I purchased a Phlatprinter Bonz kit because I wanted to change the guide rods and have more powerful stepper motors.

I bought everything as per the instructions except for:

McMaster Carr
P/N 8893K44 O-1 precision ground shaft – 7/16” x 3ft $7.03 ea
P/N 6338K466 7/16 ID Bronze Flanged Bushing $1.54 ea

Hobby CNC
P/N 23-130-DS8 Stepper Motors 185oz-in, 2.1A $38 each

Easy CNC
I bought just the driver card, $169 including shipping. Mark has negotiated a better price now, you should get it for $165


Notes & variations from the original Phaltprinter construction instructions:

General
• I used Liquid Nails for Granite Surfaces and had good luck with it. It is a bit difficult to control it out of a caulking gun, but a very small hole and a nail used as a plug to eliminate drooling helps a lot. I used Gorilla Glue for those areas that Mark used it, (except he refers to it as “super glue”).
• A heat gun will relax the ¼” air hose and you can straighten it out nicely. Don’t forget to do this step, a curled coupling will put a lot of friction into your system, especially when the axis is close to the coupling.
• Make very sure when you buy the ¼-20 threaded rod that you get a good piece. Go to several different hardware stores if necessary. Take your tee-nut with you and make sure it will easily spin along the entire length. I found one 36” piece that was perfect without a ding in it. The 12” didn’t look bad in the store, but in comparison it was terrible. It turns out that you only need 36”total so don’t bother buying the 12” piece. You can run a die over the all thread, but the surface finish will not be as good as the original rolled thread finish.
• Changing the tee-nut to HDPE or PolyAcetal plastic would be a good step and I may do this in the future.
• I replaced the 7/16” cold rolled steel guide rods with precision ground O-1 Tool steel from McMaster Carr. The normal tolerance for CRS stock is +0.000/- 0.003” and the straightness tolerance is usually unspecified. The O-1 steel is +/-0.0005” and straightness is 0.005”/ft
• Instead of the PEX pipe, I used oil impregnated bronze flange bushings from McMaster Carr. These fit tightly over the precision ground guide rod. This is a two edge sword, the tight fit requires some precision in the assembly
• If I were doing it over again, I would change the guide rods to ½”, although the 7/16 seem stout enough to cut foam.
• Also, I would try to find a cheaper stepper motor package, especially for the X axis. No one is reporting any problems achieving speed on their X-axis. The belt reduction gives you a 16.66:1 torque increase so a low torque motor works fine.
• The Hobby CNC stepper motors are 8 wire motors. I connected the Blue/Yellow wires together and the Brown & Orange wires together to make it into a series Bi-polar motor. Then the remaining 4 wires connect per the directions, Coil 1 Red +, Black -, Coil2 Green + White -.

Z-Gantry
• Next time I would put the Z-axis tee-nut so the screws retaining it face toward the motor. This will allow it to be changed as some point in the future if necessary.
• The rubber coupling for the Z-axis is shortened to 1-1/8” long. This helps to reduce the influence any banana shape in the coupling has on the lead screw.
• Like others, I used Nylok nuts for the U-bolts that hold the Dremel on. My guess is the Dremel will only be good for a few hundred hours. That would probably be a lifetime of use in a handheld environment, but in the Phaltprinter with some projects taking several hours of spindle time it seems we could easily wear one out.
• I put bronze bushings in the Z-axis to replace the PEX tubing. This requires that you change the centerline distance to match the guide rods. The PEX tubing is biased outward to take up the clearance. Changing to close tolerance bushings requires you to move the bushing holes towards each other. I assembled the Z-axis gantry and let the glue dry, then assembled the Y-axis gantry and measured over the guide rods to get an accurate center to center measurement. The Z-axis gantry can then be machined to match. You might just drill the existing holes way oversize and allow glue to make up the gaps, I preferred not to do that. I used a 7/8” Forstner bit to counter bore the ends of the Z-gantry to fit the flange of the bushing flush. This maximizes the possible travel of the Z-axis, which is needed.
• The HobbyCNC stepper motors I used had a double shaft, one coming out of each end. I had to cut off the extra Z-axis shaft so it would not interfere with the surface the Phlatprinter sets on.
• I had to grind flats on the Z-axis lead screw for the rubber hose coupling to have something to bite into. These stepper motors have enough torque to spin the lead screw inside the coupling without it.

