Here is a list of all the postings Adam Harris has made in our forums. Click on a thread name to jump to the thread.
|Thread: DRO magnetic encoders - generic?|
What I am looking for first is a cheap source for a 3rd generic chinese magnetic tape encoder 5 micron (5v TTL quadrature) - the magnetic scales are super thin and impervious to coolant so great for small machines
Well I have learnt that there are consoles from the far east like Shumatec DRO-550 that run DRO-open source software which allows them to receive a variety of Chinese signals (24 Bit, BCD7, BIN6, 21 BIT) and also 5v TTL quadrature, but the big names of Newall and Heidenhain each run their own completely closed system whereby proprietary encoder signal technology must be used (and does not work on any other consoles). However popular generic consoles that take 5v TTL quadrature signals from magnetic tape encoders will take that format signal from any encoder producer and indeed from any glass slide product that gives a 5v TTL quadrature signal.
All sounds good. Thanks. Will check out the M-DRO/Allendale stand at Warwick ME show and see to what extent most consoles have the flexibility to receive a variety of different types of signal from 5v TTL quadrature to others such as Spherosyn and glass scales.
I have cannibalised a pair of 10 year old M-DRO 5 micron magnetic tape encoder heads (with 10 feet of cable and 9-way D-type connectors) from an M-DRO "Budget Console" lathe kit that back in 2010 did not garner good reviews on MEW. I assume today consoles are better and cheaper, so I am thinking I would not mind having a 3-axis milling DRO and wonder if these magnetic encoder heads are generic and will work fine with any magnetic tape DRO system and in doing so save me some money, or are some 5 micron encoder heads significantly better than others. These have an output signal of 5 volt TTL quadrature with 90 deg phase difference - is that the generic signal that most magnetic tape consoles use today?
Also any recommended budget Milling DRO consoles that take magnetic encoder input?
Edited By Adam Harris on 16/10/2019 17:14:29
Edited By Adam Harris on 16/10/2019 17:43:38
|Thread: Bright EN24T steel vs Black EN24T for cutting gears|
"But as they like it rough, very often the answer to a disappointing cut is to push carbide harder, the exact opposite of HSS where slowing down usually helps" - thanks Dave, that is useful to know. And I will try carbide Inserts at 4x "Coated" speeds and experiment increasing from there.
Edited By Adam Harris on 14/10/2019 22:21:33
Thanks Andrew, so are you saying that my chart of speeds is acceptable for HSS and Coated tools but if using carbide inserts I should go at as much as 4 x those speeds? Ie Stainless I should be looking at 240-360 ft/min with inserts, and aluminium I should be looking at 1600 - 4000 ft/min with inserts?
Well my chart does give for 400 ft/min material in 1" diameter exactly 1528rpm using HSS tools (actually it gives 1986 rpm for Coated tools). My chart (and I cannot remember where on earth I found it on the internet) offers that a general category of material has a wide "range" of speed in ft/min, depending presumably on its alloy variations. It gives Aluminium at 400-1000 ft/min, but I see that L.H. Sparey gives Aluminium a rate of 300 ft/min. My chart gives Stainless 60-90 ft/min and I see that Sparey gives it 50 ft/min and David Clark's Teach In article in MEW 216 (corrected by Neil Wyatt) gives "Carbon Steels, Stainless Steel and Alloy Steels" all at 50 ft/min . My chart gives High Carbon steel a range of 40-70 and Low Carbon steel a range of 80-140 and Stainless a range of 60-90. Perhaps, embarassingly, my chart is all nonsense, or fit only for large industrial machines, but until now it is fairly academic because I use it as a broad indication, since the best speed (and feed) for me has been one found by trial and error that produces nice chip formation and partly because I am rarely sure of the spec of material I am cutting! I do try to follow the principle that one should start erring on the slow side. However I have always believed that harder material should be turned much slower than softer material, hence my surprise that this hard EN24T stuff should be turned as fast as Aluminium. Have I been doing it all wrong, or is the major discrepancy the difference between Coated tools and Carbide Inserts (for which I have no data and actually hardly any experience)? I know inserts can be used faster than Coated cutters, but how much faster, and is the faster speed an option or a necessity? And if my chart's ft/min ranges for materials are no good, can you point me to a chart that you recommend as giving better results?
Edited By Adam Harris on 14/10/2019 20:34:01
Edited By Adam Harris on 14/10/2019 20:47:35
Thanks Andrew - that turning is INCREDIBLY fast! According to my charts for 1" with carbide inserts that is almost at maximum speed for Hard Brass at 1200 - my chart range for Medium Carbon steel with inserts is 350-500 for 1". I was thinking for 4" around 100-120, but I take your point and will experiment at higher speeds but 600 is at Aluminium speed...
at 70 rpm
Hi Andrew , cutter is 10T & 70mm diameter (made by HBM incidentally) so therefore feed 2.8 inches/minute (given my cutter circumference is 0.849 of yours)?
Yes Andrew 3.8" - not quite sure how 98mm slipped in but probably because i understand Black is only made to 2% tolerance so I was pondering about 100mm diameter, is worst case 98mm size enough to turn down to a perfect 96.52 and I have decided possibly not so bought some 105mm Black instead
Fantastic video Jason!
Andrew thanks I'll adjust the RPM and thus feed accordingly when I get the actual cutter dimensions .
Edited By Adam Harris on 10/10/2019 12:12:39
so 12 x 60 x 0.004 = 2.9 inches/minute a much more sedate rate of feed!
Edited By Adam Harris on 10/10/2019 12:02:31
Aha that make more sense!! Thanks for the correction. Well the cutter comes from RDG and expect to receive it tomorrow so will know then, but probably as you say 12!
Edited By Adam Harris on 10/10/2019 12:00:33
Aha thank you Jason. 36T x 60RPM x 0.004" = 8.6 inches/minute
Edited By Adam Harris on 10/10/2019 11:50:34
Andrew many thanks - so 60 rpm, full depth "one pass" cut, but rate of table feed (I don't understand what you mean by 4 thou per tooth)?
Edited By Adam Harris on 10/10/2019 11:44:06
So Andrew what speed, rate of feed and depth of cut, do you recommend in my situation ?
I was looking at M-Machine prices - Bright EN24T 130mm @ £10.32 / 25mm, Black EN24T 130mm @ £11.14 / 25mm. Maybe it is an aberration to do with their particular stock levels
So I am expecting to have the mill scale disappear in a pile of chips as I turn down the 100mm Black EN24T bar to 98mm (at about 80 rpm with carbide insert?), but when I then attack it with the HSS involute cutter these 10DP teeth are pretty large requiring a cutting depth of about 5mm - with a 1.5kw motor on a horizontal milling arbor, how many passes of the HSS involute cutter should I be planning on? I read somewhere that the feed of HSS to EN24T should be moderately aggressive ....given a cutter diameter of for example 65mm, what speed , rate of feed , and depth of cut should i be aiming for? I would like to get all 36 teeth cut with one new cutter without having to resharpen it.
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.