PM-932m CNC Conversion

[gmoschini]

Introduction

I placed an order with Precision Matthews for a lathe and a mill a week ago, originally the order was:

• PM-1030V Lathe
• PM-30M Mill

The lathe was backordered, so a week later I reconsidered my choice of the mill and decided to go bigger and heavier for just a bit more money.

So, I changed the mill order to be the PM-932m with the Power Down Feed and cast iron stand.

Both the lathe and the mill will be here in December, and that is when I will start planning to convert the PM-932m to CNC.


Wishlist

Here's what I'd like to do to the mill:

• Convert the leadscrews to ballscrews.
• Start the CNC electronics with simple steppers, upgrade to full AC servos later.
• Change the R8 Spindle to an NT30 spindle such as the one from Charter Oaks Automation.
• Epoxy Granite All the Things
• Convert the motion from dovetail ways to linear rails.
• Replace the spindle head with a Chinese belt-driven BT30 spindle, rated for 10,000 RPM / 12,000 RPM Max.
• Replace the 1.1kw/1.5hp AC motor with a 1.5/2.2kw AC Spindle Servo, rated for 6000 RPM, 8000 RPM Max.
• Belt drive the spindle with the servo with a 2:1 overdrive.
• Add a BT30 carousel ATC

Initial Designs

Thanks to KCJ for sharing his excellent CAD models, it's helped me get a much better idea and a quicker head start on designing the upgrade.

KCJ's models:
https://github.com/KurtJacobson/RF45...r/CAD%20Models


So the initial design for the BT30 spindle and 1.5kw AC spindle servo was based on taking a giant block of cast iron and making an entire head out of it.

Assuming I get the mill converted to CNC first, it should be able to mill its own replacement head.






Initial Parts List

Ball Screw Kit:

TBD, have to find a matching kit for an RF-45/PM-45/ZX45/etc.

Steppers / Servos:

TBD, prefer to start with less expensive plain steppers just to get things moving.

BT30 Spindle:

Plenty of inexpensive 6000 RPM BT30 spindles listed on AliExpress, but here's one example rated for 10,000 RPM with a 12,000 RPM maximum:
high speed ATC BT30 automaitc spindle for cnc machine / cutting machine 12000rpm

AC Spindle Servo

Found a AC Spindle Servo that comes in 1.5kW or 2.2kW sizes that fit within a 150x150mm square frame, complete with servo, driver, and brake resistor - and single-phase 220V compatible.

How do these torque ratings compare to the stock AC motor? I don't know yet..

• 1.5kW AC Servo Spindle
• Manufacturer's page: https://www.szghauto.com/product/91.html
• Features: Rated Speed 6000 RPM, 8000 RPM max, 9.5 N.m / 1345 Oz-In Torque between 4000-6000 RPM, size 150x150x300mm body length, weight 25kg/55lb.

• 2.2 kW AC Servo Spindle
• Manufacturer's page: https://www.szghauto.com/product/93.html
• Features: Rated Speed 6000 RPM, 8000 RPM max, 14 N.m / 1982 Oz-In Torque between 4000-6000 RPM, size 150x150x365mm body length, weight 30kg/66lb.

ATC

• ISO30/BT30 ATC

All comments and suggestions are welcome, this will most likely be a multi-year build.


I am located in Atlanta, GA, if anybody else has a large mill and is willing to help, let me know!

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[gmoschini]

Steppers / Servos:

I think for the motors for motion, I'll pick closed-loop hybrid steppers like these from Lichuan:

• 3 x Lichuan NEMA 34 12Nm Hybrid Stepper + Driver
• 3 x 720W Ring Transformer

With the AliExpress Sale starting on November 11th, I can get three of these beefy closed loop steppers for just under $600 with shipping.

Toroid Transformers add to the cost, one per stepper driver.


AC servos are also available, but they start at around $200 and the torque ratings are different...


