DIY Sandblast Gun Casting - Sub Optimal Results

[@SharkyMoto]

i think a big part of those 3000 subs came like me from mrpete. i'm really thankful for that, your videos are informative, well made and without any bs advertising. i love elder youtubers, they reached all they wanted and do this for the pure joy of sharing stuff. thanks preso!

[@Preso58]

Mr. Pete shared one of my videos on his channel a while ago. We were working on similar projects and he was kind enough to mention my video. I knew something was up when I checked my email and found hundreds of notifications for new subscribers. He and I both have a background in education and when I retired I missed being in the classroom but then I realised that I could continue teaching without having to put up with incompetent administrators and politicians telling me what I could and couldn't do. I have no interest in making any money from what I do. As you have identified, I and many others like to share and that is one of the things that gave me real enjoyment from doing KZbin. All sorts of people from all over the world have made contact as you have and that is particularly gratifying. Even my son now watches my videos! It seems like only yesterday that he was a resentful teenager. 😁

[@markfryer9880]

@@Preso58 Teenager is my current problem.

[@ironhead65]

File abuse! File abuse!!! Thanks for keeping it real as well as sharing your story along with the project build!

[@Preso58]

Dan, I knew someone would report me! 😁

[@hokepoke3540]

I have used epoxy sand mix for cores in the past and like you I had gas problems, venting the pattern does help but epoxy produces a lot of gas and that can even penetrate your casting with small gas bubbles. It helps to have a little more pressure on your metal, higher risers. Thanks for the neat video, you have more nerve than me. I can watch videos but not star in one.

[@UKenGB]

Although I have my own machine shop, I will never attempt to cast my own aluminium but I have been captivated by Mark's videos of the process. A measure of their effectiveness is how totally gutted I felt at the imperfections of this first casting. I see so many similarities in how I and Mark use machine tools and I thoroughly enjoy his delivery in the videos. So much better than most. Keep it up Mark. I have subscribed. BTW, even in the UK I feel frustrated at our inability to access the vast wealth of resources available in the US.

[@tobhomott]

This whole series with the blaster parts has been great so far, keep it up!

[@Arouth249]

This was a really cool project. I’d love to see more like this. Great job!

[@danburch9989]

I vaguely remember from my high school metal shop days over 55 years ago that we LIGHTLY dusted the mold form with talc and left it there. We didn't remove it. That was the release agent to keep the sand from sticking to the mold. We also used larger vent & pour holes and cope chanels so that the liquid metal fills the cavity before it has a chance to solidify.

[@Preso58]

Dan, the more I look at casting videos the more I am convinced that it is one of those dark arts that are shrouded in mystery. There seems to be a multitude of methods and approaches all of which get results. When I think back to the first casting I did I am now surprised that it turned out to be a usable tool, (it was a lathe carrier for mounting work between centres). Now it is all about finessing the quality of the casting and avoiding the catastrophic failures like the one in this video. Each time I try this I learn a bit more. I think that this is what makes it such a fascinating process. Thanks for watching and commenting. Regards, Mark P

[@millie19301]

Mark I enjoyed watching your video including all the problems encountered. The project was much more work than I would have expected, I've just bought a foot feed for my SkatBlast cabinet but I live in the US where Amazon solves most acquisitions. Keep up the great videos.

[@Preso58]

Steve, Lucky you. Amazon Australia is seriously understocked compared to the US site. I was able to buy some powder coat paint from the US site a while ago but our wonderful federal government stuffed that up when they asked Amazon US to impose GST on purchases from Australia. Amazon just shut down all sales from the US and referred the buyers to the Australian site. So, now we can only choose from about 5% of the inventory. Must be nice to be able to buy from McMaster Carr as well. I received a foot pedal from China yesterday. Seriously cheap and looks it too but it does work. Thanks for watching. Regards, Mark

[@matthewf1979]

You uploaded the video an hour ago and you have 3.1k subs now! Congratulations 🎉

[@yeagerxp]

So You got me. I subscribed. 1.As for the release agent try using cooking spray oil. 2. As for the rain I live in Toronto Canada. It has been raining and is cold and damp. You live in Australia it is warmer than here. 3. get your friend to weld the part, see if the design works.👍👍👍

[@Preso58]

Thanks, we were able to TIG weld the part and it looks perfect. I have already machined the casting and fitted all the extras. It is working and I am doing some tests to measure the suction. I was in Toronto two years ago. We loved it there but the drive in along the Gardiner Expressway nearly finished me. Bad enough in a left hand drive car but so many lanes! Our busiest roads here in OZ are usually 8 lanes but I think we counted 16 in some places coming in from Kingston. I think the Distillery District was our favourite spot. Regards, Preso

[@markfryer9880]

@@Preso58 16? Oh Gawd! 5 lanes each way on the Eastern Fwy is more than enough for me to worry about. If I go for a visit someone else can do the driving.

