lose a lot of tooth before there are any problems. There are two areas of importance for complications due to lack of precision from wearing parts; the aluminum cam that pushes the steel punch, and the plastic ratchet gear and arm. Fortunately both parts are incredibly easy to fabricate. I have the file for the plastic ratchet gear and arm saved, and takes about 20 minutes to cut out a new one on the CNC router, and the aluminum cam can easily be machined in 30 minutes.

So as long as I can put a few hundred stoves through each set of gear, and I am guessing I can put a couple thousand through, I don't mind changing those parts out often. Although it would be nice to not be doing it as often. However, I suppose there is something to be said for designing parts for planned failure. At least I know, probably, maybe:) what parts will fail.
Bonecaya2 years ago
A Geneva motion drive could have also been used to get the indexing. I quickly drew up an example ( not to exactly to scale )


geneva.jpg
padeutsche2 years ago
It is amazing that this manufacturing machine is made from wood and it works very well, and replacement parts will be easy to produce and it is powered by a hand drill. Very nice work and very impressive use of the KISS principle of engineering .
pastprimitive (author)  padeutsche2 years ago
Thanks. Wood is amazing stuff. When you don't have lots of capitol to invest it encourages you to think a bit different about your problems. In this case I think a much better solution was devised as opposed to traditional tooling techniques.
jamstir2 years ago
Hey.. well done.. I have a few Q.. for yourself, I going to build a CNC milling machine using servo motors/ steppers/ etc, and use Mach3. Now i come from 16 years welding fab and operating or designing using Cad is all new to me, from what i been reading, can Cad design be used to put commands into CNC Mach3?

What i looking is an easy way to tell mach3 what i want it to do.

I have to say again well done on your business, i come from the UK and its manufacturing is near died, so died in fact 5 years ago i had a small workshop were i would build gates/railings/trailers/ and general welding fab work, China at the time were building Shenzhen and bought a lot of steel up, so the price of steel in the UK went up by 3 times the price over night, then the property crash happened and it all went pear shape.

Last year i reg.. a new company within the UK { supply } and i took of into China, everything is near made here, or at least you can get a copy of it. lol
The supply company not doing to good because i am taking a cut and acting as a middle man between people. also China is about to reach its Global export market, which means unless they build a complete new country it cant grow anymore. This will have a knock on with a lot of company,s.

Which takes me back to start manufacturing again, only this time i will be doing it in China, so many company,s have come here from the west due to cheaper labour cost and import tax is lower than manufacturing cost, or it is in the UK anyway. I looked into plastic injection machines and wanted to start making my own plastic moulds for pc tablets and other after market kits like Apple cover,s etc. Which lead me to a big problem... to get a company to make a metal mould for the injection machine is costing anywhere from $5.000 to $50.000 depending on how complex the mould is. So looking at making my own metal moulds brought me to looking at CNC machines here in China, and to be honest at a cost of over one hundred thousand USD thats a no go.. lol I went and looked at one of these machines and the driver,s and motors are not even a brand name from the west. After looking on youtube i found guys that were building these out of wood and some cases aluminium, which is all fine for milling wood/plastic but not when it comes to + / - 00.5 milling metal.

So now you have a clear idea what i up to, can you shed some light on CAD and running Mach3, i am very good at operating programs and working with pc,s linux manly, which i might add is by far better than windows. I am half way though completing my own web site using an old pc with linux, if i had have tried this using windows there would be no end of problems raging from port forwarding to keeping none static ip address up to date.

Anyway, once again, well done and i hope your business all the best.

pastprimitive (author)  jamstir2 years ago
Any decent CAD program (Autocad, Solidworks, Turbocad, etc...) should be able to save files into the appropriate format for your CAM software. Although those programs are not necessarily my recommendations just ones I know about. I am sure there are plenty of other options, probably even some open source ones as well. I believe Mach 3 is a controller software, but it does not have any CAD or CAM functions.

General Design Workflow for CNC Machines:
  1. Design part, product, etc... in CAD (Computer Aided Design) program.
  2. Export file into your CAM (Computer Aided Manufacturing) program and create tool paths for CNC.
  3. Save tool path file for use with your CNC controller software (Mach 3, etc.)
  4. Using CNC controller software execute tool path file and let your CNC machine go to work.
Of course there are some software packages that combine the rolls of the CAD, CAM, and Controller software into one program. Although I have only seen that for consumer use cnc products like vinyl cutters, etc... However there are a few CAD/CAM combination programs out there.

As far as building your own cnc I have seen some people do some nice conversions of mini mills and mini lathes for an extremely affordable price of around $2,000 - $3,000.  I know LittleMachineShop.com sells a prebuilt CNC mill for $6,000 or $7,000.  