Control Electronics

I will probably go with the Mesa US PCIe Stepper Kit, and run LinuxCNC.

[gmoschini]

Also possible alternative for the Z-axis stepper, a closed loop stepper with a brake:

https://www.omc-stepperonline.com/cl...tic-brake.html

[gmoschini]

Might choose the Leadshine versions, their documentation seems to be better (it exists):

Leadshine CS-M234120 (without Brake) for the X/Y axis.
Leadshine CS-M234120B (with Brake) for the Z-axis.

Stepper Driver CS-D808

[gmoschini]

Ball Screw Kit:
linearmotionbearings2008 on eBay has this kit:
X Y & Z ball screws kit 772mm/397mm/602mm for ENCO RF45 CLONE CNC conversion


If the pictures look familiar, they're from KCJ:
https://www.cnczone.com/forums/rf-45...ml#post1991518

But these are sold with double-ballnuts instead of two separate ball nuts.

[gmoschini]

Playing with the idea of mounting Hiwin QR-series heavy-duty rails on the axises (axii?).

The QR Series uses rollers instead of ball bearings, so they're for super heavy duty motion.

These are the 30mm wide models, with flanged carriages.


I got the idea from CNC4RX7 on YouTube, who's doing something similar with a PM-727.

He has his ballscrew inside the column, I'm thinking of moving the ballscrew forward and filling the column with epoxy granite.

[gmoschini]

Linear Rails

I think I'll go with Hiwin genuine HG series rails, from motionconstrained.com:

Z Axis: 2 x HGH20CAZAC rails with normal blocks, 20mm rails 760mm long. $288
X Axis: 2 x HGH20CAZAC rails with normal blocks, 20mm rails 820mm long. $299
Y Axis: 2 x HGH20CAZAC rails with normal blocks, 20mm rails 520mm long. $245

Total: $832


The rails are longer than the dovetail slots, so I'll have to support the ends for some overtravel.

[gmoschini]

Hybrid Closed-Loop Steppers

Prices from Leadshine USA (leadshine.com):

2 x $148: Leadshine CS-M234120 (without Brake) for the X/Y axis.
1 x $208: Leadshine CS-M234120B (with Brake) for the Z-axis.

3 x $129: Stepper Driver CS-D808

So total cost: $891

[gmoschini]

Hiwin RG Series Rails

I am also getting quotes for the Hiwin RG Series rails, which use angled rollers instead of ball bearings.

RGH20CA2R520ZAHII: $671

2 x RGH20 rails, Heavy Load, Standard Block, Medium Preload, Precision H, 2 blocks per rail, 520mm long.


RGH20CA2R760ZAHII: $718

2 x RGH20 rails, Heavy Load, Standard Block, Medium Preload, Precision H, 2 blocks per rail, 760mm long.


RGH20CA2R820ZAHII: $741

2 x RGH20 rails, Heavy Load, Standard Block, Medium Preload, Precision H, 2 blocks per rail, 820mm long.


Total: $2282


This quote was from Braas Automation, brassco.com.

What's interesting about these prices is that the rails are cheap - but the bearing blocks are $132 each!

[gmoschini]

I'm looking at the TBI Motion store for Ball Screws:

https://www.aliexpress.com/store/1797664


They have some double-nut C3 or C5 grade ballscrews in 2005 series that are interesting:

https://www.aliexpress.com/item/32942915298.html


The manufacturer's page has info and drawings/cad:
https://www.tbimotion.com.tw/en/page...e-catalog.html

https://www.tbimotion.com.tw/en/download/index.html

[gmoschini]

X-Axis Ballscrew

Came up with a simpler mount for the X-axis ballscrew and motor mount, allowing for a full length ball screw and more travel.

The parts are designed based on off-the-shelf components:

• MBA15-F Nema 34 Motor Mount
• FK15-F Fixed End Flanged Bearing Block
• FF15 Floating End Flanged Bearing Block
• MGD-20 Ballnut Mounting Block, modified with 6mm cut off from the bottom and the top.