[@jimintaos]

I was giving some thought to what you said about your siphon gun not delivering as you would like it to. It occurred to me that the problem might not be with the gun but with the siphon pick up tube. In my own DIY cabinet I use a length of 1/2 inch copper pipe capped at the bottom end. Actually I pounded the bottom end flat with a hammer and then folded it over and pounded the fold flat. I then drilled a 1/4 inch diameter hole about an inch up from the closed end. I connected clear plastic hose to the top of the pipe and ran that to my gun. If the sand flow is spotty the size of the hole can be increased little by little until the flow is good. I think 3/8 or 10mm is about optimal but this will change depending on how far above sea level you are. I am at 7,000 feet where I live. When I lived in DC and was only a few hundred feet above sea level the hole needed to be a bit smaller. Hope this is helpful.

[@Preso58]

Jim, I have researched the shortcomings of the siphon arrangement on these sandblast units till the cows come home and the solutions all seem to centre around mixing air in with the blast media at the pickup location so the fix you are suggesting would do that. I did make a metering valve which has a variable air bleed and although it does help the feed to the gun is still intermittent. Curiously though, the gun still seems to be able to deliver a continuous supply of media. I have just finished the MKII gun and tested it and it has some minor improvements but I am going to build a gun with a transparent acrylic body so it is possible to see inside the venturi of the gun. That way I can visualise what is happening where the air meets the blast media. Stay tuned, it should be interesting.

[@jimintaos]

@@Preso58 The best siphon gun I've ever used is the Port-A-Blast. I modify it to use a siphon bucket that I build out of drywall buckets. The Port-A-Blast is designed to use a little quart sized pot right under the gun itself. I ditch the small pot and replace it with a threaded tube and a plastic hose that goes down to the sand bucket. The next time I am in the shop I'll take some measurements and a couple of pictures and send them along. I've been intending to make my own version of this gun.

[@AlbiesProductsOnline]

Just a suggestion when you print the core boxes add in a beveled edge between the joint lines and add tabs in key places to pry against to help with separation

[@Preso58]

Thanks, I will try that.

[@sdunca4864]

Bravo Mark! Even with the fail its another great video- As before- great watching the process and like your approach and the epoxy tip! Subscribed and I'll tell you straight up- awesome work.

[@ChaosOptional]

Have you considered making the core mold more than two parts? Especially if you don’t want or can’t maintain a draft angle.

[@MyllerSWE]

Never forgett that compressed air works really good to pop things out of moulds!

[@Preso58]

Thanks, I must remember that. We used to remove GRP canoes from their moulds using compressed air. We used water if they were really stuck. I could place some strategic holes in the corebox and shoot the air in there. Good idea!

[@mikevars8979]

I love your Videos, I learn a lot from them. I am glad you show your failures as we all learn more from what doesn't work than from what does. Is it possible for you to share the 3D files of your mold patterns? I could design my own but you have already gone through some design changes to improve performance. I am in the process of building my own home manufacturing workshop. I am studying Mechanical Engineering at University and fell in love making a vice from raw material in our Machining class. From Foundry work casting Aluminum base mold, using mills to shape the casts into spec to cutting the screw on the lathe. I now have a 3d printer, 13" Lathe and an old Atlas Metal Shaper. You are a great inspiration.

