L-Plate Rider
In my experience, learning to work with 3D CAD software just takes time and practice practice practice.
It took me about 2 to 3 full days before I understood how I should accurately build the shapes of transfers in Siemens NX. Lots of planes, intermediate planes, splines, sketches, integrated sketches, etc. further I finally mastered the trick. Then, drawing the cylinder and a waterjacket with equal wall thickness everywhere was the same kind of drama the first time
Muddler/Dabbler.
That doesn't happen too often!Originally Posted by Frits Overmars
Politicians and bean counters, using computer 'wizz kids' will always rule the roost, all living in a world of fantasy - not engineers who actually live the real world.
Having said all that, I think Peiter is right!
Forum whore
Yes you are right, I just have to get over myself and practice practice.In my experience, learning to work with 3D CAD software just takes time and practice practice practice
It took me about 2 to 3 full days before I understood how I should accurately build the shapes of transfers in Siemens NX. Lots of planes, intermediate planes, splines, sketches, integrated sketches, etc. further I finally mastered the trick. Then, drawing the cylinder and a waterjacket with equal wall thickness everywhere was the same kind of drama the first time
Bogeyman
Similar interface then. I learned to use Rhino, it had some features then that made it good to work with a big CMM I was using. I've learned some solid works since, and some NX11....
Rhino tends to want a different approach to modelling, and watching others learning I've noticed that those who pick up SW type front ends reasonably easily don't "get" Rhino, and vice versa.
https://www.rhino3d.com/download
It's free, for 90 days. Also free to students.
Go soothingly on the grease mud, as there lurks the skid demon
Anorak
Neil I started shaping the transfers on my pattern model and I noticed the RSW has a huge negative draft on one side of the transfers.
So the question is did they machine this side out afterwards (I don't think they did)
Or did do you think they make it in pieces ie multiple patterns in resin glued together?
Kinky is using a feather. Perverted is using the whole chicken
Forum whore
Ha, with my new found skills I'd 3D machine it
No probably done with a core print or just made that part of the sand mold come appart separatly, slide the sand part horrizontal first before the pattern comes out vertical.
Scooter boy
Most engineers I've met, live a long way away from "the real world"
Muddler/Dabbler.
Unfortunately today's 'real world' is a world of fantasy and as you'd expect, engineers will live a long way from there! I should have said the "sane world"
Forum whore
Yessiree, fantasy and fairy dust, thats where I liveUnfortunately today's 'real world' is a world of fantasy and as you'd expect, engineers will live a long way from there! I should have said the "sane world"
I don't know that I will live long enough to finish drawing this angled manifold, all well and good drawing on the angled plane but then try to tie it back to the rest of the dam drawingO well, off to ask someone again.
I guess it's just a matter of knowing when to cut your losses (time) and just make it.
Muddler/Dabbler.
Back to the dull old world of sanity now - I'm hoping to make a Co2 mould (just a bold experiment into the wonderful world of metal casting, where many have ventured before)
Should I 'rap' the pattern half before the Co2 is applied, in order to make it more easily removed when it has been hardened? - guess it would be silly to remove the pattern half while the sand is in in the soft state - or would it?
Forum whore
Your pattern should be so smooth as to just be pulled straight out. HARDEN the sand first, a light tap wont hurt. I cover the pattern in graphite powder first to make it real slippery. Rub it in to the pattern surface with your fingers. Sometimes you have to use some threaded rod and a slide hammer arrangement to knock the pattern free. The sand should go resonably hard if mixed well.
Forum whore
I know the feeling Neil. Sometimes when I look back over a couple of weeks or even months it's like I didn't accomplish anything at all.
But then, when I look back over a year, it wasn't so bad.
Forum whore
My problem, one of many I guess, is because I can just make stuff, I do. For a long time now I've concidered drawing things up in CAD a wast of time. BAD mind set!! But that is just how it's been, I arrange everything in my head and work from there. Because I've put off this CAD process for so long it's real painfull now. Still as you say look back over a year and it won't be so bad, I hope.
I've just managed to loft a hole through the manifold, finaly, seem you can't just go leaving spare lines in the drawing, computer doesn't like it.
Hardcore Biker
I just finished watching this 115 minute video on the casting of a replica of the Wright Brothers Model B aeroengine crankcase. It was shot by the folks at Model Engine Builder Magazine at a foundry here in the San Francisco Bay area.
https://www.youtube.com/watch?v=6kcUJeg4Ifk
This is an amateur video shot in a foundry where work is going on. I think 10-15 minutes could probably have been edited out, and it isn't uncommon for dialog to be drowned out by a compressor or people chatting nearby. It was not scripted but rather just follows along as the process progressed. But there is a lot of detail on the process that is shown, and I found it very interesting.
There's discussion and display of patterns and core boxes through creation of the mold, melting the iron, pouring the casting and the demolding of the finished casting.
Unfortunately, the boss didn't answer the "how long did it take to design and make all the patterns and core boxes" question, as I would have been interested to hear the answer.
I had the first foundry day at my house a week ago and thought I'd share some info since "can I use a pottery kiln to melt metal?" seems to be a not uncommon question for DIY foundry fun.
