After looking over the components, documentation, and some a gecko document. I've been able to determine that we needed only 4666 micro Farads. This was determined with the following equation:
C = (80,000 * I)/V
C = (80000 * 2.1 Amps) / 36Volts = 4666 mF
Since we are running our steppers in unipolar mode the steppers will draw 2.1 Amps. Bipolar i believe was 2.8 Amps, so we calculated it with 3 Amps and that necessitates a 6,666 mF capacitor. The hobbycnc documentation recommends using a capacitor that is 20% higher than what is requested. From these calculations we see that our capacitor is more than sufficient.
This was not the 27,000 mF that was previously thought. Also from inspection the capacitor Troy purchased is rated for 22,000 mF and 50V. So we are good! We have almost all the components we want for our power supply. We would have built it tonight, but I believe we want some fuses, power switch, and wire. We also need to design and fabricate a power supply box.
I've made some progress on the frame, i'm now toiling with some geometry issues with the frame, and trying to ensure frame stability. The issues are occuring with mounting the THK rails to T-slot bars that will inevitably have to be drilled.
http://buildyourcnc.com/supply1.aspx
http://www.cnczone.com/forums/showthread.php?t=61976
http://www.geckodrive.com/upload/Step_motor_basics.pdf (page 11)
http://www.5bears.com/cnc03.htm
Saturday, August 29, 2009
More purchases, and more to come
I've purchased the spindle bearings for Troy's spindle design. He ran some calculations on the angular contact bearings, and also found some ebay bearings that had an ABEC-3 rating. I also purchased a CNC4PC control board that will be used to interface and control the DC motor for the spindle.
Short of 1 Capacitor, I think we have all the major electrical components. I've begun frame design once again starting from scratch, as I've learned some assumptions were not correct that I was working with before. I am particularly concerned with of each axis, as I found in my research that it is difficult to find swarf guarding material of the appropriate size. I want to completely model the frame before making the ballscrew purchase, as we know where to do that. Although, i'm feeling the pinch of time. So i'm thinking I should get that done within the next week.
As I keep track of the fiscal performance of our project. We are in the clear so far, I hope we can stay on track. If anything we are slightly under our projected cost.
In other developments, I reassembled my M4 airsoft rifle, after Troy and I inspected the internals for future projects. You can see some points in the procedure from the pictures. It was actually a lot more complicated to re-assemble than the picture's show. With the anti-reversal latch, and some springs that just didn't want to stay put, I had to come up with some clever ways to hold them in place. Using my Allen wrenches, and some electrical tape, I was able to fix the components in place until I could close the mechbox and remove them. I also had to use the motor's magnets to magnetize my screwdriver, so I could manuever the screws into the pistol grip successfully.
I also setup and started up an old computer, that had problems in the past. I confirmed that the primary harddrive has some bad sectors, and cannot boot to windows. I used a bootable linux OS to take a gander at the drives. The Raid-0 array was fine, all the data on those drives were unscathed. Ironically, it was the single OS hard drive that failed. I was pleased to find no faults in any of the other hardware.
Tuesday, August 25, 2009
Gathering resources
As I keep my projects moving along I realize that one of the major aspects of projects that can easily be underestimated, is simply the selection and purchase of a given raw material or tool.
Several educated decisions must be made before making a purchase in the hopes of minimizing lost money or time. Today, to keep the ball rolling on one of my airsoft projects I had to make a quick decision about a ball-end mill purchase. As I was modeling my CAM file for the part, I had to choose between a 3/16" diameter or 1/4" diameter. I picked 3/16" because I can interpolate curves with the 3/16" that should be near to similar geometry of the 1/4" ball end mill. A quick run over to Hall tool, and I got the tools. I also purchased a VERY small double sided endmill (1/16"), for some detailed work.
I also received the Toroid Transformer the mail from Antek Inc. It looks like in good condition to me. It is a surprisingly heavy piece of equipment. I need to locate 1 more medium sized capacitor to run in parallel, and we will have all the components for our powersupply. If I can get all these things to Grant, we should be able to fabricate, and finish off the control board. Basically - we will be able to test the brains of the CNC machine. This will let us also test and configure the stepper motors. I'm sure if we can get the board, and the steppers running, the project will quickly accelerate.
