Fixed Gantry, Light Duty PBC-Plastic Engraver

[Drools]

The is my attempt to make a small fixed Gantry machine. I want a machine to be able to do PCBs with excellent results and plastic with equally good results. The foot print is 2’ square with a cutting area of about 12” on the fixed axis (moving table) and 16”-18” on the moving axis (gantry) with about 3” on the Z.
I built an 8020 moving gantry machine a few years ago with less than perfect results. The mistake I made was on the frame, it was way to flimsy. I decided to make a new moving gantry machine which can be seen here 80/20, THK, CNCRP. The new machine got a brand new frame and linear rails but it does have some of the parts from the original machine. This left me with quite a bit of 8020 1530 to make a small machine. With the large machine done (for now) I wanted to get working on the PCB machine. The large machine was used to cut/mill all the aluminum used in the PCB machine.

Details:
Frame: 8020 1530 with .5x3 Ali and .75x4 ali.
Linear rails: SSR25 for moving table, HSR25 for Gantry and SHS15 for Z.
Screws: ACME 1/2 – 10 single start with CNCRP nuts.
Steppers: 280oz 2.8amp Nema23 by Tormach
Bearing blocks: Mix of CNCRP and my own.
Couplers: Unknown make/model but they look good with rubber centers. .25” to .25”
Spindle: Wolfgang (for now)
Drivers: An AVR-Based Microstepping Bipolar Chopper Stepper Motor Driver (STMD) http://avrstmd.com/ (Worked well on original machine)

I just did a trial assembly of the frame to see how the parts fit and to make sure I have enough hardware to assemble everything.
I need to find something to use as a base, I was thinking MDF but I would like to use something else, it has to be 2’ square (maybe a visit to the local cabinet makers might turn up something).
The pictures show what I have done so far. I still need to make the Z axis adaptor plate and the Z axis.
Comments are welcome.

Brent

[flojor10]

Are those mdf bearing blocks?

[Drools]

no, the MDF blocks on the rail are alignment blocks to make sure the rail is mounted center on the Ali.

[FandZ]

Hey I've made MDF inserts before to get my rails aligned. Makes the job a super fast cinch. I think you'll be able to do a lot more than plastics but I'm sure you know that.

When you say base do you mean the table? If so I'd recommend some King starboard. It's very stiff, cuts wonderfully, and can take a tap nicely. It's also fairly flat. http://www.boatoutfitters.com/cut-to...ing-starboardv

The only negative is it can be very slippery. But using some aluminum T slot inserts or drilling/milling and tapping some stud holes would fix that. I'm using some on a project now and am very impressed with it.

[Drools]

Hi FandZ, that starboard looks interesting. Actually I need both a table and a base. The base is something I wand under the machine and the starboard if water-resistant might do the trick. I'm going to order a piece of Mic-6 for the table once I have the gantry blocks are mounted, this way I will know exactly how much travel I will have on the gantry.
ya I might be able to cut a little more than PCBs but the Wolfgang will not last long if I do. I have a lot of PCB projects that I want to tackle once this machine is done.

[BanduraMaker]

It's also fairly flat.

Until you surface it. I've used it for several holding fixtures and while everything you say is true, in my experience once you surface one side, it tends to cup like mad in that direction. Not a problem with what I'm doing as I can pull it flat against my table but to use as a table itself, I wouldn't recommend it.

[FandZ]

Until you surface it. I've used it for several holding fixtures and while everything you say is true, in my experience once you surface one side, it tends to cup like mad in that direction. Not a problem with what I'm doing as I can pull it flat against my table but to use as a table itself, I wouldn't recommend it.

Thanks for the info. I've recently used it to make several parts and have been happy with the results. I've yet to try to surface any length of it though. It seems so stable. What feeds and speeds did you use to surface yours? I was planning to use some for fixtures myself. But with the bowing I may need to look elsewhere.

[RomanLini]

Nice work! It's good to see some small machines.

I take it you have seen Don Frambach's small machine?

[Drools]

Hi Roman, thanks for the comments.
Yes I have studied Don's build quite a lot, he has done a very good job.

[BanduraMaker]

It seems so stable. What feeds and speeds did you use to surface yours? I was planning to use some for fixtures myself. But with the bowing I may need to look elsewhere.

I haven't machined any lately but I think I was using feeds around 200ipm or so.

It still works pretty well as a fixture, you just have to clamp it down really well. As I understand it, this is pretty common with the UHMW type plastics.

[Drools]

I did a bit more on the little monster.
I decided to make a temporary adaptor plate and table from baltic birch, this allowed me to test the alignment of the rails. Since I just used my last bit of cash for an upgrade of the bigger machine I may have to use the wood table top for a bit.
The movement is reall smooth for both axis, I'm very happy with it so far.
I'm thinking if I had not gone with direct drive on the table axis I could have used 3" Ali instead of the 4" Ali and this would allow the table to move past the end plates.

[ickee]

was just wondering if there are any updates? I'm building a similar machine