Wednesday, April 19, 2017

CNC Alloy Candelabra

While learning Fusion 360 I thought it would be fun to flex my new knowledge of cutting out curved shapes from alloy. Some donated LED fake candles were all the inspiration needed to design and cut out a candelabra. Yes, it is industrial looking. With vcarve and ball ends I could try to make it more baroque looking, but then that would require more artistic ability than a poor old progammer might have.


It is interesting working out how to fixture the cut for such creations. As of now, Fusion360 will allow you to put tabs on curved surfaces, but you don't get to manually place them in that case. So its a bit of fun getting things where you want them by adjusting other parameters.

Also I have noticed some issues with tabs on curves where exact multiples of layer depth align perfectly with the top of the tab height. Making sure that case doesn't happen makes sure the resulting undesired cuts don't happen. So as usual I managed to learn a bunch of stuff while making something that wasn't in my normal comfort zone.

The four candles are run of a small buck converter and wired in parallel at 3 volts to simulate the batteries they normall run of.

I can feel a gnarled brass candle base coming at some stage to help mitigate the floating candle look. Adding some melted real wax has also been suggested to give a more real look.

Sunday, March 5, 2017

Non self replicating reprap 3d printer

The reprap is designed to be able to "self replicate" to a degree. If a part on a reprap 3d printer breaks then a replacement part can be printed and attached. Parts can evolve as new ideas come along. Having parts crack or weaken on a 3d printer can be undesirable though.

A part on this printer was a mix of acrylic and PLA, both of which were cracked. Not quite what one would hope for as a foot of the y-axis. It is an interesting design with the two driving rods the same length as the alloy channel at the back of the printer.



A design I thought of called for 1/2 inch alloy in order to wrap the existing alloy extrusion with a 3mm cover. The dog bone on the slot is manually added in Fusion 360 so it is larger than needed. The whole thing being a learning exercise for me as to how to create 2.5D parts. The belt tensioning is on a 6mm subassembly that is mounted on the bracket in the right of the image below.


The bracket and subassembly are shown mounted below. Yes, using four M6 bolts to tension a belt is overkill. I would imagine you can stretch the belt to breaking point quite easily with these bolts. The two rods are locked into place using M3 tapped grub screws. The end brackets are bolted to the back extrusion using two M6 bolts.


The z-axis is now supported by a second 10mm alloy custom bracket. This combination makes it much, much harder to wobble the z-axis than the original design using plastic parts.




Sunday, February 12, 2017

Printer bracket fix

Similar to many 3d printer designs, many of the parts on this 3d printer are plastic. Where the Z-Axis meets the Y-Axis is held in place by two top brackets (near the gear on the stepper is a bolt to the z alloy extrusion) and the bottom bracket. One flaw here is that there are no bolts to the z-axis on the bottom bracket. It was also cracked in two places so the structural support was low and the x-axis would droop over time. Not so handy.


The plastic is about 12mm thick and smells like a 2.5D job done by a 3d printer 'just because'.  So a quick tinker in Fusion 360 and the 1/2 inch thick flatland part was born. After removing the hold down tabs and flapping the remains away 3 M6 bolt holds were hand drilled. Notice the subtle shift on the inside of the part where the extrusion and stepper motor differ in size.


It was quicker to just do that rather than try to remount and register on the cnc and it might not have even worked with the limited z range of the machine.


The below image only has two of the three bolts in place. With the addition of the new bolt heading into the z axis the rigidity of the machine went right up. The shaft that the z axis is mounted onto goes into the 12mm empty hole in the part.


This does open up the mental thoughts of how many other parts would be better served by not being made out of plastic.


Monday, January 23, 2017

OHC2017 zero to firmware in < 2 hours

I thought I'd make some modifications along the way in the build, so I really couldn't do a head to head with the build time I had heard about (a lowish number of minutes). The on/off switch being where it was didn't fit my plans so I made that an off boarder and also moved the battery to off board so that I might use the space below the screen for something, perhaps where the stylus lives in the case.


I did manage to go from opening the packet to firmware environment setup, built, and uploaded in less than 2 hours total. No bridges, no hassles, cable shrinks around the place and 90 degree headers across the bottom of the board for future tinkering.

This is going to look extremely stylish in a CNCed hardwood case. My current plan is to turn it into a smart remote control. Rotary encoder for volume, maybe modal so that the desired "program" can be selected quickly from a list without needing to flick or page through things.

Friday, January 6, 2017

Machine Control with MQTT

MQTT is an open standard for message passing in the IoT. If a device or program knows something interesting it can offer to publish that data through a named message. If things want to react to those messages they can subscribe to them and do interesting things. I took a look into the SmoothieBoard firmware trying to prize an MQTT client into it. Unfortunately I had to back away at that level for now. The main things that I would love to have as messages published by the smoothie itself are the head position, job processing metadata, etc.

So I fell back to polling for that info in a little nodejs server. That server publishes info to MQTT and also subscribes to messages, for example, to "move the spindle to X,Y" or the like. I thought it would be interesting to make a little web interface to all this. Initially I was tempted to throw over websockets myself, but then discovered that you can mqtt right over a ws to mosquitto. So a bootstrap web interface to the CNC was born.



As you can see I opted out of the pronterface style head control. For me, on a touch panel the move X by 1 and move X by 10 are just too close in that layout. So I select the dimension in a tab and then the direction with buttons. Far, far, less chance of an unintended move.

Things get interesting on the files page. Not only are the files listed but I can "head" a file and that becomes a stored message by mosquitto. As the files on the sdcard of the smoothieboard don't change (for me) the head only has to be performed once per file. It's handy because you can see the header comment that the CAM program added to the G-Code so you can work out what you were thinking at the time you made the gcode. Assuming you put the metadata in that is.

I know that GCode has provisions for layout out multiple coordinate spaces for a single job. So you can cut 8 of the same thing at a single time from one block of stock. I've been doing 2-4 up manually. So I added a "Saves" tab to be able to snapshot a location and restore to it again later. This way you can run a job, move home by 80mm in X and run the same job again to cut a second item. I have provision for a bunch of saves, but only 1 is shown in the web page in the below.




This is all backed by MQTT. So I can start jobs and move the spindle from the terminal, a phone, or through the web interface.


Sunday, January 1, 2017

Keeping an eye on it

The CNC enclosure now sports a few cameras so I can keep an eye on things from anywhere. The small "endocam" mounting worked out particularly well. The small bracket was created using 2mm alloy, jigsawed, flapped, drilled and mounted fairly quick. These copper coated saddle clamps also add a look good factor to the whole build.



A huge plus side is that I now also have a good base to bolt the mist unit onto. It is tempting to redesign the camera mounting bracket in Fusion and CNC a new one in 6mm alloy but there's no real need for this purpose. Shortest effective path to working solution and all that.