hi
i am having a few silly problems
sketchup wont(afaik) give me a model or simple shape to export to cambam/solidworks-hsm.
what toolchain are people here using?
how do i take this and turn it into parts? i know its me and not the files. or if someone can give me dimensions of holes ect i can redraw in solidworks.
sorry for all the questions, been making mostly "pretty" things in wood, these will be my first "parts" where everything has to fit together perfectly.
thnx
mevo

 

I've been doing research on Spindles and I'm quite takes with this idea. this seems to be one of the few ways we might get to a 1 killowatt spindle on 120V house current. If you have a 240V circuit then there are any number of VFD units that you can use in the 12KW range. On 120V its either small DC spindles (<500W) or bulky, noisy, heavy routers.

My only issue is I don't see how you can make one without a lathe or perhaps a really well sorted out CNC machine.

 

To be fair, there are VFDs that'll convert 120VAC 1~ to 220VAC 3~ for spindles(check out LightObject), but the problem there is that you're limited by the current capacity of a single ring main. Assuming a standard 15A circuit, you can get 1.8kW out of the wall. If VFDs are reasonably efficient (and I hear that's one of their main selling points, depending on how much you believe the manufacturers' claims), you might be able to get 1.2-1.5kW into your spindle. That's at full power too, which isn't necessarily all the time. 1kW shouldn't be hard.

Obviously, a 220V 40A line will provide over four times that, and if you can afford it, VFDs higher than the typical 1.5-3kW are readily available. There doesn't appear to be any real need if you're using aluminium extrusion to build, though- all you're going to end up doing is flexing your structure. Once you're up to and beyond 1kW, I'm not sure 8020/V-Slot is realistically the way to go, depending of course on the size of your machine, unsupported spans, all that good stuff. Some simple beam deflection calculations would help there, assuming typical load and instantaneous cutting forces by workpiece material, cutting bit, spindle power and maybe feed rate are tabulated somewhere.

This seems to be rather OT for RC BDC motor conversions though.

 

Saw this today and instantly thought of this thread. Checkout the spindle being used: https://www.kickstarter.com/projects/2003668803/5axismaker-first-ever-affordable-5axis-multi-fabri

 

Been a minute since anyone has shared anything in here.

Any thoughts on using a slower motor such as this 380kv but running it with a 24v psu?

 

Looks good but you may need an 80 Amp PSU with adequate cooling.

Tweakie.

 

I've been investigating using a smoothie controller board for a future build. Since it has a few pwm outputs available it "should" be able to control the ESC. Is this the circuit I need to build to control the brushless motor? I read this thread start to finish again and it seems like there were some jumps from here to the end.

 

Hi Nick,

The circuit you have linked to should be just fine. The ATiny (or whatever) needs to be programmed to measure the incoming PWM pulse width (min. / max.) and scale it from 0 to 100% then convert that into a pulse width of between 1 mS and 2 mS which is repeated every 20 mS.
The theory behind this is explained here http://openbuilds.com/builds/software-speed-control-of-a-brushless-dc-bldc-motor-from-mach3.762/

Tweakie.

 

Ah yeah. That's the part that puts a wrench into the works. I knew there was something I missed.

 

Hey Guys,

I decided to give this a go, fortunately I have access to a full size CNC mill so modified the design slightly. I haven't had a chance to test the spindle out yet but have a 60A brushless ESC and servo tester which should do the trick.

Pics Below:



I did have one question though, I had planned to mount the ESC to my Z axis V-slot and have power cables running all the way to my power supply. I was reading up on some RC aircraft stuff and they recommend adding a pair of capacitors across the power cables for each 10cm of added power cable! Did any of you bother with that? I did notice my ESC already has a pair of caps but the info I read advised adding more.

Cheers
J

 

I'm not sure to be honest, I just picked one which had the right specs. Managed to get it for $5.74!

http://www.ebay.com/itm/400812731219?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT

 

Hi Everyone,

@Shinohara expressed an interest in using my model to machine a spindle for himself, so I have exported the models as .STP files and attached them. Obviously you will need access to a CNC mill but feel free to use these models to machine your own.

A couple of things to consider:
- These housings are designed to fit 608 2RS bearings (same as 608ZZ, but with rubber instead of metal shields) so the holes are modeled as 22 mm diameter. I altered my CAM sequence to take an extra 0.01 mm of material off to get a perfect push fit on the bearings (22.02 mm overall diameter). I often model on the safe side and perform this "on machine" adjustment as I am machining to get the perfect fit on critical parts.
- Be sure to assemble the housing and motor using the shaft to align all the components.
- When mounting to the Z-axis v-slot, the clearance to insert and tighten the mounting screws (10 mm allen cap screws) is quite tight and you'll need to use a ball ended allen key to tighten them, alternatively you could use hex head bolts.

