In progress - 8020, linear rails, ball screws, steppers

[stevespo]

After many months of reading the forum and scribbling on graph paper, I have finally put chopsaw to aluminum and started building. My basic design goals were to have a solid benchtop (moving gantry) machine that I can use for woodworking - with enough accuracy to (hopefully) cut pearl for inlay. My budget ruled out commercial units, so I chose the DIY route. Also I guess I was looking for a challenging project that could bring together a bunch of interests.

I accumulated a lot of great materials off of eBay and through the Zone classifieds.

PC 890 (new)
Parker Actuator 6.5" travel (Z axis)
Lots of 8020, connectors, etc
33" THK SR15 rigid rails
39.5" IKO SR15 rigid rails
2 38.5" rolled ballscrews with preloaded nuts and bearings
Honeywell 914/924CE switches for home switches
Freud Diablo 10" non-ferrous table/chopsaw blade
Xylotex 3 Axis with 480oz steppers

Months ago, I purchased the Xylotex 3 axis controller kit and installed it in a box with PS, etc. I was able to test out the actuator and ballscrews by driving them from my laptop with Mach2. The accuracy blew me away, and made me very hopeful. While I was playing with the electronics I went through several iterations of design and did some mockups with the 8020.

This past Monday I finally decided it was time to stop planning. I was nervous about cutting the aluminum, but it's actually very easy with my 10" chopsaw and contractor's saw. Using a spray can of Tap-Magic to keep things lubed.

I've been able to put in 4-5 hours each day this week and have made some good progress. I'll post some pictures on a sort of day-by-day basis.

So, Monday & Tuesday got the basic framework together for the base, measuring 37" wide by 34" deep. 8020 extrusions and some 1/2" extruded bar stock (4 1/2" wide). The side rails are 3"x3" and the rest is 1.5"x3" on it's side. My drill press is lousy, so getting the holes lined up took some time. A small mill with a nice sliding table would have saved me many hours.

[stevespo]

Made some mounting brackets out of 1/2" stock and the gantry uprights out of 1530 stock and some 1515 for 45 degree bracing. Cut the 3/4" holes with a Forstner bit and bolted everything together. Took some fussing to get everything square and plumb, but pleased with the results.

With a temporary bar clamped between the uprights, the "gantry" just sails on those rails. As best I can measure, they are within .002" of being parallel and very square. Given that I'm assembling this on a fairly flat MDF tabletop and not a surface plate, I'm going to get things as close as I can and then move onto the next step.

Steve

[stevespo]

Keeping busy. Made a sturdy arm to hang the Z-axis on. This is 2 pieces of 1530 (1.5"x3.0") stock bolted together on edge, and then bolted to the uprights. It is very rigid. Added the lower part of the gantry using a piece of 3075 (.75" x 3"). I can't seem to get this to rack, so I feel like I've made a good choice by going with the 8020 and using the larger extrusions.

The rails are attached with long strips of steel, that were pre-drilled and tapped for 4mm socket head screws on 60mm centers. Very handy. I knew I wouldn't be able to accurately drill/tap those holes, so this helped me out tremendously. Thank you 8020 Surplus. All my 8020 supplies were purchased through the outlet and very easy dealing with them.

I then made a bracket to mount the actuator, and attached the Z-axis. I debated about how to handle this detail. I wanted to have a decent amount of clearance under the upright, but didn't want to sacrifice too much rigidity. I placed the bottom of the rail 6.75" above the table. This will be 6" above the MDF workboard. Then factoring in clamping/fixturing, router chuck, etc - I should still have decent clearance. The nice thing about this design is that if I run into problems, I can lower the entire arm by unbolting and sliding it down the upright.

I was a little hestitant about mounting the actuator this way - so that the stepper is moving the router, and the weight of the actuator and itself. In testing things out, the stepper had no problem with the weight, and I felt it would be the stiffest way to mount the router. I could hang the router off of the moving table and keep the actuator/motor fixed, but will reserve that in case my first choice doesn't work out. Would appreciate any ideas on that.

Now I need to get the 2nd ballscrew mounted and attach the moving parts to the drive system. I can move the Z up and down and I'm anxious to get all 3 axis going. Not sure if I'll have any time this weekend, but I'm hopeful.

Steve

[GaryCorlew]

This is a great looking build, I made mine from 8020 extrusions as well

[stevespo]

Less than a year ago, I knew almost nothing about CNC. Now I feel like I'm getting close to having something really useful and accurate in my shop.

Seeing other people's success with the 8020 really inspired me to give it a shot. I hope the combination of choices I have made (and the attention I've given to the design) will pay off. I'd like to hear any feedback people have, because I'm sure I've done some things in a less than ideal way.

This forum has been invaluable in helping to educate me. I've definitely been inspired by all the great work people are doing and their willingness to share that experience. I'll keep the photos coming and hope to eventually post a short video when I'm making some cuts. I know I will encounter some problems before that happens and I look forward to getting more help along the way.

Steve

[epineh]

Nice work Steve, keep the pics coming.

Russell.

[stevespo]

Progress sure does slow down when you have to stop and think about things. Needed to finalize how I was going to attach the drive mechanism to the gantry. Managed to make 2 flanges which thread onto the ball nuts. 7/8" Forstner bit and a 15/16-16 tap worked very nicely.

