My Bridgeport Series 1 CNC Conversion Using Centroid Acorn

All things related to the Centroid Acorn CNC Controller

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Reedfirst
Posts: 69
Joined: Wed Aug 09, 2017 1:02 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: none
Location: Boynton Beach, Florida

My Bridgeport Series 1 CNC Conversion Using Centroid Acorn

Post by Reedfirst » Tue Aug 22, 2017 10:38 pm

There are some really nice machines popping up in the forum already running Acorn. So I thought I'd share my work in progress converting my Bridgeport to cnc using the Acorn controller. This is a learning experience for me as I have no CNC experience. Oh, I am also slowly teaching myself how to use fusion 360 cad.

The machine is a 1993 Bridgeport Series 1 with the hard chrome ways. I've already installed precision ground ball screws on the x and Y as well as angular contact bearings in the bearing mounts. My plan is to get the X and Y under cnc control to assist in machining the brackets for the Z axis. I'll be running DMM Dyn4 controllers paired with their 750 watt servo motors on X,Y, and Z. I might add a 4th axis at a later time. But one step at a time.

Here is a picture of the Machine I am working with.
20170703_184845.jpg
Last edited by Reedfirst on Wed Aug 23, 2017 9:04 am, edited 1 time in total.

Reedfirst
Posts: 69
Joined: Wed Aug 09, 2017 1:02 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: none
Location: Boynton Beach, Florida

Re: My Bridgeport Series 1 CNC Conversion Using Centroid Acorn

Post by Reedfirst » Tue Aug 22, 2017 10:51 pm

They X and Y axis will be driven in a 2:1 ratio. I'm using gt2 5mm pitch timing pulleys.

I am not a fan of using a set screw on a shaft so for the Y axis I took an old dial holder machined it into a hub to mount the timing pulley to. I bored out the timing pulley and drilled and tapped it to match the bolt hole pattern I drilled into the old dial holder. It now fits onto the ball screw and uses the original woodruff key to drive the ball screw. The pressure between the angular contact bearing and the handle /nut eliminate any play between the connections.
20170805_214846.jpg

Reedfirst
Posts: 69
Joined: Wed Aug 09, 2017 1:02 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: none
Location: Boynton Beach, Florida

Re: My Bridgeport Series 1 CNC Conversion Using Centroid Acorn

Post by Reedfirst » Tue Aug 22, 2017 10:57 pm

The DMM servo Motors have a 14mm shaft with a 5mm keyway. So out comes the 4 jaw chuck on my Rockwell 11" lathe so I could bore the motor side pulleys to fit. Once bored to the right size, I broached the pulleys for the 5mm keyway right on the lathe. It was slow but I don't have an arbor press and it worked perfectly. Don't worry about the dead center...... The tip was already trashed.
20170803_143250.jpg
20170803_145129.jpg

Reedfirst
Posts: 69
Joined: Wed Aug 09, 2017 1:02 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: none
Location: Boynton Beach, Florida

Re: My Bridgeport Series 1 CNC Conversion Using Centroid Acorn

Post by Reedfirst » Tue Aug 22, 2017 11:21 pm

For the X Axis I designed a simple motor mount using three individual plates to mount the servo motor to the Table. The servo motor will be attached to a "sliding plate" that is adjustable so the belt tension can be tightened as well as loosened for removal.

Here is a picture of the sliding bracket that the servo motor mounts to. I am boring the counter bore for the boss on the servo motor for a nice registered fit.
20170813_201624.jpg
Here is the servo motor mounted to the X axis. I sill need to make a sheet metal chip shield.
20170822_231119[1].jpg
20170815_003125.jpg
To attach the timing pulley to the ball screws I used a taper lock bushing. It was just a matter of boring the timing pulley to fit.

