Joe's 1000x600x200 steel and aluminium router started

[devmonkey]

Machine is going really well, I've made a few parts for the local flying club.

I'm now in need of a rotary axis, I have a couple of options:
1. Use the headstock and tail from an old rusty taig lathe I have with a belt drive off of a stepper or servo,
2. Convert a rotary table,
3. Buy one.

I need it quite quickly, can anyone recommend anything that is known to work, even if it is one of those chinese harmonic drives? I need something with a 100mm chuck and minimal backlash as it will be used for continuous processing not stop/lock.

I was looking at this, seems extremely cheap for a harmonic drive but they have them in europe so I could get it fast:
https://www.aliexpress.com/item/33025578546.html

Cheers, Joe

[devmonkey]

I needed an HTD5 pulley for a project, this was a bit odd as it needed to be fixed to a spinning bearing housing rather than to a shaft so I decided to make one on the machine. I used the cambam trochoidal plugin for the roughing allowing the entire part to be milled with a 3mm endmill, took a bit longer but meant no tool change. Part was cut dry with air to clear chips, worked out really well.



Trochoidal clearing is excellent, no gummy chips sticking to the endmill. This was cut from some 5000 series (not sure exact spec) scrap plate, it is quite gummy, would have been better in 6061 but I didn't have any to hand. Still the part is more than serviceable for its intended purpose which is to drive a multi-turn encoder (near zero load). Was cut at 3mm DOC, 15% stepover, 24k rpm, 3000mm/s for clearing (although the machine never gets anywhere near this on this part due to the tiny radius of the spirals).



I will probably recut it with a high speed profile to finish, the finish pass was way too slow (600mm/s) which led to rubbing and the surface finish not being perfect. This was entirely my fault for rushing the CAM and not setting the feed.

[Clive S]

Very nice. I happen to make two the other day for an encoder 28 tooth .

.

[devmonkey]

Very nice. I happen to make two the other day for an encoder 28 tooth .

.

They are nice, what are they made out of and how did you cut that thread on the inside of the hollow one?

I just made it a baby brother, this one is going on an 8mm shaft with a 2mm shaft stuck in the end to go onto the encoder gearbox.

[Clive S]

The thread was done on a Myford S7 converted to cnc with an encoder to do threading.
They are made out or 6082 I think

Didn't do a vid of the thread but had to make a male thread first. The hollow one is being fitted on the end of a spindle lathe to drive the encoder. The pin nut was off the lathe and used that for the fit 35x1.5mm



https://www.youtube.com/watch?v=MyLwFqa02Bc

https://www.youtube.com/watch?v=ZR_W3w_rews

https://www.youtube.com/watch?v=IiMME9BcBHw

[Voicecoil]

I needed an HTD5 pulley for a project, this was a bit odd as it needed to be fixed to a spinning bearing housing rather than to a shaft so I decided to make one on the machine. I used the cambam trochoidal plugin for the roughing allowing the entire part to be milled with a 3mm endmill, took a bit longer but meant no tool change. Part was cut dry with air to clear chips, worked out really well.

Well done, nice bit of work that. BTW, how did you hold it whilst machining? Pieces like that where the finished part doesn't have a lot of thickness I always find a bit of a challenge to hold down rigid.

[Kitwn]

'Great minds' and all that.

Yesterday I used the CamBam trochoidal pocket plugin to cut out the teeth for a ratchet made from Jarrah hardwood. Conventional shallow cuts tend to take the corners off the teeth where the grain is tangential to the wheel so being able to do a 12mm depth of cut with a 2mm diameter tool is a bonus. I still had to redraw the original ratchet design (produced in Gearotic which will also draw HTD and many other pulleys for you) with rounded teeth to avoid some chipping. This cut used a two-flute straight cutter with a speed of 1000mm/min and a stepover of 0.15 (0.3mm) and the maximum 24000 rpm. This took about 25 minutes for the 110mm diameter wheel.

[devmonkey]

'Great minds' and all that.

Yesterday I used the CamBam trochoidal pocket plugin to cut out the teeth for a ratchet made from Jarrah hardwood. Conventional shallow cuts tend to take the corners off the teeth where the grain is tangential to the wheel so being able to do a 12mm depth of cut with a 2mm diameter tool is a bonus. I still had to redraw the original ratchet design (produced in Gearotic which will also draw HTD and many other pulleys for you) with rounded teeth to avoid some chipping. This cut used a two-flute straight cutter with a speed of 1000mm/min and a stepover of 0.15 (0.3mm) and the maximum 24000 rpm. This took about 25 minutes for the 110mm diameter wheel.

Very nice Kit! This was the first time I'd used trochoidal clearing, definitely a keeper for thin endmills in metal.

Now I have a question for you pulley experts. I need to make a very large 157 tooth 8m timing pulley ring that will be fitted to the perimeter of a winch drum. The pulley needs to be made of a ring of material ~25mm thick with an outer diameter of 400mm and inner of 340mm. It could be made from aluminium, SRBP, delrin or even hdpe.

Trouble is I don't want to waste a large piece of material just to make the ring, any ideas? I've even considered casting a blank in aluminium but I don't have a foundry. Are there any castable machineable urethanes that are strong enough for timing belt pulley teeth?

[Sterob]

Very nice gentlemen....I want to be able to do that when I grow up.

[Kitwn]

I'm well pleased with the trocho pocket plug-in, it's a major step forward in being able to make hardwood clock wheels sucessfully.

How are you designing the ring of teeth for the pulley? I have the Gearotic software which can create accurate timing pulleys in all sorts of formats. If you need help with that I can send you a PDF for importing into CamBam (that's another plug-in).

Well if you want to get into a new hobby that involves playing with fire, melting aluminium is easy. The YT video below gives you the idea. Use previously cast aluminium alloys (old water pumps from your friendly neighbourhood motor mender etc.) rather than cans or other scrap. Sawing off the bottom of an old fire extinguisher makes a good crucible. Getting a sucessful cast with it is another story however.

Not sure on the use of 2-part plastics for something this robust or how well they machine but one option to consider is to make a master in MDF with your CNC machine and then a silicone mold to cast the final pulley ring, or a blank for final machining. I've done a bit of this for arty stuff but not for engineering. You aren't going to buy from Australia but the Barnes site linked below has info on materials and how to use them. Similar stuff will be available in Pommieland.

https://www.barnes.com.au/

https://www.youtube.com/watch?v=lSoWxG30rb0

Good luck

Kit