There are also online services like emachineshop.com that will take your design and machine it for you.  Although those service are very pricey.  But could provide you a way to get up and running with your production and earn some more cash to buy your own CNC set up if capitol is a challenge for you.
 
Anyhow best of luck with your endeavor and I hope that was helpful.
Permit me to answer that, you could go indeed the way of Mach3 and fork out cash or you might take a peek at a linux-version centered around CNC called EMC-linux which is an UBUNTU with enhanced features.
You will probably interject and say "But I want support! " but then would give the riposte and tell you that support comes in form of forums peopled with persons who used this distribution before and who give their advice for free.
Several other GPL-cad programs have a G-code generator.
And also have a look for DIYLILCNC , this looks a very promising project , one of its creators has a youtube-tut on how to convert a bitmap-drawing into G-code.
Very nice work and great explanation of process etc...It is always nice to see how other people think their projects. I do some laser cutting myself and find the process of laying all the parts flat a real pain. There is still huge opportunity in the improvement of these workflows for the future.
Thanks for sharing.
pastprimitive (author)  technomupet672 years ago
Thanks. What software do you use for the CAD work?
That's great - I love the machine you've built.

Best of luck & success with your business.
pastprimitive (author)  simonrafferty2 years ago
thanks.
svereecke2 years ago
Your right about Blender not being suited for CAD , it is a visualisation package (CGI), but there is an alternative to AutoCAD called FreeCAD.
On the sourceforge site it is available as Win/Mac/ Linux program.
http://sourceforge.net/apps/mediawiki/free-cad/index.php?title=Main_Page
Although it is continuous development ( as most linux based products are),
it has ripened enough to be used for small design projects.
it uses an Inventor approach for designing and has multiple other uses
( even a robotics workbench).
As I am partial to the linux ,my version is continuously updated via the package manager.
pastprimitive (author)  svereecke2 years ago
Thanks for the heads-up. I may have to download a copy and try it out.
I think there is a few scripts that one can run with GIMP that is used to convert the formats. I knew of a friend long a go that done something like this. I do not know if it was his homegrown script or if he got it from a freely available resource. he was a good code hacker he might of chopped it out of other software.
perfo2 years ago
Nice instructable,
I think maybe you missed a point in your design ethos and that is sometimes designers go with a particular design just because they like it and knowing it may not be the best or the easiest. I guess this may be the case here where even if you'd thought of a much easier way of doing it, once the idea of cogs and timing devices entered your head it was a must do. After all, that mind set is how we progress things.
As for this design it's pretty good and interesting on all angles but maybe not the best fit for your product. You have a weak point which you had the most difficulty in setting up and that was the accuracy of the indexing. This indexing maybe the thing that will drift over time and wear but could be designed out. I think you mentioned you had tried a punch and die set up but gave it up due to the holes having to be at an angle. This is fairly easy to get around by using a multi stage punch with the hole punchers penetrating then retracting. The advantages of the punch are, little change due to wear and greater reliability due to no timing components. The punch could push the work piece off itself on the up stroke (or use compressed air) and you could have a magazine of stoves to feed in to it and thus get the production time down to maybe 2 or 3 seconds. The other nice to have function of a punch and die is you could stamp a nice logo on to the stove at the same time. Please don’t take my comments as a criticism as that’s not what I intended I’m just offering discussion points. The down side of the punch of course would be a nowhere near as interesting instructable.
pastprimitive (author)  perfo2 years ago
That is correct that i have tried the punch and die set, and the main problem is that the punches for the holes need to be angled in. After 24 angles in points, 360 degrees the blank became trapped. So than It was going to include 24 spring loaded punches that would retract in order to release the blank. That was the main challenge I ran up with that solution.

Of course it could be done, but my resource pool was not a good fit for that type of machining, and build. The other issue I had with using 24 punches with a central die was that I had to machine 24 punches with a high degree of precision for my little machine shop. While not impossible very time consuming for the tools I have access to. For my available resources it's very easy for me to replace the ratchet gears and other items related to indexing to restore accuracy, because I can simply cut out a new ratchet gear and ratchet arm on my CNC router in 20 minutes or less including setup.

But I definitely agree that often we get stuck on a particular solution, and have a hard time seeing past it because of the emotional appeal inspiration carries with it. Even when it's not really the right solution. In fact in the first version of the porting machine ( which was quite a bit different in indexing design) I think that was my main problem. But like you said sometimes that's how we make progress.

