Look into buying a new spindle motor for the Kinetic CNC machine.
Opened this issue · 25 comments
With the latest broken collet (#1909) on the Kress Spindle motor and the known issue of play in the spindle motor bearing, I would suggest that it is time we investigated replacing the spindle motor with a newer unit that as a minimum takes standard collets.
I have identified 2 reasonable options for suitable replacements, being variable frequency spindle motors complete with a suitable VFD (Variable Frequency Drive) inverter. These are also air cooled, so no additional cooling paraphernalia is needed either.
This first one is a 1.5KW spindle that takes ER11 collets and comes with 3 collets as standard. The listed price for this unit is £148.99, but this is shipped from China, with a shipping cost of a minimum of £41.34 and a typical delivery time of 3-7 days. There will likely be VAT and import duty to add to this cost as well. I did find a similar looking unit on Amazon as well, with next day delivery, at a cost of £218, which might not be a bad option, as obviously VAT and import duties are covered.
The second unit steps up the power to 2.2KW and uses larger ER20 collets, coming with 6 collets as standard. The listed price for this unit is £189.20, again with shipping costs from China of £51.09 and the same shipping time of 3-7 days. Import Duty and VAT should be added to this price as well. Another similar unit from Amazon works out as £270, again with next day delivery.
So it’s time for other interested folks to give their comments and suggestions.
Personally, I am tempted by the larger 2.2KW spindle, as this accommodates the larger collets which will add quite a bit of flexibility to the tool. I would also be tempted to pay the extra to get them from Amazon, for speed and no delays with customs and the uncertainty of the VAT and import duty costs.
Happy to go with the consensus on an upgrade, and in favour of improving the CNC router. I'm up for chipping in £50 towards getting it sorted.
From my little understanding of the difference between ER11 and ER20 is the size (diameter) of tool it can hold with ER11 being up to 7mm and ER20 being up to 13mm, so suggest going for the ER20 model.
I can put in £50 towards this
I will be chipping in £50 from my interest as well.
Also, here are the links to the Amazon units for completeness.
1.5kW spindle
2.2kW spindle
I’ll post a link to this issue on our Google Group, to see if we can generate a bit more interest quickly, as I know that Luke would like to use the CNC machine in the very near future ideally.
DD can chip in £50. Maybe a kind soul could train me up in how to CNC too 😁
Happy to show you how I use the router!
Arthur has said he will chip in also which means I can go ahead and purchase the 2.2kw spindle through my company Scintilla to get it here this week if thats ok with everyone?
That sounds good to me 👍
That sounds great, I was concerned that we weren’t getting a quick enough answer to fit your requirements.
Let me know when it arrives and we can agree some time in the coming days to install it.
Additionally, I have a newer Ultra Small Form Factor PC that I was planning to loan to DoES as an improvement to the current CNC PC. I’ll see about getting it configured fully in the next few days as well. It is a much better spec than the current PC.
Great! Ill order it now and keep you updated.
A newer pc would be great Mike!
The spindle has arrived (was delivered to a neighbour). @magman2112 are you available this week to have a go at installing this?
I’m planning to be in DoES quite a bit this week, given it’s MakeFest on Saturday coming.
I will definitely be in tomorrow and any other days we can likely work out.
Great. I'll come along tomorrow and we can come up with a plan
After a bit of assesment from @Evans-Luke and I today, we found that there are a few items needed to fit the new spindle to the CNC machine.
First, the power requirements.
The Spindle driver is going to need 8-10A of mains current, so this is outside the limits of the CNC controller at preesent (which has a maximum current capacity of 8A). To get the new spindle working, we are going to get a similar Isolation switch to that used for Gerald and some 1.5mm mains flex, which we can connect to the mains socket on the wall directly. This will allow safe manual switching till we get a properly spec'd mains relay to switch the motor directly from the controller. A switch and cable have been identified locally from CEF and Screwfix - Luke will pick these up.
We also need some 1mm 5 core flex to connect the spindle motor to the motor controller, again Luke will pick this up locally from Screwfix.
