Rudy Kouhoupt's Open Column Steam Engine - Cast & Double Size

[Brookesy]

I'm keen to see where this goes since it will probably cover a lot of stuff I want to learn. Excellent project.

 

[vederstein]

Well, I have the 3D printer on order. It's a Cetus 3D extended with the heated bed. The printer is on back order so I will be several weeks before I get it.

Equipment on backorder isn't necessarily a bad thing. If it's due to a high volume of orders (as Cetus claims), then the product is apparently successful and there's less of a chance that the company goes belly up leaving my with an anchor when parts need replaced.

I've read many reviews and there have been very few gripes about it considering the price point (~ $450 US).

Yes this video is from the manufacturer's website, but its a decent overview of the machine..

Next up: Taking my part models and modifying them for casting molds. This will entail:

• removing/resizing holes
• adding sprues
• ganging parts together (where appropriate for either machining or casting)
• scaling 2.4% larger to account for shrinkage

I don't think adding a draft is really necessary here because the lost was method doesn't have any split mold to pull apart.

...Ved.

[ame]http://www.youtube.com/watch?v=fZTYfo1o7Lg[/ame]

 

[Brian Rupnow]

Be careful--Many old Volkswagen blocks were made from magnesium, and when heated to a near melt temperature would burst into flame and burn with a very intense white heat. You can do a web search to verify this.---Brian
[ame]https://www.youtube.com/watch?v=nhY0xzKcPoE[/ame]

 

[Brookesy]

Definitely be very careful with any old Volkswagen parts. High magnesium content and extremely dangerous. Also, I've been told that the first thing to print on a 3D printer is spare parts for the printer if you can find files for them... Just a thought

 

[bmac2]

Magnesium is very simple to test for. Just clean a spot with emery and put a few drops of vinegar, If it bubbles up it magnesium.

 

[vederstein]

I went back to the CAD and modeled up some castings:

• I scaled the CAD files 1.024 for a 2.4% oversize to account for shrinkage.
• I put like parts together where it seemed to make sense (e.g. cast the main bearings together).
• I added flow paths.

I'm going to start with what seems to be the simpler parts (cylinder head & bearings) then as I figure out what I'm doing , I'll modify my molds as I learn and then go onto the more difficult parts (e.g. flywheel, base plate, cylinder). Some of these will require printing separate parts then sticking them together. This isn't a problem because I plan on using printable wax and can therefore melt the bits together.

 

[pp2076]

Just to play the Devil's Advocate here, how do you reconcile this statement:

In a month (Christmas gift to myself) or so I'll be obtaining a 3D printer to do lost PLA or lost wax casting on the components.

with this one from the same post?

I simply cannot justify spending over $300 US on what is essentially a toy.

:hDe:

 

[vederstein]

How do I justify? Easy: This project will expand my capabilities. Buying another casting kit would be more of the same. To do my own castings is a learning experience.

The 3D printer has the possibility of being more than a dust collector.

You raise a good point. Perhaps I`m a bit hypocritical.

...Ved.

 

[pp2076]

I'm just pulling your leg mate

 

[vederstein]

Well I've been a bit quiet on this project.

I received the 3D printer four days ago. Yesterday the electronics took a crap, so I'm further delayed as I wrangle with the Chinese company to get some sort of fix.

But all is not lost. I have been working on the barstock parts.

The picture below is of the eccentric & valve rod with a 6" (~300mm) scale next to it. This is going to be one big engine for a model....

 

[Cogsy]

Hope your printer fix goes well. Touch wood, so far my cheap Chinese printer (Anet A8) has been virtually flawless, bar a few teething issues and with some printed upgrades, but I have heard horror stories.

I have to mention your scale though - 6" is reasonably close to 150mm, but a bit of a stretch for 300mm. You did say approximately though...

 

[vederstein]

150mm, you're correct. DUH....

 

[ddmckee54]

Ved:

When you do start printing parts, print a part with known dimensions and then measure that part carefully. I recently discovered that my printer was printing parts about 2% oversized. It's a Prusa I3 clone that I had to assemble since it was a kit and I've had it for about 2 years now. It was only about $300 at the time so I really wasn't expecting that great of prints from it.

I am now scaling the models to 98% in the slicer and I'm actually getting the fit between the printed parts that I wanted to get. If I want an interference fit, or a sliding fit, I can get it.

Don

 

[vederstein]

When you do start printing parts, print a part with known dimensions and then measure that part carefully. I recently discovered that my printer was printing parts about 2% oversized.

The one and only thing that I was able to print (and even then I had bed adhesion issues) was a 25mm cube. Amazingly it was within plus/minus 0.4mm of nominal. For casting purposes, I thought this was very good. So if I can actually get this thing to work, I think printing tolerances will be fine.

As for an update, I requested from Cetus an RMA to return the faulty unit. They offered an alternative of sending new electronics and a monetary discount of the purchase price. I accepted the offer.

Time will tell.

...Ved.

 

[ddmckee54]

Ved:

When I started printing I felt the exact same way. What I was printing was within a few tenths of a millimeter of the specified size and for most of what I printed the size difference didn't really matter. I tried printing the one-piece crescent wrench and I was able to get it to work, although I did de-laminate it in one spot when cracking the parts loose. I made a test fidget spinner for a guy that I work with who collects them. The fit was OK, barely, everything was loose.