There's always a defining moment in a project, where you find out if it is inevitably going to work. I believe we have one coming of those moments coming up with the power supply, control board, and steppers. I mean if we get that done, we essentially need to attach a few more mechanical components, ballscrews, THK rails, and spindle and we have ourselves a CNC machine!
Several educated decisions must be made before making a purchase in the hopes of minimizing lost money or time. Today, to keep the ball rolling on one of my airsoft projects I had to make a quick decision about a ball-end mill purchase. As I was modeling my CAM file for the part, I had to choose between a 3/16" diameter or 1/4" diameter. I picked 3/16" because I can interpolate curves with the 3/16" that should be near to similar geometry of the 1/4" ball end mill. A quick run over to Hall tool, and I got the tools. I also purchased a VERY small double sided endmill (1/16"), for some detailed work.
I also received the Toroid Transformer the mail from Antek Inc. It looks like in good condition to me. It is a surprisingly heavy piece of equipment. I need to locate 1 more medium sized capacitor to run in parallel, and we will have all the components for our powersupply. If I can get all these things to Grant, we should be able to fabricate, and finish off the control board. Basically - we will be able to test the brains of the CNC machine. This will let us also test and configure the stepper motors. I'm sure if we can get the board, and the steppers running, the project will quickly accelerate.
There's always a defining moment in a project, where you find out if it is inevitably going to work. I believe we have one coming of those moments coming up with the power supply, control board, and steppers. I mean if we get that done, we essentially need to attach a few more mechanical components, ballscrews, THK rails, and spindle and we have ourselves a CNC machine!
Wednesday, August 19, 2009
Keeping things ontrack
After a short hiatus due to finals, Troy being gone, and a general state of busyness we started things back up. Oh and I think something or someone is starting to really spice up my life. I hope good things come of that...
CNC Power supply
All that aside, I've been keep things alive with my little airsoft business, Troy seems to have finished the basic shape of the new airsoft part that is under development. We are considering design enhancements, and the serious complications to actually fabricating the part. I just got the ball rolling on the powersupply for the control board thanks to Troy's help. We were able to clear up a few questions I had lingering. From his help I was able to determine:
-The powersupply must have a matching voltage to the control board. In our case we want it at full voltage of 36VDC.
-The current is variable, and will need to draw up to a max of 12 Amps, because each stepper is rated to 2 amps, but according to the information on the hobbycnc kit we need twice the amperage that the stepper motor is rated for. So with 3 steppers that adds up to 12 Amps in unipolar mode.
A quick look on ebay yielded a few subpar powersupply's, and a few way overkill powersupplies that cost 400$. With some searching we found Antek should be able to land us a quality Toroidal transformer for about 55$ + shipping. Troy already bought a bridge rectifier, and capictor. Although the calculations indicate that we will need to run another small capictor in parallel with the large 22,000 mF. This is because we need about 27,000 mF as dictated in http://www.geckodrive.com/upload/Step_motor_basics.pdf on page 11.
=======================
Frame deliberations
After discussing 80-20 extrusion availability and cost we are considering getting some budget extrusions off of ebay. The only problem with this is that it will not be end machined or have any tapped ends. Going with the more expensive Bosch option will give us that, saving us some trouble. I think i'll need to get a price quote from bosch to ensure that ebay is indeed the better option.
The biggest issue I was encountering was mounting the Z-axis to the X-axis similar to 5-bears. After consulting Troy, he came up with a great idea to simply bolt the Z-axis to an intermediate base that serves no function other than to be a stationary mounting base.
The base most likely will be two 45-90 extrusions of full length attached to mic6 plate which will also mount the Z-axis. I'll need to calculate the deformation induced by the weight of the X-Y axis with a 45-45 section modulus to be sure they will be sufficient. If not I'll have to step it up to a stronger section modulus that can prevent the deformation.
