|Ian P||19/04/2019 21:45:58|
2352 forum posts
I saw this on Twitter and however its done its impressive engineering. The link below is to a short video.
133 forum posts
That is almost unbelievable. For the joints to be invisible to the naked eye the gap must be microns...
|Mike Poole||19/04/2019 23:41:46|
2542 forum posts
Probably an apprentice filing test piece
|Jeff Dayman||20/04/2019 01:26:10|
|1789 forum posts|
It is microns and it is CNC. Lots of shops in China can do that level of matching particularly in moulds. However it is time consuming and expensive and of very little practical use except for very small parts.
One thing that mouldmakers do in China that has been a continuous annoyance to me in industry for many many years is the use of 4 locators between inserts, at the corners, as the test piece in the video shows. To restrict all the degrees of freedom of the inserts, only two locators, at diagonal corners, and a flat area on the parting line are needed. To make 2 totally unnecessary close fitted locators at the other two corners is a waste of money and in many cases leads to confusion and errors at final fit up and bluing-in of the mould. Several times I have seen a toolmaker miss his bearings and grind off the wrong locator causing a loose fitting mould insert, and unless it could be welded, could result in a $20,000 to $50,000 insert being scrapped. I gave up arguing with mouldmakers in China about this around 25 years ago. It is just a tradesman's bad habit that probably started very early on in the development of the trade in China. As great as some of these guys are, they keep doing the 4 locator thing over and over again despite frequent fit cockups and despite about 100,000 Western toolmaking / tool design guys like me asking them for 35 years PLEASE don't do it! I may as well talk to the wall.
When I first started programming CNC wire edm machines for mouldmaking I got a panicky call from a toolmaker in our company shop "the four insert sets we just cut don't fit the blocks. Your programs must have been rubbish". I went down ASAP, heart in mouth of course. Sure enough, they didn't fit. I did notice that he had blued them as we usually did when machining them conventionally. Bystanders were coming around for a look at the disaster. As a last hope of the off chance I'd get lucky, I said "can we try cleaning off the blue?" We did, and the inserts fit, dropping in by gravity with a light suction sound. Everybody on the toolmaking team was quite shocked. I resumed breathing, because I still had a job.
You may say oh there was a speck of dust the cleaning cleared out, or a tiny chip, but this was the same case on ALL FOUR sets of inserts and blocks...... I'm not blowing my own horn, but my programs were proved right. But just as important, if not more important, the wire edm operator was damn good and very careful about all parameters, and the guys at Japax that built that old wire edm machine in the early 1980's really knew their stuff.
With this team and that machine, that sort of ultra close fits in our tools became our shop standard - 30 odd years ago in Toronto Canada.
|Donald Hill||20/04/2019 02:26:19|
|16 forum posts|
Take a look at this : www.youtube.com/watch?v=sFrVdoOhu1Q
|not done it yet||20/04/2019 02:56:36|
|4495 forum posts|
Guessing that uses of these would be injection moulding, diesel fuel injectors and clearly air bearings. Any examples of others?
Do they, I wonder, really need to fit piston rings to F1 engines these days! Although a minute temperature difference between parts might cause interference?
|391 forum posts|
Simply stunning level of accuracy and work.
I would love to see a video of the work being done but that would be like seeing how a magic trick was done and spoil the magic.
|Michael Gilligan||20/04/2019 14:02:14|
15462 forum posts
I find it rather frustrating that the initial posting on Twitter did not include a reference to the source of the video clip ... just the 'witty' comment: 17th qualification in passes plus 14th grade polishing.
Translation via DeepL **LINK**
... Such lack of simple courtesy seems to be the way of the world these days.
Edited By Michael Gilligan on 20/04/2019 14:02:50
|Barrie Lever||20/04/2019 14:17:56|
|479 forum posts|
Not sure about the setup on F1 engines regarding piston rings, however high performance model two strokes do not benefit from piston rings in any way, in fact you cannot get the performance from a ringed engine that you can from a tapered bore (chrome plated) non ringed alloy piston engine.
Main benefits in this setup for model engines are a very superior seal at TDC, low friction away from TDC, an ability to run huge ports with no bridges because the ring is not constantly try to jump into the port and seizures being unheard of due to well matched expansion rates.
I know Aprillia tried the tapered bore ringless piston setup on a 125cc racing motorcycle engine but it was not successful.
|Mick B1||20/04/2019 15:00:45|
|1547 forum posts|
I know I have a suspicious mind, but I think the deployment of a bit of CGI to those sequences would be pretty easy, certainly at the resolution levels we're seeing there...
|Bill Phinn||20/04/2019 19:57:33|
|310 forum posts|
I'm not quite sure what you mean by "source", Michael, but the four character company name cut into the side of the piece is 北京精雕 (Beijing Jingdiao), which just translates as "Beijing fine engraving". Their website is here, and they have an English version too.
Edited By Bill Phinn on 20/04/2019 19:57:54
|Michael Gilligan||20/04/2019 20:08:13|
15462 forum posts
By "source" I just meant the originator of the video
Thank you for the translation and the link
|Neil Wyatt||20/04/2019 20:14:21|
17712 forum posts
Don't leave them fitted together for too long!
|martin perman||20/04/2019 20:49:27|
1810 forum posts
|jimmy b||20/04/2019 21:26:05|
622 forum posts
|Tony Pratt 1||22/04/2019 14:27:33|
|1099 forum posts|
Nice bit of photography.
|Neil Lickfold||22/04/2019 22:54:56|
|591 forum posts|
If the gap is less than 4 um, and all the same height/geometry , you will not see the line on fitted parts. Like on silicon moulding tools, the ejector pins need to fit better than 5 micron on diameter clearance, or else the material will go down the sides of the ejector pin. Skim wire edm to my knowledge was the 1st to be able to achieve these sort of tolerances on shaped parts. Now with sub micron machining centres, this level of accuracy can be achieved with milling cutters even with hardened parts. The way it came about with more than one reference was from the introduction of cad cam, and the new generation of designers and machine tool users not being trained in the traditional methods of toolmaking. Now there is another generation that have almost no knowledge of making something from solid, and they only know about additive processes and EBM Electron beam Machining, and EBP Electron beam Polishing.
|Nick Hulme||23/04/2019 17:11:58|
|743 forum posts|
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.