[@Preso58]

Mike, I am happy to send you the STL files for the patterns and the core boxes. Just send me an email. My address is in the "about" tab on my channel. I can also send you the raw Inventor files in case you want edit the models to suit your own needs. I am glad you are enjoying your adventures in engineering. When I was still teaching I got involved in an organisation here in Australia called Re Engineering Australia (REA) Their mission was to encourage young people to take up careers in engineering and manufacturing. They were a not for profit company and they did it for the right reasons. We used the F1 in Schools competition www.f1inschools.com/ as a way of providing the right environment for motivating the students and although it was a lot of work on top of my normal teaching load I saw, over the years, kids moving on to really exciting and rewarding careers in all facets of engineering and design. One student went on to work for Red Bull Racing in England as a designer. My own son, who was the manufacturing engineer for his team is now an "Advanced, Manufacturing Technologist" at Callaghan Innovations in Wellington, New Zealand. The world needs good engineers. Keep up the good work! Regards, Mark

[@curtisroberts9137]

When working in the firearms industry with various epoxy mixtures I found that any wax with carnauba worked well as a release agent. Thats most car and floor waxes.

[@Preso58]

The wax that I was using was a mixture of Carnauba and bees wax. Bees wax is very soft and the Carnauba is quite hard. We used to use Carnauba as a wax for polishing wood turnings and the heat from the spinning wood part would melt the wax and impregnate the pores of the wood. Regards, Mark

[@matthewf1979]

Still a nice piece and entirely serviceable after the weld patch. Have another 🍺 beer for me!!

[@MrLukealbanese]

Mark, I notice that many people seem to pour a couple or three of any crucial patterns at the same time, just in case. Wouldn't take much more time but would dramatically improve the likelihood of success perhaps.

[@Preso58]

Luke, You are correct. I had two cores, I should have done a second flask. I am going to do a second casting when I have worked out all the bugs. Already, I have had lots of useful suggestions on how to improve the design. That's one of the good things about sharing this stuff on KZbin. Regards, Preso

[@thisnicklldo]

Good video. It'll be fine. I thought when I saw the core go in that it was very thin-walled at that point. I've seen Myfordboy make stuff with sections that thin, but typically smaller parts with less thick sections to contract on cooling and pull the thin section around. If you do another one (and there's probably no need really), you could reduce the diameter of that central section of the core a touch, or taper it a bit. Good thing the old core 3D print is ruined, really? Anyway, very interesting stuff, thanks for posting.

[@Preso58]

I will do another one. The part you saw in the video was repaired and it is now working but as you have observed there are some refinements I want to incorporate... and I have been told that it needs to have lightening bolts on it. 😁

[@IBWatchinUrVids]

Nice video :) I've done some casting. I'd wager it's a combination of lack of gas venting, and temperature. Looks like either there was a gas bubble there, and / or the aluminium cooled in the thin section before it filled in. As always, I enjoyed watching your project!

[@markfryer9880]

Forgot to mention that to myself and many others a close up post casting CSI is just as interesting as the rest of the video. Commiserations about the failure.

[@markfryer9880]

Hi Mark, was the failure caused by the core floating out of alignment or gases venting with no escape path? It seems to me that the failure was on the cope side of the mold and my suspicion is core gases lacking an escape route.

[@Preso58]

Mark, I think you are correct. I didn't bother to vent the core. I did vent the core on the metering valve casting and it worked perfectly. I will do a second casting when I have figured out all the bugs. Stand by for included lightening bolts on the side!

[@markfryer9880]

@@Preso58 Won't that then require rubber gloves and AC/DC music set to 11 when operating?

[@markfryer9880]

@@Preso58 On a serious note I think that a vented core would make removal easier.

[@user-qy9rg3nt2l]

Here's a thought.. why not incorporate a runner and gate into the 3d print itself? A sprue and riser would be easy to locate after looking at the impressions in the cope after pattern removal. Just a thought if only doing one at a time.

[@Preso58]

I have seen the use of 3D printed patterns for runners and gates but it seems like a lot more printing time for something that is likely to be used once. Regards, Mark

[@ianbertenshaw4350]

My sentiments exactly ! Beer makes everything better !

