To provide more information I tested my power supply. It is producing 23.6V DC with no load but can be adjusted between 21.6V - 26.4V. Should I perhaps dial the voltage output up closer to 26V? I noticed Ryan’s power supply unit is a bit more powerful being a 2.5Amp/60W unit. Is it possible my power unit is a little under done at just 50W? It is relatively inexpensive to replace my power unit with a 75W power unit if it is more suited to the job.
Thanks for any feedback.
I think you might be able to go to 0.85 amps but much above that, take it in 0.01 increments and watch your heat closely.
One thing that can allow running slightly higher is to print the tool mount parts with something such as PETG or PET-GF or PET-CF that takes higher temp to print and can sustain higher temps without deforming.
If your mounts are printed in PLA, I think 0.85 amps is pushing the heat limit.
If your holding amps are lower, then part of their time in service may be on lower amps, thus you get a cooler temp overall. I need to let those with more knowledge and experience than I have chime in here.
Just so you’re aware 3.8.0 is not recommended - the last known good version at the moment is 3.7.17.
A compression bit is probably the slowest bit you can use. Your speeds actually seem pretty good to me. Have you checked to see if you actually need it? You can probably remove 2-3x the material with an upcut bit. If you get the finishing pass right you should have little to no tear out on the top surface that the bottom edges should be great.
If you really want to use a compression bit for both top and bottom edges you should use a roughing pass with an upcut, and a finishing pass or two with the compression. Bulk material removal with a compression bit is as far from ideal as you can get. It forces all waste material into the center of the cut…you want all the material out of the cut.
Just to make sure we are on the same page, a Compression bit only works at full depth, in a material that is made for that specific bit. I have never seen a 6.5mm compression bit, usually they are for at least 12-30mm.
In short I think you have a bit/cam issue not a machine issue.
If you really really think you are using the right bit I suggest maybe switching to a straight flute endmill instead. They have a slightly better material removal rate and very similar tear out performance…and you do not need to always be at full depth.
Double checked. My FluidNC version is actually 3.7.8. Would you recommend I update to 3.7.17?
All good Ryan. Overall I am very happy with the Low Rider just now looking to find my limits. Most projects I have done are with a 4mm diameter single upcut bit with multiple passes. The attraction of the compression bit (also 4mm diameter) was cutting 6mm MDF in a single pass but it was the compression bit that showed the limits of my machine.
Of more interest to me is the power supply I am using. Being rated at 50W, if all 5x motors are being driven at 24V, the current per motor is only just over 0.4Amps (theoretically but I don’t expect all motors running at the same time happens ever). I see your power supply is rated at 60W so maybe this gives more “grunt” than I am getting? I think I will try a 75W 24V power supply and see if my motors work harder and start getting warmer but not too hot.
Will report back on what I find. Thanks all for your replies. Cheers
Eeeh, only if it’s misbehaving. The important thing is not to go past 3.7.17 yet.
@vicious1 I was going to link to the docs here but they still say 3.8.0 is recommended.
It doesn’t actually work that way, the stepper are actually like 3.5V or something. They are chopper drivers 50W should be fine.
I use a single flute upcut bit from the shop and cut 12.5mm slotting full depth at 20mm/s on the LR3. A compression bit is 100% not the right bit for MDF.
This is where I am showing my limited electronics knowledge. I was starting to think the 50W power supply was limiting me. So the Jackpot board is distributing the power to the stepper motors at a lower voltage, good to know. Do you see any benefit in increasing the DC voltage supply from the measured 23.6V to closer to 26V? (it is adjustable) I know my “12V” car battery supplies 13.2V when fully charged and will not start the car when it drops close to only 12V.
Good to know a compression bit is not right for MDF. When I started this journey I had some 16mm MDF cut commercially and they told me they used a compression bit for their cutting but it was on a big commercial cutter.
I will try cutting some 12mm MDF at full depth and 20mm/s with a 4mm diameter single flute upcut bit. If I can match this then I know I am close to the machines capability.
It would be useful to have some benchmark cutting examples to test machine limits. Perhaps this already exists and I have missed it. I have seen the LR4 providing some impressive cutting speeds with bigger 1/4" bits. Would like to do my own before and after testing so looking to find the limits of my LR3. Certainly have been impressed with the LR3’s cutting accuracy to date.
Cheers
There is no benefit to running higher voltages for the situations you’re seeing. If you’re seeing anywhere close to 24V and it’s stable while the system is running then your power supply is fine. Most off-the-shelf power supplies like that will cut out completely if overloaded so as long as the whole system isn’t freezing and resetting then you’re probably fine.
The stepper driver regulates the current into the motors by switching them on and off rapidly. If you are using 12V then it will get full current into the motors by applying 12V to them about 25% of the time, the other 75% of the time they’ll be off. If you up that to 24V then it will get to full current by applying 24V to them for half as long, or around 12.5% of the time. In both of those cases you get the exact same performance in terms of low speed torque.
The difference comes at higher speeds (hundreds of mm/s movement speeds) where the inductance of the coils starts to matter and the extra voltage lets the drivers get the coil up to rated current a little quicker. Even then, 23V to 26V is going to be negligible difference.
The other thing is that people get quite confused with power when it comes to stepper motors. 1A into a stepper motor coil isn’t 1A from the 24V power supply because of the switching I mentioned above. It’s actually 1A at 3.5V which is the same as 0.15A at 24V. That supply is heaps for what you’re doing.
Stepper motors = ~10W
Jackpot = ~10W
Plus whatever else you might have hung off it.
To provide some feedback on this topic. This weekend I did some speed testing and I am convinced my LR3 is cutting as well as it should.
Before I did this test I turned up my voltage supply from 23.6V to 25.4V. Something that is easy to do on the small power supply unit I have. I also did these cut with a new 4mm diameter, single flute upcut bit. So I can’t be sure what impact these changes may have made but the results are impressive. (remember this is a LR3 not the new bigger brother)
I cut the 5x slots shown with increasing speed. Starting at 20mm/s and increasing the speed on each cut up to 30mm/s on the last one. These slots have a 12mm DOC done in a single pass in a 16mm MDF panel. The last cut still looks good and the dimensions are virtually identical across all cuts so perhaps I can go faster still but I am happy knowing these speeds are where they should be for an LR3.
Thanks all for your comments and feedback.