Lastly, I still need to find out where to get the T-slot steel stock for mounting the fasteners for each axis.
The good news is after today, we have a real plan for all the major components of the CNC. Where to buy them, how we will integrate them. Now we are down to a few of the details, and the daunting task of coalescing it all together! But oh my, it is so much fun.
CNC Power supply
All that aside, I've been keep things alive with my little airsoft business, Troy seems to have finished the basic shape of the new airsoft part that is under development. We are considering design enhancements, and the serious complications to actually fabricating the part. I just got the ball rolling on the powersupply for the control board thanks to Troy's help. We were able to clear up a few questions I had lingering. From his help I was able to determine:
-The powersupply must have a matching voltage to the control board. In our case we want it at full voltage of 36VDC.
-The current is variable, and will need to draw up to a max of 12 Amps, because each stepper is rated to 2 amps, but according to the information on the hobbycnc kit we need twice the amperage that the stepper motor is rated for. So with 3 steppers that adds up to 12 Amps in unipolar mode.
A quick look on ebay yielded a few subpar powersupply's, and a few way overkill powersupplies that cost 400$. With some searching we found Antek should be able to land us a quality Toroidal transformer for about 55$ + shipping. Troy already bought a bridge rectifier, and capictor. Although the calculations indicate that we will need to run another small capictor in parallel with the large 22,000 mF. This is because we need about 27,000 mF as dictated in http://www.geckodrive.com/upload/Step_motor_basics.pdf on page 11.
=======================
Frame deliberations
After discussing 80-20 extrusion availability and cost we are considering getting some budget extrusions off of ebay. The only problem with this is that it will not be end machined or have any tapped ends. Going with the more expensive Bosch option will give us that, saving us some trouble. I think i'll need to get a price quote from bosch to ensure that ebay is indeed the better option.
The biggest issue I was encountering was mounting the Z-axis to the X-axis similar to 5-bears. After consulting Troy, he came up with a great idea to simply bolt the Z-axis to an intermediate base that serves no function other than to be a stationary mounting base.
The base most likely will be two 45-90 extrusions of full length attached to mic6 plate which will also mount the Z-axis. I'll need to calculate the deformation induced by the weight of the X-Y axis with a 45-45 section modulus to be sure they will be sufficient. If not I'll have to step it up to a stronger section modulus that can prevent the deformation.
Lastly, I still need to find out where to get the T-slot steel stock for mounting the fasteners for each axis.
The good news is after today, we have a real plan for all the major components of the CNC. Where to buy them, how we will integrate them. Now we are down to a few of the details, and the daunting task of coalescing it all together! But oh my, it is so much fun.
Sunday, August 16, 2009
Batman would be proud. Progress.
This is my second attempt at making a post, because firefox decided for me to crash. Thanks firefox! Anyways... onto the real stuff.
(Picture of grant owning this PCB)
Today, I went over to Grant's house and we started to build the hobbycnc control board. We put Grant's fancy soldering iron to work on the PCB. For the most part he was doing the soldering, and I was ensuring component placement based on the schematic and instructions from the kit. What was nice, was that the board was clearly and neatly ordered/organized. I did solder a few components just for good measure, and to remind myself how fun it can be. I see it as a miniature TIG welder without the annoying foot pedal.
(I'm soldering on a few parts just to make sure I can still do it; and I can yay!)
If I build another CNC I will seriously consider using this company again. The only two shortcomings that i forsee with this board is the lack of opto-isolation (although troy believes he has a fix for this), and secondly the lack of high voltage so we can't overdrive the stepper motors much. While this board can only go to 36V the Gecko Drivers can go to 80V, although the nice thing about this board is that it is almost all contained on this board.
So we built almost all the board, with exception to some of the logic chips. The reason is you want to test the board for solder bridges and continuity before applying current and voltage that could potentially damage the expensive logic chips. Once you are sure your board is functioning properly with the powersupply connected you can install the logic chips.
Given that we didn't purchase a powersupply yet we could not finish off the board completely. This is because Troy and Grant were going to explore the option of fabricating a powersupply from old parts from a microwave power supply. From the documentation it looks like we need an 18A powersupply; at this point I don't know if it's okay for us to exceed that, although my gut says its fine.