[@clydeulmer4484]

Even though honeycomb infill is strong. you might -- depending on your slicer -- investigate other infill patterns You could also play with infill densities and wall number. Short, of course, of making it solid :-) Wrt release agents, I've had the best luck in my experiments using several coats of silicone release agent. I suspect that oils, waxes & greases char and get sticky. To be clear, that's just a suspicion, since I've not actually done any comparative testing. This whole series has been entertaining. Best of luck, and I'll be looking forward to the rest. Clyde

[@Preso58]

Clyde. I have just recently started using Cura as my slicing software. I tried using it years ago and didn't like it because I couldn't connect my printer directly to it. I had been using Repetier Host as I could control the feed rate, heat setting etc. direct from my PC. Now I find that Cura does a much better job. I am just printing a prototype part for a bandsaw blade guide and it does the rafts and support perfectly. Buying a new printer has helped too.. I now have a Creality Ender 3 and it seems to do a great job. I purchased an UP! printer for the school where I worked about 7 years ago and we paid north of $2000 for it! I am going to make the casting for the blast gun again although I was able to fix the original casting and machine it. I want to try out some ideas that I have been given as suggestions and I do have some silicone dry lube so I will be trying that. I am going to do several castings at once so that I can mitigate against failures.

[@clydeulmer4484]

@@Preso58 The jaw-dropping price drops on these printers is what sucked me in, and I now have an Ender 3 Pro, which I agree is a great little machine. Of course, I've now spent a chunk of cash upgrading the motherboard & drivers, the hot end, the extruder, the bed springs, adding a BLTouch and a color touch screen... But that's part of the fun :-) Cura is my slicer choice too. Be aware that silicone lubricants and silicone mold releases are very different critters. The CRC brand release agent I use has a working temperature range of 35 to 600 degrees F. The lubes have a much lower high temp limit. Clyde

[@gasonthebrain3738]

Also, where did you get the idea to try epoxy resin. It seems to work great. Especially the knock out and the finish. I see another Aussie, that does a lot of casting, is also using it now. Well done for introducing the method.

[@Preso58]

I first saw the technique on luckygen1001's channel. He is probably the other Aussie you are referring to. I was looking for advice on alternatives to traditional core making. I have since had some others comment on ratios for resin to sand and I have heard that between 2 and 12% works. When I did the video I was really trying it for the first time and although I mixed more resin than I needed I was shooting for a 2% ratio. In the end I just added the resin until it looked about right. It seems that the precise ratio is not critical. When it looks and feels like regular greensand it should be OK to use. Regards, Mark Presling

[@gasonthebrain3738]

@@Preso58 Yep. He is the one. Thanks for that info. I look forward to giving it a go one day. Regards Stephen

[@paulmuff9883]

Nice video and love your honesty 👍👍

[@colincreedtattoomachines]

Mark, you've done a great job regardless of the failed cast & the result is a great video, Well done!! With regards to the casting fail, I'm wondering if that could be related to the gases generated from the epoxy burning away..? ...I say that as an old Jeweller having had similar problems when using plastic items as the model with lost wax castings. HTH, Colin

[@yvesdesrosiers2396]

Ah the best laid plans of mice and men...... stuff happens. Thanks for sharing and nice job Mr P.

[@Preso58]

Thanks Yves, Improved version coming out soon.

[@sheph7ceo799]

Like the design, looks like a Flash Gordon Atomic Space Gun. And yes needs a lightning bolt on side.

[@Preso58]

Lightening bolts coming up! 😁

[@SeanBZA]

Release agent use weld spatter protection spray, or silicone mould release spray. In a pinch a few coats of furniture polish will work as well.

[@Preso58]

I am going to do this casting again when I have worked out all the bugs. I will try silicone spray on the next one. I was able to get my mate to weld up the missing sections and it looks perfect now. I think it's worth incorporating some refinements even though the one I have now is working

[@rodneykiemele4721]

I agree, the casting might have failed, but you’ve made a great video Thanks

[@theonlybuzz1969]

Hi Mark, great show you have if you are after more casting from the home, then have a look at Myfordboy channel, he rocks and doesn’t talk during the show (must have a awful voice or something), but his casting process more than makes up for it. Btw isn’t it a bit risky to have a functioning gas bottle next to the furnace "? Another thing that I have noticed would be at the ends of the cores when in the mould would be to have a 1 to 2mm wire going through the top part as it’s going to make a vent for the cores (this helps a lot) . You don’t seem to have like a metal cylinder on the top of that mould with casting sand inside on both the feeding points and one on the main vent too. Have a look at Myfordboy and he shows some nifty tricks to degas the molten alloy and another component that acts like a flux to help get a better product. I wish you all the very best wishes Mark, and look forward to seeing some more of your videos....Phil in the UK

[@Preso58]

