Re: [Emc-users] polyurethane resin casting
For the high speed vacuum, why not just use an external tank, with plumbing valve or equivalent to switch to whichever has highest vacuum? On Sat, Sep 28, 2013 at 12:13 AM, Gregg Eshelman g_ala...@yahoo.com wrote: On 9/27/2013 6:29 PM, Erik Friesen wrote: Do you think vacuum alone would pull into every nook and cranny? I have looked for other people that have tried something similar, but didn't find much. By vacuum, my idea is to in some way place the mold under vacuum, and fill it using atmospheric pressure, perhaps using some type of funnel and valve. If you do calculations on a 4 sq in mold at my pump rating of 10pa, it calculates to a .07 cubed volume at atmosphere of 101kpa. Whats the demold/depressurisation time for pressured polyurethane? It depends a lot on the resin. Fast cure ones like you're using could come out in a few minutes to an hour, just to be sure. Most of what I use is Smooth-On Crystal Clear and I leave it under pressure 24 hours. I also post-cure at 145F with convection heat so if not left under pressure long enough I've had problems with small bubbles forming. I've also used some of Smooth-On's faster resins like Onyx and have been able to take out of pressure in about 30 minutes. That one cures hard enough it doesn't need post curing. Think of using pressure like what a deep diver experiences, except for with the resin and silicone keeping it under pressure long enough ensures the gasses never get back out. You can speed up the cure by shining a halogen work light on the pressure tank or putting the tank in a very warm room. I've cast silicone molds under pressure in the middle of winter in a poorly heated shop, with a halogen lamp shining on one of my larger tanks. Most resins and silicones need to be at least 75F to cure properly. Therin lies a useful property that can be exploited some times. Chill the components prior to mixing to stretch out the pot life, then after pouring into the mold, apply heat to speed up the cure. However, some resins can fail to cure properly if they're not at the proper temperature or higher when mixed. In such a case, mix the resin then fill the mold in a cold room, then transfer to a warm room to get some more working time. If you have a bunch of leftover silicone after casting a mold, freeze the leftovers. It'll bring the cure nearly to a halt. I've frozen mixed silicone up to a week and still been able to use it to make molds. It will be thick but will still flow. Another trick I've used to alter curing times is mixing resins from the same product line with different cure times. I had to cast some large but thin parts. The longer cure time resin wouldn't properly set in such thin castings and the short cure time that would set in thin castings would kick too fast to be able to get the mold filled. So I mixed the two in a 50:50 ratio and the properties came out somewhere between, stretching the time long enough to be able to fill the mold and get it in a tank, while still generating enough heat from the chemical reactions to fully cure. I told Smooth-On what I did. No reply but they later added another resin in the Crystal Clear line with cure properties between the 202 and the longer cure time number. I think they've also altered the 202 because I can use it as-is in the molds that I couldn't when I was mixing the two, and even if I do heat the tanks or set them on the concrete in front of my shop on a sunny day, the castings still need post curing. -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] polyurethane resin casting
The current resin I use has a 50 second gel time. Its a little like flying rc, if it gets ahead of you you are in trouble. I wonder if a person could make a inlet control valve with a piece of tubing and clamp, or special clamp? Something that would take about 15 psi forward pressure to open the clamp. On Sat, Sep 28, 2013 at 7:16 AM, Erik Friesen e...@aercon.net wrote: For the high speed vacuum, why not just use an external tank, with plumbing valve or equivalent to switch to whichever has highest vacuum? On Sat, Sep 28, 2013 at 12:13 AM, Gregg Eshelman g_ala...@yahoo.comwrote: On 9/27/2013 6:29 PM, Erik Friesen wrote: Do you think vacuum alone would pull into every nook and cranny? I have looked for other people that have tried something similar, but didn't find much. By vacuum, my idea is to in some way place the mold under vacuum, and fill it using atmospheric pressure, perhaps using some type of funnel and valve. If you do calculations on a 4 sq in mold at my pump rating of 10pa, it calculates to a .07 cubed volume at atmosphere of 101kpa. Whats the demold/depressurisation time for pressured polyurethane? It depends a lot on the resin. Fast cure ones like you're using could come out in a few minutes to an hour, just to be sure. Most of what I use is Smooth-On Crystal Clear and I leave it under pressure 24 hours. I also post-cure at 145F with convection heat so if not left under pressure long enough I've had problems with small bubbles forming. I've also used some of Smooth-On's faster resins like Onyx and have been able to take out of pressure in about 30 