Here's a website with some good information about building or buying a powersupply http://www.solsylva.com/cnc/power_supply.shtml
(Picture of grant owning this PCB)
Today, I went over to Grant's house and we started to build the hobbycnc control board. We put Grant's fancy soldering iron to work on the PCB. For the most part he was doing the soldering, and I was ensuring component placement based on the schematic and instructions from the kit. What was nice, was that the board was clearly and neatly ordered/organized. I did solder a few components just for good measure, and to remind myself how fun it can be. I see it as a miniature TIG welder without the annoying foot pedal.
(I'm soldering on a few parts just to make sure I can still do it; and I can yay!)
If I build another CNC I will seriously consider using this company again. The only two shortcomings that i forsee with this board is the lack of opto-isolation (although troy believes he has a fix for this), and secondly the lack of high voltage so we can't overdrive the stepper motors much. While this board can only go to 36V the Gecko Drivers can go to 80V, although the nice thing about this board is that it is almost all contained on this board.
So we built almost all the board, with exception to some of the logic chips. The reason is you want to test the board for solder bridges and continuity before applying current and voltage that could potentially damage the expensive logic chips. Once you are sure your board is functioning properly with the powersupply connected you can install the logic chips.
Given that we didn't purchase a powersupply yet we could not finish off the board completely. This is because Troy and Grant were going to explore the option of fabricating a powersupply from old parts from a microwave power supply. From the documentation it looks like we need an 18A powersupply; at this point I don't know if it's okay for us to exceed that, although my gut says its fine.
Here's a website with some good information about building or buying a powersupply http://www.solsylva.com/cnc/power_supply.shtml
Sunday, August 9, 2009
Keep chugging along
Steppers ordered
While dealing with my Discrete math class (scored 100% on the midterm wooo), and keeping my airsoft business alive (shipping product); I managed to select and order some 425 oz-in stepper motors for all 3 axis on our CNC machine. All together with shipping it was 163.17$, We could have gone with a ~300 oz-in motor for 30$ less, but the price/performance difference was warranted an increase in power. We wanted to be sure we could meet our torque requirement. We are happy with rapid speeds of around 70 IPM, but we are confident with appropriate gearing/microstepping we can hit whatever targets speeds we need. Other than the previous research and calculations that were conducted a few days/weeks ago (with that program I wrote), I did additional research on cnczone. The interesting reads I found were:
http://www.cnczone.com/forums/forumdisplay.php?f=193&order=desc&page=17
http://www.cnczone.com/forums/showthread.php?t=27527&page=2
http://www.cnczone.com/forums/showthread.php?t=80245
http://www.cnczone.com/forums/showthread.php?t=75192&page=2
http://www.designworldonline.com/articles/3807/21/Improving-High-Speed-Performance-of-Hybrid-Stepper-Motors.aspx?utm_source=mcnl&utm_medium=newsletter&utm_content=feature&utm_campaign=MCNEWSLETTER
http://www.homeshopcnc.com/StepperMotorFAQ2.html
Also while inspecting specs on keling's website I needed to convert 2.15N-M to oz-in, a quick google solution was found at:
http://www.unitconversion.org/torque/newton-meters-to-ounce-force-inchs-conversion.html
It looks like our machine will be severaly limited on the Rapid speeds based on the controller board, with a max voltage of 36V. So we can't overdrive the steppers much. They run 6V stock. So we will only be able to run them about 2x their rated voltage even though we could go up to 20x their rated voltage. With the stepper order aside, I continued my frame research for our machine.
-----------------
Frame Research
For awhile we were seriously considering making the whole frame out of epoxy/granite composite. But after eyeing the costs, the difficulty in manufacturing and the time frame we are on, Troy and I decided it would be wise to follow the KISS principle. I had found several instances of aluminum Bosch framing for homebuilt CNC machines. Given the repeated success I had found, I pushed for what we know works, and with ease. Given our constraints on the project Troy, agreed heartily. Although, we both conceded it would be very cool to incorporate some E/G aspects into the project later to enhance rigidity and vibration absorption.