Phil, I have been following Myfordboy for years and it was after watching lots of his videos that I realised that metal casting at home was something that I could do and not some black art that was totally impossible for an amateur. I used to explicitly follow his methods including making the large bore risers and feeders with the tin can extensions and it worked for me. Recently though I have been watching another channel called Olfoundryman. He is a fellow Aussie who seems to have a background in metal casting (as a profession) and he has totally different views on fluxing, degassing and methods of making sprues and risers. I have tried a number of his methods and they also work well. I guess it is one of those contentious issues that creates a lot of debate. I learned a lot from making that mess of the casting for the blast gun and now I do vent the cores and the mould and I have invested in a pyrometer for measuring the temperature of the molten metal. Since then I have been having relatively few failures. With regard to the gas cylinder. I took some measurements on the temperature around the furnace. The outer walls radiate about 70C and the lid about 100C. I know it looks awfully close to the furnace in the video but I try to place the cylinder off to one side and not directly in line with the burner entry. Regards, Preso

[@theonlybuzz1969]

Mark Presling good onyx Mark, Myfordboy is probably the best channel for casting information on how to do this process, I’m going to have a go to making a furnace and do some castings myself, in the past I have a idea to make a custom adapter for the Mitsubishi pajero / shogun door mirrors to fit the American van called an Astro, in the uk a lot of owners have had “encountered l situations and ended up loosing the door mirror, I’m going to offer a kit that will adapt the pajero mirror to the Chevrolet Astro base. Where they can buy a kit for just the adapter and leads etc, up to full set of mirrors on the correct base, plus the pajero mirror controller, the reason I chose the mirrors was that they’re plentiful and cheap. Plus the can integrate into the main wiring, as to automatically close when the doors locked, no an easygoing task but I really like the van and want to help the other owners out (plus line my pockets with plastic that has the queens head on, bank notes). Anyway apologies for going on a bit, I have enjoyed your channel and subscribed to keep up seeing you make something new. Have a good week 👍👍👍 5 hrs and back into work....

[@ChristianRThomas]

There are some really nice techniques in this series. I'm learning a lot. Being a huge fan of epoxies and what they can do the sand epoxy mix is fantastic to know about. (BTW, on most composite mouldings it's usual to put down about 3 layers of release agent, letting it dry in between coats and polishing it each time. I actually buy release agent but soap or furniture polish are supposedly just as good. In fact soap might be a really good one since it was stearates that were used to release LPs from their moulds and that's holding indentation up to 20kHz and at the sub micron level. ) Is there a reason why you have chosen a cylindrical chamber rather than something more contoured? Do you want additional turbulence to get the mixture better? A smoother shape might also be easier to get out of the mould. I'm genuinely interested in why.

[@Preso58]

Christian, There is very little epoxy in the sand mix so there is probably less need to build up a really good layer of release agent. I think the most of the issue I had with removing the core from the core box was to do with the texture of the 3D print. There are striations on the walls of the corebox which can be seen quite clearly when you do remove the core. They seem to give the moulded core something to grip onto. It is also quite fragile otherwise you would be able to lever it out. I am experimenting with a core box design which is split almost all the way through so you can bend it away from the core rather than relying on levering the core out of a fairly rigid core box. I should have made the core box in more than two parts as well. The next one is made as four quarters rather than two halves. I get what you mean about the abrupt change in the cross section of the core. making a smoother transition from the inlet passages to the larger void would help to strengthen the core and maybe create better flow inside the gun. I was sort of replicating a design that I saw which was fully machined from bar stock but I should have taken advantage of the nature of a cast component which can have pretty much any geometry inside it. Having said that, I have had a friend weld up the defects and I have been testing the gun. So far it seems to be creating more vacuum than the original gun with less air consumption. I will be showing the results of the optimisation on the next video. Regards, Mark

[@watahyahknow]

think wax would work better s a release , maibe it allso helps to make the core mould in one half and two quarters as for the speus , my idea on that is to look at two flowing rivers comming together , thinking of that my guess is that you put the spreus at exactly the wrong ends , i would put it in the "armpit" of the gun and put the channels to both outer corners flowing from there to the end of the gun

[@Preso58]

So much to learn..... Sigh! Just when I think I have things figured out some curveball comes in and whacks me on the head. In the past I have not had much trouble placing sprues and risers but adding a core seems to add another layer of complexity. Thanks for the tips.