minutes. That one cures hard enough it doesn't need post curing. Think of using pressure like what a deep diver experiences, except for with the resin and silicone keeping it under pressure long enough ensures the gasses never get back out. You can speed up the cure by shining a halogen work light on the pressure tank or putting the tank in a very warm room. I've cast silicone molds under pressure in the middle of winter in a poorly heated shop, with a halogen lamp shining on one of my larger tanks. Most resins and silicones need to be at least 75F to cure properly. Therin lies a useful property that can be exploited some times. Chill the components prior to mixing to stretch out the pot life, then after pouring into the mold, apply heat to speed up the cure. However, some resins can fail to cure properly if they're not at the proper temperature or higher when mixed. In such a case, mix the resin then fill the mold in a cold room, then transfer to a warm room to get some more working time. If you have a bunch of leftover silicone after casting a mold, freeze the leftovers. It'll bring the cure nearly to a halt. I've frozen mixed silicone up to a week and still been able to use it to make molds. It will be thick but will still flow. Another trick I've used to alter curing times is mixing resins from the same product line with different cure times. I had to cast some large but thin parts. The longer cure time resin wouldn't properly set in such thin castings and the short cure time that would set in thin castings would kick too fast to be able to get the mold filled. So I mixed the two in a 50:50 ratio and the properties came out somewhere between, stretching the time long enough to be able to fill the mold and get it in a tank, while still generating enough heat from the chemical reactions to fully cure. I told Smooth-On what I did. No reply but they later added another resin in the Crystal Clear line with cure properties between the 202 and the longer cure time number. I think they've also altered the 202 because I can use it as-is in the molds that I couldn't when I was mixing the two, and even if I do heat the tanks or set them on the concrete in front of my shop on a sunny day, the castings still need post curing. -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing
Re: [Emc-users] Is this feasible: BBB running LinuxCNC to Gecko G540stepper driver
Richard, sure it can. All you need is to provide some level shifting (BBB is 3,3V, gecko takes 5V iirc) and connect them. Or you can use an existing cape: BeBoPr, Replicape, etc Or you can wait a bit on a parport cape I'm currently working on.. (schematic mostly done, layout in the works..) Should be a couple weeks for a tested prototype.. I'll post updates Regards, Alex -Original Message- From: Richard Thornton Sent: Saturday, September 28, 2013 12:45 PM To: emc-users@lists.sourceforge.net Subject: [Emc-users] Is this feasible: BBB running LinuxCNC to Gecko G540stepper driver Hi, I have seen a bunch of info on using BBB with capes and a lot of 3D printing specific stuff like Replicape and BeBoPr++. My thought was can the BBB replace the PC in LinuxCNC and drive the G540 directly? Thanks for looking. Cheers Richard -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Is this feasible: BBB running LinuxCNC to Gecko G540 stepper driver
On 9/28/2013 4:45 AM, Richard Thornton wrote: Hi, I have seen a bunch of info on using BBB with capes and a lot of 3D printing specific stuff like Replicape and BeBoPr++. My thought was can the BBB replace the PC in LinuxCNC and drive the G540 directly? The gecko will happily work with 3.3V signals (as will just about anything designed to connect to a standard PC parallel port...they have all had 3.3V signaling for ages). So if you want, you can just hook up some wires from the BeagleBone connectors to a DB25, maybe using a prototype cape if you want to be fancy: http://www.adafruit.com/products/572 -- Charles Steinkuehler char...@steinkuehler.net signature.asc Description: OpenPGP digital signature -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Is this feasible: BBB running LinuxCNC to Gecko G540 stepper driver
On 09/28/2013 05:38 AM, Charles Steinkuehler wrote: On 9/28/2013 4:45 AM, Richard Thornton wrote: Hi, I have seen a bunch of info on using BBB with capes and a lot of 3D printing specific stuff like Replicape and BeBoPr++. My thought was can the BBB replace the PC in LinuxCNC and drive the G540 directly? The gecko will happily work with 3.3V signals (as will just about anything designed to connect to a standard PC parallel port...they have all had 3.3V signaling for ages). So if you want, you can just hook up some wires from the BeagleBone connectors to a DB25, maybe using a prototype cape if you want to be fancy: http://www.adafruit.com/products/572 The bottom line is, that for some G540 inputs one only needs to turn on and off the LED in a LTV846 opto-coupler. http://www.wallacecompany.com/machine_shop/G540/G540_upper_bottom-2.jpg http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTV-8x6.pdf The forward voltage for the LTV is typically 1.2 V. there is a 200 Ohm resistor in series with