Author Topic: Yet another Denford for the Collection  (Read 6785 times)

mc

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Yet another Denford for the Collection
« on: November 19, 2016, 12:48:09 PM »
So, after a bit negotiation, this got dropped outside the workshop a few weeks ago -


I'd been looking for a Denford Triac for a while, and this one ticked most of the boxes (enclosed, coolant, ATC, autolube). My only complaint is it's a BT35 taper, however it also came with this-

Which should be enough holders to keep me going for a while. I have possibly found a source for new holders, however I'm weighing up the options between buying new holders, or converting it to BT30.

One thing I do have to mention, is a set of machine skates has got to be one of the best things I've built. Made rolling it into place very easy -


I'll gradually add to this thread, but at the current moment, the machine is still partially dismantled, mostly cleaned, and the old controller stripped from the cabinet.

mc

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Re: Yet another Denford for the Collection
« Reply #1 on: November 19, 2016, 12:50:23 PM »
Since I'm still waiting for a computer to finish updating, I'll add some more.

The machine didn't appear to be in the best of condition, however on close inspection all the slides are in excellent condition, they just needed a bit clean. The spindle on the other hand didn't feel so good. Removing the spindle motor didn't improve the feel, so after removing a bit more, the problem became obvious-

The machine had got wet at some point, as there was rust around the spindle from where water had been sitting, so a couple new bearings, some grease, and the spindle is as good as new.
I still need to decide on the final preload of the bearings, as even the Denford guys say they were just done by feel in the factory.

The other issue, in true education system style, the mill had been used to machine wood. My lathe was the exact same, with dust everywhere, and a nightmare to clean.

mc

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Re: Yet another Denford for the Collection
« Reply #2 on: November 19, 2016, 12:51:30 PM »
Rather than have this thread as just another "look at what I got/done" thread, I'm wanting to explain some of the reasoning behind the choices.
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Denford use pretty industrial type setups for their electrics, so all the control electrics in this machine already run 24V, which I'll be sticking with, as 24V controls pretty much eliminates all noise problems. (If there is demand I'll go into the details of the why higher voltage is better)
This particular machine is a VMC version (basically means it comes with inbuilt computer/display/keyboard), running stepper motors courtesy of a parker SD rack.
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Here's a few pics.
Original control cabinet setup-

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It powers up!

Check the whopping 1024kb of memory and 33MHz clock speed :-)
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I love old school tech-

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Now that's how it came. Cutting edge technology for the early nineties, and would likely still work if I could be bothered finding a working floppy disk drive to create a new floppy disk. But I need this machine working, not stuck running archaic software/hardware.
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In an ideal situation, I'd install servos, however I don't have the budget or time to rework everything to fit servos.
Instead, I'm going to stick with the original steppers for now, and using modern drivers.
I've opted for Leadshine EM806s. A lower end drive would also of worked, but I want to make this machine as reliable as possible, so the stall-detection of the EM drives gives an extra bit protection should something go wrong.

mc

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Re: Yet another Denford for the Collection
« Reply #3 on: November 19, 2016, 12:52:20 PM »
Now having decided what general direction I wanted to go with the mechanics, it was time to look at controller options. For me personally, I prefer Dynomotion KFlops, as they are probably one of the most versatile controller available for the price, but this left me the problem of deciding what add-on boards were needed.
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The first thing to consider was what input/output capability was needed.
For this purpose, I create a spreadsheet, and list every input/output I need, along with a note of the type of input/output needed. At the current count it's 28 inputs (2 analogue for SSO&FRO, 1 encoder input for a MPG, with the rest being basic on/offs), and 9 outputs (1 analogue with rest on/offs), along with the currently required 3 step/dir outputs.
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I could of opted for a KStep board, which would of met the needs for driving stepper motors, albeit at a slightly lower voltage (it has a max Voltage of 50V), but it lacks any kind of analogue input.
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The other option, was to use a Kanalog. Now this is primarily aimed at retrofits on machines using +/-10V servos, however as I'd like to keep my options open, it provides a good upgrade path. It also has analogue inputs, and differential encoder receivers.
It also so happens I already had a spare one sat on a shelf, along with a Konnect expansion board, which means I've got more inputs and outputs than required.
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The only draw back was I'd like to make use of the differential inputs on the EM806's, and Dynomotion have nothing that outputs differential step/dir signals. So a solution was needed, and it came in the creation of this board-

On the KFlop, in standard configuration, the encoder pins also double up as the step/dir pins, of which 8 of them happen to go through a separate RJ45 connection (the other 8 go through one of the ribbon cables). This board takes those 8 lines, and by moving the jumpers, either routes them directly through to the Kanalog to be used as encoder inputs, or to the line driver chips on the board to be used as differential/line driven outputs.
So that was the step/dir differential outputs taken care of.

mc

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Re: Yet another Denford for the Collection
« Reply #4 on: November 19, 2016, 12:54:10 PM »
I was going to post about some of the intricacies of the machine wiring, however I'll stick with controllers for now.
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Now I've got all the boards, I need to mount them.
The old computer, which was bolted to the control cabinet door was removed, and a suitable bit 3mm aluminium sheet was cut to size. The reason for 3mm, is it's strong enough to bridge pretty big areas with minimal support, and thick enough for drilling/tapping for directly mounting items. Thinner would be marginal for drilling/tapping, and thicker just adds expense for little to no benefit.
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First step once the sheet had been cut and drilled for mounting to the cabinet door, was to play tetris with the various boards-

Which highlighted the first non-ideal thing. My lovingly designed and built differential driver board would of been better had the in/out RJ45 jacks been the opposite way around. As it stands, it just means I need to make the cables a bit longer and they'll cross.
If noise was to be a problem, I choose the shielded jacks so shielded cable could be used if needed.
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So now things are positioned, it's a case of marking out all the various holes, followed by drilling and tapping all the required holes.
When doing this, is I like to drill the required holes slightly undersized. Everything mounts via M3 stand-offs, and Standard/Course M3 has a pitch of 0.5mm, so the ideal tap drill size is 2.5mm. Instead I use a 2.4 or 2.3mm drill, as it allows a bit margin for if the drill isn't perfectly straight, or isn't drilling perfectly on size.
I then tap using a M3 spiral flute drill in the cordless drill, before hoping my marking out and drilling was on target-

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Managed to only get one hole slightly off, but thankfully it was for the IDC breakout board, so a quick file and everything bolted together perfectly-

Something I like to do here, is although I fitted all the boards on the bench, I never tightened the screws until I had the plate bolted to the cabinet door. My reasoning for this is to minimise the amount of strain placed on the PCBs should the back plate twist any when finally bolted down.
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And you may be wondering why the IDC breakout board has been added. I may need to use a couple of the feeds provided by the Kanalogs IDC header, so it's far easier to fit the board and not need it, rather than fitting it later and risk getting some swarf somewhere I really don't want to.