[@gasonthebrain3738]

Hi Mark. Thanks for the videos. In this video you stated that the ratio of resin to sand was 2% (2 parts resin to 98 parts sand). Put then you weighed them out and it appeared to more like a 18% ratio. )18 grams resin to 100 grams sand) Then you added a little more sand to make it less wet, which probably changed it to about 15%ish. Can you confirm all that.

[@SharkyMoto]

you should look into mpcnc, its a cnc rounter that can be made from 3d prints, conduit pipe and a cheap trim router, that combined with a ballnose endmill could make some pretty neat core molds out of mdf or plastics wich you could sand perfectly smooth. dont know if its worth the effort, but i just built one and it was a very satisfying process. still searching for usecases, that might be one of those!

[@Preso58]

When I was teaching we had a Denford CNC router we used to machine balsa wood model F1 cars for a competition called F1 in Schools. I used it for lots of "foreigners" which is code for private jobs. Now that I am retired I feel sad that the machine is just sitting in a store room gathering dust. It was worth over $16000 but it didn't belong to the school and as such they cannot sell it. I am still looking into some DIY router builds but if I do it I will probably use a lot of cast parts for the gantry, motor and spindle mounts. My biggest issue is finding somewhere to put it. Maybe if I sell the wife's car? 😁

[@SharkyMoto]

@@Preso58 you can built the mpcnc with lets say 75x75cm footprint, doesnt have to be a huge thing :) buy your wife an aussie UTE and put the cnc in the back, that would be fair!

[@anthonymagnani4100]

Says 3,178 subs when I look! Keep it up, love’em!

[@Preso58]

Yes, for some reason the channel has taken off just recently. It's a bit of a mystery. Someone must have shared something on social media which I tend to avoid but It's gratifying just the same.

[@Watchyn_Yarwood]

What did you think of myfordboy's Centrifugal Lost PLA handwheel casting? Will we see you trying something similar in the future?

[@Preso58]

William, I have been watching his experiments closely. I did do some centrifugal casting when I was at college back in the 70's. We used a wind up spring operated type of casting machine and we were casting pewter into jewellery. Myfodboy's latest experiment looks great although I think if I were to do it I would use VegOilGuy's vacuum system. It seems inherently safer and I already have a vacuum pump. I think that lost PLA casting is a lot more technical and I don't have an electric kiln to burn out the PLA but I have yet to find out if you need a controllable electric kiln to correctly burn out the plastic or if it is to correctly cure the investment plaster.

[@markfryer9880]

@@Preso58 VegOilGuy uses his kiln to firstly cure the plaster mold and then lifts the temperature to melt/burn out the PLA.

[@markfryer9880]

@@Preso58 I watched myfordboy do his centrifugal casting for the first time yesterday. I have to admit that I don't like the idea of having flying hot metal near me if something goes wrong.

[@Preso58]

I watched Veg Oil Guys latest video which was the summary of what he has learned so far. He does it really well.

[@Watchyn_Yarwood]

@@Preso58 Thanks. I'll check out the Veg Oil Guys. p.s. I really enjoy your videos, especially the honesty! A rare commodity anywhere these days.

[@dirtyknuclesde]

Can you make the .stl files for the corebox and gun available? This looks like fun.

[@Preso58]

Hi, flick me an email at [e-mail] and I can send them as an attachment. Regards, Mark Presling

[@garyskowbo3564]

Good job, thanks for sharing your videos. Just wondering did you buy your molding sand or did you have to mix it up your self?

[@Preso58]

Gary, I made my own sand. It is a mix of "Ballina White Sand" which is almost pure silica, washed, fine beach sand and about 15% bentonite clay which was run through an old blender to make it into a texture like talcum powder. It has not been mulled but I find that it gets better over time. Still not as good as petrobond or some of the naturally occurring clay bearing sands but it does work.

