Trying Something New Today, My Latest Experiment - A Linear Slide Carriage
idbruce
Posts: 6,197
Hello Everyone
Let me tell you about my latest endeavor.
A couple of years ago, I built a PCB saw from some Zebco 202 gearing, old printer parts, a DeWalt drill motor, and a Dremel diamond cutter. When building the saw, I opted to use UHMWPE plastic for my carriage, which would also act as the bearings for the linear shafting. Since building this saw, I have used it quite a few times, but it was always highly tempermental to temperature changes. Last week I decided to disassemble the saw, drill out the plastic and install some bronze sleeve bearings. Let me just say that did not work out well, and I ruined the saw. Considering that I need to make several circuit boards, I really need to fix this saw.
After pondering my predicament and considering my various options, I have decided to make a new carriage for the saw, which will include bronze sleeve bearings. Considering that I do not have a milling maching and all the various reamers, which are necessary for highly accurate work, I have decided to try something new. Instead of milling, drilling, and reaming, I have decided to cast my new carriage, not out of metal, but out of JB Weld.
At this point in time, I am currently gluing together a five sided, rectangular, wooden mold, which closely matches the dimensions of the original carriage, with the exception of the width, which will be approximately 0.001 less than the combined length of two bronze sleeve bearing end to end. When the glue has dried on my wooden rectangle, I will drill four holes slightly larger than the linear shafting, but slightly smaller than the bronze sleeve bearings.
When I get ready to cast, I will slide the linear shafting through one end of the wooden rectangle, slide on two sleeve bearings, and then slide the linear shafting out the other end of the wooden rectangle. Please note that the sleeve bearings will be a slight press fit within the mold. At this point, I will then align and secure my linear shafting, so that the carriage moves freely back and forth, meanwhile also properly positioning the mold. When the alignment has been done, or perhaps prior to the last described procedure, I will coat the mold with petroleum jelly as a release agent.
To make the JB Weld more accomodating for casting, I will be thinning it with laquer thinner.
Anyhow, that is my project for today, and I hope it turns out successful.
Let me tell you about my latest endeavor.
A couple of years ago, I built a PCB saw from some Zebco 202 gearing, old printer parts, a DeWalt drill motor, and a Dremel diamond cutter. When building the saw, I opted to use UHMWPE plastic for my carriage, which would also act as the bearings for the linear shafting. Since building this saw, I have used it quite a few times, but it was always highly tempermental to temperature changes. Last week I decided to disassemble the saw, drill out the plastic and install some bronze sleeve bearings. Let me just say that did not work out well, and I ruined the saw. Considering that I need to make several circuit boards, I really need to fix this saw.
After pondering my predicament and considering my various options, I have decided to make a new carriage for the saw, which will include bronze sleeve bearings. Considering that I do not have a milling maching and all the various reamers, which are necessary for highly accurate work, I have decided to try something new. Instead of milling, drilling, and reaming, I have decided to cast my new carriage, not out of metal, but out of JB Weld.
At this point in time, I am currently gluing together a five sided, rectangular, wooden mold, which closely matches the dimensions of the original carriage, with the exception of the width, which will be approximately 0.001 less than the combined length of two bronze sleeve bearing end to end. When the glue has dried on my wooden rectangle, I will drill four holes slightly larger than the linear shafting, but slightly smaller than the bronze sleeve bearings.
When I get ready to cast, I will slide the linear shafting through one end of the wooden rectangle, slide on two sleeve bearings, and then slide the linear shafting out the other end of the wooden rectangle. Please note that the sleeve bearings will be a slight press fit within the mold. At this point, I will then align and secure my linear shafting, so that the carriage moves freely back and forth, meanwhile also properly positioning the mold. When the alignment has been done, or perhaps prior to the last described procedure, I will coat the mold with petroleum jelly as a release agent.
To make the JB Weld more accomodating for casting, I will be thinning it with laquer thinner.
Anyhow, that is my project for today, and I hope it turns out successful.
Comments
When I use JB Weld, I always reinforce with Epoxy.
Or
I build up my part in stages with thickened Epoxy.
Just my 2 cents worth.
There really isn't going to be too much to break (at least I hope
During assembly and prior to cast, I knew I had one slighty loose fit of a bearing against the mold surface. This slighty loose fit provided an escape route for a minute portion of the epoxy. I am just hoping that it did not make it's way in between the two bearings and onto the shaft, because that would be a real bummer. As it stands now, for the portion that did escape, it is already on the shaft and I will have to break that free when it has cured.
If you really must resort to cutting PCB using a saw, (I've done it a few times) then take it outside and wear a filter mask. PCBs are things you really DON'T want to inhale.
You're saying it's sheer madness not to use a shear cutter?
I knew you would!
