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.

Tuesday, December 27, 2016

First alloy on the 3040 cnc (with 2.2kw spindle)

There are times when words are not needed. When you see a 3040 or 6040 cnc without any enclosure there is a good chance that the machine doesn't see heavy alloy cutting. It only takes a few videos to see how chips are thrown around when a 24krpm bit touches a block of alloy. As a prelude to any alloy being cut I enclosed the 3040 in a "terrarium". This was itself an interesting build and as usual I overdid the design. The top and bottom box frames are made of 5cm square timber with a fairly solid base panel. The back is just light junk with plywood bolted to tabs on each side so I can replace things as I feel. The door opens beyond 90 degrees to get right out of the way and closes to rest on the base 5cm timber at the front of the enclosure.


For anybody reading this I have one word of advice, any gaps in the first 50cm from the machine base will have chips thrown at them. So make sure that the angles the chips might come from near the spindle have been accounted for with your air venting that allows some cooling into the mix. The sides of this case are more than 80cm in height.

The next modification is a mister to help clear local chips and bring some light amount of cutting fluid into the cut zone. The first runs were just using a light spray of CDT over the cut zone before job start.

The very end of one of the first runs is shown in the below video.



The parts being cut are wheel mount crossover plates to allow an outdoor robot to have larger wheels attached. The wheels want M8 bolts, the motor mount is an actobotics pattern, so an M4 hole was a good fit there. Because it's CNC the part itself was cut with many splines to include material where it could do structural good and exclude it otherwise.

I found it useful to cut templates in MDF to test the fit before a final run. This fed into part 3 which includes mounting holes for all 4 bolts of the hub mount. The alloy version 4 also has rounded ends and is shown attached to the wheel. This will let some cheap $10 wheels which are 12 inch across mount to an actobotics based robot.


I'll have video of the "houndbot" in action using these mounts next time.

Sunday, December 11, 2016

3040/24,000 CNC first dry run in place

The progression has finally reached an upgraded CNC with high power spindle. Things still move around fine to the eye, the next step is likely to do some test drills at known distances to see if the additional weight has had an impact on the steppers that can't be easily seen.


A few interesting times when spinning up to 24,000. At around 320hz there was a new loud rattle. I think this turned out to be resonance with either something that was on the cutting plate or the washers on the toggle clamps.

There is going to be video once this machine starts eating alloy. The CNC needs to be lowered into an enclosure (the easier part) so that chips and the like go into a known location. The enclosure itself needs to be made first ;)

Ironically a future goal is to be going smaller. Seeing if twice the number of microsteps can be pulled off in order to get better precision and cut QFN landing zones on PCBs.