Y-Gantry
• Bronze bushings are used for the Y-axis as well. I used the original locations and drilled the existing holes 1/32” oversize. I did not counter bore these because there is clearance inside the cabinet so there is no need. I used glue to hold them in place, use a lot to make sure the glue fills any gaps. I installed the Y-gantry in the assembled cabinet hanging it on the guide rods while the glue is still wet. Slide it towards the motor and allow the glue to cure. Then 24hr later check the opposite end to see how the fit is. I had to adjust the lower guide rod up about 1/32” to get the gantry to slide freely. I opened up the hole in the end of the cabinet and added a patch piece on the inside of the cabinet to hold the rod in position.
• #10-24 tee-nuts mount the Y and Z-axis motors making disassembly and reassembly nice. The style I bought from Lowes is 9/32 long so the Y-axis nuts must be ground down to ¼” or less to match the MDF thickness.

Cabinet
• I didn’t glue in the Y-axis guide rods. This allows them to be pulled out and then the Y and Z-gantry can be dropped out the bottom of the Phlatprinter. I tapped the end of the Y-axis guide rods and bolted them through the cabinet end panel opposite the motor. I don’t think this step is really necessary. I doubt that the rods will work back and forth, but this ensures that they won’t.
• For the X and Y-axis motors I put a hole through the motor side end panel so I didn’t need to cut the shaft off these. A knob or handle could be mounted to allow them to be turned while power is off. I’m not sure there is a need for that yet.
• I bolted on the right side end panel. I used 8-32 tee-nuts from the inside to hold it on. This allows access to remove and replace the stepper motor, Y-axis coupling, Y-axis lead screw or drive tee-nut.
• The Hobby CNC stepper motors are square and this requires the openings for each of the motors to be changed from round to square.

Setup
• I obtained 40IPM on all the axis easily. I decided to back the Z-axis down to 20IPM. Hitting the end of travel causes things to bind pretty tightly, especially at full speed. To help reduce this effect, I adjusted the VREF pots so I had just enough power to move at 40IPM, (20IPM for the Z). This ended up being 0.8V on the Z, 0.9V on the Y. I set the X to 1.0V just because. The motors are cold, the heat sinks are barely warm. I started out a 1.5V and messed up the Z coupling on my first trials. When I hit the end of travel it torqued it enough to cause runout and binding in the leadscrew. When I replaced it I shortened the coupling length and put flats on the leadscrew as noted above.
• I used grease on the Z-axis leadscrew. It looks protected enough to prevent debris from collecting on the grease. I used spray on lubricant on the Y-axis since it is more likely to collect foam dust out in the open.
• Use 32000 steps/unit for the Y and Z axis calibration, it will get you really close, (assuming 1/8 step dip switches).
• I tried to calculate the proper calibration for the X axis, but the number I come up with is about 2X what is actually needed.
• Go ahead an buy your license for Mach3 ahead of time. You won’t be able to do much without it.

I’ll get some pictures and add them to this posting later. Hopefully this will help anyone else just getting started.

Let me say that Mark has done a wonderful job putting this together and getting it on the market. I can only imagine the hundreds of hours this took to develop. The modifications I made are really just a little bit of icing on the great big cake he’s already made. Thanks Mark and Trish, great job, glad to be part of the Phlatboyz family.

Dave

 

Thanks for posting your build notes WW8S.

The resulting speeds you got sound awesome! I was thinking about the McMaster O-1 rods also, and will use the .5" diameter rods if I make the switch because of your suggestion in you build notes. I was also thinking of sliding the gantry one side and gluing the O-1 rods in place like you did, now I know it will work. Actually I was thinking of using silicone glue to hold all rods in place to absorb sound even more.

Over and over again I see mention of no problem with the X axis being fast due to the pulley and belt drive and can't help thinking that doing the same belt an pulley on the Z and Y axis would result in higher speeds with the stock steppers?

