My Workshop

 

Robotics is such a multi-disciplinary field - you have to have a decent workshop! 

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I have been slowly building up tools and machinery over a long time, usually each purchase being driven by a definite project requirement at the time. Over the years, I have developed from a low cost cheap approach point of view to the idea of the right tool for the job.  Case in point is milling operations - I successfully made some small aluminium parts using the drill press and a cross slide vice, but after having purchased a 'real' (although very small by industrial standards) milling machine, I couldn't believe I had struggled along without one for so long.

HAFCO HM-45 Mill/Drill

The single most useful bit of gear the robot experimenter can own! The Chinese manufactured Hafco brand machine is similar or identical to the 'Rong Fu' machines available elsewhere in the world. Quite solid, with a dovetail column for raising and lowering the head without disturbing the XY location (too much). It also has a drill press style quill with fine feed hand wheel. 

I have fitted out the machine with a three axis 'Meister' brand DRO system, and I am in the process of converting the machine to CNC control (on hold during the construction of Quadruped4!). I obtained an old monitor mounting swing arm for free, and have bolted that to the wall beside the machine, intending to put a monitor on it for the upcoming CNC conversion. In the mean time, it is very handy to have a movable table for calipers, nuts and bolts and clamps etc close to hand! 

My main complaint about the HM-45 is the design of the lead screw end mounts which leads to a huge amount of backlash. I need to address this to effectively CNC control the machine. Apart from that quirk, it is quite a solid performer of a machine.

3 Axis Digital Readout (DRO) 

I purchased the DRO and glass scales from Ebay from a manufacturer in Singapore, and was quite nervous about it, however being about a third the cost or less of locally available units, I couldn't resist. 

The purchase followed an earlier unsuccessful project to construct a DRO out of commonly available optical mice and some clever software. 

I put a lot of effort into the idea (as you can see from the photo and screenshot!) using high performance 2000 cpi laser diode based mice in custom aluminium housings. You can just see the red glow of the laser diode from underneath the X axis mouse enclosure in the picture (top right image). I wrote the software so it could distinguish between multiple mice inputs and associate each with an axis. Unfortunately although the resolution was high enough, too many counts were lost during direction changes, and the effect was pretty inconsistent and difficult to model. Mice aren't meant for totally accurate positioning, a few counts lost here and there during a computer game or normal computer use don't worry people, but they upset a machinist! I would persevered and tried different target materials for the optical sensors, but around that time I discovered the cheap Meister brand of glass scale DRO's and for three axis at around AU$850 delivered to Australia, I really couldn't justify spending any time on the home built effort.

CNC Conversion 

Eventually I would like to convert the mill over to CNC operation. This would be an enormous boost in capability, freeing me from the confines of sharp angles on parts and allowing free form curves to be cut.  I have purchased some high torque stepper motors, and constructed a controller out of some constant current source and stepper motor kits available from Oatley Electronics. I intend to use the mach3software which is low cost (free to evaluate) and high capability. Current status of the conversion has the controller physically built (see photos) and awaiting wiring up, and brackets and parts for one axis built and mounted onto the mill. I am keeping the ability to use the handwheels even though most people who have converted machines seem to report that you would never go back to turning wheels - but sometimes the soft touch you get with hands on, or the speed of a quick job will benefit from keeping the wheels. I do need to address the huge backlash the machine has at the moment, which will prevent it from being that useful as a CNC mill. The usual approach is to replace the acme thread leadscrews with high precision (and cost) ball screws. However I am not sure that is necessary, as when I took the table off to look at the leadscrew, most of the backlash is actually due to the poor design of the leadscrew mounts rather than the acme nut on the table itself. The nut has backlash adjustment on it, but it is totally redundant due to the design flaws in the rod end mounts. Basically when you change direction on the handwheel, the rod winds through the nut for a distance before the end of the rod pushes against the mount at the end of the table to push the table in that direction. When the direction changes, the rod must wind back in the other direction a certain distance before it pushs the table again. I have designed and made some split collars which I can fit over the shaft at each end which should take a lot of this slack out, and improve things enormously, though I haven't yet fitted them. I will report on the success or otherwise when they go on to the machine!

 HAFCO AL-60M Lathe

The AL-60M lathe is my most recent purchase, and to date it has only produced a few parts for friends. I went for the AL-60M as a good compromise machine without spending too much. Some advice I read once said that on a budget, you should buy as good a mill as you can afford, and get away with the smallest lathe that will do the job. I agree with that, as most complex jobs I find require a combination of the machines, but the mill seems to be predominantly required. The AL-60M is a small lathe, however since it is designed to accomodate a bolt on optional milling head attachment, the bed is quite solid and definitely outweighs other small lathes.

Rexon DP430F Pedestal Drill Press

This is the first large machine I obtained (apart from a Triton woodworking saw bench), and cost a fair bit compared to some of the cheaper drill presses available. Although I thought I was buying a more solid machine than the cheap ones, I never really was that impressed with the drill. The keyless drill chuck that came with the unit was not very accurate (didn't run quite true) and I replaced it with a standard chuck, the weight of the table and vice causes a bit of sag, and the housing seems to resonate and makes the drill quite loud. On the other hand, it has quite a good depth stop system that lets you set both the lower and upper limit of quill movement, and an inbuilt work light. These days however it only gets use when the part to be drilled doesn't fit on the mill table, or for really quick jobs that don't require any level of precision!