Spring-loaded Replicator 1 Drive Block

by ivc, published

Spring-loaded Replicator 1 Drive Block by ivc Mar 16, 2013
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This is an derivation of the "Spring-loaded Replicator 2 Drive Block" by MakerBot to make it compatible with the Replicator 1 (single and dual extruder). Only minor changes has been made, as outlined in the list below. Based on the work of Thingiverse users MakerBot, whpthomas, emmett and whosawhatsis.

It is the same spring-loaded arm used to squeeze the filament between the drive gear and a bearing with a constant amount of pressure. Minimizing the chance of skips due to variance in filament thickness. Both normal and mirrored models are available to fit either side of the carriage. The models are offered as STL and STEP files.

A simple spring height adjustment part is included to easily increase the spring rate if needed. This piece fits over the stub on the base part.


  • Cut upper-left corner wall from the lever to fit the Replicator 1 extruder mount carriage
  • Changed the lever and base screw hole to accept a regular countersunk M3 hex screw (easy to find find)
  • Cut a slight piece off the cover to avoid resting on the drive gear
  • Decrease the bearing bolt stub diameter to fit the readily available 623ZZ bearing (3 mm vs. 4 mm ID)


Follow the excellent instructions by MakerBot: http://www.thingiverse.com/thing:53125


  • 1x M3 x 16mm Flat Head Cap Countersunk Hex Screw
  • 1x M3 x 8mm Flat Head Cap Countersunk Hex Screw
  • 1x Ball Bearing, 3mm ID x 10mm OD x 4mm Width, typ. 623ZZ bearing
  • 1x Compression Spring, 0.360"OD 0.276"ID 0.630"-0.900"L (9mm OD x 7mm ID x 16-22mm L), 32lbs/in spring rate

I used the following webshops to get the needed parts:
http://www.a2stainless.co.uk (Socket Countersunk Screw DIN 7991 - M3 16mm, 8mm)
http://myworld.ebay.com/bearingoptions (Bearings 6000 Series - 623ZZ)
http://myworld.ebay.com/switchedkwb/ (2x Compression / Pressure Springs - 31 x 10 x 1mm)

The hex screws has to protrude 3 mm behind the base to properly secure the base and lever, any longer and the screw will hit the stepper motor mounting bolts. Cut the screws down to length if needed or loosen the stepper motor bolts.

After mounting the lever and base to the stepper motor, make sure to leave enough slack/space to allow the lever to move freely up and down. Add some medium thread-lock if needed.

The compression spring should have enough force to squeeze the filament fairly well. If rated on a scale from 1 to 10, where 1 is super soft and 10 massively hard, the spring should be in the 6-7 range.

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What is the thing Spring Adj? I don't unterderstand where he goes.

To adjust the tension of the spring, you have to cut it where you think you get enough but not over tensioning the clamp. I suggest you get two springs in case you need to make adjustments.

rep1 dual/ sf 7.6

I kept going heavier until I got good "teeth" marks on the filament. Then I tweaked the steps per mm. 97.193858376729976042066420380161.

just make sure whatever number you use is arrived at by using the formula usually found in the machine def. in my case

So we get: 3200/(PI*10.58) = 96.275...

don't round

I printed these for my Replicator, and it turned out great. A few things weren't obvious, so I'll post notes here for reference, in case they're useful to anyone else.

First, you have to print using Makerware, with support enabled, because there are overhangs that are important to get right. I used 'medium' setting. Printing with ReplicatorG/Skeinforge didn't quite work right.

You have to flip the covers over so that the "front" is flat on the build platform. It loads upside down, which (oops) burns a lot of support material and isn't usable.

After printing you have to rip out the "support" block that sticks out from the largest piece, and a "ring" around the hole that the gear goes through. It's important to clear that out, and clear out all generated support, so that the piece fits on the face of the motor, which has a raised ring. So it's worth the effort to clear it out (e.g. with a razor blade or sharp knife), and test fit onto the motor, before screwing everything together. If it's not flat against the face of the motor, there's more material that needs to be cleared out.

And you have to test fit into the Replicator. It's very tight both on the top and bottom, because it fits very tightly in place. In particular, it has to fit over the top of the hot end, and below the top plate. I had to file it down a little bit to fit properly - before that, it caused the screw holes to not quite line up right.

To get it properly mounted, I couldn't install with the motors in place, but had to remove the motors and assemble on a table.

The thin vertical pin that goes through the center of the bearing breaks off easily (both of mine did), but that's OK - put it back in place, put the bearing on, and put the cover over it. Between the bearing and the hole in the cover, everything will hold together fine - the bearing is held in place by the ends of the pin on the base and in the hole in the cover.

I had to mail-order the screws, in boxes of 100, so I have lots of extras. If anyone needs just the screws, I'm happy mailing them to people - stamps are cheap! :-) The springs and bearings are easier (in the US) to source locally. I found springs that worked fine in a cheap assortment pack at Home Depot.

I printed with 3 walls and 10% fill, and it seems to be working fine (20 hours of printing ABS so far). It looks and works great. The only 'down side' is that you can't get to the gear to clean it as easily as with the "minimalistic" designs. But I don't have to do that too often...

I found I was able to use Delta Faucet springs for this upgrade, they are right at the shorter end of what will work but seem to apply enough pressure. I've been able to do several 2.5 hour plus prints since the upgrade with no feed issues. I got mine at Lowes for a few dollars. The part number is 80703, Seats and Springs for DELTA, prior to 1976.

I've printed this out and everything looks about right, except for one thing: When I put the main block on the stepper motor, the whole thing sits several millimeters away from the motor assembly. It seems that the inset ring on the back of the printed part is getting in the way of the flange around the motor rod.

Even if I cut away the top and bottom "tabs" on either side of that ring, I think the problem will remain.

Are there different stepper motors out there? Might that be why I'm having this issue?

Since I'm impatient, I decided to simply remove the ring around the hole, along with the tabs, with a razor blade...and all appears well.

the only issue is that little peg for the bearing is flimsy and breaks but that's why i've printed backups!

16 mm seems too short for the main screw. It's barely visible in the other side. Mine needs at least 20 mm.

I'm assuming the small tab that prints with the main drive block body is to be removed? I don't see it present in any of your printed parts...

Yes correct. Remove the support where the stepper motor head insert.

Thanks! Getting my vitamins in the mail tomorrow, looking forward to the upgrade.

It's not working for me, the filament just isn't getting pulled hard enough by the motor to go through the extruder. Did you also have this problem? How do you fix it?

Would appreciate any advice. Printed out two copies just in case it wouldn't work (go figure). Thanks in advance!

I had this problem when I used a spring with too little spring rate. The pressure has to be really good, almost to the point where you can't compress the spring by hand. After this adjustment both extrudes has worked flawlessly for 3-4 prints since.

Seem to have the same problem here. I just couldn't imagine the spring I was trying to use to be too weak for the task :)
But by manually adding a little bit of additional force on the leaver the plastic flows nicely.
Makes me wonder why the Replicator works in the first place, with the flimsy plastic thingie they are using :)
And it worked oh so well ;(
Did You ever encounter problems with overheating in the stepper motor when using so much pressure on its axle?

[ Overheaters Anonymous - where do You join? :) ]

Thanks for the reply. I'll have to search for a tougher spring and try it out! Good to know that yours is working :)

"Dat documentation..." Superb!

Intrigued by this as I'm still using the original plunger design on my rep1...it would help if there was a plate stl with all the parts on it for left and right. How has the printing been with it?

If it works - don't change anything. I did and I'm suffering ;)


With the correct spring rate, the prints have been really good and no skips or stops.