[@garyskowbo3564]

Thanks for the information, also I meant to ask about percent of water added. I have done some casting, but it has been mostly quite crude as far as the molds are concerned. Am working on a new shop now, and I hope to get back to doing some casting again. So your videos are quite interesting to me! Please keep them coming, as you are able.👍🤙😁

[@Preso58]

Gary, The amount of water you have to add depends on what state the sand is in when you reuse it. Sometimes I might not use it for several months and by that time it is bone dry. Other times it might just need a refresh with just a little water to make it good. The general rule is that it should compress into a fairly solid lump if you squeeze it in your hand. You should then be able to break it cleanly in two without having the sand stick to your skin. You have to add the water slowly and test it often. If you make it too wet you might have to wait several days for the excess to evaporate out of the mix. Sadly, it is one of those things that you have to develop a feel for. I have heard suggestions to keep the greensand in an airtight drum so that it will hold it's moisture level once sealed. I keep mine in a large rectangular tub with a loose fitting lid so it is easy to shake out the moulding flasks. The down side is that it does dry out when not being used.

[@stevenmitchell6347]

I was noticing that the core doesn't create a cavity conducive to promoting the venturi effect necessary for optimal flow of the blasting media. Instead of a cylindrical cavity in the center, a tapered "teardrop" shape should work better and eliminate the "shoulder" that resulted in the shut you had to weld. Just a thought from one fabricator to another. I really appreciate the effort you put in to create that which is difficult if not impossible to aquire otherwise.

[@Preso58]

Steven, I made a second version of the gun body with a much more streamlined internal cavity and it works great. I am still using it in my sandblaster some two years later and it has proven to be quite efficient. I also redesigned the core box to make it easier to get the core out. kzbin.info/www/bejne/rH6xiHaLa5aVl9E Most of the ideas came from viewers so I cannot claim credit for many of the refinements. Regards, Mark

[@pgs8597]

G’day Presso, shame about the flaw. The core with its larger centre section is not tapered down to the nozzle end of the inner housing won’t this cause you problems with the flow of air and media, maybe creating a turbulent flow rather than a smooth flow?? Even on the rear end a low pressure zone where the air enters the larger chamber. My two cents worth from the beer garden engineering department. Cheers Peter

[@Preso58]

Peter, I have sort of come to terms with the failure and I have had my mate weld up the faults. I have already done some tests on it and the results seem encouraging. I am using this casting as a test bed and I think I will make a new one with some changes to the internal shape. More taper towards the front and rear of the internal chamber as you have suggested. I want to experiment with the corebox, release agents and this time I will vent the core and leave a bit more metal around the cored space. Regards, Mark

[@andrewwaters2354]

You should use honey wax as a release agent, at any fibreglass supply,or if you can't get that any type of carnauba wax will work

[@Preso58]

Thanks. I have a few more cores that I need to make so I will have plenty of chance to try out different solutions.

[@mrdr9534]

Thanks for another great and very funny video. Best regards.

[@slypig24]

What are people's thoughts about doing the welding repair with the Core still in place. I know it's too late now, but as a discussion point.

[@ChristianRThomas]

It's a lot harder to visualise but that's a really good idea.

[@mrgreenswelding2853]

What state are you from? Im in brissy qld

[@ronaldnickell6110]

If you have a soft edge use some sugar and water mix with a hobby spray gun to lightly spray the soft area, you can dry lightly with a hair drier. This will harden the edge. Old old foundryman trick, only they used a perfume spray bottle with a squeeze bulb.

[@Preso58]

Thanks for the tip. I hadn't heard of that one before. Regards, Mark

[@dougiearmstrong9992]

why dont you ever vent your mould and core just a few scratch vents at the crore print. and stop ramming the mould so hard you pushed the cope pattern into the drag pattern that is why you get an uneven joint line cheers from an old moulder

[@kevinl5878]

Thank you for your time like your work

[@lv_woodturner3899]

The old two steps forward one step back. I am very familiar with such setbacks. I would also try at fixing this. I do not have aluminium welding equipment so I would have had to try fixing the hole and fracture with JB Weld. This would seal against air leaking, although may wear out with use. Have you considered using a flexible filament instead of PLA for the cores? This may be easier to peel away from the core. The con of flexible filament is that it may move with the force of the packed sand. I am looking forward to the next and perhaps final episode. Dave.

[@Preso58]

Dave, I was able to get the casting welded up and it looks like it was never broken! I have already machined it and fitted all the jets and couplings and it is working quite well. I have never worked with flexible filament but I am keen to try it.

[@crazyfeller5704]

Good stuff. Thanks for sharing.

[@rallybbek]

Ahhh so close ! You think that was an air bubble trapped to cause the void?