I bought off of Craigs List a Skutt model 818-240 pottery kiln, 240v single phase, 21.7A, 5200W. Internal dimensions are about 17" ID x 17" deep. It has a manual "kiln sitter" power control, but for melting it runs at full power all the time. The kiln looked pretty much unused, and I paid about $300 for it. I run it on a 50A circuit that normally feeds my air compressor.
On Friday I did a test run on the empty kiln and monitored the temperature with a K-type thermocouple and thermometer display. I had the kiln control dials set on 3 of 10 to start but after 6 minutes I realized there was no reason to not run the thing on 10, so I changed at that time.
Starting temperature was 71F. The rate of rise at the lower setting was about 15F/minute, and after changing to full power that jumped to 57F/minute, so I wasted a few minutes with the lower setting.
I let it run for 60 minutes, checking every 5 minutes (or so). The rate of rise drops as the temp goes up, starting around 57F/min and ending at 11-12F/minute. The final temp was 1568F, for a 1500F degree increase over 60 minutes.
The next day my friend Jeff came over with some of our supplies - scrap aluminum, Petrobond sand, flasks, silicon carbide crucible (rated for 10 pounds of aluminum), tongs etc.
The crucible weighs 11.6 lbf when empty. The refractory plinth it sat on in the kiln was 4.4 lbf, and we put 5.5 lbf of aluminum in it to start.
The rate of temperature rise with that 21.5 lbf added was significantly reduced compared to the empty kiln. Starting at 68F ambient and at full power it took 91 minutes to reach 1400F which showed a partial melt of the metal. The temp dropped to 1360F from that brief look but recovered quickly. At 100 minutes it was 1450F and the melt temperature was 1280F. We let it go to 111 minutes at which time the kiln temp was 1508F and the melt was at 1380F. I then removed the crucible and poured 4 flasks totaling 2 lbf. The lid was left open (I should have shut it) and at 116 minutes the temp in the kiln was showing 827F. About 6 lbf of scrap was added to the heel in the crucible making for about 9 lbf of metal. That was poured out into ingots at 158 minutes. The kiln temp was 1447F and melt temp was 1270F and parts of the melt seemed a bit slushy. But I didn't feel like waiting another 10 minutes to get the melt hotter since we weren't going to pour any more flasks.
I've attached a graph that Jeff generated showing the relative temperature curves for the empty and filled kiln. The equations shown are for the two curves. Jeff's a scientist so he does that thing as a standard practice. The curves were plenty for me.
The molds were of that 4" medallion for Jeff's annual ride in the Sierras that I showed after his first foundry day a couple months ago. This time we tried different gating with the sprue off to the side instead of coming directly into the back of the part, and also varied putting the pattern in the drag and the cope, detailed side down or up, to see if we could learn anything from that.
Pros & cons for a powerful propane furnace (Jeff's) vs the electric furnace:
The propane furnace runs a lot hotter and has a melt ready in about 15 minutes with the crucible glowing white hot. We think that the blower/fuel can be turned down from that setting, as at a good melt temperature the crucible came out of the electric kiln with only a slight reddish glow (I couldn't see it, Jeff did).
The melt seemed more turbulent in the fuel furnace. In the kiln it just sat there and there wasn't any movement breaking the oxide layer or dragging oxides down into the melt. That may improve in the fuel furnace by turning the fuel/air down, and even if that doubles the melt time it will still be much faster than the electric kiln.
Electric is quiet and discreet. There's no roaring sound or flames shooting out of it to attract the neighbors' attention. Electric can be run inside, and there's no need to worry if the branches of a nearby tree are far enough away to not be in danger of igniting.
Electric may be less expensive to operate and own. A residential kW/hour appears to be about $0.23 here in San Francisco. The kiln is rated at 5.2 kW, but even if rounded off at $0.25 and up to 6 kW, that's US$1.50/hour running costs which seems pretty reasonable to me. We don't have any running costs for the propane furnace, but Jeff mentioned that he had the big cylinder available because small ones wouldn't even keep up with his big BBQ much less the furnace. Used pottery/glass kilns seem to be pretty common on the SF Bay Area Craig's list, and if you don't need fancy kiln sitting controls you may be able to pick up something at a very reasonable price. The 10 lbf capacity crucible is about 7.5" OD x 8" tall, so the 17x17 inside dimensions on this kiln are very roomy and a smaller kiln would have plenty of space inside.
Electric may be more convenient. No big tanks have to be carted around to get refilled nor does storage space have to include the tank(s) as well as the furnace. Jeff's propane tank was getting pretty frosty after it had run for a while which might change the available pressure. The electricity keeps running as long as needed and the supply doesn't vary. Fuel and air had to be fiddled with now and then on the propane furnace.
This time, since it was at my house, I did all the handling of the furnace/melt. I wore my hot suit, foundry gloves and electronic TIG helmet, and there were no accidents other than sitting the hot crucible down near the temperature reader for the thermocouples, resulting in a slightly warped plastic case on the gauge.
Now we need to get some patterns made for real parts that will use the A356 ingots and filters in the gate before the part to trap oxides. Jeff's been working on the air-cooled cylinder head pattern for his 400cc Kawasaki triple, and that is looking very nice. It may be ready to pour in a week or so.
cheers,
Michael
Muddler/Dabbler.
Excellent video Michael, got a lot of tips from that one! I am just about to try the Sodium Silicate/Co2 method, thank you for the link. They need to oil the bearing on that muller though!
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