A simple way to do that would be to fill the cavities of the aluminum framing with E/G. Also we also conceded it would be very nice to have a solid head, so we may make that solid later. At the moment I am toiling with fasteners. I measured one of the THK rails we obtained from ebay. They appear to have 7mm holes for SHCS (Socket Head Cap Screws.) and 9mm countersunk holes. A quick google search is not promising for 7MM SHCS.
http://www.roymech.co.uk/Useful_Tables/Screws/cap_screws.htm
Shows some typical metric SHCS sizes. M7 is not on the list. I wonder if they are specialty screws for the rails, or if they simply use M6 screws.
In my research I began to learn that these so called aluminum frames, are sometimes nicknamed "80-20" extrusions. Which I guess is some sort of industry standard. Apparently there is even a whole section on cnczone dedicated to 80-20 frames. (i'll have to read into it more before making final design decisions.)
From an inspection of Bosch's website and manuals it looks like a 45x45H extrusion section should meet our demands for the X/Y tables. I am a little concerned because milling flat that extrusion will be a hastle on the bridgeport mill that hasn't been opened up yet at our shop. Not to mention we don't even know if the bridgeport's ways are true. Any error in that machine will be amplified in our own base if they are off. And from my research it is not uncommon for these extrusions to have about .008" of variability across a single piece. I also read some individuals using T-slot inserts that are premachined and have SHCS holes in it. I hope i can find more on this.
Some websites concerning 80-20 framing:
80-20 surplus
80-20-T-Slot-Aluminum-Extrusion-45-S-45-4545-
Bosch 3D models
Bosch Website
http://www.3dpublisher.net/SWDownloads1/2044316659-857082/Machining.PDF
I know I will be ordering some Mic6 precision ground plate for bolting some of these frame parts together, just don't know the physical dimensions yet. So that's on hold. I want to model the whole thing in solidworks first.
So to review:
I need to:
The truth about building a CNC machine
Gosh everything about this project is Read, Read, Read, process, learn, discover how very little you actually know, rinse and repeat. And somewhere in there you feel confident enough that you aren't going to make a disastorously horrible mistake, and that it is about time to learn by doing.
While dealing with my Discrete math class (scored 100% on the midterm wooo), and keeping my airsoft business alive (shipping product); I managed to select and order some 425 oz-in stepper motors for all 3 axis on our CNC machine. All together with shipping it was 163.17$, We could have gone with a ~300 oz-in motor for 30$ less, but the price/performance difference was warranted an increase in power. We wanted to be sure we could meet our torque requirement. We are happy with rapid speeds of around 70 IPM, but we are confident with appropriate gearing/microstepping we can hit whatever targets speeds we need. Other than the previous research and calculations that were conducted a few days/weeks ago (with that program I wrote), I did additional research on cnczone. The interesting reads I found were:
http://www.cnczone.com/forums/forumdisplay.php?f=193&order=desc&page=17
http://www.cnczone.com/forums/showthread.php?t=27527&page=2
http://www.cnczone.com/forums/showthread.php?t=80245
http://www.cnczone.com/forums/showthread.php?t=75192&page=2
http://www.designworldonline.com/articles/3807/21/Improving-High-Speed-Performance-of-Hybrid-Stepper-Motors.aspx?utm_source=mcnl&utm_medium=newsletter&utm_content=feature&utm_campaign=MCNEWSLETTER
http://www.homeshopcnc.com/StepperMotorFAQ2.html
Also while inspecting specs on keling's website I needed to convert 2.15N-M to oz-in, a quick google solution was found at:
http://www.unitconversion.org/torque/newton-meters-to-ounce-force-inchs-conversion.html
It looks like our machine will be severaly limited on the Rapid speeds based on the controller board, with a max voltage of 36V. So we can't overdrive the steppers much. They run 6V stock. So we will only be able to run them about 2x their rated voltage even though we could go up to 20x their rated voltage. With the stepper order aside, I continued my frame research for our machine.
