So, the build has been going great so far. Its surprisingly its almost done... the only thing i'm waiting for is the controller from hong Kong... The next thing on the build log is to design the belt mod... I have made sure and will continue to take pictures of all the areas that I've made modifications from stock. ill post mods and my progress soon.

 

foamflight - Many of us have added the belt-drive mod to our MKI's, so you can look through our build logs and get an idea of what NOT to do.
I already did the "quick and ugly", so you can be another person to "do the right thing" when you modify your machine.

 

Okay. So i'm going to sit down and upload some of my pictures of my build. by the way the build is basically complete with exception of the lid and the controller board... but its okay, since I didn't have the controller yet it allowed me to take my time with the build.

Now i'm not a perfectionist in any sense, so when it comes to esthetic's dont expect this build to the the prettiest, but I think I did a fair job in most of the modifications.

















Thanks for all the help and advice so far. ill be posting more pictures as I have time to take them. Attached files

 

Thanks for the comments guys!

rjarois - I used 1/2in on the top of the y axis and 5/8ths on the bottom. I did this due to clearance issues at the top of the z gantry. down the road I might move up to the 5/8ths for the top as well but for now ill stay with that. oh I used 1/2in on the z carriage as well.

kram242 - The acme rod does look great in there. I didn't use a bushing on the acme rod. should I have?

3DMON - Yeah, I figured it was a perfect fit for the motor so why re invent the wheel...

 

I got the X and Z axis all up and running. WOOP WOOP!! i'm waiting for some ordered items to complete the Y however...
one question for you db-25 pro's out there... what would be a safe maximum length for a db-25 parallel cable? the reason I ask is because i'm considering running a cable from my bedroom through the attic into the garage. I found this
http://www.mpja.com/prodinfo.asp?number=11459+CB
and I figured that since they sell it that it would work... but I don't want to buy the cable only to find out that there is too much signal loss or something like that and have wasted my time by doing the wiring job. thanks guys!

 

I read on CNCZone, I think, that the cable should not be longer than 6' or you're going to run into problems.

 

I think I would go with this quote from Marks link. Not to say those are good number to go by, but that I seriously doubt you are going to get by with a long cable:

"Parallel Cables Length Limits

Older style Centronics parallel cables, can rarely be more than 15 feet long and still operate correctly, and 9 to 12 feet is a safer limit. The IEEE-1284 can go up to 30feet in length."

 

Those length limits for parallel port cables were in relation to using them on a printer. Our CNC controller boards are a LOT more sensitive to noise and have a much higher requirement for quality signals than printers ever had.
After all, that is why the parallel ports on laptops are useless for our CNC needs - the ports are good enough to run a printer but useless for CNC. I would bet you'd have endless problems trying to run a PP with a long parallel cable.

 

Dorsal - thats exactly what I was worried about. I wasn't sure how data intensive cnc is as compared to a printer. but it makes sense that it wouldn't have the ability to go long distances as it is such an old technology. now i'm assuming a wireless print server wouldn't have the capability to do what were looking to do right? Thanks again for your help. I should be up and running around Tuesday...

 

Even if you had a SmoothStepper (to allow you to run through a USB cable), you'd need 6 5M cables and 5 hubs to get to its limit of 30Meters. http://www.usb.org/about/faq/ans5
There might be an Ethernet option, to network to another 'puter out with the PP.
Or go wireless to network to another computer with the PP.

Personally, I can't imagine attempting to run my machine from another room. I want to be right there when some dumb little dropout piece tries to jam up the foam sheet, or I forgot to "Home" the router, or . . . . .
My suggestion: Get a SmoothStepper so you can run the PP from a laptop, then take your laptop out to the PP so you can be right there.

 

yeah, I think ill give up that idea... the plan to control the computer was to use vnc with my laptop to control the desktop. but since it cant handle the long cable i guess that plan is out.

 

I have my machine up and running! i'm working on speeding up my machine right now. I've gotten my y axis up to a consistent 5-600 ipm. however as soon as I put a load on it it begins to miss steps(forcing me to pull back to 50-100ipm). i'm not sure if its the bit that i'm using or if its just my setup. i'm using the standard 1/8ths bit from lowes. it seems to me that the bit really causes a lot of drag in the foam. i'm not sure if this is normal but it seems like a very limiting factor. also what do you guys use for microstepping settings on your printers? i'm using vexta's and a 4 axis ebay controller. its on 1/2 step as default. i'm curious if that might be a causing a problem.
Its amazing how much I've learned about this machine. Thanks for all your help.

 

Check for binding on you gantry, It should move very freely. any binding will impact the overall performance, I am running an Ebay board, set at 1/4 steps and Just added the Vextra motors to mine and can push mine to over 1000ipm not cutting and cut at 200ipm, It can go LOTS faster but I'm happy with the consistent and clean cuts I get at that speed. My rapids are well over 700ipm on both X and Y, My problem child is Z and I still get 25-30ipm's using a 3/8 12acme screw. So it's not as fast As I would like but it is now 100% consistent.

With Steppers, ALL of their torque is in the low RPMS that's why the belt mod or Multi start screws works so well. Also being at 1/2 step rather than 1/4 or 1/8 should be better, (less precision, but enough for what we do) So I'd look to motor tuning, in the SW as well as if you have the option unlike mine to adjust the current, you could try giving it a boost.

BTW: what PS are you running, I may have missed it listed earlier in the post. If the PS dosn't supply enough current it could be a problem as well. I'd guess we need about 6 or so amps for the Vextras, to get their full potential.

 

I just realized that its been quite a while since I gave you guys an update. Everything is going great on my machine. I have it running very stable at 100ipm without any missed steps. z is my only dissapointing axis, i can only get about 30ipm out of it... i'm going to take it apart one of these days and polish the rods and figure a way to polish the acme thread as well. one more mod i'm looking to make is to change out my dremel for the rotozip, it just seems like the obvious choice to widen my options for cut mediums.
last night I was cutting some foam with the standard bit when I noticed my cut path was about half an inch wide and my bit had a giant clump of melted foam on it. has anyone else had a problem like this? after it cooled I was able to cut the melted foam from the bit and it hasn't done it since. but i'm still afraid that it might happen again.