Cheers,
J

 

Unfortunately the upload didn't work, so I have put it on my dropbox..

https://www.dropbox.com/s/imtjcaoiz7i07qu/spindle_housing_models.zip?dl=0

Hopefully that works, although I'm not sure how long I will be able to keep it there so maybe someone could put it in the files section if needed??

J

 

Hi Guys,

I have finally gotten my machine all together, here's a video of it doing it's first cuts.

www.youtube.com/embed/ExGllS2Ewg0

This is through 20mm plywood using a 4 mm solid carbide End Mill, 1 mm step-downs, feeding at 1000 mm/min. What are everyone else's experiences with this type of cutting? It's quite slow cutting large pieces but sounds like it's working quite hard, do you think I can take deeper cuts and/or move faster?

I am slightly worried because I tried cutting aluminum which didn't go so well. It seemed like the machine was struggling, taking 0.1mm cuts at 500 mm/min and in one instance the cutter caught an edge and got thrown around a bit. I feel like the gantry head and z axis just isn't stiff enough to handle metal cutting.

The other issue could be that the spindle isn't up to the task? Do you think i'd fear better with a router than spins 20k+ RPM??

Would appreciate some guidance on this!

Cheers
J

 

Hi Jeremy,

I am pleased to see you have your machine up and running - nice job with the build.

Whilst some have cut metals with a gantry design of machine it is never going to be totally as successful as a milling machine design. Rigidity is the problem here so anything you can do to stiffen everything up will be beneficial but wood, plastics and many composites are where this design of machine really excels.

Tweakie.

 

Hi @Tweakie, thanks for you reply.

Yeah obviously there are limitations with this style of machine.

I would really like to be able to cut at a slightly faster rate, even through wood, do you think I would benefit from moving up to a 6mm cutter? Hopefully this spindle is powerful enough to handle it.

Also, do the polycarbonate extreme V-wheels make a big difference?

I do have my eye on some linear rails and ball screws to build a super mill! Still gantry style though.

Cheers,
J

 

I think you will do better with a 6mm cutter but spindle power is something you may have to try and see.
Unfortunately I have no experience with the polycarbonate wheels, perhaps someone else can advise on this.

Tweakie.

 

I got hold of a 6 mm wood routing end mill and managed to do some good cuts for a friend that is prototyping a stool design.

Ended up running at 500 mm/min and taking passes of 3.8mm, still took 5 passes to get through 19mm plywood though! Cut quality was good, even if a bit slow. Does this sound about the same as what you guys would run your machines at with this spindle?

I feel like I might be able to take deeper cuts, it really was getting very noisy though, so much so that we were wearing ear protection. It was hard to tell, but it sounded like there may have been some cutter chatter happening due to the cutter running through such a deep channel/cut.

Cheers
J

 

the poly carb wheels are a really good addon for the Z axis.

Not quite finished with the build so no real world cutting result differences but I can feel the Z is FAR stiffer at the longer travel compared to the standard solid V wheels

 

Forgive me if you've already mentioned it, but have you measured the runout of the RC spindle? Currently I am using a DeWalt DW660 and my runout is horrible, .007" to .010" typically, measured at the cutter shank. This is mostly due to the fact that I can't buy a precision collet for that router.

 

I was going to ask about this. Given the load, I can't see this pulling a lot of amps, even when cutting. Have you measured the amps while cutting? I have several ESC's laying around 40-50A.

I just won a motor for $15 w/ shipping from HK. Assuming they follow through with fulfilling the auction.

 

Looking for some help on this build.

I've built this setup using a mystery cloud 80A esc and a servo tester, but it seems like my RPM isn't as high as it should be. Would bearing drag cause this problem?

Also, could someone give me their max feeds and pass depth they've been able to achieve in aluminum? I've only been able to manage 1/64 pass with a 150mm/min feed

 

It's the 890kV motor described in this project running on a 12V 40A meanwell power supply adjusted up to 13.9V. According to the math, I should be running up to 12k RPM. It doesn't seem to be capable of running at that rate and I get an oscillating noise from the spindle, it sounds like my bearings are dragging and are maybe slightly out of alignment. I've done a tear down and reassembly with no real difference in performance.

Just did another teardown and there's finally evidence that my bearings were toasted. I'm going to remove them and get rid of the spacer stack and run it like the version 1 of this project.