the input which will also need to be considered. At 3.3 V, V=IR, I=V/R, I=(3.3 - 1.2)/200=0.0105 A= 10.5mA. It looks like 5mA should be enough to drive the LED, so if the BBB output can drive 10mA and survive, a direct connection should work. The charge pump signal is different. http://www.wallacecompany.com/machine_shop/G540/G540_upper_bottom_z-1b.png The input charges a capacitor and diode bridge which needs a lot more current and is more sensitive to voltage, frequency and duty. This shows a parallel port signal in 5 V SPP (low drive) mode, which doesn't work: http://www.wallacecompany.com/machine_shop/G540/g540_mb_spp.jpg Here it is in 5 V EPP (high drive) mode, which does work: http://www.wallacecompany.com/machine_shop/G540/g540_mb_spp.jpg This signal peaks at just over 3 Volts and takes its time getting there. The SPP signal peaks at 2 Volts. The situation gets more difficult when one considers the length and type of cable used. Noise can put significant + and - voltages on the signal, so reverse voltage protection, filtering, conditioning and termination will need to be considered. So direct connecting a BBB and a G540? ... It depends. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Is this feasible: BBB running LinuxCNC to Gecko G540 stepper driver
On 28 September 2013 16:13, Kirk Wallace kwall...@wallacecompany.com wrote: The charge pump signal is different. http://www.wallacecompany.com/machine_shop/G540/G540_upper_bottom_z-1b.png The input charges a capacitor and diode bridge which needs a lot more current and is more sensitive to voltage, frequency and duty. I have a feeling that there is an option to not use the charge pump? (Though clearly it would be good to) -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Is this feasible: BBB running LinuxCNC to Gecko G540 stepper driver
On Saturday 28 September 2013 11:24:35 Kirk Wallace did opine: On 09/28/2013 05:38 AM, Charles Steinkuehler wrote: On 9/28/2013 4:45 AM, Richard Thornton wrote: Hi, I have seen a bunch of info on using BBB with capes and a lot of 3D printing specific stuff like Replicape and BeBoPr++. My thought was can the BBB replace the PC in LinuxCNC and drive the G540 directly? The gecko will happily work with 3.3V signals (as will just about anything designed to connect to a standard PC parallel port...they have all had 3.3V signaling for ages). So if you want, you can just hook up some wires from the BeagleBone connectors to a DB25, maybe using a prototype cape if you want to be fancy: http://www.adafruit.com/products/572 The bottom line is, that for some G540 inputs one only needs to turn on and off the LED in a LTV846 opto-coupler. http://www.wallacecompany.com/machine_shop/G540/G540_upper_bottom-2.jpg http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTV-8x6.pdf The forward voltage for the LTV is typically 1.2 V. there is a 200 Ohm resistor in series with the input which will also need to be considered. At 3.3 V, V=IR, I=V/R, I=(3.3 - 1.2)/200=0.0105 A= 10.5mA. It looks like 5mA should be enough to drive the LED, so if the BBB output can drive 10mA and survive, a direct connection should work. The charge pump signal is different. http://www.wallacecompany.com/machine_shop/G540/G540_upper_bottom_z-1b.p ng The input charges a capacitor and diode bridge which needs a lot more current and is more sensitive to voltage, frequency and duty. This shows a parallel port signal in 5 V SPP (low drive) mode, which doesn't work: http://www.wallacecompany.com/machine_shop/G540/g540_mb_spp.jpg Here it is in 5 V EPP (high drive) mode, which does work: http://www.wallacecompany.com/machine_shop/G540/g540_mb_spp.jpg Those 2 look identical because they are Kirk. :) This signal peaks at just over 3 Volts and takes its time getting there. The SPP signal peaks at 2 Volts. The situation gets more difficult when one considers the length and type of cable used. Noise can put significant + and - voltages on the signal, so reverse voltage protection, filtering, conditioning and termination will need to be considered. So direct connecting a BBB and a G540? ... It depends. It should work well IF the + side of the optos are at Vcc, while the - side is connected to the BBB's output signal. That assumes the BBB has a TTL- like output stage, which I do not know for a fact. Cheers, Gene -- There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order. -Ed Howdershelt (Author) Diplomacy is to do and say, the nastiest thing in the nicest way. -- Balfour A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Is this feasible: BBB running LinuxCNC to Gecko G540 stepper driver
On 09/28/2013 08:30 AM, Gene Heskett wrote: On Saturday 28 September 2013 11:24:35 Kirk Wallace did opine: ... snip The input charges a capacitor and diode bridge which needs a lot more current and is more sensitive to voltage, frequency and duty. This shows a parallel port signal in 5 V SPP (low drive) mode, which doesn't work: http://www.wallacecompany.com/machine_shop/G540/g540_mb_spp.jpg Here it is in 5 V EPP (high drive) mode, which does work: http://www.wallacecompany.com/machine_shop/G540/g540_mb_spp.jpg Those 2 look identical because they are Kirk. :) ... snip Oops: http://www.wallacecompany.com/machine_shop/G540/g540_mb_epp.jpg -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