-----------------
Frame Research
For awhile we were seriously considering making the whole frame out of epoxy/granite composite. But after eyeing the costs, the difficulty in manufacturing and the time frame we are on, Troy and I decided it would be wise to follow the KISS principle. I had found several instances of aluminum Bosch framing for homebuilt CNC machines. Given the repeated success I had found, I pushed for what we know works, and with ease. Given our constraints on the project Troy, agreed heartily. Although, we both conceded it would be very cool to incorporate some E/G aspects into the project later to enhance rigidity and vibration absorption.
A simple way to do that would be to fill the cavities of the aluminum framing with E/G. Also we also conceded it would be very nice to have a solid head, so we may make that solid later. At the moment I am toiling with fasteners. I measured one of the THK rails we obtained from ebay. They appear to have 7mm holes for SHCS (Socket Head Cap Screws.) and 9mm countersunk holes. A quick google search is not promising for 7MM SHCS.
http://www.roymech.co.uk/Useful_Tables/Screws/cap_screws.htm
Shows some typical metric SHCS sizes. M7 is not on the list. I wonder if they are specialty screws for the rails, or if they simply use M6 screws.
In my research I began to learn that these so called aluminum frames, are sometimes nicknamed "80-20" extrusions. Which I guess is some sort of industry standard. Apparently there is even a whole section on cnczone dedicated to 80-20 frames. (i'll have to read into it more before making final design decisions.)
From an inspection of Bosch's website and manuals it looks like a 45x45H extrusion section should meet our demands for the X/Y tables. I am a little concerned because milling flat that extrusion will be a hastle on the bridgeport mill that hasn't been opened up yet at our shop. Not to mention we don't even know if the bridgeport's ways are true. Any error in that machine will be amplified in our own base if they are off. And from my research it is not uncommon for these extrusions to have about .008" of variability across a single piece. I also read some individuals using T-slot inserts that are premachined and have SHCS holes in it. I hope i can find more on this.
Some websites concerning 80-20 framing:
80-20 surplus
80-20-T-Slot-Aluminum-Extrusion-45-S-45-4545-
Bosch 3D models
Bosch Website
http://www.3dpublisher.net/SWDownloads1/2044316659-857082/Machining.PDF
I know I will be ordering some Mic6 precision ground plate for bolting some of these frame parts together, just don't know the physical dimensions yet. So that's on hold. I want to model the whole thing in solidworks first.
So to review:
I need to:
- M7 screws- do they exist for the THK rails?
- Precision ground t-slot rails for 80-20 t-slots to bolt the THK rails to - do they exist/where?
- 80-20 End machining options at bosch are confusing, figure it out!
- Model it!
The truth about building a CNC machine
Gosh everything about this project is Read, Read, Read, process, learn, discover how very little you actually know, rinse and repeat. And somewhere in there you feel confident enough that you aren't going to make a disastorously horrible mistake, and that it is about time to learn by doing.
Saturday, August 8, 2009
Progress, but slow
I'm getting this lingering feeling that all the projects I'm doing are getting spread too thin. There is considerable progress when you look at the big picture, but I feel they are getting off track. This shotgun approach to picking tasks I don't think works for the longterm. I may need to review my project goals, and evaluate what would be the most worthwhile use of my time. Despite this I'm still having fun, and doing really cool things.
Like today I started and finished an End-mill box. I'm becoming more proficient at developing and converting designs to be used with the Epilogue laser cutter. Here are two things I made today:
An endmill box and a Metric/English Ruler. I accounted for the laser's thickness to be .004" this made a very snug fit. So snug in fact that when i first assembled it - it took me a full 10 minutes to pry it apart to put the ribs in. I'm going to have to come up with a solution for that. Possibly a bit of simple sanding. I'll have to make a second box as I apparently have about twice as many endmills as depicted.
The ruler, didn't come out that great because the driver interpreted some of the lines that I intended to be engraved, as cutting lines. So the ruler is fairly serrated as the image shows. I'll have to make more later, but hey at least its decently accurate and useful!