One other part we identified is a Brake resistor, which for this spindle motor needs to be 200 Ohms at 250W. I identified a 300W resistor on eBay, this has been ordered and should be delivered in the next few days.
The final item needed is an adaptor plate to fit the spindle motor to the CNC machine, which I will add the drawing for shortly. Luke is going to see if he can have this made at the University.
The 1mm 5 core flex, 1.5mm flex and the rotary isolator switch are on top of the spindle.
I'll bring the plate along to maker night (probably around 8pm) along with tap and drill bit.
I think we need two M4 countersunk allen bolts 20mm in length. Ill try and find some but if somebody else has some they could bring along that would be great!
There are some M4 countersunk torx bolts in the carousel near my desk, but they're only 12mm
The motor has been installed onto the plate and onto the machine. The next step is to route the cables and final connections which will be done on Monday.
When installing the motor, Mike noticed that the thrust bearing was not located properly, which may have been the cause of previously reported issues with tolerances . This has been re-seated but it should be checked to ensure it does not move again.
If it does happen, the method we used to re-seat the thrust bearing was to use levers that pivoted off of the z-axis motor plate and push down on the bearing. The z axis raise and the process repeated. Mike and Luke will be able to show you.
The new spindle requires a 21mm spanned for the shaft and a 30mm spanner for the main nut which will need to be purchased and kept with the machine.
Picked up a 21mm and a 30mm spanner from Screwfix. So one less item in the to-do list.
Whilst looking for a wiring diagram from the spindle to the VFD, I discovered that the wiring we have used at present is not the best solution. At full speed I believe the witing gauge may not be sufficient and also the cable should be shielded as the VFD can generate a lot of Electrical noise.
I have connected the drive up now, using the current cable though and the spindle does work well for testing. We will need to build a look up table to match the frequency on the VFD to the RPM of the cutters, which we can do with the optical tachometer that we have on hand. But we should monitor the temperature of the VFD to spindle cable until we can obtain the higher spec cable I believe we need.
RPM vs frequency for the new motor:
| Frequency [Hz] | RPM | RPM / freq |
|---|---|---|
| 59.6 | 1150 | 19.2953 |
| 69.9 | 3915 | 56.0086 |
| 90.1 | 5332 | 59.1787 |
| 100 | 5945 | 59.4500 |
| 120.1 | 7167 | 59.6753 |
| 140.3 | 8385 | 59.7648 |
| 160 | 9573 | 59.8313 |
| 180.2 | 10788 | 59.8668 |
| 313 | 18757 | 59.9265 |
| 325.2 | 19489 | 59.9293 |
| 335.9 | 20132 | 59.9345 |
| 360.4 | 21595 | 59.9195 |
| 379.8 | 22753 | 59.9078 |
| 400 | 23955 | 59.8875 |
The spindle motor doesn't spin below 50 Hz, so recommend minimum of 80 Hz to start with (for linearity). The motor is rated 24k RPM max) which comes to 400 Hz.
Looking into some recomendations for similar spindle motors, it appears that we need an 18swg gauge screened cable from the spindle to the motor driver. This equates to a 1.2mm per core, in a 4 core cable (we mistakenly thought we needed 5 cores originally).
It appears though that 1.2mm cable isn’t in standard supply in the UK, so we may have to step up to a 1.5mm per core cable instead.
The cheapest option I have found so far is at Screwfix, at £1.65 per metre, but it isn’t clear whether they will send it in metre pieces or actually cut to length. I’ve ordered this anyway for delivery to DoES, so we will likely see in a few days. This cost is actually less than the delivery cost from other suppliers, but these are a fallback if required.
A parcel arrived for @magman2112 which looked like this delivery. I've left it on the CNC machine either way 😀
Having issues trying to open the pc used for the cilla, windows was asking for username and password to link to a microsoft acount. Although there were no options to skip, ctrl alt delete and logging off managed to bypass this
sacrificial bed has been installed and levelled. last job is to install the new pc
Awesome! Who are we sacrificing and to which dark God? Not me I hope?