Hacking the Hack 8020

[snowgrains]

Well, I've lurked here for a long time, so I suppose it's time to publish my build thread.

For background, I've already built one machine from plans. I bought the "MiniMill" plans on eBay that Mike Walach sells and actually completed it almost two years ago. Uses the Xylotex 3-axis controller and the 269 oz. motors. Bought a license for Mach 3 about a year ago and finally learned enough to make my first cut last November.

I'm an IT person, not a machinist, if that helps explain what took me so long to get going. This stuff can be a bit obtuse, and I'm probably a bit dense, so it's tough to build inertia.

That first cut was pretty exciting. I'd finally transitioned from theory to reality. Pictures of the MiniMill and a few things I've cut are below.

The piece with the red letters is Cyrillic for my daughter's name, "Yulia." My wife and I traveled to Kazakhstan for 2 months in Dec-2004 through Jan-2005 to adopt her at the age of 7. She spoke only Russian and we spoke only English. She was totally fluent within 6 months of coming to the United States and now is an all-American girl. I want to keep her vested in her heritage, so I'll probably be making a few things on the CNC mill that call back to her Russian beginnings.

Before I'd even finished the MiniMill, I realized that it was going to be lacking in size and speed. I figured I'd finish it and use it as a training ground while I scoped out a larger and faster machine.

I bought the Solsylva plans and Hack's 8020 plans (back when he was selling them).

Solsyva's plans were incredibly thorough, but I was worried about how much tuning would be involved with all that gas pipe and roller bearings.

Hack's plans looked much easier to build and I hadn't done enough research to worry about the 8020 bearings. I know he later made the plans free and stopped selling the MDF kits. I think I bought the last kit he had available in April-2007.

Now, with the holidays over and a Chicago winter burying me periodically with snow, it seems like a good time to get going on Hack's design.

I spent a lot of time reading the forums and saw more than a few posts warning that the 8020 bearings were not a good choice. I also saw that automation-overstock.com had Hiwin linear motion for reasonable prices. Finally, I noted that Ahren was marketing his aluminum carriages for use on 1/4" thick cold-rolled steel.

What I have so far is Ahren's carriages on the 49" long X-axis and Hiwin 25 mm rails and bearings for the 34.5" long Y-axis. Pictures are below.

I'm thinking of using the same 269 oz. motors with 1/2-8, 2-start Acme and dumpstercnc anti-backlash nuts.

Anyway, I wanted to contribute something back to this great community. I've learned a lot over the past couple years thanks to the many wonderful people who post here.

Any thoughts, advice, comments, etc. are greatly appreciated.

Greg

[ahren]

Greg,
Your machine is looking great! I'm slightly biased, of course, but it looks like you have a solid foundation to start adding to. It's great to see the linear carriages in action.

I wouldn't hesitate to recommend Dumpster's AB nuts -- they work really well on my machine. I get about 300 IPM rapids on the X and ~150 IPM on the Y with the 5 start screws and nuts. I have 300 oz-in motors, and you're close to that, so you'll hopefully get similar performance if your gantry mass is about the same.

Best of luck!

Ahren
www.cncrouterparts.com

[joecnc2006]

On your gantry sides, you may want to add some steel angle to stiffen it up, you will get allot of flex in single sheet of MDf, other than that looking good so far.

Joe

[hsgreer]

Greg,

What model Hiwin's do you use on the Gantry. Any reason you opted for the Hinwins on the Gantry over Ahren's linear carriage?

Thanks,

Steve

P.S. Nice work! I'm inspired!

[snowgrains]

Thanks, Ahren. The carriages roll smoothly on the 1/4" steel.

I did have some issues with the steel theough. I ordered two pieces from DiscountSteel.com and when I received them, the 49" pieces had a significant camber across along the 3" width. They were also curved along the thickness, but I expected that and it's no issue since the dozen 5/16 holes bolt it to the 8020 extrusions.

They were good about refunding my money. I ended up ordering replacements from SpeedyMetals.com and had better luck.

As far as the motors are concerned, I'm thinking of ordering three of the 425 oz. steppers that I see on the Xylotex web site so that I don't have to take apart my first machine.

Based on your comment, it sounds like I should get the 5-start Acme rod to go with the DumpsterCNC AB nuts.

Anyway, thanks for the nice carriages.

Greg

Greg,
Your machine is looking great! I'm slightly biased, of course, but it looks like you have a solid foundation to start adding to. It's great to see the linear carriages in action.

I wouldn't hesitate to recommend Dumpster's AB nuts -- they work really well on my machine. I get about 300 IPM rapids on the X and ~150 IPM on the Y with the 5 start screws and nuts. I have 300 oz-in motors, and you're close to that, so you'll hopefully get similar performance if your gantry mass is about the same.

Best of luck!

Ahren
www.cncrouterparts.com

[snowgrains]

Thanks for the tip, Joe. I'll keep that in mind as I go along. I checked the clearance and it looks like I can get some 1/4" steel angle onto the bottom two gantry supports if I need to.

Greg

On your gantry sides, you may want to add some steel angle to stiffen it up, you will get allot of flex in single sheet of MDf, other than that looking good so far.

Joe

[snowgrains]

Steve,

I'm using the 25mm rail and blocks from automation-overstock.com for the Y-axis motion.

Ahren's carriages made sense to me lying on top of the 1.5" profile of the 8020 extrusions. I would have liked to use them on the Y-axis too, but it seemed like I might end up with some alignment issues trying to attach two separate pieces of steel to the upper and lower gantry cross members.

I guess my thinking was that the rails would self align with the 8020 slots and leave me with a simpler install.

I wish I could say it's been that simple, but it hasn't. My decision to go with four 2-hole blocks resulted in a lot more friction than I expected once I attached a plate to them. I then ordered two 4-hole flange blocks. This was better but I was still running into more friction that I wanted.

After a lot of testing, I finally isentified that the lower Hiwin rail is a tighter fit on the blocks than the upper one. I spent a lot of time over the last two weekends trying different configurations, but I finally arrived at using the 4-hole block on the top rail and a 2-hole block on the lower rail.

I also laid the plate out in TurboCAD and used the first CNC machine to mill it out of MDF.

It has been a struggle and I now have three 2-hole blocks and one 4-hole block leftover. I'm thinking of buying two 12" Hiwin 25mm rails for the Z-axis to use up two of the blocks and finish the linear motion.

Greg

Greg,

What model Hiwin's do you use on the Gantry. Any reason you opted for the Hinwins on the Gantry over Ahren's linear carriage?

Thanks,

Steve

P.S. Nice work! I'm inspired!

[snowgrains]

Well, I finally finished the router yesterday and had a chance to jog the motors. The 1/2"-10, 5-start Acme really does move things along!

I'm getting 3000mm/min. along the X-axis and 2000mm/min along the Y-axis. Not sure what this will translate into when actually cutting something, but it seems like a good start.

Attached are some pictures of the completed router.

[anotherjonesy]

Hi Snowgrains.
Like you, I’m in the shadows reading as much as I can before deciding on the design spec and costs of a CNC for home project work.

Im looking at the Ahren's carriages as well as Hiwin rails and blocks.

Firstly, your machine is a hybrid of these 2 rail types. How are you getting on with them? Are the Hiwin providing measurably more accuracy that Ahren's carriages and CRS rails?

How did you fit the Hiwin rails to the 8020 extrusions?

How is your selection of 8020 fairing?

Thank you in advance.

-Chris