The ballscrew and bearing blocks attach to a piece of 1530 that runs down the center of the frame. I can pull this out quickly and work on things. You will notice the high precision Baltic birch end blocks - don't laugh. They're temporary, just to get things together and tested. I plan make "real" ones out of aluminum (maybe delrin?) when the mill is functioning. If I can't do it myself, I'll have a local machine shop do it.

Photos include closeups of each end block (front and back). Another shot of the back of the machine, showing the stepper in place. I'm able to move the gantry back and forth quite easily. Speed right now is limited to 54 ipm. I'm running on a 400Mhz laptop (7 years old), and I have problems if I try and go any faster. I have an old 800Mhz desktop (AMD) that I plan to setup and use. One of my neighbors was tossing this out and all it needed was a new hard drive. I hope that's fast enough. If not, I will have to scrounge something else. What burns me is I have a fast new laptop with no parallel port! From what I've read, the PCMCIA -> parallel adapters won't do the trick.

Tomorrow I will attach the last ballscrew and I should be able to drive all 3 axis independantly and simultaneously (PC willing). Then I just need to make one last mounting plate for the router and take it for a spin.

Steve

[Mike F]

This is one, good looking machine. That 8020 really does make a professional job. Of course, it does take a modicum of genius to put it together properly too and it looks like you're doing a cracking job.

Please do keep the pics coming as a lot of would be builders get lots of ideas from them rather than the text. Once they are hooked by the looks, they will start reading, and this one's a looker.

Mike

[stevespo]

Thanks for the comments. The 8020 does make for a clean looking machine, IMO. I'm a long way from being a genius with it, but happy with the results. It's a wonderful tool for prototyping - I hope it will hold up for this use. I'm sure a bit of Lock-Tite wouldn't hurt.

Today I needed to fabricate a couple of brackets and a mounting plate (nema-23) for the X axis. I oriented things so that you face the long (X) axis when standing in front. I guess this isn't typical, but it seemed to make more sense for my workspace and the way I hope to use it.

Couple of pictures of the X-axis ballscrew, mounting brackets and then a few shots of the results of my "Sharpie" testing. Just kept drawing a circle and a square (offset by .5").

At first, I was encountering some hesitation and lost steps when moving the gantry, but backed off the speed and it performed very well. Not sure if it's my slow computer, my Mach2 setup, my controller/motors, etc. I need to go over my settings again and read the manual.

I can run the gantry at 45 ipm reliably, but faster caused problems. Definitely no problems with racking/alignment. I can chuck the ballscrew in my portable drill (lowest torque setting) and fly the entire gantry around. Smooth and very fast at over 180 ipm.

Interestingly, I can move the upper part (what the Z moves on) at 190 ipm using the stepper. Moving a lot less mass around, but both parts are just silky smooth on the rails. I will keep trying to figure that one out and will get the faster computer setup ASAP. I don't know what to expect as far as performance goes with the Xylotex board and the 480 oz. steppers - any ideas?

Next step is to mount the router, home/limit switches, etc. I'm confident that I have everything lined up well and I'm ready to tackle some routing... after the Thanksgiving holiday. Hoped to be further along, but still happy with the progress.

Steve

[stevespo]

Success! I made another mounting plate and attached the PC890 to the Z axis. After some "air routing" I decided to cut for real and the results were great. Only tried the simple circle/square, but they were just about dead on (within .001").

Circle is 2" diam, and 4" square. Cut to .375" deep with a .250" upcut bit in 3 passes. I've been playing with the Mach 3 motor tuning and have things running smoothly at 45 ipm, cutting around 30 ipm. I hope to improve this, but will require some playing around with the controller and software.

I still need to wire up the home/limit switches, and deal with dust collection. I might need to counter-balance the weight of the Z actuator and router. I seemed to notice some slipping on the Z, but can't say for sure.

I'm eager to start cutting some more complex shapes. So far, my expectations have been exceeded with the accuracy. I'd like to improve the speed, but it seems like a usable setup as-is. I'd appreciate any ideas as to what to expect with 5 tpi ball screws, the Xylotex and 425oz/in steppers.

Steve

[stevespo]

Spent the day cutting parts and getting some practice. I'm amazed at the quality of cuts that I am getting. When I tried to cut one of the sample PhotoVCarve pictures, I definitely saw slipping on the Z-axis. I had suspected it before, but it was very minor. After a few minutes of VCarve, it was very noticable.

So, I read up on counterbalancing and decided to go with a gas strut. I happened to have 2 struts from a pickup cab's rear window, each rated at 24 lbs. My Z mechanism and router weigh 28 lbs. So, I attached one strut with the hope that my 425 oz/in stepper can maintain the 4 lbs or so differential. I think this will work ok. You can see the strut towards the right hand side of the photo, attached between the base plate and the upper part of the Z actuator.

I'm going to need to upgrade my computer at some point. It runs Mach 3 ok, but could definitely be faster. The real issue is when I want to edit a drawing w/BobCAD and then use Mach 3 to cut the part. Pretty slow trying to multitask. Maybe just stick a new motherboard and more memory into it - or look for a cheapo on sale.

Steve

[robe_uk]

Hi Steve
Great looking machine you have there, I always like the look of a 8020 machine.

I am sure i have seen somewhere a link to an interface which will connect to a computer usb and allow connection to the commond stepper drivers, am at work at the mo so will try and dig it out later, details are sketchy as i never paid to much attention at the time, maybe someone else has seen it?