Pardon the hijack, idbruce. Good luck on your project. BTW I'm still waiting for a figure 8 from you.
Well Beau, it is all a matter of accuracy and the type of exposure system that I use.
Seriously, I use a CNC mill with a special FR4-cutting router bit. It makes lots of dust. But I also have a vacuum collector with a HEPA filter that sucks the dust up as it's created. I also make sure to clean any remnant dust from the mill's bed and ways, since it's highly abrasive.
Anyway, because of the way some of my multiple proto designs are panelized, it would not even be possible to separate them with a shear. But if you're careful about the dust issues (dust mask, vacuum), a saw or router is a perfeclty fine way to cut PCB material, IMO.
-Phil
precision of the cast. Make sure the sides(if possible) are square, or if you concentric concerns,
all sides should be measured off of the center, insofaras a 90 degree angle, to ensure you can
have the other sides accurate.
You may want to consider vacu-forming techniques, if you need accessory
covers. Good luck!
LOL
Even just one or two pieces embedded into the longest stretches will help alot,
Might be a little late, being as you already poured the casting, but maybe next time..
-Tommy
You keep mocking me about the things I say and attempt. What have you done? Show me some of your verifiable endeavors so that I may laugh at your junk.
EDIT: In fact, PLEASE tell me and all the forums members about your great achievements, so that we all may marvel at your greatness, and at least then I will know more about the all knowing genius that keeps picking on poor little old me.
Due to some seepage and perhaps shrinkage, I need to put a skim coat across the top of the casting. When you build in stages, do you allow the epoxy to fully cure before applying the next layer, and do you scuff up the existing layer for better adhesion?
Patience was never one of my better virtues.
After looking at various points of seepage around three of the bearings (no longer just one), and approximately 14 hours after casting, I decided to remove the mold, because I did not want the casting permenantly attached to my linear shafting, so I completely disassembled my casting setup. Using a razor blade ever so gently, I scored the JB Weld attached to the shafting and pryed it from the shaft in pieces, at which point the shafting became free, and I could remove the carriage. Upon inspection of the carriage, I noticed buildup from the seepage around the various bearings, and so I removed this buildup and any other interference with a deburring tool. Additionally, some of the seepage had entered into the bearing openings, not too much, but just enough to cause a slight interference during travel. Using an Exacto knife, I lightly scraped the JB Weld from the inner bearing surfaces. I then reassembled my setup, minus the mold and excess JB Weld, and realigned my shafting. At which point I tested the action of the carriage on the shafting.
RESULT = FifteenInchesOfSmooooooooothLinearTravel
Once the cast completely hardens, I will drill out all of the necessary holes and reassemble my saw.
For those folks that need a light duty carriage, I would recommend this procedure to anyone with a fair amount of mechanical aptitude.
Looks like your project with JB weld is working out for you.
I use West epoxy system.
West #105 Resin
West 205 Hardener
West 406 Colloidal Silica filler.
I mix up small batch of resin/hardener.
brush on a light coat 'neat', without filler.
I then thicken the batch with 406 filler to a consistency of about peanut butter.
I apply the thickened epoxy to a max of about 3/8"
After 2 hours, the thickened epoxy will have set up and cooled down, It will be slightly sticky and soft, but solid.
At that time, I immediately mix up another thickened batch and apply it to the slightly cured epoxy.
This usually will finish the buildups that I need.
or
If I'm only doing reinforcement on the outside of say a coupling type thing.
I apply a coat of epoxy 'neat' to the thing, leave it sit for about 5 minutes or so, then
I wrap the thing with polyester sewing thread neatly and saturate the thread with another
coat of epoxy 'neat'.
This makes a good reinforcement also.
I hope this info helps you in some manner.
As it turns out, I should have made an exact duplicate in size of the original carriage. Truly a case of 20/20 hindsight, because as it stands now, some of my other pieces will not match up properly.
Although this saw was highly functional, before I destroyed it
Information on various techniques is always nice to have. I often refer back to threads and techniques people have talked about.
I know you don't like to here it but OSHPark and many others can do a cheap and beautiful job for you. Leaving you free to concentrate on more satisfying endeavours.
Yep, I screwed up and it is costing me serious time. However, on the other hand, it is my goal to design equipment. As long as I am designing, building, or modifying a piece of equipment, I suppose it is all good. However, I would much rather be working on the 3D printer.
This time around, I believe I will wrap a piece of masking tape around where the bearing pairs meet, as added insurance to prevent seepage into the bearing cavities. Additionally, I may try using plexiglass for making my mold, just to get a nice smooth finish on the casting. For the first casting, I used thin strips of oak for the sides of the mold, and the finished casting has oak grain on the sides
Just in case someone decides to try this project, I suppose I should tell you that for approximately a 3/4" X 2" X 2" mold, with (4) - 3/8" X 1/2" X 1" sleeve bearings, you should expect to pay around $25 just for the bearings and JB Weld, not including mold materials or glue.