Reedfirst
Posts: 69
Joined: Wed Aug 09, 2017 1:02 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: none
Location: Boynton Beach, Florida

Re: My Bridgeport Series 1 CNC Conversion Using Centroid Acorn

Post by Reedfirst » Wed Aug 23, 2017 11:12 am

Got the Y axis all buttoned up early this morning. I need to find some round folding handwheels as I'd like to be able to manually use the machine with the control turned off. When I made the bracket for the Y axis motor I decided to leave some room for the linear scale. just keeping my options open :D
20170822_220721.jpg
20170822_220754.jpg

Reedfirst
Posts: 69
Joined: Wed Aug 09, 2017 1:02 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: none
Location: Boynton Beach, Florida

Re: My Bridgeport Series 1 CNC Conversion Using Centroid Acorn

Post by Reedfirst » Wed Aug 23, 2017 11:13 am

Here is the Machine as it sits right now.
20170822_220627.jpg

Reedfirst
Posts: 69
Joined: Wed Aug 09, 2017 1:02 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: none
Location: Boynton Beach, Florida

Re: My Bridgeport Series 1 CNC Conversion Using Centroid Acorn

Post by Reedfirst » Wed Aug 23, 2017 12:03 pm

Now on to building the PC. Marty posted a great video documenting his process. You should check it out.

For the mother board. I am using a Gigabyte H110n Mini ITX board. The board is really small at about 6.75" x 6.625". It was about $75.00

The processor is an Intel Pentium G4400 3.3 GHZ with a single thread rating 1880. About $55.00

Memory is a 4gb ddr4 2133 stick from crucial. About $38.00

Hard drive is a 120 GB Samsung SSD that I salvaged out of a P/C that someone was throwing away.

Power supply is a Antec 430 Watt. Also salvaged.

Led Lights and switches. You guessed it, Salvaged.

As you can see, building a P/C was very affordable. And actually fun to put everything together.
20170823_112240.jpg

tblough
Posts: 115
Joined: Tue Mar 22, 2016 10:03 am
Acorn CNC Controller: No
Allin1DC CNC Controller: Yes
Oak CNC controller: Yes
MPU11 & GPIO4D -w/ 3rd Party Drives: Yes
DC3IOB: No
CNC11: Yes
CPU10 or CPU7: No
System Serial Number: 100505
100327
102696
Location: Boston, MA
Contact:

Re: My Bridgeport Series 1 CNC Conversion Using Centroid Acorn

Post by tblough » Wed Aug 23, 2017 12:30 pm

Look into Fenner Trantorque couplings instead of keyways and setscrews to lock your pulleys onto the shafts. Setscrews loosen and keyways develop slop leading to backlash. Trantorque couplings will not slip and will stay backlash free. Your local bearing supply house should carry them and you can get them from McMaster as well (they just won't tell you who makes them). McMaster also has the 3D CAD models for them.

Cheers,

Tom
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.

Reedfirst
Posts: 69
Joined: Wed Aug 09, 2017 1:02 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: none
Location: Boynton Beach, Florida

Re: My Bridgeport Series 1 CNC Conversion Using Centroid Acorn

Post by Reedfirst » Wed Aug 23, 2017 1:29 pm

Thanks Tom,

I am actually using a trans-torque on the x axis. They are awesome! I was able to use a trans-torque here because the angular ball screws bearings are on the opposite side of the servo drive.

The picture of the hub I posted is for the Y axis. The dial holder which is now connected to the timing pulley is sandwiched between the angular contact bearing and the handle. When the nut to torqued,it pre-loads the angular contact bearings and locks the dial holder into place at the same time. I cant't detect any backlash between the pulley and the screw. I would have used a trans-torque here, however I'd have to machine a spacer to pre-load the ball bearings, then machine the pulley for the trans torque and install that over my spacer.

When I was checking the dimensions, if I were to use a trans-torque, the OD of the trans-torque bushing that would fit a spacer over the 5/8 ball screw shaft was too large for the hub on my timing pulley. Since I already had the pulley I thought I'd give this a try.

cnckeith
Posts: 518
Joined: Wed Mar 03, 2010 4:23 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: Yes
MPU11 & GPIO4D -w/ 3rd Party Drives: Yes
DC3IOB: Yes
CNC11: Yes
CPU10 or CPU7: Yes
System Serial Number: none
Contact:

Re: My Bridgeport Series 1 CNC Conversion Using Centroid Acorn

Post by cnckeith » Wed Aug 23, 2017 1:33 pm

looking good, nice work and thanks for posting the photos..worth more than a thousand words!
great info on the couplers as well.

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