The only custom parts are the 15mm thick plates on each end of the table which serve as the mounting points for the ballscrew assembly.

The Ballscrew is looking to be a 2005 series (20mm, 5mm lead), with a DFU/OFU double-ball nut.

The saddle will need some minor pocket machining to fit the MGD-20 mounting block, I could probably even bolt it down to my tiny X2-series mill to do that.

[gmoschini]

AC Servos

Decided to splurge and go for DMM AC Servos and DYN4 drives:

• 86M-DHT 0.75 kW AC Servo on X
• 86M-DHT 0.75 kW AC Servo on Y
• 86M-DHT 0.75 kW AC Servo with Brake on Z
• 3 x DYN4 AC Servo Drives

Cost: $1643


The DYN4 AC Servo drives have the benefit that they can run directly off of single-phase 110/220V AC, so a DC power supply or an AC toroidal transformer isn't required.


For controlling hardware, I'm going to with the Mesa electronics 7I77 6-Axis Servo control board, and either a PCI/PCIe 5i25 or 6i25 card and LinuxCNC.

5i25-7i77 PCI Kit
6825-7i77 PCIe Kit

[gmoschini]

Test fitting a NEMA 4 enclosure sized 20" x 20" x 10", with 3 x DMM DYN4 AC Servo Drivers inside the box.

I probably won't put the NEMA enclosure on the mill itself, but it gives you an idea of the scale.

Also added the DMM 750W AC servos on the X/Y axis.

[ninefinger]

I'd ask DMM for their recommendation on controlling the servos. They take step & direction inputs so may be better with a "stepper" control board rather than a servo control board. The drives themselves handle the feedback from the encoder, not the control board so no need for that on the control. Also, look at the ethernet MESA cards, (7i76e), card can go in the control box and the PC can be completely separate, connected with a dedicated ethernet cable. Lets you use almost any format PC and not have to have a slot for the card. Plus the 7i76e has lots of IO, no real need for another card right away.

[gmoschini]

I'd ask DMM for their recommendation on controlling the servos. They take step & direction inputs so may be better with a "stepper" control board rather than a servo control board. The drives themselves handle the feedback from the encoder, not the control board so no need for that on the control. Also, look at the ethernet MESA cards, (7i76e), card can go in the control box and the PC can be completely separate, connected with a dedicated ethernet cable. Lets you use almost any format PC and not have to have a slot for the card. Plus the 7i76e has lots of IO, no real need for another card right away.

Thanks for the feedback.

I looked at the Ethernet stepper board, but kind of decided against it because it didn't appear to have the encoder feedback with steppers (?).

I thought it was important that LinuxCNC have the feedback from the servos so it can do its own servo driving with PID loops.

So I'm going to start with the PCIe card... And maybe if they ever release a Ethernet servo board I might switch to it then.

Sent from my Pixel 3 XL using Tapatalk

[gmoschini]

I found a like-new Hoffman CSD202012 (20x20x12") NEMA 4 enclosure on eBay for about $100, plus the panel board (sold separately) for another $40, so I'm going with that size.

Hoffman also has excellent 3D STEP models of their products, so that's also helpful.


It's big enough that I might be able to fit a Mini-ITX board in there for the CNC computer.

I have two Mini-ITX boards lying around, an older Intel Avoton C23750 fanless board, and another with an Intel Xeon-D server processor - also low power.

[gmoschini]

Came up with a Y-axis motor mount that should allow me to re-use the existing hole for the ballscrew, with only drilling and tapping mounting holes required.

The motor end has the DMM NEMA34 servo, a MBA15-F motor mount, the aluminum mounting block, and then a FK15 block for the threaded end of the ballscrew.

The free end of the ballscrew will be supported by a FF15 block, mounted to a T-shaped aluminum block which should bolt to the underside of the casting.