[Emc-users] Meeting minutes, 2013 September 28
We just finished our monthly IRC meeting. Meeting agenda vote results are included in this email, and on our wiki here: http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Meeting201309 Meeting log: http://meetlog.archivist.info/meeting.php?id=201309 moderator: Dave Caroline secretary: Dave Caroline Agenda Items # I propose we formalize the current practice of freezing the agenda on or around the Wednesday before the fourth Saturday; I think it is good to avoid last-minute additions for several reasons: so people have time to thoughtfully consider the agenda items, so they have time to start a discussion, and so they have full knowledge allowing them to decide whether to plan to attend. [cradek] Vote Yes with a reminder going out the Monday before that Wednesday to at least the user mailing list # I would like to propose again Michael Haberler's 'jog-while-paused'. This is really not a nice to have but a feature that is sorely missed.[mariusl] A long discussion on the way forward with people volunteering to do parts of this, no need to vote. NEXT MEETING: Saturday 2013-10-26 1600UTC Dave Caroline (archivist) -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] polyurethane resin casting
Did a vacuum pour test. Complete failure as far as I am concerned. The small amount of air introduced in the connection, as well as the small amount of air in the mix becomes an instant mini volcano. One option that could work for me is a double pour. Does polyurethane water tight seal on cold joints? On Sat, Sep 28, 2013 at 7:43 AM, Erik Friesen e...@aercon.net wrote: The current resin I use has a 50 second gel time. Its a little like flying rc, if it gets ahead of you you are in trouble. I wonder if a person could make a inlet control valve with a piece of tubing and clamp, or special clamp? Something that would take about 15 psi forward pressure to open the clamp. On Sat, Sep 28, 2013 at 7:16 AM, Erik Friesen e...@aercon.net wrote: For the high speed vacuum, why not just use an external tank, with plumbing valve or equivalent to switch to whichever has highest vacuum? On Sat, Sep 28, 2013 at 12:13 AM, Gregg Eshelman g_ala...@yahoo.comwrote: On 9/27/2013 6:29 PM, Erik Friesen wrote: Do you think vacuum alone would pull into every nook and cranny? I have looked for other people that have tried something similar, but didn't find much. By vacuum, my idea is to in some way place the mold under vacuum, and fill it using atmospheric pressure, perhaps using some type of funnel and valve. If you do calculations on a 4 sq in mold at my pump rating of 10pa, it calculates to a .07 cubed volume at atmosphere of 101kpa. Whats the demold/depressurisation time for pressured polyurethane? It depends a lot on the resin. Fast cure ones like you're using could come out in a few minutes to an hour, just to be sure. Most of what I use is Smooth-On Crystal Clear and I leave it under pressure 24 hours. I also post-cure at 145F with convection heat so if not left under pressure long enough I've had problems with small bubbles forming. I've also used some of Smooth-On's faster resins like Onyx and have been able to take out of pressure in about 30 minutes. That one cures hard enough it doesn't need post curing. Think of using pressure like what a deep diver experiences, except for with the resin and silicone keeping it under pressure long enough ensures the gasses never get back out. You can speed up the cure by shining a halogen work light on the pressure tank or putting the tank in a very warm room. I've cast silicone molds under pressure in the middle of winter in a poorly heated shop, with a halogen lamp shining on one of my larger tanks. Most resins and silicones need to be at least 75F to cure properly. Therin lies a useful property that can be exploited some times. Chill the components prior to mixing to stretch out the pot life, then after pouring into the mold, apply heat to speed up the cure. However, some resins can fail to cure properly if they're not at the proper temperature or higher when mixed. In such a case, mix the resin then fill the mold in a cold room, then transfer to a warm room to get some more working time. If you have a bunch of leftover silicone after casting a mold, freeze the leftovers. It'll bring the cure nearly to a halt. I've frozen mixed silicone up to a week and still been able to use it to make molds. It will be thick but will still flow. Another trick I've used to alter curing times is mixing resins from the same product line with different cure times. I had to cast some large but thin parts. The longer cure time resin wouldn't properly set in such thin castings and the short cure time that would set in thin castings would kick too fast to be able to get the mold filled. So I mixed the two in a 50:50 ratio and the properties came out somewhere between, stretching the time long enough to be able to fill the mold and get it in a tank, while still generating enough heat from the chemical reactions to fully cure. I told Smooth-On what I did. No reply but they later added another resin in the Crystal Clear line with cure properties between the 202 and the longer cure time number. I think they've also altered the 202 because I can use it as-is in the molds that I couldn't when I was mixing the two, and even if I do heat the tanks or set them on the concrete in front of my shop on a sunny day, the castings still need post curing. -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- October