 

123

 

I don't agree. It has to do with the power needed to drive the axis. The x axis roller needs very low rpms to move the foam huge distances. Not needing the rpm, you can trade for more torque using the pulley gearing (gearing might also have been needed for accuracy?). So if WW8S is right with his data, that's 16X more torque than the other axis. And that's torque it probably doesn't need, because it doesn't have that very inefficient stock thread rod design. So the x axis is simply doubly blessed. It's not a surprise to me, that is runs the best.

If you go and gear up the y axis, that will simply drop it's toque by that factor. Torque which is already lacking in the y axis. You will need to get a huge replacement motor, to make it work. That's not even considering the wear, damage or possible destruction of the iffy stock threaded rod setup, with the heavy handed approach. Switching over to a acme threaded rod for y axis, would be the better fix (as seen in one of the mod threads). Also, making sure the thread rod is aligned and supporting the ends with bearings would help alot, too. And getting a new nut made from a advanced plastic, like HDPE, instead of metal. Well, that's my take on things.

-Kwok

 

To achieve 40IPM on the Y-axis the motor has to run at 800RPM. To achieve 40IPM on the X axis the motor only needs to turn ~25RPM. I’m just guessing here but comparing to motors I have specs on, at 800RPM the torque is down to about 70%. If you put a 2:1 ratio to decrease the motor RPM it doesn’t really get you anywhere. Like kyyu says, you now have ½ of (lets guess) 85% of your torque at the lead screw so you’re most likely worse off. If the motor had to turn 2000RPM then a reduction would probably help.

As far as accuracy, we have 32000 steps per inch on the Y & Z axis, plenty of room to give here. Truthfully, 500 steps/in would be plenty for cutting foam. That would be a 0.002” step. For the X axis mine has something like 1050 steps per inch, plenty of resolution as well.

Changing to a coarser pitch lead screw doesn’t really help matters either, I just think that some of the builds have more friction than Mark’s design allows. That friction can either be in the guide rods or in the lead screw. To me it is most important to have a free turning screw/nut combination, then secondarily, but almost as important is to have free running linear guides. I bought a set of the ZBN nuts from dbtoutfit, but I doubt if I’ll install them until I see a need. I started out with a liquid spray lubricant but changed to good quality Moly-Disulfide grease on the all-thread and it really quieted things down.

I did not glue the Y-axis guide rods in, I want to be able to drop out the entire gantry and do maintenance on it outside the cabinet. I’ll try to get some pictures up soon.
Dave

 

Hi WW8S,

Can you tell me how much your shipping was from McMaster Carr? Just for future ref, if I ever need to buy rod length stuff. It was $4.50 for my order (just the bushings) from New Jersey, which was very reasonable and only 2 days. It's just that you don't get to see the shipping cost, before committing to the purchase.

btw, the belt is like $1.50 cheaper there, than the recommended place. So I picked up an extra.

-Kwok

 

My total order was $45 so shipping was about $11. You got 8 bushing for $4.50??? OK, I just looked and you can get 1/2" flanged bushings, 3/4" long for $0.59 each. Are you using 1/2" rod? The 7/16" bushings are a bit more expensive.
Dave

 

Sorry, $4.50 was just my shipping. I got 12 of the exact same bushings you got; but unless the price went up, mine were only $1.43 each. The prices are alot cheaper than I thought, especailly 1/2". I will definitely go with 1/2", if I build a new machine. But I decided it would be much easier to stick with 7/16" for the PP. And the stock 7/16" felt stiff enough. Here is what I got:

6338K466 SAE 841 BRONZE FLANGED-SLEEVE BEARING, FOR 7/16" SHAFT DIAMETER, 5/8" OD, 3/4" LENGTH (12 EA $1.43EA)

2938T3 SAE 863 FLANGED-SLEEVE BEARING, FOR 1/4" SHAFT DIA, 3/8"OD X 1/2"L X 1/2"FLANGE OD (2EA 0.54EA)

1679K639 TRAPEZOIDAL TOOTH URETHANE TIMING BELT, .080"PITCH,TRADE SZ 124MXL,12.4"OUTER CIRCLE,1/4"W (1EA $2.61EA)

Merchandise Amount: 20.85
Shipping Charge: 4.50
Invoice Total: $25.35