The Aliexpress store (TBI Motion) I'm looking at offers C3 ground ballscrews, and they also offer C3 class FK blocks with real Angular Contact bearings.

I'm going to wait until the machine arrives so I can double-check the measurements before I order the ballscrews and such.

[gmoschini]

I'd ask DMM for their recommendation on controlling the servos. They take step & direction inputs so may be better with a "stepper" control board rather than a servo control board. The drives themselves handle the feedback from the encoder, not the control board so no need for that on the control. Also, look at the ethernet MESA cards, (7i76e), card can go in the control box and the PC can be completely separate, connected with a dedicated ethernet cable. Lets you use almost any format PC and not have to have a slot for the card. Plus the 7i76e has lots of IO, no real need for another card right away.

Looking into this further, Mesa actually offers two other Ethernet boards that would work:

• 7I95 Ethernet interfaced Step & Dir & encoder plus I/O Interface
• 7I97 Ethernet interfaced Analog servo plus I/O interface

Description for the 7i95:

The 7I95 is a Ethernet connected motion control interface designed for interfacing up to 6 Axis of step&dir step motor or servo motor drives and includes encoder feedback for each axis. Step rates up to 10 MHz are supported. The 7I95 also has 24 isolated inputs plus 6 isolated outputs for general purpose I/O use. 6 high speed encoder interfaces are provided axis feedback and for spindle synchronized motion. Two RS-422/RS485 serial expansion ports and a parallel expansion port are also provided.
All step and direction outputs are buffered 5V signals that can drive 24 mA. All outputs support differential mode to reduce susceptibility to noise. The encoders can be used with TTL or differential input.
24 isolated inputs are provided for general control use including limit switch and control panel inputs. Inputs operate with 3V to 36V DC and can have a positive or negative common for sourcing or sinking input applications. 8 inputs can be used to support up to 4 quadrature MPGs.
Six 36V 2A isolated outputs allow sinking, sourcing combinations of both.
Two RS-422/RS-485 interface is provided for I/O expansion via a serial I/O daughtercard. In addition to the on card I/O, A FPGA expansion connector compatible with Mesa's 25 pin daughtercards or standard parallel port breakout boards allow almost unlimited I/O options including additional quadrature or absolute encoder inputs, step/dir or PWM/dir outputs, and field I/O expansion to hundreds of I/O points. All field wiring is terminated in pluggable 3.5 mm screw terminal blocks. The 7i95 runs from a single 5V supply.

MesaUS.com doesn't list the card, so I may have to ask about it.

[dautry]

AC Servos

Decided to splurge and go for DMM AC Servos and DYN4 drives:

• 86M-DHT 0.75 kW AC Servo on X
• 86M-DHT 0.75 kW AC Servo on Y
• 86M-DHT 0.75 kW AC Servo with Brake on Z
• 3 x DYN4 AC Servo Drives

Cost: $1643


The DYN4 AC Servo drives have the benefit that they can run directly off of single-phase 110/220V AC, so a DC power supply or an AC toroidal transformer isn't required.


For controlling hardware, I'm going to with the Mesa electronics 7I77 6-Axis Servo control board, and either a PCI/PCIe 5i25 or 6i25 card and LinuxCNC.

5i25-7i77 PCI Kit
6825-7i77 PCIe Kit

Look at EBay. I ordered my DMM servos and drives from them on Ebay. Saved a couple hundred and free shipping. I’m working on getting them up and running. I bought them for a PM45.

[gmoschini]

DMM has some really fast shipping, the servo motors arrived today!














Decided to cancel my order from MesaUS while I reconsider my controller options.


I'm leaning towards one of these two:

• Mesa 7i97 - Ethernet Analog Servo Control + Encoders
• Mesa 7i95 - Ethernet Step + Direction Control + Encoders

I think my preference will be for the 7i97, analog servo control...


However I did send an e-mail to DMM asking their feedback.