The Craftmans Shop > New from Old
The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
tom osselton:
Looking good! I’ve been watching eBay boards for a while they can be quite expensive. Our lathe has been sitting for a while it did work but now just says “Host control initializing” but everything passes there is a guy that is suppose to look at it in the near future that has worked on them before so fingers crossed!
awemawson:
Thanks Tom :thumbup:
To gain a bit more confidence with it I set up a parting tool, roughly measured the tool offsets with a ruler, then used the automatic system to measure accurately. Of course it is only as accurate as the accuracy of the tool probe location has been measured, and I've not grasped that particular nettle yet !
Interesting to see the correction that the program has made to the tool table - first picture is my initial manual measurement, and the second one the result of running the program.
The manual measuring step is necessary to get the the tool 'in the zone' before launching it at the probe.
awemawson:
Then I got really brave - or maybe reckless - and tried a Type 4 tool. In fact this was because I wanted to define an offset for the 'second edge' of the parting tool so that dependant on which offset you choose, the kerf comes from the part left in the chuck (D7 offset) or the bit you've turned (D17 offset). This controller lets me define up to 99 offsets, so with twelve positions in the turret there are lots of options.
With this operation, the tool has to go past the Tool Probe, and come back away from the chuck to measure the correct side for Z
. . . anyway it worked with remarkably little tweaking :thumbup:
awemawson:
Having got a bit more understanding about the tool setting process, I've spent some time creating a 'Tool Crib' in FeatureCAM that replicates the tools so far installed.
By way of a test of this process I drew up a simple dome ended bar, ran it through the Post Processor, uploaded it to the 820T controller and made it. All went very well until the last 'finishing pass' when the index-able insert chipped. This is quite consistent - I know, I've chipped four tip edges so far :bang:
Assuming I was doing something wrong a lot of head scratching ensued :scratch: :scratch: But then the penny dropped - the program is driving the tool well past centre on the finish pass - in fact 6.6 mm past centre - then engaging with the work resulting in an upwards force on the tool until it is back the correct side of the centre line. It is probably made worse by the fact that the tool has only a very small clearance angle on the chuck facing side. However I tried it with the TNMG1604 illustrated below and also with a DCMT11T3 with identical results.
Still, I'm pleased that the lathe is at least now producing swarf for the first time in a decade :thumbup:
It was then I looked at the FeatureCAM simulation screen, and saw the finish pass going well beyond centre - not sure how I can tweak that - I need to do some digging in the bowels of FeatureCAM and see if there are limits or whatever that I can set.
Amazingly the finish was not at all bad on the dome end considering the wrecked tip, but of course it can't be to size with a bit of carbide missing !
Will_D:
Nice clogs!
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