[@Preso58]

I am not sure. I originally suspected that the melt was too cold. I was running low on gas and decided to pour anyway. I also think that I should have vented the core and the area directly above the larger cavity. Some people have suggested that the epoxy may have created a gas bubble or may have vented out of the thin area which caused the missing section. I will do a second casting when I have worked out some of the bugs. I did fix the casting and it has been machined and it is working but I think I can improve it.

[@kmcwhq]

No offense intended! Great lessons in foundry work in these vids....but the prices for those parts on eBay seem a lot more reasonable now!

[@markfryer9880]

Mark's point is that it's not so much about the price of an item but rather the freight cost to Australia which is the killer in the transaction.

[@danielfogli1760]

Yay for positive energy 🤣 (And for having a beer)

[@TheDeerInn]

I think it failed because light from Venus reflecting off a weather balloon excited the swamp gas inside the mold, certainly repairable, nice job.

[@R2.0]

I'm guessing you already know this, but that chamber will need an eductor (venturi.) Also, the quarter corners on the outlet side of the changed need to be more conical. US patent #US6383062B1 (Google will have it) has some excellent diagrams.

[@R2.0]

Gah. "Outlet side of chamber."

[@Preso58]

Hi, Looking back on the design now I realise that it is quite crude but I wanted to be able to reuse the ceramic nozzle that came with the original gun. It has a conical inlet but the remainder of the bore is cylindrical. If I could somehow machine a tapered outlet it would become an eductor nozzle. Back in 2009 I worked with a group of students who were selected to represent Australia at the world championships of F1 in Schools. (google it) We designed an eductor nozzle which clipped onto the back of the car with the aim of drawing in air to mix with the stream of high velocity CO2 gas. We made up a test rig to see if it worked and we were able to show that it increased the mass flow of gas through the venturi. We called it an aspirator but essentially it is similar to an eductor. The difference being that an eductor has a single point of entry for the fluid being pumped whereas an aspirator draws in fluid, usually air, from all round the inlet. Richard Hammond did a documentary on the Airbus A380 showing how they use aspriators to inflate the emergency slides in under 3 seconds. I am going to make a MKII version of the blast gun with some improvements and I am currently doing some tests to optimise the design. I am going to try machining a nozzle with tapered inlet and outlet from CrMo steel fully hardened to see if it makes a difference. I did a search for the patent but couldn't find the exact patent number but there were lots of designs of similar devices. Regards, Preso

[@tamiamibusch]

use PVA mold release

[@Preso58]

I wish I had some. We used to use it at school for GRP moulding. We had gallons of it!

[@tamiamibusch]

@@Preso58 in the USA its easy enough to order online and cheap, last a long time. Also a heavy coat or car wax applied and not buffed off works well.

[@jaredwilliams5252]

Instead of lithium grease just use some paste wax that's used for waxing cars.

[@Preso58]

Jared. I am using wax now. It does a much better job.

[@singlehanded12]

Down tools, that's how we did it back in the day. keep the bastards honest.

[@johnwestbrook2476]

Mark, check out mrpete222, your KZbin teacher. He demonstrates in great detail what you are doing.

[@Preso58]

John, I am already subscribed to Mr Pete. I also check out Myfordboy, Sandrammer, Luckygen1001, SWDweeb, Olfoundryman and so many others. All have really great content and I learn a lot from them all. I wish I had started doing home casting years ago. I always thought it was too hard and that you would need lots of specialised equipment but it turns out to be less complex than I thought. It's still hard to get consistent results but at least 90% of my castings have turned out usable and useful. Still so much to learn though!

[@dhc4ever]

Mark Check out swdweeb and old foundry man on youtube. You will find answers to a few of your issues.

[@markfryer9880]

His use of the pouring basin, tapered sprue and talcum powder to smooth the basin and tapered sprue indicates to me that he is a follower of Olfoundryman. Or should that be Disciple?

[@dhc4ever]

@@markfryer9880 Follower yes Disciple? I dont think Martin has made it to deity as yet...

[@Preso58]

Yes, I recently got to watch a lot of SWDweeb's content via Olfoundryman. That in turn led me to Andy Martin. So much good content and so much to learn! Veg Oil Guy seems to have perfected lost PLA casting as well. I have yet to try that. It's a bit more technical than sand casting but he gets really great results.