This year I decided to make fidget spinners for my great niece and great nephews for Christmas stocking stuffers. The version I was printing uses 1/2-13 nuts as the weights for the spinner. Some of the kids have pretty small fingers and I didn't want them getting their finger stuck in the threads of the nuts so I decided to make a plug for the nuts. I'm new to 3D and hadn't tried drawing a 3D thread, let alone printing one. No matter what you might believe drawing an imperial thread in a CAD program that thinks in metric is not easy. After the fourth prototype not fitting, and WAY more than that many hours I decided to run the plug through a 1/2-13 die to see how bad my thread design actually was. It was when I saw that I was cutting threads on the un-threaded portion of the plug, which was supposed to be smaller than the minor diameter of the threads by at least 0.1mm, that I realized something was definitely off. I broke out the micrometer and found that the plug was about 2% larger, in all dimensions, than it was supposed to be.

It took me 2 years of frustration with the printed parts not fitting correctly before I finally realized what was happening. All that time I was blaming it on my printer not being of that high of a quality, it's a Sunhokey Prusa I3 clone, along with my in-experience in 3D printing. I was also thinking that this was what I had to expect from 3D printed parts. I have since re-printed the one piece crescent wrench scaled to 98%. While it still required a bit of fettling to get it to work properly, the difference between this wrench and the first was like night and day. Just trying NOT to share the grief.

Don

 

[Cogsy]

For bed adhesion with PLA I initially had quite a few problems until settling on 50 degree bed temp and mobs of glue stick, over 2" wide 3M blue painters tape. The downside was a horribly pitted finish on the face touching the bed. Eventually I discovered a 50 degree bed (might not even need the heat) over the same blue painters tape was all that is required, as long as your first layer is laid down close enough to the bed. I now never have lifting on PLA parts and sometimes have the opposite problem of getting the things to come off the bed after the print is finished. There is a learning curve to 3D printing that can be very frustrating but you'll get there in the end.

 

[ddmckee54]

I also print PLA on blue painters tape. Some people say heat the bed, others say don't heat the bed. On small-ish parts, 25mm square or less, I don't use any bed heating and normally don't have any problems with print bed adhesion. On larger parts where the print head travels more than 50-75mm of linear travel before the next filament is laid down, I've found that with my printer I need to heat the bed(I use 60°C) - otherwise no matter what I do the first layer won't stick. After you get the 1st layer successfully stuck down, the rest of the print is usually a piece of cake. When I'm printing something where quality matters, I'll watch the 1st layer as it prints. If it screw ups, I'll abort the print, fix the problem, and re-print.

Of course now that I think about it, I've got a cold drafty old house that was built in 1890 and my printer is sitting in the corner next to 2 outside walls. That could explain some of my 1st layer problems, maybe not such a great location for the printer? YMMV - depending on your printer. Your printer may or may not respond exactly the same way as somebody else's machine, even if the machines are supposedly identical. I print at 215°C for the 1st layer and 210° for the rest. I know this is supposedly too hot, but if I go much lower I can hear the extruder drive gear popping as it slips and grinds on the filament. You'll find that you'll print a lot of test cubes. I made mine look like dice, that way I know how the cube was oriented when it was printed - helps when troubleshooting problems with an axis. Everybody at the office that wanted any has 3D printed dice on their desk.

Have fun with your machine and don't expect flawless prints right away - maybe never. After all, these things are just glorified hot glue guns.

Don

 

[vederstein]

After about three weeks of haggling with the printer manufacturer they've finally shipped the replacement electronics. I should receive them in about a week.

In the meantime I made a hot wire foam cutter so I can cast some of the simpler parts via the lost foam technique.

It's currently an ice/snow storm as I type is in central Indiana, USA. So who knows? If the weather is decent enough I might actually be able to cast some engine parts in a few days.

I started making my melting furnace September 2017. Therefore considering I've been making tools for the last five months, it'll be a big milestone if/when I cast some actual parts.

To be continued....

 

[vederstein]

Using the hot wire cutter I made my first lost foam molds today.

The results were bad as expected considering I`ve never done this before..

I tried first using green flower arrangement foam. It had too high of a melt temperature and didn't cut very good.

Therefore I went to cheapo white foam. It cuts easily (low melt temperature) but I've seen others use this foam on Youtube and they tend to get lousy casting finish.

Anyways, printed the drawings full size, cut out the paper doll and traced around on the foam. Then I free handed cutting the foam on the hot wire cutter. I've never had a very steady hand, so after gluing the sections together I sanded the edges.

I don't expect a good pour, but I'm going forth anyway as a learning exercise...

 

[Cogsy]

I haven't cast anything with it yet, but I've picked up some quite dense insulation foam from the local hardware store and I expect it to work better than normal Styrofoam. I have cast quite a few pieces using Styrofoam and the results were really good - so good in fact, that you can make out each circle of Styrofoam on the finished surface. So basically the finished part looks just like it is made from the foam. The denser insulation foam slices very smoothly and I anticipate more of a uniform surface finish. It's quite surprising the results you can get from lost foam.