Re: [Emc-users] polyurethane resin casting
On 9/28/2013 5:16 AM, Erik Friesen wrote: For the high speed vacuum, why not just use an external tank, with plumbing valve or equivalent to switch to whichever has highest vacuum? That's fine if you have the space and funds for a big tank, and a good vacuum pump. I bought an old but excellent condition Gast rotary vane vacuum pump, but haven't used it in some years since for the mold making and casting I do pressure has worked much better. Pulling a vacuum in a large tank takes quite a bit of time, unless you get a very high volume pump - and you'd best have a high volume bank balance to get one. ;-) Instead of one large tank some smaller ones can be ganged together with a manifold. Propane tanks with the valves removed so they can be hooked together with as large of pipe as possible will work, but getting the smelly stuff out can be a problem. I tried it with one tank, with the insides of the valve removed and opened up some with a drill to reduce restriction as much as I could. The stink would draw right through the vacuum pump and smell up the whole shop. To sorta on-topic this, one of the tasks I plan to put my mill to is making prototypes of things in metal to use as masters for RTV molds to make plastic castings. -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] polyurethane resin casting
On 9/28/2013 5:43 AM, Erik Friesen wrote: The current resin I use has a 50 second gel time. Its a little like flying rc, if it gets ahead of you you are in trouble. I wonder if a person could make a inlet control valve with a piece of tubing and clamp, or special clamp? Something that would take about 15 psi forward pressure to open the clamp. With the mold in vacuum? Could work if you mix exactly the amount of resin to just fill the mold and can shut the valve at just the right time. The vacuum would pull the resin in and should fully fill the mold but you'd have to be careful so it wouldn't suck it all out the vents in the mold. Using the ~14.5 PSI surface pressure of the atmosphere to push the resin in, you shouldn't need very much vacuum. Too much pressure difference and it might simply blow the resin through the mold. Don't want resin in your vacuum pump! Experimenting with one of those cheap compressed air powered venturi types could be a good idea so you don't chance ruining a rotary vane pump. I'd try a couple of ways. Just vacuuming the resin in and vacuuming it in followed by applying pressure. -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] polyurethane resin casting
On 9/28/2013 1:13 PM, Erik Friesen wrote: Did a vacuum pour test. Complete failure as far as I am concerned. The small amount of air introduced in the connection, as well as the small amount of air in the mix becomes an instant mini volcano. One option that could work for me is a double pour. Does polyurethane water tight seal on cold joints? In my experience, urethanes bond to themselves extremely well, as long as nothing is allowed to contaminate the surfaces you want to bond. I've had incomplete castings that I've topped off and the join is invisible - when all goes well. Sometimes the mold doesn't fit quite exactly back onto the casting and resin flows over one or both sides of it. Goes in the trash. Also some times the join is visible, trash too. Most of what I do is clear or colored transparent resin for non-stressed parts so appearance is most important. For your pump housing it's probably not a good idea to try salvaging an incomplete casting for anything but testing. If you want to deliberately do partial castings, that's another can-o-resin. For example you could machine away parts of the housing and mill slots into the edges to get more bonding area, then cast clear into the cut out sections for a 'cutaway' demonstration model that can be used with fluid flowing through it. Just be sure to pressure test *before* doing a demo for people you want to buy the thing! 'Sides that, having a bi-color product ups the Oo! factor to make your technical prowess look even better. -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] polyurethane resin casting
On 09/28/2013 10:03 PM, Gregg Eshelman wrote: ... snip To sorta on-topic this, one of the tasks I plan to put my mill to is making prototypes of things in metal to use as masters for RTV molds to make plastic castings. ... snip I may be a little biased, but this might be an option to resin molding. http://www.tormach.com/store/index.php?app=ecomns=prodshowref=32079 -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register http://pubads.g.doubleclick.net/gampad/clk?id=60133471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