Thanks for taking the time to bring up these points. I love the discussion.
I often get grandiose in my thinking. My saying is I end up trying to build a jumbo jet when I really wanted a paper aeroplane :)
iFirefly2 years ago
Bravo! An elegant solution and presentation of your innovation and principles. I think you have what it takes to be a great teacher that can inspire young, hungry minds. More power to you!

Now for my 2 cents:
When working with plywood gears, I have found that the life if the gears is extended by impregnating them with epoxy resin and polishing the mating surfaces.

I saw the drill's handle bobbing up & down with the cam lobe; you may want to support the drill/driver so as not to over-stress the chuck-driven connection. if it is equipped with a 1/4" x 20 attachment point on either side for a removable handle, that is where I would attach the brace.
pastprimitive (author)  iFirefly2 years ago
Thanks, and I will remember the epoxy resin for future gear replacements. I used oil on them this time. Although I suspect an extremely long life out of the gears because they are except for the ratchet gear merely power transfer vehicles.

Also extremely good idea to use the threaded holes for the removable handle for the attachment point on the drill to stabilize it. The drill I used was one I had handy lying around, but I will need to get a new one to replace it so I can have my corded drill back. I will use your suggestion when I get the new drill to support the new gear.

I really like all the great upgrades and improvement ideas everyone is giving.
Hi, I am not trying to put your Instructable down but, you should check this out http://www.dhgate.com/mini-3-quot-picnic-stove-camping-stove-gas/p-ff80808131dded210131e330e3cf6ddd.html
pastprimitive (author)  foreverdisturbed2 years ago
Don't take it as a put down as all. I love when people show me other products they really like.
The solution to incorporating the cnc machine is to build a new cnc machine! One stepper for the rotation of the workpiece, one stepper for the punch. I doubt, however that the steppers would match the speed of your solution. It seems to be a perfectly acceptable contraption! And it makes a lot of really cool noise :)
pastprimitive (author)  stringstretcher2 years ago
I agree. But like you say cool noise, and plywood with a drill is cheaper than stepper motors and a controller.
odalcet2 years ago
You can use Blender for your CAD drawings (and animations!) Here is an example:

http://www.nextwavemultimedia.com/html/3dworksamples.html

You can find many more looking for "blender cad" in Google

Blender is open source so you pay nothing. http://www.blender.org/
pastprimitive (author)  odalcet2 years ago
From what I heard Blender is lacking in the appropriate precision for engineering design.
kaddyshack2 years ago
The captions for the pictures in step 1 made me laugh so hard. They're too true.
pastprimitive (author)  kaddyshack2 years ago
Good, I wondered if anyone would actually read those captions. I though people may just think I was a narcissist or random, both, or something even worse.
neutron72 years ago
just wondering, why dont you put a batch of 25 cans or so on a jig on your CNC router and poke the holes by putting a punch in the z axis?
pastprimitive (author)  neutron72 years ago
Really excellent point. There are a few reasons why that's not ideal in this particular case. In order for the stove to have the airflow necessary for peak efficiency in the burn the holes need to be punched at an angle. So I would still have to create a jig that rotates the cans, since once at an angle I can only punch one hole at a time. We tried a series of straight punched stoves and they just didn't work very well. Also I would be tying up machine time with my CNC that I need to keep available as much as I can for prototyping and other operations.

So while we could do a big redesign on the stoves to try and take advantage of a straight punched holes, and we might; those are the main reasons why we can't right now.

We had the stove design done long before we had access a CNC machine. So honestly your idea really is a great idea if we didn't need to punch at an angle. And regardless of those issues I wish I would have thought of that solution myself at least for the sake of being thorough. I think this is an excellent example of opportunities for improvement and redesign. Your idea is a really good one. Thanks for sharing!
Ok i can see why that wouldn't easily work, but i had a (maybe a bit farfetched) idea.

you could use one of the outputs on your CNC (usually they have extra outputs to controll cooling or fluids or whatnot) to control a small tube of Magnetorheological fluid with an electromagent by it. the punch pin is on the end of the tube.

When the punch goes down and pokes the hole it is turned on and stiff. then the electromagnet turns off and the tube becomes flexible, you move the punch radially out fom the center of the can and the punch pin bends the hole to the appropriate angle, then retracts, the magnet turns back on and you start the next hole.

I am not suggesting you do this of course, it was just an idea because i was thinking about it. By the time you built and set it up you could have pokerized thousands of Pocket Stoves with your present machine.
pastprimitive (author)  neutron72 years ago
I like the exploratory thinking. I especially like the thought of using a magnetorheological fluid.
askjerry2 years ago
Excellent work. Getting the gearing ratio down, the two axis coordination, etc... very impressive. Thanks for sharing.
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