Tuesday, August 4, 2009
Airsoft Business on its feet
Airsoft Business
I visited the USPS post office today and figured out the shipping details for the airsoft products that I've developed. After figuring that, and some tests with the hopup arms that I developed; I released it to the public. After a few sales, I quickly discovered why secretary's are useful for this sort of work (it takes a surprisingly large chunk of time and effort.) I now have a newfound respect for them. It is so rewarding to see a product you've developed being distributed to help others with their goals. (Albiet, that is for playing airsoft lol)
CNC Progress
We fairly accurately priced out several of the future components we need. From this assessment the total cost of the CNC will be around 1733$. So split among our team that will be 577$ per person. Not bad.
Pricing the frame was interesting, because we decided to make it almost entirely of a aggregate/resin mix. We will use what is called "play sand" found at your local hardware store for about 5$/50 lbs. We estimated a "log" geometry where it will be formed from a series of legs that are connected together with a log geometry of 4"x4"x35" we overestimated a required volume of about 840 in^3 for the composite frame. With about 20% resin usage that puts us at a required resin volume of 4 gallons. (924 in^3) The cost of resin is about 200$ for that much. If we get lucky and can get away with only 2 gallons which would be ideal because that would insure a good dampening effect from the frame.
I think a good mixing idea would be to mix the resin without hardener in the aggregate mix before adding the hardener, that way we can ensure the resin is fully distributed through the aggregate.
I visited the USPS post office today and figured out the shipping details for the airsoft products that I've developed. After figuring that, and some tests with the hopup arms that I developed; I released it to the public. After a few sales, I quickly discovered why secretary's are useful for this sort of work (it takes a surprisingly large chunk of time and effort.) I now have a newfound respect for them. It is so rewarding to see a product you've developed being distributed to help others with their goals. (Albiet, that is for playing airsoft lol)
CNC Progress
We fairly accurately priced out several of the future components we need. From this assessment the total cost of the CNC will be around 1733$. So split among our team that will be 577$ per person. Not bad.
Pricing the frame was interesting, because we decided to make it almost entirely of a aggregate/resin mix. We will use what is called "play sand" found at your local hardware store for about 5$/50 lbs. We estimated a "log" geometry where it will be formed from a series of legs that are connected together with a log geometry of 4"x4"x35" we overestimated a required volume of about 840 in^3 for the composite frame. With about 20% resin usage that puts us at a required resin volume of 4 gallons. (924 in^3) The cost of resin is about 200$ for that much. If we get lucky and can get away with only 2 gallons which would be ideal because that would insure a good dampening effect from the frame.
I think a good mixing idea would be to mix the resin without hardener in the aggregate mix before adding the hardener, that way we can ensure the resin is fully distributed through the aggregate.
Sunday, August 2, 2009
What a wonderful Day
I finished making a batch of airsoft parts that I will be distributing. I had do prototype tests to ensure they fit properly. I had some issues with localized heat in the acrylic which was causing deformation to occur. A few tweaks to the geometry of the part fixed that. I also finished making the "wooden box" except I used what i had available - which was acrylic. I may make some more boxes later out of wood. Here are some pictures.
Some of the airsoft parts i manufactured (in clear) compared to the original stock factory part. I made all of these parts with a 45 watt CO2 Laser.
Saturday, August 1, 2009
Wooden box
Not much happened with engineering today. I had discrete mathematics today, came back from class and received a letter from the MECOP program saying that I had been accepted! http://mecop.ous.edu/
I finished modeling a wooden box to cut out of .25" thick wood on the Epilogue laser cutter at the tech shop. It was surprisingly more difficult to model then the rotary table... This is because the geometry of the lid required me to do some math. Also the corners of the boxes required some interesting thought which I had not performed before.
I'm going to have to convert it to a DXF file, or make a drawing file from the model because the Epilogue 45 Watt CO2 laser cutter needs lines defined as hairlines and converting between file types sometimes you lose that vector based geometry in the image.
Reference:
http://www.woodworkingcorner.com/kschest.php
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