EDIT: Also as a side note, I think it is worthwhile to mention that the petroleum jelly worked very well as a release agent for the mold. Additionally, thinning the JB Weld with laquer thinner worked very well also. It mixed well and poured right into the mold, encasing the bearings with ease (no putty knife necessary). The JB Weld company recommends 1 TSP of laquer thinner or acetone per 2 oz(s) of JB Weld.
Just a while ago, somebody broke their eyeglasses. Expensive ones too. I used fine thread fibers and layers of JB Weld to reconnect the glasses at a complex joint, which of course is where the metal fatigue and stress caused a fracture. In the case of the glasses, I painted on a clean coat, then set the fibers, let cure some, paint over fibers, let cure some, lay down more fibers in a cross direction, paint over that, cure a lot, paint final coat. Then color with model paint. Took a few hours spread out over a couple days.
Honestly, I'm stunned at the improvement. Might be worth it for something like this.
I believe this application should be okay without reinforcement, because it is very low stress. However, since the first carriage turned out so nice, I have now been thinking of the various possibilities at my fingertips, which would definitely require reinforcement.
Approximately thirty years ago, I built my first linear slide, more specifically, a panel saw for accurately cutting square sheets of plywood. It was crudely constructed, but yet it was very effective. It did not have polished linear shafts, sleeve bearings, or roller bearings. The linear shafts were made from common black pipe and the carriage was simply made from larger pieces of black pipe and plate steel. I have always wanted a nice panel saw for the garage, for cabinetry work and other general woodworking projects.
The potential for linear slides have always been of interest to me, ever since I saw my first panel saw. Looking back now, that crude panel saw was the first tool I ever built
Anyhow, as mentioned, I have been pondering the concept of expanding this idea for larger projects, ones that would be able to handle fair amounts of torque, and ones that would require reinforcement.
EDIT: Since I mentioned panel saws, I thought I would add a pic of this giant PCB cutter made by Milwaukee Electric Tool, which cuts both vertically and horizontally
I still don't have a camera, but I do need to take some pics of other things, so when I borrow a camera, I will take some of the mold, the carriage and the portions of the existing saw. I have changed my my mind however, I am going to completely rebuild the saw with the carriage that I already cast. I am completely altering the design and drive system, by doing away with the Zebco 202 gears and swaping them out for timing pulleys and a belt.
I will post them when I can.
EDIT: Keep in mind that the mold is now in pieces again
- 14.4V DeWalt Drill motor
- Motor mount (angle aluminum)
- Timing pulley
- Bearing
- Assembly screws, 2 required
- Bearing
- JB Weld carriage assembly
- Timing pulley
- Rotary shaft housing (aluminum bar)
- Rotary shaft with pulley flat, wrench flats, (2) retaining grooves, and internal threads for the blade mounting screw
- Dremel diamond blade
- Blade retaining screw
***Please note that the bearings within the rotary shaft housing have not been indicated, nor have the rotary shaft retaining rings. Additionally, the timing belt has been omitted.EDIT: Additionally, the dust shield has been omitted. This shield prevents the dust from flying everywhere, as welll as keeping the dust out of the motor.
Didn't have any channel stock on hand but did have some angle stock to give a quick test. Took about 5 mins. to do.
Well I have good news for you... You don't have to..... You can get all the DeWalt drill motors you want from this location:
http://www.robotmarketplace.com/products/dewalt_motors.html
Before anyone complains, I want to update my latest discovery. As mentioned earlier in this thread, the orginal casting had some flaws, such as the wood grain left from the mold and depressions due to shrinkage or seepage. Yesterday, I added a little more JB Weld to the depressions, and this morning I did a final sanding of the cast, to make it look nice, and I had it looking pretty darn good.
Just a few minutes ago, approximately 14 hours after sanding, I noticed that oil had seeped into the JB Weld. There are several possible causes for this, but I will not go into all the possibilities, instead I will simply wipe it down with laquer thinner and see if it returns. However, this is not a major concern to me, but it may be for some people.
I purchased my sleeve bearings from the local Lowes, and I always had the impression that they were simply cast bronze bearings, as opposed to oil impregnated sintered bronze bearings, but I could have been wrong. On the other hand, I could be right, and it could simply be a light coating of oil on the bearing.
If you plan to attempt one of these carriages and the sight of oil bothers you, then you should probably special order bronze bearings (without oil) from McMaster or some other source, where you know exactly what you are getting, and thoroughly wash the bearing before casting.
I am just throwing this out there, because I do not want to hear about oil complaints