Some months ago I made a simple tool tray to go on The Shiz. This would take up to 8 tools, which would be enough for a typical job. I also made a couple of larger ones for the shelf unit, to take the remainder of my myriad toolholders. As you know, it's not possible to have too many toolholders.
They've been pretty handy and were certainly worth the minimal effort. However, as they were made from 18mm MDF, the smaller tray didn't enjoy being exposed to the coolant, with the result that it is absorbing coolant and swelling. It won't last long at this rate. I suppose it was entirely predictable but it served a purpose.
Having been away from home during the week for the last 6 months, I've missed out on machine action. So what better than a quick(?) and simple(?) job such as a plastic toolholder tray? By plastic I mean something that will machine nicely and not cost an arm and ten legs. I've never machined acetal before but it sounds like a good material to work with. I have some Tufnol that would be ideal for this work but having machined it before on various occasions, I can tell you it stinks and makes a real mess.
Acetal and Delrin seem to be very similar, with Delrin being a (very) slightly better material from an engineering POV. Found a supplier on ebay that sells acetal in various formats and soon the old mouse finger was twitching away. Within a couple of days, I had myself some 17mm thick (as measured) sheet and a couple of lengths of round stock for good measure. Well why the hell not.
From the above photos and some data from the ISO40 taper drawings, I modelled something suitable up. Instead of a 2 x 4 array, I went for a 3 x 3 array, as this results in a slightly wider length of the sheet and a shorter unsupported span. I should end up with a bit more material left over, as the width of the supplied stock is a nominal 1m.
Fusion 360:
Started with a single sketch that captures most of the requirements. While I haven't used a parameter table, I've defined many of the positions so that they will readjust if I play with the primary dimensions. I could have parameterised(?) the array of holes to accommodate alternative hole patterns but the whole idea here was to flash something up reasonably quickly so I could cut some swarf.
This was then extruded to the depth of the stock. The taper bores were simply added as chamfers using he value of arctan (7/24) to set the angle.
Finally, a 2D drawing to help cut off a suitably sized piece of the stock.
Workholding will be a bit of a PITA unless I want to sacrifice a fair bit at each end. It's too big for the vise, so some form of clamp / MDF / screws might be in order.
Setting up on The Shiz:
Here's my solution to workholding. 2 pieces of leftover 2" x 2" box section, left over from welding up the console arm from earlier. I'll drill the 8 (M6 clear) fixing holes through the acetal and MDF, then hold the acetal down using hex socket cap head bolts. It will be a royal PITA getting the nuts fitted inside those box sections but it won't be the end of the world.
I could have drilled and tapped the holes in the box section but that would have required more buggerage, drilling out the holes in the acetal later. I'll just position them manually using the Centroid MDI display, then probably just counterbore them with an end mill using the MPG.
Clamped down:
Acquiring the top of the stock:
Centroid Acorn vs Windows Defender Firewall:
Although I thought I'd had the system working fine last time I cut swarf (the Z axis yoke), the damned thing just refused to wake up when I came to it. I found I was able to ping both the main controlelr and the Acorn itself (aka the Beagle Bone Green), the CNC12 s/w couldn't see it. Seems that although I'd turned off the firewall, some features of it had managed to turn themselves on in my absence. I'm suspecting a Windows "update" to be the culprit but may never know for sure.
Tool libraries again:
As it's been a while since I set a job up on The Shiz, I'd forgotten some of the critical steps. Like how to acquire the part position (using the Renishaw probe and the probing functions) and set the tool length offsets (using the Chinesium tool setting thing). Not 100% certain what the issue was but the upshot was that I had double checked / set the tool lengths but when I changed the selected tool using MDI, the G54 Z coordinate didn't change. WTF??? More work to be done on that but I'm suspecting some confusion due to trying to move beyond the define machine movement during tool setting. Getting this wrong would be the ideal way to ping some of the expensive tooling.
I suspect the issue centres around the "Zref" setting process. For this, you have to use the tool number that was pre-specified in the config to set the position of the tool setter so it can then determine the relative offsets of the other tools. I'm pretty sure that's defined as my Renishaw probe (tool #10) but if I actually used tool #1 (the 6mm dia loominum pointer), I'd end up with an unwanted offset corresponding to the difference between tools #1 and #10. IIRC, I was trying to specify which tool to use to set Zref, when in fact you can only change it in the config. I vaguely recall some objection from CNC12 around that time but The Stupid Fat Bloke told me not to worry about it. I shouldn't have listened to him, as it never seems to end well when I do.
This should provide some fun and hopefully result in some plastic swarf over the Xmas break....
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